A reflective mm-wave photonic limiter

Abstract

Millimeter wave (mm-wave) communications and radar receivers capable of processing small signals must be protected from high-power signals, which can damage sensitive receiver components.Many of these systems arguably can be protected by using photonic limiting techniques, in addition to electronic limiting circuits in receiver front-ends. Here we demonstrate, experimentally and numerically, a free-space, reflective mm-wave limiter based on a multilayer structure involving a nanolayer of vanadium dioxide (VO 2 ), experiencing a thermal insulator-to-metal transition. The multilayer acts as a variable reflector, controlled by the input power. At low input power levels, VO 2 remains dielectric, and the multilayer exhibits resonant transmittance. When the input power exceeds a threshold level, the emerging metallic phase renders the multilayer highly reflective while dissipating a small portion of the input power without damage to the limiter. In the case of a Gaussian beam, the limiter has a nearly constant output above the limiting threshold input.Millimeter wave (mm-wave) is a valuable network and sensing technology which utilizes frequency bands in between 30 GHz and 300 GHz [1][2][3]. Operating in this spectral range has important advantages over lower frequency bands. Not only do mm-waves allow larger bandwidths to transmit data at multi-gigabit speeds [4], they also provide higher spatial resolution due to shorter wavelengths, which can be exploited for a variety of accurate sensing applications [5]. Another advantage of mm-wavelengths is that the size of system components required to receive and process mm-wave signals is small enough to allow using standard optical techniques [6][7][8][9][10][11][12].Optical limiting is a technique to protect photosensitive devices from damage caused by intense optical radiation [13,14]. Optical limiters are therefore designed to block highintensity laser radiation while transmitting low-intensity light. Most passive optical limiters utilize materials with nonlinear absorption, which are transparent to low-intensity light but turn opaque if the light intensity exceeds a certain (limiting) threshold level [15][16][17].However, a typical passive limiter absorbs a significant portion of high-level radiation, which can cause overheating and damage to the limiter itself [14,18].To overcome this problem, the concept of a reflective photonic limiter, which reflects rather than absorbs high-intensity radiation, has been introduced [19][20][21]. A passive reflective photonic limiter involves a photonic bandgap structure, such as a multilayer cavity,