Method for simulating the signal and noise for terahertz radiation generated by photomixing in laser-assisted field emission

摘要

Photomixing in laser-assisted field emission offers promise as a new mechanism for generating terahertz radiation. A nanoscale field emission tip is much smaller than optical wavelengths, so the potential of the tip follows each cycle of the incident radiation. Electron emission responds to the total electric field (DC + radiation) in T < 2 fs, and the current-voltage characteristics of field emission are highly nonlinear. Thus, two lasers cause current oscillations by photomixing, which can be tuned from DC to 500 THz (1/τ) by shifting the offset of the lasers. 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 time-independent Schrodinger equation at discrete time steps for which the 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 the specified total current. The one-sided power spectral density is calculated with the FFT to produce periodogram estimates.