Fast Swept-Wavelength, Low Threshold-Current, Continuous-Wave External Cavity Quantum Cascade Laser

Abstract We present a low threshold-current and fast wavelength-tuning external cavity quantum cascade laser (EC-QCL) using a scanning galvanometer in the Littman-Metcalf cavity geometry. The EC-QCL could repeatedly swept at 100 Hz over its full tuning range of about 290 nm (2105 cm−1 to 2240 cm−1), providing a scan rate of 59.3 μm s−1. The continuous-wave (CW) threshold current of the EC-QCL was as low as 250 mA and the maximum output power was 20.8 mW at 400 mA for a 3-mm-long QCL gain chip. With a sawtooth wave modulation, a scan resolution of < 0.2 cm−1 can be achieved within the tuning range. The low power-consumption and fast swept-wavelength EC-QCL will be beneficial to many applications