Temperature-insensitive high-efficiency LDs for over 85°C uncooled operation

Abstract

We have developed temperature insensitive high-efficiency LDs that can operate at wavelengths around 1.3 um for TOSA (Transmitter Optical Sub-Assembly) modules, which are our proposed light source solution for compact transmitters. Since the modules should be used without temperature controllers, a high slope efficiency and high output power operation at over 85degC is essential for LDs. We eliminated the leakage current flowing outside of the active layer using a buried-hetero structure. This resulted in excellent lasing characteristics. The slope efficiency at 25degC and 85degC was 0.49 W/A and 0.38 W/A, respectively. The slope efficiency degradation defined as a ratio of the slope efficiency value at 85degC to that at 25degC was -1.1dB, which to our knowledge is a record value to be reported for practical InGaAsP DH LDs. Excellent uniformity and reproducibility for lasing characteristics of 85degC were verified through multiple wafer runs. The fairly stable long-term operation test of ASM LDs was performed and estimated MTF (Median Time to Failure) at 85degC-10mW conditions was over 1 x 105 hours. Using newly developed ASM LDs, we have assembled the world smallest TOSA modules that could be realized for suitable light source solution under severe ambient temperature conditions.