Radiation enhancement in unbiased array of CW terahertz photomixer emitters with nano-slit waveguide resonant modes

An array of unbiased CW terahertz photomixer emitters based on excitation of different waveguide modes in the bimetallic contact grating is introduced. Unlike previous structures, this emitter does not require any external bias voltage. For photocarrier acceleration it rather makes use of the built-in electrostatic field formed in the vicinity of the Schottky contact (electrode-photoconductor) interface. We show that in the designed emitters with the excitation of the second order guided modes of the subwavelength nano-slit waveguides formed between two adjacent bimetallic gratings, the effective current density is approximately about 8 times that of the structure in absence of the resonance modes with the same beat frequency of 0.5 THz. As a result of this enhancement, the resultant terahertz radiation power increases by more than one order of magnitude. A hybrid numerical simulation method is used to model and analyze this phenomenon.