Because there is just too much going on to see it all: here is a small sampling of presentations heard at SPIE Photonics West 2016.
From the OPTO Symposium
Progress in building photonics design software
As an update to a project presented two years ago at SPIE Photonics West 2014, Lukas Chrostowski, University of British Colombia, briefed his colleagues in an invited talk on Tuesday morning (9751-2) about his group's progress in developing software to aid in silicon photonics design.
With the goal of achieving "first-time-right designs," the software takes inspiration from the silicon electronics industry, which has well established design and testing software for electronics components.
Chrostowski's software now has the ability to provide either schematic-first design or layout-first design; both require mature libraries and process design kits (PDKs) as data embedded within the software tools. It provides drag-and-drop component design interface, circuit simulators capable of monitoring interference between photonic and electronic components, and export functionality to allow use of designs as "black box" devices.
In addition to developing automated methods of identifying design flaws, Chrostowski is currently working on incorporating assessments of manufacturing variability. Case studies have demonstrated the necessity of the latter, as many of the designed devices will be intended for mass market manufacturing where variations from chip-to-chip, or even within-chip can cause device failure.
Extending silicon applications for hybrid photonic devices
Dong Liu, University of Wisconsin-Madison, (9767-33) on Tuesday afternoon presented a review of the state of the art in silicon and hybrid silicon photonic devices for the optoelectronics market.
Addressing the mainstream areas of wafer or membrane bonding, Liu noted how the lattice mismatch between silicon and III-V imposes restrictions on the use of silicon beyond a simple passive optical waveguide or reflective mirror.
With his research team and collaborators from the University of Texas at Arlington, Lui developed a low-cost, high plug-in efficiency 1.55 μm InGaAsP edge-emitting laser with a silicon hole injector and demonstrated the first use of Silicon as an electrical injection material for III-V optoelectronic devices.
Past, present and future of solid-state lighting
Sessions on LED manufacturing Tuesday afternoon in the conference on Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting brought together advances of solid-state lighting systems in the marketplace to date.
John Edmond, Cree, Inc., presented (9768-29) a holistic view on considering various aspects of the lighting system and emphasized that focus should not only be about optimization of the chip and component brightness but also aim at improving the system performance for efficiently catering wide application needs ranging from outdoor displays to hand-held devices.
Edmond described various LED-components that make together the LED chip and component toolbox and discussed how these components would impact the growth of the solid state lighting market going forward.
'LED 2.0' technology: GaN LED on GaN substrate
From a mere crystal in radio receivers to the biggest optical innovation in energy-efficient lightning, LEDs have been brightening our lives for over half a century now. Due to several advantages over incandescent light sources including low energy consumption, long lifetime, and smaller size, LEDs have found diverse applications, from car lights to lighting up the entire Super Bowl stadium.
In the Wednesday morning session on LED applications and solid-state lightning, Aurelien David of Soraa, Inc., (9768-35) presented an overvew of GaN-on-GaN LEDs - known as the "2.0 version" of LED technology.
Formed by an elite team of scientists and luminaries of the LED and lasers worlds -- Steve DenBaars, James Speck, and Noble Laurate Shuji Nakamura -- the Silicon Valley start-up Soraa has been manufacturing a new class of LEDs by using a unique GaN LED on GaN substrate process, where the tight lattice match propels more efficient light generation at lower overall cost.
Unlike most of the first generation GaN-LEDs on sapphire substrate, the LED 2.0 enables ultrahigh power, half the chip size, low power consumption, and a thousand-fold decrease in dislocation density.
David presented details about the fabrication process, status, and future trends of these GaN-on-GaN LEDs and highlighted how this technology would revolutionize the LED industry for cost-effective directional as well as nondirectional lightening applications.
Next generation cloud computing solutions
From ultrafast signaling and network I/O to 100 Gb/s optical discrete multitone transceivers, all the big trends, product innovations, and challenges in datacenter networking were discussed in the Datacenter Network Trends session chaired by Philippe Absil, IMEC, and Hai-Feng Liu, Intel Corp., on Wednesday afternoon (9775 Session 8).
Triggered by the challenges and complexity of achieving high-speed transmission networking for datacenters worldwide, networking luminaries presented new solutions that would migrate the future networking landscape towards high-speed, smaller form-factor transceivers/components, power, and high-bandwidth optical interconnect technologies.
These developments included building data center systems based on 50Gb/s SerDes / signaling, use of 100/200/400Gb/s as network I/O as well as exploiting single-carrier coherent optical modules (400 Gb/s) and 100 Gb/s optical discrete multi-tone transceivers for high capacity links over short transmission reach.
The role of standardization bodies to appropriately conceptualize the high-speed networking components was also emphasized.
Self-assembled photonic crystals aid label-free molecular sensing to target pollution
Céline Bourdillon, Université Pierre et Marie Curie, on Thursday morning presented innovative developments on the synthesis of self-assembled 3D photonic crystals ordered at the nanometric scale for ultra-sensitive and label-free chemical sensing applications (9756-56).
Photonic crystals are periodic optical structures that offer new ways to repel and trap as well as steer light. This is achieved by multiple scatterings from structure surfaces that lead to blocking the optical beam from propagating through the crystal in every possible direction.
Bourdillon investigated the light emission for opals made from self-assembled dielectric spheres and discussed how the photonic bandgap was directly dependent on sphere diameter of the opal nanostructures.
By efficiently engineering the photonic band gap of an inverse opal and combining it with special sensor materials, Bourdillon demonstrated a label-free approach to achieve very high sensitivity and specificity in optical detection of the target molecules of pollutants.
Combining techniques in a single LED device
Whether they are used for efficiently pumping lasers or as backlights on LCD screens, there is always room for new LEDs capable of producing unique wavelength emission bands in the optics and photonics world. Stacy Kowsz, a graduate student at University of California Santa Barbara, is working with a group developing methods to accomplish just that (9748-71).
Kowsz reported Thursday afternoon on results from growing, fabricating, and demonstrating a novel LED device that takes advantage of both optically pumping and electrically injecting InGaN quantum wells (QWs). Combining these two methods is the critical component of their approach to achieve an ultimate goal of producing polarized white light emission without phosphor.
Optical pumping avoids degradation effects from high temperatures, and increases the intensity as well as color range of the device by utilizing multiple QWs. By applying an additional electric field in the same direction as the polarization-induced field on one of their channels, the wavelength emission range is red shifted to longer wavelengths.
The performance of the first generation of this novel device shows promising results, and Kowsz is optimistic that improvements in their fabrication techniques will yield the desired product.
Miniaturizing gas sensors with QEPAS
In a prime example of the power of international collaboration, Vincenzo Spagnolo, Politecnico di Bari, presented research (9755-91) on Thursday afternoon in developing "smaller and smaller" gas sensors. The collaboration is primarily a shared investigation between the Università delgi studi di Bari Aldo Moro and Rice University.
Spagnolo and his fellow researchers use custom-designed quantum tuning forks (QTFs) to perform quartz-enhanced photoacoustic spectroscopy (QEPAS). The physical geometry of a QTF makes it act as a resonating acoustic transducer. While resonant mechanical vibration is induced by an acoustic wave, optical radiation is focused between the fork prongs. The subsequent electrical QEPAS signal is proportional to the optical power, providing spectroscopic measurements that are immune to environment noise.
Spagnolo identified key figures of merit for assessing QTF design, and demonstrated the performance of several QEPAS sensors employing their customs QTFs. These include both THz and near-IR based QEPAS sensors for H2S detection. In a particular design of note, Spagnolo reports the same detection sensitivity for a 46mm double tube on-beam QEPAS as a 26mm single tube on-beam QEPAS system, validating progress towards minimizing sensor footprints.
Cleaning up spatial modes with HCWs
Laser beam spatial modes are a common metric for assessing resonator stability and waveguide quality, and it is often desirable to produce a single spatial mode output. Pietro Patimisco, Università delgi studi di Bari Aldo Moro, reported Thursday afternoon how he has employed hollow-core waveguide fibers (HCWs) to accomplish this task (9755-92). In another collaboration between his institution and Rice University, Patimisco "cleans up" lasers with poor spatial modes by coupling them with HCWs.
HCWs are desirable for their high coupling efficiencies (which can be >95%), lack of end reflections, ruggedness, and small beam divergences. Patimisco coupled three 200 micron diameter HCWs of varying lengths to a quantum cascade laser, and assessed performance at several mid-IR wavelengths by measuring the beam profiles before and after the waveguides, and quantifying their M-squared values (beam spatial quality metric).
Despite losses being slightly more than predicted in theoretical calculations, there was <7% discrepancy and good data agreement. Patimisco concluded that HCWs with bore sizes less than fifty times the wavelength are "a convenient and relatively low-loss means of delivering mid-IR laser beams with a single mode output."
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Contributors: Jacqueline Andreozzi, Khushi Vyas