Near Threshold Operation of Semiconductor Lasers and Resonant-Type Laser Amplifiers
نویسندگان
چکیده
The characteristics of a semiconductor laser operating in the threshold region are investigated systematically. In this transition region from below to above threshold, the linewidth versus injection current characteristic is found to be nonmonotonic: a local minimum of linewidth just below threshold and a local maximum just above threshold are confirmed experimentally. If a semiconductor laser works below threshold as a resonant optical amplifier or optical filter, the small-signal frequency bandwidth is found to be equivalent to the spontaneous emission linewidth. When the laser amplifier is used simultaneously as a photodetector, the maximum value of photodetection sensitivity is achieved with the laser amplifier biased between 98-99% of the threshold current. The Fokker-Planck equation method is employed in the linewidth calculation. A numerical computer simulation is also performed using the rateequation model. A reasonable agreement between theory and experiment is obtained.
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