KEYWORDS: Semiconductor lasers, Near field optics, Optical resonators, Active optics, Optics manufacturing, Electronics, Diodes, High power lasers, Absorption, Laser scattering
Detailed reliability studies of high-power, CW, broad-area, GaAs-based laser- diodes were performed. Optical and
electrical transients occurring prior to device failure by catastrophic optical-damage (COD) were observed. These
transients were correlated with COD formation as observed in laser diodes with an optical window in the n-side
electrode. In addition, custom electronics were designed to fault-protect the laser diodes during aging tests, i.e. each time
a transient (fault) was detected, the operating current was temporarily cut off within 4μs of fault detection. The lifetime
of fault-protected 808-nm laser-diode bars operated at a constant current of 120A (~130W) and 35°C exceeded similar
unprotected devices by factors of 2.
KEYWORDS: Semiconductor lasers, Near field optics, Near field, Electroluminescence, Scanning transmission electron microscopy, Interfaces, Crystals, Laser optics, Diodes, Aluminum
The present model of formation and propagation of catastrophic optical-damage (COD), a random failure-mode in laser
diodes, was formulated in 1974 and has remained substantially unchanged. We extend the model of COD phenomena,
based on analytical studies involving EBIC (electron-beam induced current), STEM (scanning transmission-electron
microscopy) and sophisticated optical-measurements. We have determined that a ring-cavity mode, whose presence has
not been previously reported, significantly contributes to COD initiation and propagation in broad-area laser-diodes.
Absolute intensities of spectra in a dense-plasma-focus (DPF) source have been recorded and analyzed. This DPF source has been identified as one of the more promising sources for X-ray lithography. The source, developed by Science Research Laboratory, Inc., is currently undergoing testing and further development at BAE Systems, Inc. The DPF operates at 60 Hz and produces an average output pulse of ~5 J of X rays into 4π steradians in a continuous operation mode. In all runs, there was an initial number of pulses, typically between 30 to 40, during which the X-ray output increased and the DPF appeared to be undergoing a conditioning process, and after which a "steady-state" mode was achieved where the average X-ray power was relatively constant. Each spectral run was exposed to ~600 J of output, as
measured by the PIN. The X-ray spectral region between 0.8 and 3 keV was recorded on Kodak DEF film in a potassium acid phthalate (KAP) convex curved-crystal spectrograph. The source emits neon line radiation from Ne IX and Ne X ionization stages in the 900 to 1300 eV region, suitable for lithographic exposures of photoresist. Two helium-like neon lines contribute more than 50% of the total energy. From continuum shape, plasma temperatures were found to be approximately 170-200 eV. The absolute, integrated spectral outputs were verified to within 30% by comparison with measurements by a PIN detector and a radiachromic X-ray dosimeter.
This paper presents simulation results for the dc and transient characteristics of the n(superscript +-i-n(superscript + photoconductive diode at room and cryogenic temperatures fabricated in silicon and in silicon carbide. The simulation is carried out using a two-dimensional device simulator called MEDICI which can solve numerically the Poisson equation, electron and hole current equations, electron and hole continuity equations, as well as heat transfer equation. Relevant physical mechanisms, such as lattice heating, Fermi-Dirac statistics, high-field and doping-dependent free-carrier mobility, and various generation and recombination mechanisms are accounted for in the simulation.
Under ideal conditions photoconductive switches utilizing ohmic contacts can be made to conduct high currents that scale directly with input optical trigger power. In practice, however,
ohmic contacts can only be approximated by using heavily-doped contact/metallization regions, so that photoswitch structures employing intrinsic substrate layers to support switch voltage can
be viewed as n-i-n, p-i-n, or p-i-n, depending on the contact doping. Under bias, these contacts preferentially inject majority carriers (either holes or electrons) into the substrate that can form
high local space charge electric fields at elevated current densities. In this paper we show both experimentally and analytically that contact space charge formation in a cryogenic silicon n-i-n
photoswitch structure ultimately limits its on-state current capability.
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