Effects of Hydrogen on InP Light-Emitting Devices Etched in a Methane-Hydrogen Environment

Research has been conducted on the physical damage and hydrogenation effects during RF plasma exposure and epitaxial growth in the III-V material system. Device consequences of this damage or chemical alteration have received less attention, particularly in active light emitting devices. This paper discusses these effects for lasers and edge emitting light-emitting diodes (EELEDs) which use a ridge waveguide structure. By using analysis techniques such as SIMS we have concluded that methane-hydrogen reactive ion etching of InP induces hydrogen levels in an active device which are high enough to significantly alter the device properties. The decrease in light output is substantial, but subsequent annealing times as short as 1 min. at 430°C can restore power dramatically

Mode-Locking of High-Power Resonant-Optical-Waveguide Diode Laser Arrays

We report the first mode-locked operation of a resonant optical waveguide (ROW semiconductor laser array. Pulsewidths as short as 23 ps and peak powers of over 1W are generated in a single-lobed beam

High-Frequency Electrooptic Fabry-Perot Modulators

Electrooptic modulators built from GaAs/AlxGa1-xAs Fabry-Perot cavities operating up to 6.5 GHz are reported. The measured frequency response agrees well with the one predicted using an equivalent circuit model derived from high-speed electrical measurements. The parasitic capacitances have been reduced to approximately 30 fF by fabricating the devices on semi-insulating GaAs substrates and integrating them with on-wafer bound pads which have dimensions compatible with microwave coplanar probes

Explanation of Timing Jitter Mechanisms in Multisegment Mode-Locked Semiconductor Lasers

Multisegment mode-locked semiconductor lasers offer a simple, high performance solution for short pulse generation. Six mode-locking techniques used in multisegment mode-locked semiconductor lasers are shown. This paper concentrates on a theoretical explanation of the timing jitter mechanisms in these lasers with supporting experimental measurements. The analysis covers passive, hybrid, and active mode-locking techniques for both monolithic and external cavity devices. Timing jitter is a very important system consideration for most applications of mode-locked lasers

High-Speed Concatenation of Frequency Ramps Using Sampled Grating Distributed Bragg Reflector Laser Diode Sources for OCT Resolution Enhancement

Brandon George and Dennis Derickson California Polytechnic State Univ. (USA) Wavelength tunable sampled grating distributed Bragg reflector (SG-DBR) lasers used for telecommunications applications have previously demonstrated the ability for linear frequency ramps covering the entire tuning range of the laser at 100 kHz repetition rates1. An individual SG-DBR laser has a typical tuning range of 50 nm. The InGaAs/InP material system often used with SG-DBR lasers allows for design variations that cover the 1250 to 1650 nm wavelength range. This paper addresses the possibility of concatenating the outputs of tunable SGDBR lasers covering adjacent wavelength ranges for enhancing the resolution of OCT measurements. This laser concatenation method is demonstrated by combining the 1525 nm to 1575 nm wavelength range of a C Band SG-DBR laser with the 1570nm to 1620 nm wavelength coverage of an L-Band SG-DBR laser. Measurements show that SGDBR lasers can be concatenated with a transition switching time of less than 50 ns with undesired leakage signals attenuated by 50 dB

Analysis of Laser Pulse Chirping in Mode-Locked Vertical-Cavity Surface-Emitting Lasers

Mode-locked vertical cavity lasers have a large cross-sectional area and consequently a large saturation energy and large peak powers. The authors analyze excess optical bandwidth generation in these lasers and find that self-phase modulation due to optical pumping and gain saturation is the dominant factor in inducing laser pulse chirping. The large magnitude of the chirp makes intracavity prism-pair compensation difficult. Adjustment of the cavity length has a major impact on the pulse chirping, as observed experimentally. Proper adjustment can result in a large linear frequency chirp which can be compensated using external pulse compression technique

Multi-wavelength Polarization Scrambling Device

A polarization scrambling device randomly varies the polarization states of multiple applied optical signals. The scrambling device includes a polarization scrambler coupled to a wavelength-dependent polarization randomizer having cascaded birefringent elements in which the axes of polarization of the cascaded elements are rotationally offset. The scrambling device causes random variations in the relative and the absolute polarization states of the applied optical signals. The birefringence, lengths, and number of cascaded birefringent elements are chosen to assure that the polarization states of optical signals at the different wavelengths are sufficiently randomized, even when the applied optical signals are closely spaced in frequency

A 100-kHz - 22 GHz Instrumentation Photoreceiver

A photoreceiver consisting of a high-speed p-i-n photodetector and a 100-kHz to 22-GHz distributed amplifier is described. Photoreceiver calibration is accomplished by optical heterodyne techniques. The photoreceiver is used with a microwave spectrum analyzer to produce a fully amplitude-calibrated 22-GHz-bandwidth lightwave signal analyzer system for displaying intensity-modulated light with -65-dB (optical) sensitivity at 1300-nm and 1550-nm wavelengths

Signal Monitoring Apparatus for Wavelength Divison Multiplexed Optical Telecommunication Networks

A detector array spectrometer simultaneously monitors wavelength, power, and signal-to-noise ratio of wavelength division multiplexed (WDM) channels in telecommunication networks. A spectrometer spatially separates signals from the WDM channels according to the channels\u27 wavelengths. The separated signals are incident on an array of split-detectors that conforms to the spatial separation of the signals provided by the spectrometer. While the split-detectors are positioned to receive a signal from each WDM channel, a noise detector is positioned between adjacent split-detectors to measure noise. A common mode output from two halves of each split-detector indicates the power in a WDM channel, while a differential output from the halves indicates wavelength deviations in the WDM channels. The ratio of the common mode signal to the noise detector signal is used to monitor the signal-to-noise ratio of the WDM channel. An angled diffraction grating in the spectrometer achieves compact size and high measurement resolution for the detector array spectrometer