Temperature characteristics of 850 nm tapered semiconductor lasers

Both tapered structure and broad-stripe semiconductor laser diodes were fabricated based on the AlGaAs/AlGaAs epitaxial layers with a graded-index waveguide separated confinement hetero-structure under the excited wavelength of 850 nm. The temperature characteristics of the devices were investigated and compared at the temperatures between 20°C and 70°C. Experiments show that the measured characteristic temperature(164 K) of the tapered devices is much higher than that of the broad devices(96 K) and the wavelength-shift coefficients of the tapered and broad-stripe devices are 0.25 nm/K and 0.28 nm/K respectively under a duty cycle of 0.5%(t=50 μs, f=100 Hz) and a pulsed current of 1000 mA. When the temperature is below 50°C, the Full Width at Half Maximums(FWHMs) of the tapered devices and the broad-stripe devices are 1.12 and 1.24 nm, respectively. These results indicate that the tapered lasers have better temperature characteristics than the broad ones with the same epitaxial structure under certain temperature conditions.