Title: Nonlinear Intersubband Polaritonic Metasurfaces: from second-harmonic generation with beam shaping to widely-tunable THz sources
Abstract: Quantum-engineered intersubband transitions in n-doped multiple-quantum-well heterostructures allow one to produce semiconductor films with very large nonlinear optical response. This nonlinear response can be further enhanced by processing semiconductor heterostructures as metasurfaces in which intersubband transitions are coupled to optical modes of the metasurface nanoresonators [1]. As a result, one can fabricate large area optically thin films that display second- and third-order nonlinear optical susceptibility values 4-7 orders of magnitude higher than that of traditional nonlinear optical crystals. Using these films, one can achieve efficient (0.1-1%) frequency mixing at moderate pumping intensities (10-100 kW/cm) without phase-matching constraints associated with bulk nonlinear optical crystals [2,3]. In this presentation, I will discuss our recent advancements with these metasurfaces, focusing on dynamic electrical phase control of the nonlinear optical response at the individual nanoresonator level [4,5] and on efficient continuous-wave terahertz generation with unprecedented tuning range of 1-11 THz via difference-frequency mixing [6].
[1] J. Lee et al., “Giant nonlinear response from plasmonic metasurfaces coupled to intersubband transitions,” Nature 511, 65–69 (2014).
[2] J. Lee et al., “Ultrathin second-harmonic metasurfaces with record-high nonlinear optical response,” Adv. Opt. Mat. 4, 664-670 (2016).
[3] D. Kim et al., “Efficient second-harmonic generation from dielectric inter-subband polaritonic metasurfaces coupled to lattice resonance,” Nano Lett. 23, 9003-9010 (2023).
[4] J. Yu et al., “Electrically tunable nonlinear polaritonic metasurface,” Nat. Photon. 16, 72-78 (2022).
[5] J. Yu et al., “Complex amplitude control of second harmonic generation using electrically tunable nonlinear polaritonic metasurfaces,” under review (2025).
[6] J. Krakofsky et al., “Generation of continuous-wave 1-11 THz radiation with intersubband polaritonic metasurfaces,” under review (2025).
About the Speaker: Mikhail A. Belkin is a professor in the Department of Electrical Engineering of the Technical University of Munich and the head of the Chair for Semiconductor Technology at the Walter Schottky Institute of the Technical University of Munich. Previously, he was a professor in the Department of Electrical and Computer Engineering at The University of Texas at Austin. His research interests are in the field of mid-infrared and THz optoelectronics, integrated photonics, nonlinear optics, and metamaterials.
Dr. Belkin received his Ph.D. degrees in Physics at the University of California at Berkeley in the group of Prof. Yuen-Ron Shen in 2004 and did his postdoctoral work at the group of Prof. Federico Capasso at Harvard University in 2004-2008. His recognitions include Friedrich Wilhelm Bessel Research Award from the Alexander von Humboldt Foundation (2016), NSF CAREER Award (2012), DARPA Young Faculty Award (2012), and AFOSR Young Investigator Program Award (2009). Dr. Belkin is a Fellow of the IEEE, OSA and SPIE.