Impressive work in innovative photonics technologies that will change everyday life, enable new cures, and expand our knowledge of the universe was reported in more than 3300 talks at SPIE Optics + Photonics in San Diego in August.
The continuing celebration of the International Year of Light and Light-based Technologies, an awards banquet, and the Optics Outreach Games were also highlights of the annual green photonics event.
Technical reports covered:
- How scientists engineered the landing of the Rosetta orbiter’s probe Philae on Comet 67P and future plans for the mission
- Laser technology challenges for spaceborne active optical sensing of earth
- Single-atom-thick materials to revolutionize optical computing
- Changes in the optical “toolbox” for designing the next generation of wearable displays
- New technology for the Exo-S mission’s search for exoplanets
- Organic electrodes that improve monitoring and recording of brain function, including during epileptic episodes
- Quality and performance improvements of the hardware, software, and imaging and sensing technologies embedded in mobile phones
- Cadmium telluride and perovskite for solar energy
- Ultrafast and ultraslow imaging techniques, each with transferable potential in medicine, semiconductor R&D, and improving understanding of earthquakes
KUDOS FOR ROSETTA MISSION TEAM
US Rosetta Project Manager Artur Chmielewski’s opening plenary presentation reviewed NASA’s Rosetta Mission, which last year set down the Philae lander on Comet 67P, more than 400 million kilometers from earth.
Chmielewski, of NASA’s Jet Propulsion Lab, also announced the decision to conclude the photonics-heavy mission by landing the Rosetta orbiter itself on the comet next year.
The European and German Space Agencies built the Rosetta spacecraft, which transported Philae to the comet, and the US has donated various pieces of equipment to the project, he explained. The US also provides about 45 scientists who shared the job of navigation to reach the comet.
“It has been a very difficult challenge,” Chmielewski said. “I take my hat off to the navigators who achieved centimeter-precision control of the spacecraft over 400 million kilometers — which to me is mind-boggling.”
Rosetta is about the size of a big SUV, while Philae is a more modest refrigerator-sized probe. The mission launched about 10 years ago.
LASERS A CHALLENGE IN SPACE
Among a series of presentations on other space-related technologies, George Komar, associate director and program manager at NASA’s Earth Science Technology Office (ESTO), said ESTO was seeking to improve its capabilities to conduct active optical remote-sensing measurements of earth-environmental conditions.
“Many of today’s key science measurements made from satellites orbiting the earth rely on laser instruments, and there is a diverse range of applications” for measuring CO2 and tropospheric winds, profiling ozone and water vapor, and analyzing surface topography and vegetation, Komar said.
Only three ESTO projects have lasers on board, however, because of the difficulty of getting lasers to work in space, he said. Laser systems aboard satellites and the International Space Station must be highly efficient and powerful, and he detailed a wish list for new laser capabilities in space.
“The environment is challenging with ever-present factors such as potential for damage, degradation, and contamination,” he said. “So the coatings and materials, pump-diode reliability, and scaled power are all significant issues.”
Nevertheless, Komar said, “Active optical remote sensing remains a key technology for NASA’s Earth Science Programs through surface-, aircraft-, and space-based observations.”
INTENSE FOCUS ON SOLAR ENERGY
Commercial and technical aspects of renewable energy sources were also given a high profile at Optics + Photonics.
Four plenary speakers addressed various aspects of solar power and green photonics, ranging from the use of cadmium telluride as an alternative to silicon as a solar cell medium; converting solar energy to hydrogen; upconversion of low- to high-energy photons; and the US SunShot project’s aim to make subsidy-free solar electricity cost competitive with conventional energy sources by 2020.
Wyatt Metzger, of the US National Renewable Energy Lab, told attendees that the latest research into cadmium telluride solar cells is targeting 24% efficiency. This is “driving the cost down to less than $0.40/W and could displace the dominant silicon market share, and reach grid parity,” Metzger said.
“By maximizing photocurrent, CdTe cell efficiency has recently reached 21.5% and surpassed the performance of multicrystalline silicon. We have made cadmium telluride competitive with GaAs. Cadmium telluride can certainly capture the multicrystalline silicon piece of the solar power pie,” he said.
In his plenary talk, SPIE Fellow Yang Yang of the University of California, Los Angeles, summarized recent progress with light-harvesting hybrid perovskite materials including advances and challenges with perovskite-based photodetectors and tandem solar cells.
Calling perovskite a “dream material,” Yang said its benefits are its positive electron/hole transportation performance, low combination rate and high photoluminescence, long diffusion length, and long carrier lifetime.
“Perovskites are a really amazing material, from a purely scientific point of view,” Yang said in an interview with SPIE after his talk.
High absorption, good transport properties, and low-cost processing make them attractive for solar energy, compared to “high-end” solar cells that require special equipment, he said. Yang predicted that if perovskites can be shown to have long-term stability, they would reduce the cost of solar energy “comparable to or even lower than fossil fuels.”
MOBILE PHONE DIAGNOSTICS
SPIE Fellow Aydogan Ozcan, also of UCLA, outlined several photonics-based telemedicine technologies for the next generation of smart global health systems.
The massive growth in mobile phone use in recent years has driven significant quality and performance improvements of the imaging and sensing technologies embedded in the phones, he said.
This has transformed the mobile phone into a cost-effective and yet extremely powerful platform for biomedical tests and scientific measurements that would normally require advanced laboratory instruments, Ozcan said.
The growing trend toward use of mobile phones and other consumer electronic devices in advanced imaging and sensing “is helping us transform current practices of medicine, engineering, and sciences through democratization of measurement science and empowerment of citizen scientists, educators, and researchers in resource-limited settings.”
Ozcan described his research using computation/algorithms to create new optical microscopy, sensing, and diagnostic techniques.
SCULPTING LIGHT WAVES
SPIE Fellow Nader Engheta, recipient of the 2015 SPIE Gold Medal, also described how his lab at University of Pennsylvania (USA) is expanding the properties of natural optical materials to create novel metamaterials with properties not found in nature.
Engheta’s lab has demonstrated how waves can be confined to propagate along a single-atom-thick layer of graphene despite the wavelength of the light being larger than the height of the metamaterial surface.
These 2D metasurfaces lend themselves to being used to recreate typical wavelength guiding devices on the nano scale, such as optical splitters, fiber-optic cables, and even wavelength guides. Optical metamaterials are used to create analogs of typical electronic components, such as resistors, capacitors, and inductors.
In preliminary experiments, his lab fabricated analog optical capacitors and inductors, opening up the possibility for the future development of extremely fast optical integrated circuits.
SPIE President Toyohiko Yatagai (left) announced Engheta (right) as recipient of the 2015 SPIE Gold Medal.
STUDENTS EXCEL IN OPTICS OUTREACH GAMES
The 2015 SPIE Optics Outreach Games featured 20 SPIE Student Chapters from all over the world demonstrating various optical phenomena to show how optics and photonics education can be fun, inexpensive, elaborate, creative, magical, and all of the above.
Several chapters highlighted activities they conduct to encourage young students to try optics experiments at home. The University of Exeter Chapter in the UK, for example, showed how to make a polariscope from broken polarized sunglasses, a calculator screen, or 3D movie glasses.
SPIE President Toyohiko Yatagai (center) congratulates members of the SPIE Student Chapter at Washington State University (USA) for their prize-winning demonstration at the 2015 SPIE Optics Outreach Games.
Many chapters utilized toys and household objects as educational tools to show that optics and photonics outreach need not be an expensive endeavor. Indeed, the Three Rivers Community College Chapter (USA) made “dumpster optics” with a cardboard tube and a CD, creating an easy and inexpensive spectrometer.
The University of Laval Chapter (Canada) demonstrated geometric optics with a “house of shadows;” students use objects of various sizes to cast shadows on pre-printed outlines to make fun shapes.
Prize-winning demonstrations were:
- First place: Washington State University (USA) with a do-it-yourself spectrometer activity focusing on how light interacts with materials and how to use spectra to learn what materials are made of.
- Second place: University of Warsaw (Poland), demonstrating a water-droplet microscope and a small, simple spectrometer.
- Third place: The Air Force Institute of Technology (USA) with a demonstration of how lasers can be utilized to etch or burn materials.
- People's Choice Award: The Instituto Nacional de Astrofísica, Óptica y Electrónica (Mexico) for a simple ripple tank demonstrating how waves interact to form constructive and destructive interference.
See more coverage of SPIE Optics + Photonics 2015 in San Diego, including reports from conference rooms and photos from many special events and awards presentations.