Terahertz coherent detection via two-color laser pulses of various frequency ratios

The mechanism of terahertz (THz) pulse coherent detection via two-color laser pulses of various frequency ratios in gas plasma is theoretically investigated. Our investigations demonstrate that except for the commonly used frequency ratio of 2, other uncommon frequency ratios can also be utilized to detect THz pulse, such as 2n, n+1/2 ($n\le 3$, n is a positive integer). The well-developed transient photocurrent model is extended to our terahertz detection process. Based on this model, our simulation results can be explained by analyzing the process of asymmetric electron ionization and electron acceleration. (paper)