Phased-array sources based on nonlinear metamaterial nanocavities

Omri Wolf,John F Klem,Eric A Shaner,Michael B Sinclair,Ting S Luk,Sheng Liu,Arvind P Ravikumar,Emil A Kadlec,Salvatore Campione,Alexander Benz,Igal Brener

doi:10.1038/ncomms8667

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.

Highlights

Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams
We propose a new concept for phased-array sources at infrared wavelengths that makes use of localized nonlinear polarization to create a phase-locked ‘feed’ to subwavelength metamaterial nanocavities which re-radiate a beam with desired spectral, spatial and polarization properties
We show that a device based on split ring resonator (SRR) nanocavities and having quantum wells as the nonlinear medium allows for complete control over the polarization of an emitted second harmonic (SH) signal

Summary

Introduction

Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. The design of the individual resonator is varied across the array to achieve the desired phase and polarization response—in essence, the elements of the array acquire the role of the phase shifters and polarization converters These types of plasmonic-nanoantenna arrays have been successfully used to control the phase front[9,10] and spatial polarization[11,12] of an incident beam, while having a very small (subwavelength) footprint and being able to operate over wide frequency ranges. Such an approach cannot achieve 100% conversion efficiency and one is forced to contend with unconverted remnants of the excitation beam in the output. We envision that electrically tuning the quantum well levels or nonlinearity will allow real-time control over the output beam characteristics

Methods

Results

Conclusion