Designing an ultra-compact SOI waveguide with a high nonlinear coefficient for generating optical frequency combs and demultiplexing combs

Abstract

In this paper, an ultra-compact high capability silicon-based waveguide with a high nonlinear coefficient and engineered dispersion was designed for frequency combs generation and demultiplexing of these combs. In the first part of the structure, a silicon waveguide with two zero-dispersion wavelengths, 1552[Formula: see text]nm and 2350[Formula: see text]nm, and a length of 4[Formula: see text]mm was used to generate optical frequency combs using the four-wave mixing method. Considering the high nonlinear coefficient of [Formula: see text] in the waveguide, an input pump power of 500[Formula: see text]mW was applied to the waveguide at near-zero-dispersion wavelengths of 1552[Formula: see text]nm. The output comb spectrum of the waveguide was obtained after the length of 4[Formula: see text]mm with a spectral bandwidth of 400[Formula: see text]nm and a free spectral range of 5[Formula: see text]nm. Additionally, by similar pumping at wavelengths of 1553[Formula: see text]nm and 1555[Formula: see text]nm to this waveguide, optical frequency combs with a free spectral range of 2[Formula: see text]nm and a spectral bandwidth of 150[Formula: see text]nm were obtained. In the second part of the structure, to isolate the optical frequency combs, the given waveguide was expanded to generate an SOI demultiplexer with micro-ring resonator filters, which could separate optical frequency combs with the wavelength of 1555[Formula: see text]nm, 1557[Formula: see text]nm, 1559[Formula: see text]nm, and 1561[Formula: see text]nm due to the selection of suitable values for the radius of the ring resonators. The mean transmission efficiency, spectral bandwidth, and quality factor were obtained to be 99.51%, 0.275[Formula: see text]nm, and 5675, respectively. The channel spacing in the proposed demultiplexer was 2[Formula: see text]nm and the minimum and maximum crosstalk were −36[Formula: see text]dB and −11.3[Formula: see text]dB.