SIMULATIONS OF THE GENERATION OF TERAHERTZ RADIATION BY PHOTOMIXING IN LASER-ASSISTED FIELD EMISSION TO OPTIMIZE THE SIGNAL-TO-NOISE RATIO

Abstract

Quantum simulations and experiments show that photomixing in laser-assisted field emission has promise as a new method for wide-band tunable sources of radiation at terahertz frequencies. The tunable bandwidth is only limited by the means for coupling power from the oscillations in the field emission current from photomixing, and not by the processes that generate this current. Photomixing is simulated as a stationary stochastic process in which the frequencies and phases of the incident optical radiation are random variables. The waveform of the current is determined by solving the Schrödinger equation at discrete time steps for which the effective potential barrier is a superposition of the incident radiation field and the static barrier. These samples satisfy the criteria of a Poisson process to allow for the discrete emission of electrons at a specified total current. The one-sided power spectral density for this current is calculated with the FFT to produce periodogram estimates. The simulations show that the signal-to-noise ratio may be increased by (1) raising the power flux density of each laser, (2) raising the DC static current, (3) reducing the linewidth of each laser, and (4) using a static current density of no more than 1010 A/m.