A high speed 1053 nm superluminescent diode (SLD) with a ridge-waveguide structure has been fabricated for the first time to the best of our knowledge. InGaAs/GaAs quantum well epitaxial structure, the etched depth of the insulation channel and the area of p-side electrode were optimized to enhance the modulation bandwidth of the SLD. Bend-waveguide unpumped absorbing region structure and facet coating methods have been adopted to suppress the lasing oscillation. As a result, a −3 dB cutoff frequency of 1.7 GHz is obtained at a dc bias current of 100 mA and 25 • C heat-sink temperature, corresponding to 2.5 mW output power from single-mode fiber with spectral modulation of less than 0.15 dB and spectral width of 24 nm. The SLD module shows a good reliability.

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This paper reports on the experimental method of the determination of junction temperature and thermal resistance in 840 nm InGaAlAs/AlGaAs compressive strained single quantum well (SQW) superluminescent diodes (SLDs). The linear relation between forward voltage and junction temperature clearly occurs by utilizing the forward voltagetemperature (V -T ) method. The temperature coefficient dV /dT has been determined. Under 100 mA continuous-wave (CW) operation condition, the thermal resistance is measured to be 81.6 • C/W, which is not significantly different with the theoretical calculation result.

The unexpected decrease in measured responsivity observed in a specific GaN Schottky barrier photodetector (PD) at high reverse bias voltage was investigated and explained. Device equivalent transforms and small signal analysis were performed to analyse the test circuit. On this basis, a model was built which explained the responsivity decrease quantitatively. After being revised by this model, responsivity curves varying with bias voltage turned out to be reasonable. It is proved that the decrease is related to the dynamic parallel resistance of the photodiode. The results indicate that with a GaN Schottky PD, the choice of load resistance is restricted according to the dynamic parallel resistance of the device to avoid responsivity decay at high bias voltage.