Tunable Distributed Feedback Quantum Cascade Lasers by a Sampled Bragg Grating

A novel complex-coupled distributed feedback quantum cascade laser emitting around λ ~ 4.7 μm is demonstrated by a sampled Bragg grating (SBG). The key superiorities are to utilize the +1st-order (positive first order) transmission of the SBG for laser single-mode operation, and use conventional holographic exposure combined with the optical photolithography technology to fabricate the sampled grating, which lead to improved flexibility, repeatability, and cost-effectiveness. Selective single-mode lasing with a mean side mode suppression ratio above 20 dB and wavelength coverage range of 87 nm is achieved by changing the sampling period.