Multi-wavelength surface emitting quantum cascade laser based on equivalent phase shift.

A novel surface emitting distributed feedback quantum cascade laser emitting around λ 4.6 µm is demonstrated by employing an equivalent phase shift (EPS) of quarter-wave (λ/4). The EPS is fabricated through extending one sampling period by 50% in the center of a sampled Bragg grating. Single-lobed far-field radiation pattern with a low divergence angle of about 0.6º x 16.8º is obtained. Selective single-mode lasing with a mean side mode suppression ratio above 20 dB and wavelength coverage range of 72 nm is achieved simultaneously on a single wafer only by changing the sampling period. [ABSTRACT FROM AUTHOR]