Influence of optical forces on nonlinear optical frequency conversion in nanoscale waveguide devices

Zhen-xing Wu, Wei Luo, Shi-han Tang, Fei Xu, and Yan-qing Lu

We theoretically investigate the influence of optical gradient forces on nonlinear frequency conversion in a typical nanoscale optomechanical system, which consists of two parallel, suspended waveguides. The waveguides deform with the input power and the phase-matching wavelength changes along the waveguides. Utilizing the spread of deformations collectively allows phase matching over a wider range of pump wavelengths. The third harmonic phase-matching wavelength shift can be as large as 3.6 nm/mW when the waveguide length is 100 μm and the initial gap is 150 nm. It is analogous to chirping the poling period of quasi-phase-matched devices to extend their bandwidths, and allows broad third harmonic to be generated for uses such as biological spectroscopy. Finally, we discuss the conversion efficiency and the optimal phase-matching wavelength with a single-frequency pump.

DOI