Broad-stripe midinfrared photonic-crystal distributed-feedback lasers with laser-ablation confinement

We investigate broad-stripe photonic-crystal distributed-feedback lasers emitting at λ=4.4 μm. The beam quality improves dramatically when a laser ablation technique is used to eliminate parasitic Fabry–Pérot-like modes, by inducing loss in the regions adjoining the pump stripe. Even though the peak of the gain spectrum never fully aligns with the grating resonance, for pulsed pumping the output beam is essentially diffraction limited up to a stripe width of 150 μm, and remains no worse than six times the diffraction limit for stripes as broad as 400 μm.