Broadband wavelength conversion based on apodized χ^(2) grating

Abstract

We achieved apodization in a quasi-phase-matched (QPM) wavelength converter by changing the duty cycle of a χ(2) grating. The new design yields a large bandwidth and a flat phase-matching response with high conversion efficiency. Widely tunable 3-μm-band difference frequency generation was realized using an apodized QPM LiNbO3 ridge waveguide. We also demonstrated the simultaneous detection of the absorption lines of CH4 and C2H4 and obtained a broadband absorption spectrum of over 100 nm using the widely tunable source.