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2.7 μm GaSb-based distributed feedback lasers with laterally coupled gratings

We report on a high-performance GaSb-based quantum well laterally coupled distributed feedback laser emitting at wavelength of 2.7 μm. The first-order grating structure of chromium(Cr) is designed to obtain the maximum coupling coefficient, and is defined alongside the ridge waveguide by electron beam lithography. The DFB laser emits an output power of 4.3 mW in a single-mode operation at a heat-sink temperature of 20 °C. Continuous wavelength tuning has been obtained by varying the injection current at a tuning rate of 0.012 nm mA−1. The mixmum side mode suppression ratio is as high as 54.9 dB, which is the highest value ever reported at the wavelength region of 2.7 μm. In addition, the loss margin introduced by Cr gratings is estimated to be 5.02 ±0.33 cm−1.