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Flash Physics: Quantum cryptography for aircraft, AI boosts X-ray probe, cold nebula born in stellar collision

Cryptic quantum communications for moving aircraft

The potential of using satellites for secure quantum communication has been demonstrated in a proof-of-concept study by researchers in Canada. Thomas Jennewein from the University of Waterloo and colleagues successfully sent quantum key distribution (QKD) transmissions from the ground to a moving aircraft for the first time. QKD uses the laws of quantum mechanics to guarantee complete security when two people exchange a cryptographic key using photons. If the key is read by a third party, this act of measurement will fundamentally change the nature of the key – thereby alerting the two correspondents to the presence of the eavesdropper. On the ground, QKD transmissions can be sent via optical fibres but their range is limited to a few hundred kilometres because of absorption losses. While free space links have been shown to work over ground in both stationary and moving tests, they are also limited to a few hundred kilometres – instead being held back by atmospheric absorption and turbulence, and the need for a clear line of sight. However, these drawbacks could be avoided by using satellites outside the Earth’s atmosphere. Jennewein and team therefore developed a system suitable for a satellite. Restricted to testing the system on Earth, the researchers set up a transmitter on the ground and used a Twin Otter aircraft to fly the receiver over it at angular rates similar to those of low-orbit satellites. They successfully achieved a quantum link for seven of their 14 passes and were able to extract the secret key for six of them. “This is an extremely important step, which took almost eight years of preparation,” explains Jennewein. “We have proved the concept, and our results provide a blueprint for future satellite missions to build upon.” The study can be found in Quantum Science and Technology.

Artificial intelligence boosts X-ray probe

Machine learning has been used to improve how X-ray pulses are used to study molecular dynamics. The new technique was developed by an international team of researchers and tested using data from the Linac Coherent Light Source (LCLS-1) free electron laser (FEL) at SLAC in the US. Trains of X-ray pulses lasting just 10–15 fs are produced at LCLS-1 and can be used to study chemical reactions and changes in molecular structure on very short timescales. However, the processes involved in producing the pulses are inherently unstable, and the intensity and timing of the pulses can vary by as much as 100%. This means that large amounts of measurement data from molecular studies are difficult to interpret and have to be discarded. One way around this problem is to determine the properties of the pulses as they are produced. But this can interfere with the experiment and will become increasingly difficult to do with the shorter pulses that will be produced by next-generation X-ray sources. Now, Alvaro Sanchez-Gonzalez and Jon Marangos of Imperial College London and colleagues have developed a new artificial intelligence-based technique that can accurately predict the properties of the X-ray pulses based on real-time measurements of certain properties of the FEL. Crucially, these measurements can be made fast enough to match the rate at which the X-ray pulses are delivered. “For current instruments, which generate about a hundred pulses per second, sometimes up to a half of the data is unusable,” explains Sanchez-Gonzalez. “This problem will only be compounded in next-generation instruments, such as the European XFEL or LCLS-II, designed to generate hundreds of thousands of pulses per second.” He adds, “Our method effectively resolves the problem, and should work on the new instruments as well as the older ones we tested it on. This will allow useful data to be gathered up to a thousand times faster.” The technique is described in Nature Communications.

Coldest object in the universe born in stellar collision

Image of the Boomerang Nebula — Cold return: composite image of the Boomerang Nebula taken by ALMA and the Hubble Space Telescope (Courtesy: ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble; NRAO/AUI/NSF)

Astronomers working on the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile have come up with an explanation of how the Boomerang Nebula – described as the coldest object in the universe – formed. Recent observations with ALMA allowed the team to make precise calculations of the nebula’s extent, age, mass, and kinetic energy. The results suggest that the spectacular outflow of gas and dust was created when a small companion star plunged into the heart of a red giant, ejecting most the matter of the larger star. “These new data show us that most of the stellar envelope from the massive red giant star has been blasted out into space at speeds far beyond the capabilities of a single, red giant star,” said Raghvendra Sahai of NASA’s Jet Propulsion Laboratory. “The only way to eject so much mass and at such extreme speeds is from the gravitational energy of two interacting stars, which would explain the puzzling properties of the ultracold outflow.” Wouter Vlemmings of Chalmers University of Technology in Sweden adds “The extreme properties of the Boomerang challenge the conventional ideas about such interactions and provide us with one of the best opportunities to test the physics of binary systems that contain a giant star.” Discovered in 1995, the nebula is an outflowing of gas and dust that is about 10 times faster than could be produced by a single star. The temperature of the outflow is less than half a degree kelvin. This is much colder than deep space, which is about 2.7 K. The study is reported in the Astrophysical Journal.

Flash Physics: CERN’s high-school interns, more female engineers manage, exoplanet twins are nearly identical

CERN launches high-school internship programme

CERN in Switzerland has hosted 22 high school students from Hungary in a pilot programme designed to show teenagers how science, technology, engineering and mathematics is used at the particle physics lab. The new High-School Students Internship Programme (HSSIP) is being developed by CERN’s Education, Communications & Outreach group and is aimed at students age 16–19. The first group of students was selected by a national committee in Hungary, who chose 22 participants from more than 50 applicants. The students were accompanied by Hungarian mentors and worked on their own projects in particle physics – as well as touring the CERN facilities. “It is wonderful to get out of the classroom where everything is in theory and to see how things are happening in the real world,” says student Balazs Mehes. Another participant, Daniel Nagy, says “I definitely want to come back here one day as an engineer.” Bulgaria and France will be the next countries to participate in HSSIP and will be sending students to CERN in September. France and Norway will also take part in 2017 and the programme will be rolled out to all 22 CERN member states over the next few years.

Is having more female engineers in management always a good thing?

Photograph of Teresa Cardador — Research by Teresa Cardador suggests that female engineers are stereotyped into management roles (Courtesy: L Brian Stauffer)

While only about 15% of engineers working in the US are women, the number of female engineers in managerial roles is disproportionally larger than their overall representation in the workforce. This might seem like a victory for gender equality, but Teresa Cardador of the University of Illinois at Urbana-Champaign says that this overrepresentation could be creating a segregated workplace in which women tend to perform managerial roles and men technical roles. “There are typically two career paths in engineering organizations – technical or managerial,” explains Cardador. “So you can look at it in two ways: either women are more likely to move into managerial roles in engineering firms, or they’re less likely to stay in technical roles.” Cardador interviewed more than 60 engineers and the results suggest that gender segregation could be caused by engineering firms valuing technical prowess over management skills. “In engineering, technical ability is revered while management is what you do if you have good organizational and communication skills,” she explains. “Women are stereotyped as having less technical competence in engineering, which perhaps explains why men are much more likely to remain on the technical side and women are tracked into the management side,” she said. As well as losing touch with the highly valued technical aspects of their profession, Cardador found that female engineers in management roles also find it more difficult than technical staff to balance work with family responsibilities. “All of these things combined have the potential to increase a woman’s chances of leaving the profession, which may ultimately make the goal of retaining female engineers in engineering firms more tenuous.” The research is described in Organization Science.

Exoplanet “twins” are nearly identical

Schematic demonstrating that WASP-67 b has a cloudier atmosphere than HAT-P-38 b — Prince and pauper: almost identical exoplanets could have different pasts. Gas giant exoplanet WASP-67 b is nearly identical to HAT-P-38 b but has a cloudier atmosphere. (Courtesy: NASA, ESA, Z Levy)

Two almost identical exoplanets have surprised astronomers by having one unexpected difference – one is cloudier than the other. The gas giants – WASP-67 b and HAT-P-38 b – are nearly the same in size and temperature. They are also both in tight orbits (roughly 4.5 Earth days) around very similar yellow dwarf stars and are both tidally locked – the same side always faces the parent star. Therefore, when studying the two “hot Jupiter” exoplanets with the NASA’s Hubble Space Telescope, Giovanni Bruno from the Space Telescope Science Institute in the US and colleagues expected them to have nearly identical atmospheres. Instead, the chemical spectra of the planets indicated that WASP-67 b had more clouds at the altitudes measured by Hubble’s instruments. “We don’t see what we’re expecting,” says Bruno, “and we need to understand why we find this difference.” Hubble’s Wide Field Camera 3 looked at the spectral signature of water as a measure of the amount of clouds in the atmosphere – as WASP-67 b has more clouds, it had a lower water signal. “This tells us that there had to be something in their past that is changing the way these planets look,” Bruno explains. The team suggests that the planets formed differently and under different circumstances, and future observations with Hubble and the soon-to-be-launched James Webb Space Telescope will help astronomers understand what makes a planet cloudy or clear. The findings were presented at the 230th meeting of the American Astronomical Society in Austin, Texas.

Robust marbles are made of air

“Gas marbles” have been created by encapsulating a bubble of gas within a shell of tiny plastic particles. Developed by Yousra Timounay and colleagues at the Université Paris-Est (UPE) in France, the beads of gas could be used for isolating toxic gases or stabilizing foams.

The work by Timounay and team takes inspiration from “liquid marbles”, which were developed in 2001 by Pascale Aussillous and Davide Quéré from the Collège de France. Aussillous and Quéré had added hydrophobic powder to water droplets, thereby spontaneously creating balls of liquid securely held within water-repellent shells. The surface tension and incompressibility of the liquid allows the marbles to maintain their shape, and they can bounce and roll across surfaces without leaking.

Like soap bubbles

Now, the UPE researchers have created the gas version with a method similar to making bubbles with a soap solution and wire hoop. They carefully spread polystyrene microspheres over the surface of an organic compound solution (sodium dodecyl sulphate), where the spheres then floated in a closely packed formation. The team then submerged a rectangular wire frame (with sides roughly 1 cm long) in the solution.

Gently lifting the frame out creates a film of microspheres, just like on a wand for blowing soap bubbles. When the lift-out reaches a certain point, the film folds in on itself and detaches to form a gas marble that drops back into the liquid, automatically moving to the edge of the liquid’s surface. The marble – typically 5 mm in diameter – can then simply be scooped out. The researchers found that using larger microspheres (diameter 560 µm) and larger wire frames made it easier to create the marbles. “The full mechanism of gas-marble creation is not fully understood for the moment, but their creation is reproducible,” says team member Florence Rouyer.

Robust rollers

The resulting marble, presented in Physical Review Letters, consists of atmospheric gas constrained within a shell of closely packed wet microspheres. The spheres are stuck to their neighbours by the surface tension of a liquid meniscus. This microsphere-liquid “skin” is particularly strong – so much so that the team was able to alter the internal pressure using a syringe that could puncture the shell but not rupture it. The marble could then withstand a 10-fold pressure increase or decrease while maintaining a spherical shape with no volume change, before bursting or collapsing. “The structures are robust enough to hold and roll in your hand,” Rouyer says, “as long as your hands are clean, and you don’t press too hard.” Upon breaking up, the microspheres can be reused to make more marbles.

Timounay, who is now at Syracuse University in the US, and colleagues envisage that the gas marbles could have applications in stabilizing foams and emulsions. While they could also be used to store gases, their usefulness will depend on how easily said gas diffuses through the skin and whether the shells fall apart when the liquid evaporates.

Flash Physics: Supernova kicks black-hole spin, neutron-star probe launches, award-winning planetary scientists

Did supernova kick cause LIGO black-hole spin misalignment?

A huge kick from a supernova could have knocked the spin of one of the black holes that created GW151226 out of alignment – according to calculations done by Richard O’Shaughnessy, Daniel Wysocki of the Rochester Institute of Technology and Davide Gerosa of Caltech. GW151226 is a gravitational wave signal from two merging black holes that was detected in December 2015 by the LIGO observatory. Astronomers believe that two black holes weighing in at 14 and 8 solar masses merged to form a single, spinning 21-solar-mass black hole, some 1.4 billion light-years away from Earth. Careful analysis of the signal from the merger suggest that the spin of the larger black hole may not have been aligned with the orbital angular momentum of the binary – which could provide important information about how the system formed.

One possibility is that the two black holes formed independently and then joined together with their spins misaligned with respect to orbital angular momentum. The other possibility is that the pair started out as a binary star with aligned spins, but then one of the spins became misaligned by “natal kicks” delivered when the stars exploded as supernovae. O’Shaughnessy, Wysocki and Gerosa looked at the second possibility and conclude that misalignment could have occurred when the larger of the two stars in the binary exploded. Writing in a preprint on arXiv (which will be published in Physical Review Letters), the team cautions that the misalignment would require a “natal kick” that is much larger than predicted by current supernova theory. O’Shaughnessy adds: “That’s an exciting challenge for models of how massive stars explode and collapse”. Gerosa says: “Our study corroborates years of tentative but suggestive evidence that black holes might have received these kicks.

NASA launches neutron-star probe

Photograph of the NICER probe — The NICER probe has launched to the International Space Station. (Courtesy: Keith Gendreau/NASA)

NASA has launched the first-ever mission devoted to studying neutron stars. Launched on a SpaceX Falcon 9 rocket on 3 June from the Kennedy Space Center, the Neutron star Interior Composition Explorer (NICER) will use 56 telescopes to observe X-rays in the range of 0.2–12 keV that have been generated by the stars’ strong magnetic fields.

The probe will be installed on the International Space Station where it will operate for 18 months. NICER will also demonstrate – for the first time – the possibility of using pulsars as a “celestial clock” to test the viability of autonomous X-ray navigation. The launch of the craft comes 50 years after the British astrophysicist Jocelyn Bell Burnell discovered rapidly spinning neutron stars, known as pulsars.

Award-winning planetary scientists announced

Portrait of Margaret Kivelson painted by Pamela Davis Kivelson — Margaret Kivelson wins the Gerard P Kuiper Prize for outstanding contributions. (Courtesy: Pamela Davis Kivelson)

Six scientists have been honoured for their contributions to planetary research and communication by the Division for Planetary Sciences (DPS) of the American Astronomical Society (AAS). The awards will be presented at the 49th Annual Meeting of the DPS in October. “Announcing these prizes is the highlight of the spring planetary sciences calendar,” says DPS Chair Lucy McFadden. Margaret Kivelson of the University of California, Los Angeles will be given the Gerard P Kuiper Prize for outstanding contributions to planetary science. Her work on Jupiter and its moons has led scientists to recognize that ocean worlds in the outer solar system may represent our best chances for discovering life beyond Earth.

The Harold C Urey Prize for an early-career scientist will go to Bethany Ehlmann from the California Institute of Technology, for her work studying the mineralogy of Mars. Louise Prockter from the Lunar and Planetary Institute (LPI) in Houston, Texas will receive the Harold Masursky Award, which recognizes outstanding service. Prockter is the first female director of the LPI and has served on National Research Council boards and NASA committees. Megan Schwamb of the Gemini Observatory and Henry Throop from the Planetary Science Institute will each be awarded the Carl Sagan Medal for their public communication efforts. Among their contributions, Schwamb created the Astrotweeps project, whereby different astronomers take control of a Twitter account each week, while Throop presents to students and teachers all over the world. The Jonathan Eberhart Planetary Sciences Journalism Award, which recognizes distinguished popular writing, will go to Joshua Sokol from Boston for his August 2016 article in New Scientist entitled “Hidden depths”.

Monuments to peer review and Canada, Marie Curie as superhero, a 3D book about Einstein

By Michael Banks and Hamish Johnston

You may remember a campaign to create a monument dedicated to those hard-working people who peer-review research papers. Last year, sociologist Igor Chirikov, from the National Research University Higher School of Economics in Moscow, raised $2521 on Kickstarter to turn an “ugly” block of concrete outside the university’s Institute of Education into a monument that reads “accept”, “minor changes”, “major changes”, “revise and resubmit” and “reject” on its five visible sides. Well, after months of toil that monument has now been unveiled by Chirikov in a ceremony at the institution that was attended by over 100 supporters. “Most understand the sarcastic nature of the monument and love it,” says Chirikov. “Many also wonder what’s on the bottom side of the monument.” Chirikov is thinking of hanging a small mirror on a nearby tree so that everyone can see “Accept” on the top of the cube.

Still on fundraising, the Marie Curie Alumni Association is launching an illustrated book series for young children called My Super Science Heroes. The first one – Marie Curie and the Power of Persistence – aims to introduce children to Curie and her key accomplishments in a “fun and engaging way”. To get the project off the ground, the association has taken to Indiegogo to raise €15,000. Each scientist in the series will have a certain “superpower”, which in the case of Curie is her persistence. “Unlike being bitten by a radioactive spider, scientific achievement is a realistic goal, and celebrating these real-life heroes will encourage kids to explore the many possibilities a [science, technology, engineering and mathematics] programme offers,” the association writes. There is a month still to go if you want to donate. If the project raises the cash then the book is expected to be released by mid-October.

While that book will most likely be printed in the usual way, how about getting your hands on the world’s first 3D-printed book? Well, soon you can thanks to a project kickstarted last year by the Israeli-born designer Ron Arad. The book – Genius: 100 Visions of the Future – will contain articles by 100 leading lights including Microsoft co-founder Paul Allen and the Nobel laureates Steven Chu and the late Harry Kroto. It is part of the Einstein Legacy project that celebrates 100 years since the publication of Albert Einstein’s theory of general relativity. The book is set to be unveiled at an event in Montreal, Canada on 9 September.

Tiny Canadian flag — Big country: is this the smallest Canadian flag ever? (Courtesy: McMaster University)

Speaking of Canada, the country is celebrating its 150th anniversary this year. In honour of the sesquicentennial, Travis Casagrande at McMaster University in Hamilton, Ontario has made what just might be the smallest Canadian flag ever – measuring just one-hundredth the width of a human hair. He used a focused ion beam microscope to etch the 3D flag – complete with a flagpole – into a penny. You can read more about the tiny sculpture on the CBC website.

Flash Physics: Exoplanet has huge rings, International Day of Light for 2018, LIGO pioneer bags €750,000 prize

Exoplanet with huge rings could be detected by amateur astronomers

An exoplanet 50 times the mass of Jupiter and encircled by a huge system of dust rings may be orbiting a star 1000 light-years from Earth. That is the claim of Hugh Osborn of the University of Warwick in the UK and an international team of astronomers who have seen evidence for the ringed exoplanet in two telescope surveys. The gas-giant exoplanet appears to be orbiting a young star called PDS 110 with a period of about 2.5 years. As the planet crosses in front of the star it blocks some of the starlight from reaching Earth. By a careful analysis of crossings recorded over 15 years by the Wide Angle Search for Planets and the Kilodegree Extremely Little Telescope, Osborn and colleagues have concluded that the exoplanet is surrounded by a ring system that is many times larger than the rings of Saturn. The team is now looking forward to making more detailed observations in September 2017, when the next crossing is expected to occur. Indeed, the dimming effect is so large that it should be measureable by amateur astronomers. “September’s eclipse will let us study the intricate structure around PDS 110 in detail for the first time, and hopefully prove that what we are seeing is a giant exoplanet and its moons in the process of formation,” says Osborn. While this is not the first exoplanet with rings, if its existence is confirmed in September it will be the first ringed exoplanet with a known orbital period. The exoplanet appears to lie within the habitable zone of PDS 110, which means that if moons form from the rings, they could support life. The latest analysis of the exoplanet is described in a preprint on arXiv.

International Day of Light will debut in 2018

Following the success of the International Year of Light (IYL) in 2015, the United Nations Educational, Scientific and Cultural Organization (UNESCO) has given its support to an annual International Day of Light. Beginning next year on 16 May, the day aims to provide “an annual focal point for the appreciation of the role that light plays in the lives of the citizens of the world”. An official inauguration ceremony will take place at UNESCO’s headquarters in Paris on 16 May 2018 involving presentations from Nobel laureates, business leaders and those representing other organisations in the arts, architecture, lighting and design. During IYL 2015, thousands of events were held in over 100 countries celebrating the science and applications of light. The year involved more than 100 partners from 85 countries – including the Institute of Physics, which publishes Physics World.

LIGO pioneer bags €750,000 Körber prize

Photograph of Karsten Danzmann — Prize winner: Karsten Danzmann has won the Körber European Science Prize 2017. (Courtesy: Körber Foundation)

Karsten Danzmann, who led the development of key laser technologies used in the LIGO gravitational wave detectors, has won the Körber European Science Prize 2017. Worth €750,000, the prize will be presented to Danzmann on 7 September in Hamburg, Germany. The German physicist is 62 and is based at the University of Hannover. He is also director of the Max Planck Institute for Quantum Optics in Hannover. Danzmann pioneered the use of “squeezed light” to achieve significant noise reduction in the LIGO interferometers. The LIGO team – which includes Danzmann’s research group – has detected three gravitational-wave signals from coalescing binary black holes since September 2015. The most recent discovery was announced just yesterday. The prize is given by the Körber Foundation, which was founded in 1981 for the advancement of culture and science by the German entrepreneur Kurt Körber.

The need for speed: how Lorraine Bobb’s summer placement at Diamond Light Source influenced her career path

As I look back on the choices I have made in my career, I’m coming to the conclusion that I have always been fascinated by speed. When my friends and I discussed career ideas as early as secondary school, my preferences went along the lines of: astronaut, RAF pilot or Formula 1 engineer. All of these jobs sounded exciting, hands-on and challenging. I quickly decided that studying physics would be beneficial, regardless of which career option I chose to pursue.

After completing my A-levels, I went on to do an MSci physics degree at Royal Holloway, University of London (RHUL). At this time I was a keen sportswoman, and had secured a place on the Student Talented Athlete Recognition Scheme (STARS) at RHUL for athletics and skeleton – a sport where a person slides head-first down an ice track, while lying face-down on a small bobsled. I learned the importance of good time management and self-motivation while balancing both my academic and sporting commitments. From skeleton-sliding in particular, I learned how to channel any stress I felt as I stood at the top of the track into focus, and being able to give my best performance, even under pressure.

Particle fascination

Academically, I found myself drawn towards the field of particle physics. I was intrigued by the Standard Model of particle physics, especially the then-ongoing search for the Higgs boson at the Large Hadron Collider at CERN. I was also captivated by the observation of neutrino interactions by the IceCube experiment. However, particle physics didn’t seem to offer the hands-on lab work I enjoyed to break up the humdrum of sitting at a desk all day, studying theory and analysing data. As I mulled over this problem, I realized that behind each great experimental discovery, there must be a lab or facility where the experiment itself was conducted. It was at this point that I entered the realm of accelerator physics and beam diagnostics – the marriage between particle physics and engineering where particles travel at nearly the speed of light.

I wanted to make an evidence-based decision before choosing accelerator physics as a full-time career. With this goal in mind, I chose undergraduate courses relating to particle accelerators and detectors. At RHUL, I did a summer placement on acoustic imaging of electron beams to further my laboratory skills and to network with other lecturers and students in similar research areas. I completed my Master’s thesis on accelerator optimization at the Compact Linear Collider using different beam-steering techniques. Although I had visited CERN, I still wasn’t sure what it would be like to work at a particle accelerator full time.

Diamond ring

Growing up in the area, I was aware of the “silver doughnut” on the rolling hills of Oxfordshire. It was much later that I learned this building housed Diamond Light Source – a third-generation synchrotron light source, with a series of X-ray beamlines that study atoms and molecules. In the summer of my third year, I sent my application to Diamond, with my fingers crossed that I would get a response. Unfortunately, it was not the response I was hoping for – I was told that Diamond was not taking on any summer students that year. However, knowing how crucial it was for my future plans, I persisted.

That summer I gained first-hand experience of everyday life at a particle accelerator

Via contacts at RHUL, I got in touch with the physicists at Diamond and let them know that I was prepared to work for no pay on more or less anything relating to the accelerator. Very soon after, the Diagnostics group at Diamond contacted me directly with an invitation for a paid internship working with them – and this was ultimately my big break. That summer, I developed a portable scanning knife-edge system for stability measurements on beamlines and I gained first-hand experience of everyday life at a particle accelerator. Most importantly though, I thoroughly enjoyed my entire experience. I had finally proven to myself that this was the career I wanted.

The next step was to further my knowledge and expertise. I did a PhD that involved designing, building and testing a transverse beam size monitor using diffraction radiation on circular machines. Although it was a collaborative project between RHUL and CERN, I was based at CERN in Switzerland full-time. Initially, living abroad was very daunting (especially as I didn’t speak French), but in time I became much more independent. By the end of my PhD, I was very proud of the life I had established over the three years.

Lessons learned

In this time, I was lucky enough to travel to many countries around the world. All of the experimental tests for my PhD were done at the Cornell Electron Storage Ring (CESR) in the US. Often, I would be sent to Cornell University weeks ahead of the rest of the team to prepare for our shifts on the accelerator. Along with my technical knowledge, I learned how to manage a project that involved a lot of people and resources. I found that no-one can be expected to know everything, which is why teamwork is so important. Each person has their own area of expertise, and through a collective effort, we get to the finish line. During my time at CERN, I also had the opportunity to present my work at international conferences and to attend the annual CERN Accelerator School, which is hosted in a different member state each year. In this way, I was able to improve my presentation skills and to network face-to-face with many people at various stages of their careers.

Each day, I look for ways to improve the measurements I provide by doing my own research in the lab, on the accelerator, and with external collaborators

After my PhD, I returned to Diamond, where I now work as part of the Diagnostics group. I design and operate instruments that are effectively the eyes and ears of the accelerator and make sure that all 28 operational beamlines have access to high-quality X-rays for their non-stop, 24/7 experiments. Each day, I look for ways to improve the measurements I provide by doing my own research in the lab, on the accelerator, and with external collaborators. The best part of my job is the variety of issues that need to be solved and the opportunities to share my work, and that of Diamond, with the public through outreach events.

Diamond now has a well-established Student Summer Placement programme, which allows undergraduate students in science and engineering to gain first-hand experience of working at a leading scientific facility. I’d encourage anyone starting out in physics to do a summer internship at a working facility in the branch of physics they’re interested in. You may end up returning to that same place of work as a member of staff as I have done, or to continue your studies. Or you may learn that actually, the career path you were following isn’t the right one for you. This is still a positive outcome. You’ve been able to direct your career based on evidence, and as a physicist, having data to support a theory is key.

LIGO bags its third black-hole merger

A third gravitational wave has been detected by physicists working on the LIGO gravitational-wave detectors in the US. The wave was produced by two black holes that merged about 3 billion light-years from Earth. One black hole was 31 times more massive than the Sun and the other weighed in at 19 solar masses. The previous two sightings of gravitational waves were also produced by black-hole mergers, but LIGO researchers think this is the first event in which the spin of one of the merging black holes could have been pointing in the opposite direction to the orbital rotation of the black holes.

The latest gravitational-wave observation is also the furthest of the three black-hole mergers seen so far, with the first and second detections being 1.3 and 1.4 billion light-years away, respectively. The newly observed merger created a black hole of 49 solar masses, which sits nicely between the first detection (62 solar masses) and the second (21 solar masses). Before LIGO saw its first gravitational waves in 2015, astronomers had no idea that such solar-mass black holes existed in the universe.

The new event, dubbed GW170104, was observed on 4 January 2017 when signals lasting about one tenth of a second were recorded in LIGO’s two detectors in Washington and Louisiana, which are giant interferometers, each consisting of two perpendicular arms 4 km long. Laser light travels back and forth between mirrors at either ends of the arms and some of this light is sent to a detector, where interference occurs. When a gravitational wave passes through a LIGO detector, it can slightly stretch one arm and compress the other, thereby altering the measured interference and letting the gravitational wave be measured in real time.

Death spiral

The newly observed event began as two black holes neared each other in a death spiral. As the system rotates, it broadcasts gravitational waves that spread out across the cosmos – some reaching Earth. The signals at both Livingston and Hanford had the characteristic “chirp” and “ringdown” seen in the previous two detections. Chirp describes the rapid increase in the frequency and amplitude of the gravitational wave that occurs just before the black holes merge. Ringdown is the gravitational wave that is emitted by the non-spherical merged black hole as it relaxes to become a sphere.

By studying both the chirp and the ringdown, LIGO physicists worked out the masses of the two initial black holes as well as the mass of the merged object. The merged black hole weighed 49 solar masses – the difference being radiated away in the form of gravitational waves.

Spinning around

Another key piece of information that can be gleaned from the gravitational wave is the alignment of the intrinsic angular momenta (or spins) of the black holes. As well as orbiting each other, each black hole can be spinning on its own axis – much like the Earth does. When the black holes coalesce, the total rotational velocity of the merged black hole cannot exceed a certain upper limit. So if the spins of the two merging black holes point in the same direction as the orbital spin, some of the orbital angular momentum must be discarded to meet this criterion before the merger can occur. This is done by emitting additional gravitational waves before the merger.

Data from the first detected black-hole merger (GW150914), recorded in 2015, suggested that the spins of both black holes were aligned with the orbital angular momentum. In the second detection (GW151226), recorded last year, there is some evidence that the spin of one of the black holes could be at an angle to the orbital angular momentum – but still have a component in the direction of the orbital angular momentum. In GW170104, however, it is possible that the spin of at least one of the black holes is at an angle and has a component in the opposite direction to the orbital angular momentum.

According to Bangalore Sathyaprakash of the University of Cardiff in the UK, the relative orientations of the spin and orbital angular momenta of a binary black hole provide important information about how the system formed. If they are aligned, it is likely that the system developed in isolation as two large stars that then collapse to create a binary black hole. Misalignment suggests that the black holes formed separately and then came together to create a binary system.

Real statistics

“We’re starting to gather real statistics on binary black-hole systems,” says Keita Kawabe of Caltech, who is based at the LIGO Hanford Observatory. “That’s interesting because some models of black-hole binary formation are somewhat favoured over the others even now and, in the future, we can further narrow this down.”

This third observation has also allowed LIGO scientists to put further limits on models that modify Albert Einstein’s general theory of relativity. Einstein predicts that the speed of a gravitational wave through empty space is independent of the frequency of the wave. So any deviation from this constancy would therefore show up as a frequency-dependent distortion of gravitational-wave signals seen by LIGO. Given that this was not seen, despite the waves travelling such long distances through the cosmos, general relativity appears to be holding firm.

“It looks like Einstein was right – even for this new event, which is about two times farther away than our first detection,” says LIGO physicist Laura Cadonati of Georgia Tech. “We can see no deviation from the predictions of general relativity, and this greater distance helps us to make that statement with more confidence.”

GW170104 is the first gravitational-wave detection to be announced since LIGO began its current observational run in November 2016. The LIGO team has also identified six other candidate events during this run, which they are now analysing. The observation is reported in Physical Review Letters.

The ability to observe gravitational waves heralds a new era of astronomy in which scientists will combine observations from a number of different instruments. You can read more in Multimessenger Astronomy by Imre Bartos and Marek Kowalski

3D printing goes micro

Over the past few years 3D printing has become one of the most-hyped topics in 21st century technology. Research into the techniques used in 3D printing has already given scientists new freedom in the design of components and devices, while the ability to manufacture highly individualized parts in a cost-effective way is finding new applications all the time.

So far, much of the hype has centred on macroscopic objects such as 3D printed implants or prototype parts for the automotive industry. However, a logical extension of the technology would be to exploit the unique potential of 3D printing in the domain of microstructures. This is of particular interest for optical scientists who wish to enhance the functionality of micro-optical devices such as highly integrated cameras, or even make it possible to build entirely new categories of devices that cannot be manufactured via a combination of traditional techniques such as UV- or electron-beam lithography.

Macro vs micro

Macro-sized 3D printing relies on several well-established techniques, including the selective melting of metal powders; inkjet printing; stereolithography; and fused deposition modelling. In contrast, the realm of 3D microprinting is dominated by a single method: two-photon polymerization (2PP). In some ways this method is similar to conventional UV lithography, where a (usually) liquid photopolymer is illuminated with light at an appropriate wavelength; the polymer solidifies where the light is absorbed; and a combination of masks and subsequent removal of unexposed polymer are used to create highly sophisticated structures. The main difference is that in 2PP the trigger for solidification to take place inside the focal volume is a femtosecond laser pulse. The physical phenomenon that drives this process is known as two-photon absorption (TPA), and it can only occur if the laser light is very intense: if you focused all of the sunlight falling on the city of Würzburg, Germany, onto a single grain of sand, you would get an intensity equivalent to that used for 2PP. Under these extreme conditions, two simultaneously absorbed photons with wavelengths in the visible part of the spectrum (such as 515 nm) can trigger the same chemical reaction as a single UV photon. Because this reaction does not occur at lower light intensities, solidification is strongly confined to the focal volume, and the polymer does not interact with out-of-focus light at all. The site of solidification can then be scanned in three dimensions to generate a 3D microstructure, as with normal 3D printing.

The concept of 2PP has been well known for at least 20 years, and several research groups have used it to generate objects such as photonic crystals (which are essentially semiconductors for light), 3D structures for life-science applications and micro-optical devices. However, before the 2PP process can be exploited in commercial applications, some technological challenges need to be resolved. One constraint is that, as with many additive manufacturing processes, 2PP is limited to using a single focal volume to process the material. This “serial” process is inherently slow, comparable to painting an entire wall with a small brush instead of a roller. The second disadvantage is the limited availability of photopolymers that can be processed using 2PP while also providing superior functionality for 3D micro-optical devices. For example, some photopolymers have been optimized for the 2PP processing itself, but their chemical and physical properties leave something to be desired in terms of the performance of the completed device.

Industrial optimization

Within the optics and electronics department at the Fraunhofer Institute for Silicate Research (Fraunhofer ISC) in Würzburg, scientists are working to optimize 2PP processing with respect to industrial applications. A key aspect of this research is to develop hybrid polymers that combine inorganic or glass-like materials with substances that exhibit organic photochemistry (as in the reaction described above), and thereby unite the favourable mechanical properties of glass with the processability of purely organic polymers. These hybrid polymers, known commercially as Ormocers®, are liquid resins consisting of a [Si-O]n backbone with different organic side groups. The most important side groups are polymerizable components such as acrylate or epoxies, as they can be used to solidify the resin via photochemical processes. The choice of precursors and the processing conditions determine the conformation of the interlinked organic and inorganic networks, and thus the chemical and physical properties of the final substance. The main benefits of Ormocer chemistry are an excellent stability against temperature, resistance against chemical attack and superior mechanical properties (such as stiffness). Additionally, many properties can be tailored to meet the requirements of different applications.

Tight control: (a) In two-photon absorption, a pair of photons in the visible part of the spectrum (green lines) is absorbed simultaneously in place of a single UV photon (pink lines). This process requires high light intensities, so it can only occur inside the focal volume. (b) The two-photon polymerization (2PP) technique uses this to restrict polymer solidification reactions to the focal volume of the laser, making it possible to print features as small as 100 nm.

Recently, researchers at Fraunhofer ISC have worked to improve the optical properties and stability of parts that have been 3D microprinted using Ormocers. For example, we have demonstrated that newly synthesized high-refractive-index hybrid polymers do not turn yellow even after being exposed to high-intensity UV LED light and temperatures of 150 °C for 72 hours. Temperature stability has also been proven by creating 2PP-printed microlenses that did not change their shape after being exposed to 200 °C for more than 1.5 hours. Such robustness is important because it means that microstructures fabricated via 2PP from Ormocer material can withstand the autoclaving procedures used to sterilize medical equipment, such as an endoscope equipped with sophisticated micro-optical lenses at the end of an optical fibre.

Another key benefit of these materials is their compatibility with biological matter. Ormocer composites are used as filling materials in dentistry, and many other material modifications are biocompatible with several human cell types. Some of these materials are even biodegradable, which is important when selecting appropriate materials for 3D-printed medical implants or scaffolds for tissue engineering. The micro-patterned hybrid polymer mimics the extracellular matrix, making it possible for human cells to be grown on it either in vitro or in vivo. Once this new tissue is formed, the scaffold material can then be reabsorbed by the human body.

Active interest

Despite their advantages over conventional polymers, hybrid polymers are still “passive” materials – meaning that their properties, defined by their chemical composition and processing, remain unchanged in response to external stimuli. To truly fulfil the potential of 2PP-written microstructures, scientists are also working to develop “active” materials. Such materials might, for example, act as optical gain media, convert one wavelength of light into another, or exhibit mechanical responses to external electrical or magnetic fields. Gain media have a number of applications, including the amplification of signals in optical data communication. Mechanical responses are important for actuators, for example in human–machine interfaces or miniaturized energy harvesters.

There are two main routes for achieving these properties. One is to incorporate active components during the chemical synthesis process itself, for example by linking optically active ions directly to the polymeric network. The other route is based on a “guest–host” approach, in which active nanoparticles are introduced into a (hybrid) polymer matrix. This route can be very straightforward as long as the guest nanoparticles “match” the host system; in other words, as long as they can be dispersed homogeneously and they maintain their active properties inside the matrix.

Foundations

Researchers at Fraunhofer ISC demonstrated recently that material systems of the latter type – so-called “nanocomposites” – can be 3D microprinted using 2PP. In a proof-of-principle experiment, they introduced silica nanoparticles 48 nm and 380 nm in diameter into an Ormocer matrix and studied the material’s behaviour when it was illuminated with femtosecond laser pulses. An example of the results is shown in the “Fine structure” figure, which reveals a complex 3D pattern created in the 48 nm nanocomposite (left image pair) and the institute’s initials in the system containing 380 nm particles (right image pair). The hope is that such experiments will be the foundation for creating structures with more sophisticated particles.

Tiny prisms: The Fraunhofer emblem shown at top is made up of 10 000 tiny prisms. Bottom left: part of the symbol on the left side of the emblem, magnified 10×. Bottom middle: The same area at 50× magnification, with individual prisms visible. Bottom right: a false-colour image (redder colours indicate increased height) of a single prism at 150× magnification. (Courtesy: Fraunhofer ISC)

In addition to new materials, another key area of development for 3D microprinting relates to the optics used to control the position of the laser focus during the printing process. The goal here is to set the position of the focus quickly as well as accurately. For this reason, “galvoscanner” mirrors have become increasingly popular, since they have significantly lower moving masses than high-accuracy linear stages, and thus make it possible to rapidly accelerate and position the focal spot in the focal plane.

The huge capability for rapid 3D micropatterning using galvoscanner technology is shown in the “Tiny prisms” image on p32. Here, the Fraunhofer ISC emblem is composed of 10 000 individual microprisms, with a base area of 50 × 60 µm^² and a height of 25 µm. Printing a single microprism only takes a few seconds, even without thoroughly optimizing the process in terms of applied photon doses and writing velocity. This result clearly indicates that areas of several square centimetres can easily be filled with micron-sized elements – meaning that we could, in principle, use these 3D-printed microprism arrays in displays and other commercial technologies that rely on redirecting light with low optical losses. Furthermore, the depicted arrangement can be replicated easily, as it is only a so-called “2.5 dimensional” pattern with no undercuts.

Forging ahead

The tremendous potential of 3D microprinting using two-photon polymerization will be achieved when it is possible to employ materials that are not only compatible with the printing process, but that also exhibit new functional properties (either active or passive). Strategies for accelerating the printing process are also highly desirable, and galvoscanner mirror technology is already being implemented today. Both approaches – new materials and faster fabrication – will help ensure that 2PP is adopted on a larger scale in the future.

Succeeding as a community

What led you to start Optimax?

Mike Mandina, Optimax president I lost my job so I had a choice: I could either go work for someone else or create something new. By chance, I met a couple of entrepreneurs who had partnered with some people who were moonlighting from day jobs at Kodak. They had set up the beginnings of an optics shop in the basement of a barn. It had a concrete floor, sawdust and dirt would fall down from the ceiling if it was windy outside, and the low ceilings limited what kind of machinery could go in there. But it had a lot of power, and they had found and refurbished a number of pieces of equipment, so it was enough to get started making rudimentary optics – the basic elements of traditional lens manufacturing. That’s what became Optimax.

What had your career been like before that?

MM I went to university to study sociology and psychology, but after one semester I transferred over to the optics programme at Monroe Community College, working on an associate’s degree in optics technology. I did just over a year of full-time college and then I got a job in the optics industry, grinding lenses on the second shift. Because I was working nights, I was able to continue my education during the day. Eventually, I earned a bachelor’s degree in applied physics from Empire State College and an executive MBA from the Rochester Institute of Technology (these are all in New York, by the way). I founded my first optics company with a partner back in 1976 and sold it to Melles Griot around five years later. It became Melles Griot Optical Systems and that was the company that let me go in 1990.

Rick, how did you get involved in Optimax?

Rick Plympton, Optimax CEO I grew up in the Rochester area and my education was similar to Mike’s in that I went to the Florida Institute of Technology for a year, but I spent more time on the beach than I did in classes. So I came back and continued my education at Finger Lakes Community College in New York, US before transferring to the optical engineering programme at the University of Rochester. The first time Mike hired me was in 1984, when he was the production manager for Melles Griot Optical Systems and I was a student. We worked together for three or four years and then I went off and chased my career, working at Melles Griot’s corporate headquarters in southern California, as a field sales engineer in the south-east US and eventually at Melles Griot in Europe. After two years there, though, I came back to Rochester because this is where family is. I’d kept in touch with Mike throughout, and when I came back in 1995 there were 10 guys here struggling to make weekly payroll. Manufacturing was fleeing the Rochester community at the time: Kodak, Bausch and Lomb, Xerox, all the big players were downsizing and sending their manufacturing offshore. But when I looked at what Mike and the guys at Optimax were doing, I saw they were leveraging computer-controlled machining technology to make optical components and that meant they could make prototype lenses 10 times faster than the industry standard. Normally it takes about 10 weeks to make a lens; these guys could do it in a couple of days. So we developed a marketing plan around one-week delivery of prototype optics and started growing the business.

How did you get funding to expand beyond the barn?

MM In the very early days some of the founders put in about $30,000 in cash. The rest was credit cards and leases, and if there wasn’t enough cash coming in, the principals didn’t get paid. Rick was one of several people willing to not exactly get paid a lot of money for believing in the future. A number of those people are still here because they hung on and ultimately we developed great careers for them. They helped build the company.

RP By the time I joined, I knew the optics industry all over the US and Europe, so I went out and bragged about the capability that Optimax had developed using this new machining technology. And we really focused on being the prototype guys. Most factories are set up to do production work, so that niche – high-quality prototype optics, quick delivery if you need it – gave us an advantage in the market. And from 1995 to now, we’ve grown the business by about 25% per year.

Chill out: Optimax employees wearing the company’s tie-dye uniform. (Courtesy: Optimax)

What have been the biggest challenges?

RP Workforce development. We cannot go out on the street and hire people who know how to do what we do – we have to train everybody. The best we can do is find people who have good foundational skills through their hobbies, education or work experience. But aside from that, what’s most important is that they’re the type of people who want to learn and contribute.

What kind of technical background do you look for?

MM As time has gone on, the easy manufacturing has moved to countries with lower costs, so the complexity and difficulty of the optics that are left to be manufactured in the US has grown tremendously. Some optics can cost up to $100 000 and take months to fabricate, and they require sophisticated equipment, instruments and technical skills. We have an interesting cross-section of people at Optimax – anything from PhDs to GEDs, which in the US is the equivalent of a high-school diploma that you earn through night school. Optics manufacturing is still a cross between technology and art, so we look for people who have both a technical and an artisan mindset. They may or may not have terrific academic credentials, but if they can be productive, if they’re good people who like working with others to create value, and if they’re prepared to rely on each other for their family’s future prosperity – then Optimax is a good place for them.

What was your most difficult moment?

MM Back in the early days I had about a dozen people working for six weeks to ship products to a particular customer. Unbeknown to me, this customer was developing their own in-house capability and suddenly they sent everything back, cancelled the order and refused to pay. And that was that! It was not very nice. Most people in the industry don’t behave that way, but the person who was running this firm was a certain type of – well, anyway, that’s how they behaved. It didn’t kill us but it was very stressful trying to keep our people employed and find replacement work. That was around the time that Plympton showed up, so that was good timing; we were able to patch things up and keep going. But that could have been a defining moment for us – it was a defining moment for us. Since that time, by the way, we’ve done other work with that customer. They do pay a premium.

What are your plans for the future?

MM We’ve got big plans. Real big plans. I mean, real big!

RP Okay, enough Trump jokes – let’s see if we can give a better answer. We’re hiring about 50 people a year and our core business of optical components could easily triple in the next five to seven years, but we’re looking at ways to grow beyond that. So Mike and I have been putting together a spin-out programme for employees who are entrepreneurial-minded and want to think about market challenges that are outside our core capabilities. We’ll look at their ideas and we may fund a few new businesses, so 10 or 15 years down the road we might look more like an Optimax family of companies, addressing a multitude of market needs.

What do you know now that you wish you’d known when you started?

MM Some of the stuff you learn in business school is fundamental and will always work. But other things, by the time they do the research and understand how they work, then society, culture, the whole world has changed and those models don’t necessarily hold up anymore. Breaking away from those traditions in a sensible way sometimes pays.

RP I’d say that business schools are maybe not teaching what you need to know to grow a progressive company. Here’s an example: we take 25% of our profit every month and share it with employees. We know if we sold this business to a multinational corporation run by a bunch of MBAs, one of the first things they’d do is throw this bonus plan out the window. But we believe it’s been key to our success through the years. We also do some things to keep communication going and maintain a family sort of environment, such as monthly parties and a fun committee. We run three shifts around the clock five days a week, and building camaraderie among the different shifts is a big challenge that we’ve wrestled with through the years.

MM Another example is that we’re trying to keep our organizational structure flat. We’re at 300 employees now, and at times we’ve got to a place where the market wanted us to grow, but we couldn’t grow profitably because whatever we were doing up to that point didn’t work anymore. Things you do to run a business of 25 people don’t work as well at 50 people, and when you figure out how to run things with 50 people, that doesn’t work as well at 100 people, and so on. You start having more overhead costs; communication suffers; you’re in a bigger space; you have more geographic distances between people; your employees are in departments, so you start generating silos – it’s been quite an education about what not to do.

Any advice for someone thinking of starting a new optics firm?

MM They should come see us. Maybe we’ll partner with them! But seriously, I’d say you have to have passion in what you’re doing because there’s going to be impediments along the way, and you can choose to cave in at any time. We’ve had our trying moments – it’s not all upward rising. Things like the Great Recession happen, or a problem can occur with a technology or a customer. You’ve got to suffer through it. I think most people who’ve run a business have had to do those gut checks along the way.

RP If you’re starting out, you want to make sure you’re developing a capability that will enable others to be successful. The more you can help other people be successful with their programmes, the better shot you have at being successful in the long run.