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.

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High‐power and low‐polarization superluminescent diodes emitting at 0.8‐µm are fabricated by using a tensile‐strained GaAsP quantum well material. Under a low direct current operation with a Peltier thermoelectric element temperature control (25 °C), the output power of the fundamental transverse‐magnetic polarized mode dominateds over that of the fundamental transverse‐electric polarized mode. The total output powers of the two modes reach an equal state for the 1.06‐mm‐long device at ≈340 mA. The inherent superluminescent mode operations of the superluminescent diode with full‐width at half maximum of spectrum increasing along with the increment of current injection and temperature are discussed. The superluminescent diode is able to operate up to 85 °C and 400 mA. Output powers exceeding 40 mW and spectral ripples better than 0.14 dB are achieved.