KEYWORDS: Semiconductor lasers, High power lasers, Laser resonators, Analog electronics, Laser applications, Combustion, Resistance, Continuous wave operation, Temperature metrology, Sensors
High power single mode InGaAsP/InP DFB laser diodes with narrow linewidth and emitting near 1310nm
are key devices for Analog transmission and Sensor applications since they can be rugged and compact
sources more suited to harsh environment than solid-state or fiber-based lasers. Typically, the useful output
power of DFB sources is limited to about 100mW when sub-MHz linewidth is required Ref [1] by the so-called
"re-broadening effect" which causes the spectral linewidth to increase due to spatial-hole burning and
other effects. We report here sub-MHz linewidth at output power levels exceeding 500mW resulting from
cavity design that successfully addresses the concerns of linewidth re-broadening. Single-frequency
operation can be maintained from threshold to the high power operating point without mode hops.
We review data on the high temperature operation of a high speed data link operating at 1 micrometer wavelength. The single mode fiber packaged transmitter consists of an 'uncooled' high speed laser diode packaged with a commercial laser driver chip and operates at data rates up to 1.2 Gbit/s. The single mode fiber packaged receiver consists of a high speed photodiode packaged with a combination of a commercial transimpedance amplifier and a limiting amplifier. The link operates with high stability and very low error rates without an optical isolator. The maximum data rate and the minimum link sensitivity are currently limited by the electronic component design.
High-power semiconductor sources capable of high-speed modulation are very desirable for free-space digital telecommunications such as satellite optical communication links. Moreover, a diffraction limited beam quality is necessary for most applications. We describe advances in the development of high-power, diffraction-limited semiconductor lasers based on the master oscillator/power amplifier (MOPA) architecture and capable of high-speed modulation. Devices containing monolithically integrated electro-absorption or phase modulators demonstrate 5 GHz small signal modulation bandwidth at 1 W output power.
We present data on the wide temperature operation of a high speed data link operating at nominally 1 micrometer wavelength. The single mode fiber packaged transmitter running at 1.2 GBit/s consists of a high speed laser diode packaged with a commercial laser driver chip. The laser is not cooled in any manner over the temperature range of operation and the link operates with low error rates without an optical isolator. The single mode fiber packaged receiver consists of a high speed photodiode packaged with a combination of a commercial transimpedance amplifier and a limiting amplifier.
A monolithically integrated array of InGaAs/AlGaAs flared amplifiers driven by a single DBR laser through a power splitter network and individually addressed phase modulators is described. Phase adjustment of > 2(pi) per element by free-carrier effects is verified by monitoring the interference pattern of 4 emitters, and typically requires < 15 mA of current to obtain a 2(pi) phase shift. Phase matching is achieved among all four diffraction-limited emitters at a pulsed output power of > 5 W, and, combined with the proper external lensing, could therefore result in an ultra-narrow, single-lobed far-field pattern whose width is determined by the extended aperture of the array. This architecture is capable of providing single-mode, diffraction-limited performance from each emitter and is scalable to unprecedented power levels. Over 20 W of pulsed, spectrally coherent emission is generated at 955 nm from a 4-element array, and 39 W is obtained from an 8-element array.
The high power and broad spectral output of superluminescent diodes (SLDs) are desirable for fiber optic gyroscopes, optical sensors and short to medium haul communications. Certain applications are sensitive to spectral modulation on the subnanometer wavelength scale where coherent interference can be a source of noise. We present a simple SLD design which eliminates the optical feedback within the chip normally responsible for spectral modulation. Although the design can be applied to conventional SLD wavelengths, initial device demonstration at 960 nm has been chosen to illustrate SLD operation in a materials system in which spectral modulation is particularly difficult to suppress. Ridge waveguide based SLDs suitable for coupling to single mode fiber have been fabricated. Typical output is 10 mW cw at 140 mA with a spectral width of 30 nm and less than 5% spectral modulation over a wide range of operating conditions.
We describe 2?m wide ridge waveguide lasers emitting at a wavelength of 980nm using a strained single quantum well epitaxial structure. These devices exhibit high coupling efficiency into single mode fiber. We have coupled up to 60mW using an industry standard 14-in dual-in-line package. Such devices are ideal for pumping Er-doped Fiber Amplifiers.
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