J. Eom

Characterization of the dynamics of semiconductor lasers using optical modulation

An optical modulation technique for measuring the intrinsic frequency response of semiconductor lasers is described. This technique, which uses an RF-modulated pump laser to create an optical modulation signal to inject into a DC-biased probed laser, offers significant advantages over previous methods such as being affected by electrical parasitics of either the laser to be characterized or the photodetector. The method allows extremely accurate measurements of many important dynamic parameters, including the nonlinear gain coefficients, the amount of spontaneous emission into the guided modes, and the differential carrier lifetime at lasing threshold. >

Simultaneous measurement of spontaneous emission rate, nonlinear gain coefficient, and carrier lifetime in semiconductor lasers using a parasitic‐free optical modulation technique

An optical modulation technique is used to determine three important parameters for 1.3 μm InGaAsP diode lasers: the rate of spontaneous emission into the guided modes, the nonlinear gain coefficient, and the carrier lifetime at threshold. These results are unaffected by electrical parasitics, and are essential to understanding the noise and modulation properties of diode lasers.

Observation of positive and negative nonlinear gain in an optical injection experiment: proof of the cavity standing-wave-induced nonlinear gain theory in 1.3 μm wavelength semiconductor diode lasers

The origin of nonlinear gain in 1.3 μm InGaAsP semiconductor diode lasers is studied by measuring the magnitude and phase of a probe laser’s frequency response to optical injection with orthogonally polarized light from a pump laser. The sign and magnitude of the gain nonlinearity induced by optical injection depend on wavelength separation between pump and probe laser. The maximum magnitude of the nonlinear gain parameter is about 1.5×10−15 cm2. These results are consistent with the recently proposed theory that nonlinear gain is caused by the feedback from the dielectric grating induced by the standing wave in the laser cavity.

The relation of doping level to K factor and the effect on ultimate modulation performance of semiconductor lasers

For the first time, K, which is the ratio of the damping factor gamma to the square of the resonance frequency f/sub 0//sup 2/, is shown to depend on the doping level for bulk semiconductor lasers. Since the differential gain is known to depend on the doping level in the active layer, K also depends on the differential gain. The results presented strongly suggest that an effective means to decrease the damping is by increasing the doping level of the active region of the semiconductor laser. Since damping must be reduced in order to increase the maximum damping-limited bandwidth, this result may have important implications for improving the modulation bandwidths of bulk lasers and may be equally significant with respect to damping and the ultimate achievable bandwidth in quantum-well lasers.<<ETX>>

Determination of the gain nonlinearity time constant in 1.3 μm semiconductor lasers

By comparison of the measured K factors (ratio of the damping factor to the square of the resonance frequency) of distributed feedback and Fabry–Perot lasers, it is found that the relaxation time associated with nonlinear gain for 1.3 μm InGaAsP lasers is about 0.1 ps. This short time constant is consistent with spectral hole burning being the dominant process responsible for the nonlinear gain.

Multi-channel frequency stabilization using wavelength crossover properties of arrayed waveguide grating

To construct multi-channel systems with a vast amount of transmission capability, such as optical frequency division multiplexing (OFDM), a frequency stabilization technique is essential for minimizing fluctuation of the oscillation frequency of each channel and for getting more narrow channel spacing. This paper proposes a novel frequency stabilization method that uses the wavelength crossover properties of an arrayed waveguide grating (AWG). The zero-cross detection used in the proposed scheme does not require frequency modulation for synchronous detection unlike conventional frequency stabilization methods, but is implemented only by a simple electrical circuit.

Optical cell compressor using semiconductor optical amplifier as gate in TDM/WDM photonic ATM switching systems

Summary form only given. Photonic switching systems that are capable of switching a vast amount of information are strongly needed for future B-ISDN services. We have previously proposed a TDM-WDM hybrid photonic ATM switching system architecture with Tbps throughput, where optical cell compressor was one of the essential modules for the switching system. This paper proposes a new type of optical cell compressor with the advantages of high bit rate capability, less required hardware, and powerful output pulses resulting from the concurrence of amplifying and gating.

TDM with WDM hybrid photonic ATM switch

Optical switching networks to transport vast amount of information and process Tbit/s throughput are very important for B-ISDN services. This paper describes a ultra large capacity photonic ATM switch architecture which combines WDM frequency routers and a TDM ultrafast photonic switch.