High Power Substrate-Emitting Quantum Cascade Laser With a Symmetric Mode

We demonstrate a buried grating coupled substrate emitting distributed-feedback quantum cascade laser with high power room temperature continuous wave (cw) operation at 4.97 μm. A second-order semiconductor/semiconductor grating is used for in-plane feedback and vertical out-coupling. A surface emitting power of 248 mW is attained in cw operation at 20 °C. Single-mode operation is obtained with a good linear wavelength tuning with injection current. The far field shows a low divergence about 0.14° × 16°, indicating that the device operates in symmetric mode.