Efficient conversion of photons to electrical energy has a wide variety of applications including imaging, energy harvesting, and infrared detection. The coupling of electromagnetic radiation to free electron oscillations at a metal interface results in enhanced electric fields tightly confined to the surface. Taking advantage of this nonlinear light-matter interaction, this work presents resonant surfaces optimized for combining electrical and photonic excitations in order to liberate electrons in a vacuum-channel device for applications ranging from enhanced photoemission to infrared photodetection.

Conversion of photons to electrical energy has a wide variety of applications including imaging, solar energy harvesting, and IR detection. A rectenna device consists of an antenna in addition to a rectifying element to absorb the incident radiation within a certain frequency range. We designed, fabricated, and measured an optical rectifier taking advantage of asymmetrical field enhancement for forward and reverse currents due to geometrical constraints. The gold nano-structures as well as the geometrical parameters offer enhanced light-matter interaction at 382 THz. Using the Taylor expansion of the time-dependent current as a function of the external bias and oscillating optical excitation, we obtained responsivities close to quantum limit of operation. This geometrical approach can offer an efficient, broadband, and scalable solution for energy conversion and detection in the future.

Efficient generation of charge carriers from a metallic surface is a critical challenge in a wide variety of applications including vacuum microelectronics and photo-electrochemical devices.Replacing semiconductors with vacuum/gas as the medium of electron transport offers superior speed, power, and robustness to radiation and temperature. We propose a metallic resonant surface combining optical and electrical excitations of electrons and significantly reducing powers required using plasmon-induced enhancement of confined electric field. The properties of the device are modeled using the exact solution of the time-dependent Schrödinger equation at the barrier. Measurement results exhibit strong agreement with an analytical solution, and allow us to extract the field enhancement factor at the surface. Significant photocurrents are observed using combination of ! !" ! optical power and 10 volts DC excitation on the surface. The model suggests optical field enhancement of 3 orders of magnitude at the metal interface due to plasmonic resonance. This simple planar structure provides valuable evidence on the electron emission mechanisms involved and it can be used for implementation of semiconductor compatible vacuum devices.

A high power (~ 1W) continuous wave (CW) laser was focused on argon microplasma generated in the microgap between two electrodes with submillimeter diameters. Dependence of breakdown (V(BD)) and quench (V(Q)) voltages of microplasma to the laser power, wavelength, and spot location were studied as the gap size and pressure varied. It was observed that the laser-plasma interaction can only occur thermally through the electrodes. Also, the thermal effect of the laser was noticeable at relatively higher pressures (> 10Torr), and in most cases led to a decrease in V(BD), proportional to the pressure.

No abstract

No abstract

Using a relaxation oscillator circuit, breakdown (VBD) and quench (VQ) voltages of a DC discharge microplasma between two needle probes are measured. High resolution modified Paschen curves are obtained for argon microplasmas including a quench voltage curve representing the voltage at which the plasma turns off. It is shown that, for a point to point microgap (e.g. the microgap between two needle probes) which describes many realistic microdevices, neither Paschen's law applies nor field emission is noticeable. Although normally VBD > VQ, it is observed that depending on environmental parameters of argon, such as pressure and the driving circuitry, plasma can exist in a different state with equal VBD and VQ. Using emission line spectroscopy, it is shown that VBD and VQ are equal if the atomic excitation by the electric field dipole moment dominantly leads to one of the argon's metastable states (4P5 in our study).