Layer- and Frequency-Dependent Second Harmonic Generation in Reflection from GaSe Atomic Crystals

Abstract

We report optical second-harmonic generation (SHG) in reflection from GaSe crystals of 1 to more than 100 layers using a fundamental picosecond pulsed pump at 1.58 eV and a supercontinuum white light pulsed laser with energies ranging from 0.85 to 1.4 eV. The measured reflected SHG signal is maximal in samples of $\sim$20 layers, decreasing in thicker samples as a result of interference. The thickness- and frequency-dependence of the SHG response of samples thicker than $\sim$7 layers can be reproduced by a second-order optical susceptibility that is the same as in bulk samples. For samples $\lesssim$7 layers, the second-order optical susceptibility is reduced compared to that in thicker samples, which is attributed to the expected bandgap increase in mono- and few-layer GaSe.

6 pages and 4 figures

References in corpus (7)

• Non-linear Optical Spectroscopy of Excited Exciton States for Efficient Valley Coherence Generation in WSe2 Monolayers
• Spin splitting in 2D monochalcogenide semiconductors
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Cited by in corpus (4)

• Solution-processed GaSe nanoflake-based films for photoelectrochemical water splitting and photoelectrochemical-type photodetectors
• How strong is the Second Harmonic Generation in single-layer monochalcogenides? A response from first-principles real-time simulations
• Control of excitonic absorption by thickness variation in few-layer GaSe
• High-efficiency second-harmonic and sum-frequency generation in a silicon nitride microring integrated with few-layer GaSe