TriLumina develops and manufactures flip-chip VCSEL technology used in 3D sensing applications that must meet automotive grade 1 temperature range (-40˚C to 125˚C) performance and be tested to high reliability standards and criteria (AEC-Q102). Advances in VCSEL efficiency, performance and automotive qualification of TriLumina’s selfhermetic flip-chip VCSEL are discussed. TriLumina’s VCSEL-on-board (VoB), surface-mount technology VCSEL is introduced.
Proc. SPIE. 10938, Vertical-Cavity Surface-Emitting Lasers XXIII
KEYWORDS: Modulation, LIDAR, Distance measurement, Light sources and illumination, Time of flight cameras, Aluminum nitride, Vertical cavity surface emitting lasers, Time of flight imaging, Time of flight range image sensors
The design and optimization of two-dimensional VCSEL arrays operating with duty-cycles from 2 to 5% (quasicontinuous- wave or QCW) operating at 940 nm are presented. Designs for nominal 8 W and 100 W peak power using TriLumina’s flip-chip-bondable, back-side-emitting VCSELs are reviewed. Performance as a function of duty cycle, including peak power output, spectral width and beam divergence are presented. Performance from -40°C to 125°C, corresponding to automotive grade 1 requirements, is reviewed. Optimization of the VCSEL arrays as a function of the number of emitters per chip is analyzed for trends in wall-plug efficiency, slope efficiency and operating conditions.
EMCORE's Concentrator Photovoltaic (CPV) systems use large-format Fresnel lenses to achieve 1090X
concentration onto high-efficiency multi-junction solar cells. The use of Fresnel lenses is common in CPV
systems due to their thin profile and light weight. EMCORE uses silicone-on-glass (SOG) lens technology,
which provides a high-reliability, high-durability alternative to acrylic lenses. This paper describes
performance variations of these lenses based on the Fresnel groove depth. Both the optical efficiency and
temperature dependence of the optical system are evaluated as a function of groove depth.
Ensuring 25-year reliability of a CPV system requires knowledge of potential failure modes and material deficiencies.
While Emcore’s CPV system conforms to all IEC 62108 tests, additional tests to eliminate potential long term reliability
concerns have been performed. Performance is evaluated through all levels of integration, from cell to module. Tests at
the cell level include IEC 62108 tests where feasible, as well as several other tests to establish the ability of the cell to
survive additional integration and perform well throughout the lifetime of the CPV module. At a receiver assembly and
module level, potential reliability concerns are addressed through targeted testing, which consists of accelerated stress tests which are used to quickly evaluate material performance and designed stress tests which allow the determination of activation energies. With this information, expected lifetime can be assessed and reliability concerns mitigated. Test methodologies and results from cell, receiver assembly and full module are presented demonstrating that targeted stress testing at each level of integration is a viable approach to assessing potential CPV failure modes.
Research in erbium-doped silicon (Si:Er) is discussed in light of our effort to improve the luminescence performance of our LEDs and to demonstrate an integration scheme for a microphotonic clock distribution system. Excitation from Si:Er can occur int ow ways: (1) direct excitation of an Er ion by high energy electrons or (2) energy transfer from an injected electron-hole pair to an Er ion in the lattice. In an LED the first excitation mechanism corresponds to operation in reverse bias, and the latter corresponds to operation in forward bias. We have studied the forward bias case, and we use an energy pathway model to describe the excitation and de-excitation processes. The competing, nonradiative processes against excitation and spontaneous emission are discussed. Maximization of light output can be approached in three ways: (1) decreasing the number of nonradiative energy pathways, (2) enhancing the probability of the radiative pathway, or (3) simply increasing the concentration of active Er sties. We report specific methods that address these issues, and we discuss more device structures that can be used as emitters, optical waveguides, and optical switches in a fully integrated microphotonic system.
The silicon/silicon dioxide (Si/SiO2) materials system provides a high index contrast waveguide platform compatible with existing monolithic microelectronic fabrication processes. The large index difference between the Si and SiO2 ((Delta) n approximately equals 2.0) allows the miniaturization of waveguide cross-sectional dimensions: single-mode strip waveguides with 0.2 X 0.5 micrometers cross-sections are possible. Additionally, right angle waveguide bends with radii of 2.0 micrometers can be fabricated with insertion loss of less than 1.0 dB. Bend radii of 250 micrometers or more are required to achieve the same performance in less confined waveguide systems such as GaAs/AlGaAs. The high confinement of the Si/SiO2 system also allows Y-branch power splitters with splitting angles greater than 20 degree(s) to operate with low loss. The combination of small cross- section, small bend radius, and large splitting angle provides a highly compact light guiding technology. Calculations of the loss due to 90 degree(s) bends in these waveguides and preliminary loss measurements for bends from 2.0 to 100.0 micrometers in radius are reported. Y-branch power splitters are analyzed and measurements of branches from 2 degree(s) to 40 degree(s) are presented.
1.1 W cw has been achieved from a 10-amplifier coherent array with an electrical to optical conversion efficiency of 28%. The amplifiers were injected with 20 mW from a master oscillator via a single-mode polarization-preserving optical fiber. Approximately 90% of the output power from the amplifier array was locked to the master oscillator's frequency.
The output of a laser diode typically has a Gaussian intensity profile and is highly divergent in one axis.
The Gaussian intensity profile causes side-lobes when diodes are used to form arrays. If the intensity
profile can be changed to a uniform profile in one axis, an increase in central lobe power of 10% can be
achieved. We have developed a single optical element which performs both the intensity redistribution and
collimation of linear arrays of laser diodes.