Modeling and design of an optimum transmission metallic grating for efficient excitation of terahertz waves in small-area photomixers

In this work, we first analyze transmission metallic gratings by modal expansion and surface impedance approximation. By means of this method, an analytical model for different types of transmission resonances in metallic gratings is presented. Thereafter, an optimum metallic grating for small-area photomixers is designed and the overall performance of the photomixer is evaluated. An enhancement factor of 5.11 in terahertz current generation is achieved by using the optimized grating. It is shown that the characteristics of the designed photomixer are independent of the incident angle of the exciting laser beam.