CfD Director Figer Co-chaired a NASA technology working group with Eric Schinhelm (Southwest Research Institute) to assess the current state of the art in detectors for ultraviolet, optical, and infrared wavelengths. This activity is a precursor to the plans for the further development of competing technologies to fly on the next large space telescope after the James Webb Space Telescope (JWST). The new telescope has a notional design and is generically being called the Large Ultraviolet Optical Infrared Survey (LUVOIR) telescope. Just as with previous NASA missions, this somewhat awkward name will be likely be replaced with a name that memorializes a prominent figure in the advancement of science.
The LUVOIR point design considers the use of a large (8-12 m) primary mirror that capitalizes on the emerging heavy lift capabilities, such as the Big Falcon Rocket (BFR) to be made by SpaceX and the Space Launch System (SLS) being developed by NASA and partners. Just like JWST, the telescope will be launched in a furled configuration to be expanded and phased on orbit.
The detector technology working group solicited information concerning the technology readiness level of approximately a dozen competing detector types that could fly on LUVOIR, either in the wide area imaging camera or the coronagraph instrument. For most science applications on the proposed telescope, detectors will need to have very low noise. In fact, for the goal of measuring the atmospheres of exoplanets, the detectors will need to have single photon sensitivity.
The primary objective of this project is the realization of an integrated photonics platform compatible with photon-ion entanglement. The platform will consist of photon sources and entangling circuits that interface with the visible/UV wavelengths of ion (such as Yb+, Ca+, Be+, Mg+, Sr+, Ba+, Zn+, Hg+ and Cd+) transitions. The challenge with realizing such a platform is that integrated photonic chips are not well developed at visible wavelengths because of the traditional focus on telecom wavelength compatibility. We are developing a platform that does operate at short wavelengths by using Aluminum Nitride (AlN), which is a large bandgap semiconductor that is transparent to the deep-UV. In parallel, we are leveraging our successes in quantum integrated photonics in telecom-compatible platforms, particularly silicon photonics. This will allow rapid validation of high performance photon sources, entanglement circuits and quantum sensors. These circuits will then be transitioned to the new visible/UV platform, or interfaced with ions directly by using frequency conversion.
The world demand for, and consumption of, energy is dramatically increasing, with an increasing demand for renewable non-fossil based sources of electricity. As well, there is an ever growing demand for increased power and sophistication in the satellite systems orbiting our planet, driven by our increasing reliance on high speed communication and data links. The conversion of light from the sun into electrical energy, using photovoltaics, is one avenue that can be explored to meet these challenges both on the earth and in space. The mission of our research group is to accelerate scientific breakthroughs in the discovery of nanoscale materials and structures that will advance the frontier of the conversion of light to electricity. Our focus is new materials synthesis, device modeling and simulation, solar cell device fabrication and demonstrating proof-of-principle of devices that will deliver a major boost to the world’s pursuit of innovative and transformative energy conversion products. Our team’s expertise lies in vapor phase epitaxy (VPE) of III-V photovoltaic and photonic devices and nanostructures, bandgap engineering using epitaxial nanostructures, novel photovoltaic devices such as the intermediate band solar cell, photovoltaic characterization, simulation, design and testing.
A collaborative effort between Columbia University, RIT, and Precision Optical Transceivers, this project will develop testing capabilities for the Testing Assembly and Packaging (TAP) Hub that AIM Photonics is building in downtown Rochester, NY. The EVT is a generalized testing tool for validating functionality and performance specifications of integrated silicon circuits, such as optical switches, transceivers, photonic biosensors, lasers, etc. It is a crucial element of AIM Photonics and represents a much-anticipated capability that customers will use to prove the validity of their circuit designs.
The EVT system will first be used for the testing of a C form-factor pluggable (CFP) based package that is currently being developed at Columbia University for the purpose of controlling complex photonic integrated circuits (PICs), including high speed transceivers and photonic switch fabrics. The EVT will later be able to test a quad small form-factor pluggable (QSFP) based package that is being developed by Precision Optical Transceivers. As the project proceeds, work will continue to be done to create software for functional and performance tests in order to validate the EVT station for photonic switches and more.
The growth of various nanostructures, including nanowires and nanofins, by metal-organic chemical vapor deposition (MOCVD) is investigated through a unique crystal synthesis process known as selective area epitaxy (SAE). The SAE method relies on an oxide template with predefined windows that specify the location of preferential epitaxial atomic assembly. Growth rate enhancement, as defined by the oxide template, allows for the controlled epitaxy of arrays of vertical, III-V compound semiconductor nanostructures without the use of foreign catalytic or seeding agents. Based on the SAE technique, the EINS lab has demonstrated growth of InAs, InGaAs, GaAs, GaAsP, and GaP nanowire and nanofin arrays on Si substrates with 100% yield over large, wafer-scale areas. Our current projects aim to understand the growth kinetics of III-V nanosystems interfaced with Si and 2-dimensional nanomaterials such as graphene and monolayer transition metal dichalcogenides; to characterize the novel material properties offered by these hybrid nanosystems; and to demonstrate their utility in innovative photovoltaics and optoelectronics solutions.
The Center for Detectors is conducting a design study for software and data analysis for the Tomographic Ionized-carbon Mapping Experiment (TIME-Pilot) instrument, which is designed to make pioneering measurements of the redshifted 157.7 micron line of singly ionized carbon [CIIJ from the Epoch of Reionization (EoR). The EoR is the period in the Universe's history during which the first stars and galaxies formed, and whose intense ultra-violet (UV) radiation fields ionized the intergalactic medium. The New Worlds, New Horizons 2010 Astrophysics Decadal Report recognized the EoR as one of five scientific discovery areas where "new technologies, observing strategies, theories, and computations open . . . opportunities for transformational comprehension". This investigation is breaking ground for future investment from government and private funding agencies by improving our understanding of the instrument design and expected performance.
Infrared arrays with HgCdTe as the light-sensitive layer, such as have been developed up to sizes 2048x2048 pixels for the James Webb Space Telescope, are near-ideal detectors for imaging and spectroscopy in the region ~1-5 microns. However current construction requires fabrication on CdZnTe substrates, which are expensive and limited in availability. The key to making larger (up to 14,000x14,000 pixels) and less expensive infrared detectors lies in using silicon wafer substrates, since large silicon wafers are common in the high volume semiconductor industry and their coefficient of thermal expansion is well-matched to that of the silicon readout circuits.
While the use of silicon substrates has been a major goal in the field of developing infrared detectors, the main limitation over the past 15 years has been the large lattice spacing mismatch between silicon and commonly-used infrared light-sensitive materials. The mismatch causes defects that can result in higher dark current, or valence holes that lead to reduced quantum efficiency and image persistence.
Enlisting the expertise and fabrication capabilities of Raytheon Vision Systems, detector expert Dr. D. Figer of the Rochester Institute of Technology plans to deposit the HgCdTe light-sensitive layer on silicon using the very promising technique of Molecular Beam Epitaxy (MBE). By maintaining vacuum during MBE processing, defect density has been shown to be reduced and the resulting prototype devices have achieved the anticipated performance. Very large, affordable infrared arrays is essential for making optimum use of the proposed ~30m class ground-based telescopes and their availability has clear implications for fields beyond astronomy, including medical imaging and remote sensing.
RIT has embarked on the Cosmic Radiation Damaged Image Repair project (CRDIR) involving Dr. Donald Pettit, NASA Astronaut & International Space Station astrophotographer. This project is being conducted by graduate and undergraduate student researchers under the guidance of Dr. Donald Figer, Director of CfD.
This project continues efforts over the past few years to remove the effect of cosmic ray damage in pictures obtained on the International Space Station. This damage can lead to aberrant pixel values scattered throughout the images obtained with the sensor. This project was conceived by NASA astronaut, Donald Pettit, RIT alumnus, Peter A Blacksberg (BFA Photo '75), and Center for Detectors (CfD) Director, Don Figer. Several student researchers worked on the project over the past year, including Justin Beigel (Electrical Engineering), HanSoo Lee (Game Design and Development), and Sean Scannel (Motion Picture Science). During the past year, the students created a new user interface and implemented video processing capabilities.
Metal-assisted chemical etching (MacEtch) is an anisotropic, solution-based nanofabrication process that combines the benefits of conventional wet-etching and plasma-based ion etching. The MacEtch process relies on site-specific, catalytic oxidation of a semiconductor surface by a patterned noble metal layer, followed by preferential dissolution of the selectively oxidized regions. Continuous repetition of oxidation-dissolution cycles in a single MacEtch bath results in the metal layer sinking into the semiconductor such that vertical nanostructures are left in the path of the metal layer, having geometries that are complementary to the geometry of the patterned metal. In the EINS lab, we are interested in exploring the fabrication of III-V semiconductor nanostructures using non-conventional metallic catalysts composed of carbon-nanotubes and graphene. In this manner we define novel nanofabrication paradigms that enable low-cost and clean alternatives to conventional ion-based etching procedures, offering high-aspect ratio features with atomically-abrupt sidewall termination. Novel device applications in high-efficiency solid-state lighting and tri-gated nanofin-based field effect transistors have already been demonstrated using on MacEtch fabrication.
SPHEREx is a planned NASA small explorer which will perform an all-sky spectral survey of the in near-infrared bands. SPHEREx was recently selected for a NASA Phase A study, work is required to refine the instrument concept before a down-select occurs in mid-2016. This program is refining details of the instrument, observation strategy, and data analysis plans to create visual materials to help NASA and the public understand the experiment and expected science output.
This project's long-term objective is the creation of a workforce of proficient integrated photonic circuit designers. There is a clear industry need for designers that are able to utilize Electronic Photonic Design Automation (EPDA) methodologies to effectively design functional photonic-electronic circuitry to drive the integrated photonics industry into the future. The primary goal of this project is to meet this need with the creation of integrated photonic circuit design/test content to enable educators to teach students and industrial practitioners the principles, methodologies and practical knowledge of integrated photonic circuit design.
The aim of this project is to accurately characterize the intra-pixel response function of Kepler’s CCDs and develop a procedure to calibrate data in the Kepler archive and data from the K2 mission. We are measuring the Intra-pixel response function (IPRF) using residual e2v CCD90 detectors, identical to those on the spacecraft, provided to us by the Kepler Project. This IPRF will be used to develop a method to improve the photometry and astrometry of archival NASA Kepler data and data from the K2 mission. The calibration procedure, software, and documentation will be made available to the Kepler community through a new task in the open source community-developed data reduction pipeline, PyKE.
The measurement system illuminates a subpixel region on the CCD and measures the response in that location. The spot projector consists of a fiber-illuminated parabolic collimating mirror and a Mitutoyo Plan Apo 20x infinity-corrected microscope objective. This objective is corrected for chromatic aberration over the wavelength range 380 nm–900 nm to provide diffraction-limited performance. Furthermore, the objective has a long working distance (20 mm) which allows us to focus on the pixel surface through the window of a cryogenic dewar. The objective’s focal ratio (f/1.25) is well matched to that of Kepler (f/1.47).
Our initial scans consisted of a 70 µm × 70 µm region of interest, with steps of 1 µm in each direction. The measurements were performed at 450 nm, 600 nm, and 800 nm (with a passband of ∆λ ∼ 15 nm). The entire scan region at 450 nm is shown in Figure 24. To determine the IPRF, we normalize the intensity measured by the brightest pixel at each position of the spot scanner. This relative measurement must be combined with the quantum efficiency of the CCD at the appropriate wavelength to obtain the absolute IPRF. In the following sections, we consider the IPRF at our three wavelengths of interest. Figure 24 shows representative results. The response is similar to other back-illuminated devices, showing a considerable amount of diffusion and round contours. The peak response decreases by ∼70% at the corners of each pixel.
CCDs have been the dominant optical-wavelength detector architecture for high-end optical imaging applications for decades. However, CCDs are inoperable below 120K due to electron freeze-out effects, prohibiting their use in space exploration applications requiring cryogenic temperatures. Mega-pixel CMOS devices are known to work at temperatures as low as 10K, suggesting that imaging devices based on this technology would operate in cryogenic environments without requiring active heating. In this program, we take the first step to maturing this technology for flight applications in the cryogenic regime by developing and flying an attitude-sensing camera employing a low noise, high quantum efficiency cryogenic CMOS detector. By implementing an alternative imaging technology, we address NASA's major objective to “transform NASA missions and advance the Nation’s capabilities by maturing crosscutting and innovative space technologies.” This technology enables instruments ranging from actively-cooled star trackers for sounding rockets to low-temperature deep space cameras.
The progress made by the undergraduate CSTARS (Cryogenic Star Tracking Attitude Regulation System) team has proven instrumental in the design of a second revision of the star tracker to support the Cosmic Infrared Background ExpeRiment (CIBER). The rocket skin of CIBER-1 underwent thermal contraction when exposed to the cryogenic temperatures, resulting in a noticeable drift in the measured data. CSTARS-2 will serve as a secondary star-tracking system on the CIBER-2 payload, located within the cryogenically cooled portion of the rocket. This will allow it to maintain the attitude of the rocket while the CIBER-2 detectors are capturing data. To support a higher resolution sCMOS detector operating at twice the frame rate, new focal plane and interfacing hardware was designed and tested. The new detector (Figure 10 right) has proven fully functional at 80K and the telemetry streams have been validated against NASA ground stations. Remaining work includes finalizing the star-tracking algorithm, as well as reliability and vibration testing. The CSTARS-2 system is scheduled for integration and final testing late summer of 2018.
The objective of this project is to support AIM Academy (the education arm of AIM Photonics) by providing education modules for integrated photonics design, manufacturing, packaging and testing. We are also working to educate students, workforce, veterans and the community with: short courses, degree courses, establish an integrated photonics practice facility, assess workforce needs and develop an ME degree in Integrated Photonics Manufacturing in collaboration with MIT.
The primary objective of this DURIP (Defense University Research Instrumentation Program) project is to demonstrate quantum photonic circuits on a Silicon chip by using a quantum photonic measurement system with ultra-low noise and high efficiency. Quantum information science has shown that quantum effects can dramatically improve the performance of communication, computational and measurement systems. However, complex quantum systems have remained elusive due to the large number of resources (photon sources, circuits and detectors) that need to be tightly integrated. Professor Preble is realizing breakthroughs by integrating quantum circuits on a silicon chip and developing scalable building blocks based on ring resonators, which dramatically reduce the footprint of the circuits and enable novel functionalities. The quantum measurement system consisting of a low-noise tunable laser and high efficiency single photon detectors, is a critical enabler of these Quantum Silicon Photonic chips.
The Rochester Institute of Technology team is responsible for the delivery of a cryogenically-operable star tracking camera for attitude control of the CIBER-2 payload. RIT is building, testing, and delivering this camera to Caltech for integration into the full experiment by the beginning of Year 2. RIT is also responsible for delivering the associated documentation and interface information to both Caltech and NASA by the end of Year 2. The RIT team is also responsible for assisting with: (1) overall instrument design; (2) integration of the payload system; (3) laboratory testing and characterization; (4) flight planning and logistical requirements; (5) deployment and flight efforts; (6) data reduction and calibration; and (7) science extraction.
RIT’s Photonics and Optics Workforce Education Research group (POWER) unites STEM education research with workforce development in order to investigate the critical scientific and mathematical knowledge, hands-on abilities, communication skills, and other essential competencies for jobs in photonics. The group is conducting an on-going study of optical technician and engineering jobs in the Rochester region. Also, In partnership with AIM Integrated Photonics, the group is conducting a study about workforce needs for the emerging integrated photonics sector.
RIT is developing a silicon MOSFET CMOS imager to detect terahertz (THz) frequencies in a collaboration with the Center for Emerging and Innovative Sciences (CEIS) at the University of Rochester and Exelis Geospatial Systems. Creating an asymmetrical design within the FETs, increases the THz response. The current device being tested was designed with 15 individual test transistors with varying design dimensions and antennas along with an array of transistors for an imager. These test structures are being evaluated at RIT to determine the best design for terahertz detection for future imager designs. An advantage of this detector technology is that these MOSFETs will not have to be cooled to extreme temperatures like microbolometers. This project will advance knowledge of the detection mechanism, lead to the creation of an integrated imaging system, and has many different applications.
THz frequencies have been largely unexplored due to high absorption within water, however there has been an increase in interest with the rise in high-altitude and space-based telescopes. Emission lines in spectra within the THz regime exhibit cool molecular gas which traces protoplanetary disks and star formation rates within galaxies. This technology will also have other applications within the medical and security fields because of the non ionizing, non-harmful nature of THz radiation.
The Center for Detectors is developing solutions to key challenges in achieving high-efficiency single-mode GaN-based ultraviolet (UV) lasers with wavelength ranging from 220 nm up to 300 nm. Particularly, the research focuses on the fundamental physics understanding of the valence band structure of lll-Nitride wide bandgap gain active region, and develop promising solutions on nanostructured quantum wells and fabrication approach of large area GaN-based UV laser arrays. These lasers are a promising candidate for various naval applications in sensing and communication.
Escalating trends in global energy consumption, mandates for increased national energy independence, and mounting alarm regarding anthropogenic climate change all demand improved sustainable energy solutions. While the theoretical power generation potential of solar photovoltaics (PV) in the United States is greater than the combined potential of all other renewable resources, substantial market penetration of PV sand realization of grid-parity have been obstructed by high materials and manufacturing costs, as well as limitations in solar power conversion efficiencies (PCE). A pressing need exists for tandem solar cells utilizing two dissimilar materials (TDM) or more that are capable of PCE values beyond the ~30% Shockley-Queisser limit. In this program, we explore a transformative, bifacial solar cell design that employs arrays of TDM III-V compound semiconductor nanowires in tandem with a thinned, intermediate Si sub-cell. The use of epitaxial nanowire arrays overcomes the lattice matching criteria and enables direct III-V on Si monolithic integration. This design eliminates the need for high-cost wafers, growth of graded buffer layers, and anti-reflection coatings, while permitting ideal solar spectrum matching and capture of albedo radiation. The high risk-high payoff and exploratory research fits the NSF EAGER program, as it involves a radically unconventional approach with transformative potential to enable cost-effective manufacturing of high-efficiency TDM solar cells.
The technical approach of this EAGER project relies on selective-area heteroepitaxy of a GaAsP (1.75 eV) nanowire array on the top surface of a thinned Si (1.1 eV) sub-cell by metal-organic chemical vapor deposition. A bifacial, three dissimilar materials, tandem junction device is formed via monolithic integration of a back-side InGaAs (0.5 eV) nanowire array. The vertical nanowires comprising the top- and back-surface arrays will contain radially-segmented p-i-n junctions and will be serially connected to the central Si sub-cell via epitaxial tunnel junctions. This design enables absorption of broadband incident solar energy as well as albedo radiation. Standard lattice-matching constraints are overcome via strain relaxation along nanowire free surfaces. Therefore, ideal spectral matching is realized without a need for graded buffer layers or dislocation mediation strategies. Use of vertical nanowire arrays with coaxial p-i-n junction geometries permits key advantages, including near-unity absorption of solar irradiance at normal and tilted incidence without the use of anti-reflection coatings, decoupling of photon absorption and carrier collection directions, and dramatic reduction of 95% in epitaxial volumes. Rigorous modeling of device parameters will be iteratively coupled with extensive materials characterization and property correlation experiments for optimization of III-V sub-cell structure on the single nanowire and ensemble array levels. The ultimate target of this work is demonstration of a functional bifacial, three dissimilar materials, nanowire-based tandem junction solar cell with one Sun power conversion efficiency of 30% or better.