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Anomalous Nonlinear Optical Selection Rules in Metallic Quantum Wells
Author(s) -
Li Shilong,
Qian Haoliang,
Liu Zhaowei
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202000829
Subject(s) - materials science , nonlinear optical , selection (genetic algorithm) , quantum well , nonlinear system , metal , quantum , condensed matter physics , quantum mechanics , metallurgy , physics , laser , computer science , artificial intelligence
Intersubband transitions (ISBTs) in conduction‐band quantum wells (QWs) have attracted tremendous attention for their high technological potential, ranging from quantum cascade lasers, quantum well infrared photodetectors, to various nonlinear optical elements. One of the main characteristics of using the ISBTs is their polarization selection rule, which forbids a normal‐incidence geometry. Here, it is shown that the ISBT selection rule is not strict on optical nonlinearities in metallic QWs (MQWs). The nonlinear process of second harmonic generation nearly follows the selection rule, while the optical Kerr nonlinear process severely deviates from it. The anomalous optical selection rules result from the non‐negligible ultrafast electron–electron scattering in these plasmonic systems, and a coupled mode theory is provided to get a physical grasp of the problem. The flexible selection rule in MQWs could bring drastic improvements in efficiency and diversity of ISBT‐based devices.