Exciton spectroscopy of semiconductors by the method of optical harmonics generation

TL;DR

This paper reviews how nonlinear optical harmonics generation techniques are used to study excitons in various semiconductors and heterostructures, revealing new insights into their energy and spin structures under external fields.

Contribution

It introduces exciton spectroscopy via optical harmonics generation, highlighting the effects of external electric and magnetic fields on exciton states, and establishing it as a new research field.

Findings

External fields modify exciton states and induce new harmonic generation mechanisms.

Microscopic mechanisms include Stark, Zeeman, and magneto-Stark effects.

The approach provides unique information on exciton energy and spin structures.

Abstract

Nonlinear optical phenomena are widely used for the study of semiconductor materials. The paper presents an overview of experimental and theoretical studies of excitons by the method of optical second and third harmonics generation in various bulk semiconductors (GaAs, CdTe, ZnSe, ZnO, Cu$_2$O, (Cd,Mn)Te, EuTe, EuSe), and low-dimensional heterostructures ZnSe/BeTe. Particular attention is paid to the role of external electric and magnetic fields that modify the exciton states and induce new mechanisms of optical harmonics generation. Microscopic mechanisms of harmonics generation based on the Stark effect, the spin and orbital Zeeman effects, and on the magneto-Stark effect specific for excitons moving in an external magnetic field are considered. This approach makes it possible to study the properties of excitons and to obtain new information on their energy and spin structure that is not available when the excitons are investigated by linear optical spectroscopy. As a result of these studies, a large amount of information was obtained, which allows us to conclude on the establishing of a new field of research - exciton spectroscopy by the method of optical harmonics generation.