Phased-array sources based on nonlinear metamaterial nanocavities

Abstract

Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (∼5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.

Multiwavelength polarization-insensitive lenses based on dielectric metasurfaces with meta-molecules

“…For instance, it can be used to implement a lens with two given focal distances at two wavelengths, or a lens converging at one wavelength and diverging at the other. In addition, given the generality of the meta-molecule concept, it can be applied to other areas of interest in metasurfaces (such as nonlinear [35][36][37] and microwave [38,39] metasurfaces). Multiwavelength operation is necessary in various microscopy applications where fluorescence is excited at one wavelength and collected at another.…”

Resonantly Enhanced Second-Harmonic Generation Using III–V Semiconductor All-Dielectric Metasurfaces

“…Due to the large surface to volume ratio in semiconductor based nanostructures, the SHG contributed by surface nonlinearities is often comparable to or even larger than that from bulk nonlinearities [36][37][38] . Using full-wave time- 13 dependent simulations including second order nonlinearities we first simulated the SHG emitted from our GaAs metasurfaces assuming only a bulk nonlinearity tensor (see Supporting Information, Section 4 for more details). The bulk second-order susceptibility (2) of GaAs is non-zero only when i≠j≠k due to the zinc-blend crystal structure (4 ̅ 3 ) of GaAs 4 .…”

Advanced control of nonlinear beams with Pancharatnam-Berry metasurfaces

“…Nonlinear metasurfaces have recently provided record-high conversion efficiencies in nonlinear processes and hold a great potential to revolutionize the field of nonlinear optics by replacing bulk nonlinear crystals with flat structures of sub-µm thicknesses [1][2][3][4]. Strong nonlinear responses from such electrically small volumes requires light-matter interactions much stronger than what is attainable in bulk crystals.…”

“…This is where the field of plasmonics provides powerful tools. The use of carefully engineered subwavelength plasmonic inclusions offers a flexible and efficient way to engage strong fields in small volumes and boost the efficiency of nonlinear processes, such as second-harmonic generation (SHG), to very large values [1,2,[4][5][6][7]. In addition, ultrathin metasurfaces significantly alleviate phase matching constraints, which are of critical importance for efficient nonlinear processes [1,8].…”