Coupled-Ridge Waveguide Quantum Cascade Laser Array Lasing At Lambda Similar To 5 Mu M

In this work, we demonstrated high-power quantum cascade laser (QCL) arrays lasing at lambda similar to 5 mu m by employing an optimized coupled-ridge waveguide (CRW) structure. Five-element QCL arrays were simulated and fabricated through a two-step etching method to extend the CRW structure to a mid-wave infrared regime. A lateral far-field with the main peak near a diffraction-limited intensity curve of about 10 degrees was observed by properly designing a geometric shape of the ridges and interspaces. By introducing a buried 2nd-order distributed feedback (DFB) grating, substrate emission with a radiation power above 1 W at 25 degrees C is achieved. Single longitudinal mode operation is obtained by changing the temperature of the heatsink with a good linear wavelength tuning coefficient of -0.2 cm(-1)/K.