Highly efficient broadband second harmonic generation in a tapered zinc telluride slab using total internal reflection fractional quasi phase matching

We analytically describe broadband second-harmonic generation in a tapered zinc telluride (ZnTe) slab using total internal reflection fractional quasi-phase matching. Refractive index of ZnTe shows minimum deviation over a wide wavelength range resulting in increased coherence length which leads to fractional quasi-phase matching scenario, ensuring highly efficient second harmonic output. The simulated results, considering absorption and reflection losses, indicate 3 dB bandwidth of 192.5 nm, centered at 8.583 μm, with conversion efficiency as high as 19.6% in a 30 mm ZnTe slab. The effects of variations in incident angle at air–material interface, length and tapering angle of the slab have also been analyzed.