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High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
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Reverse Saturable Absorption Induced by Phonon-Assisted Anti-Stokes Processes.
Xiangling Tian1, Rongfei Wei2, Qianyi Guo1
1State Key Laboratory of Luminescent Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Wushan Road 381, Guangzhou, 510641, P. R. China.
Advanced Materials (Deerfield Beach, Fla.)
|May 26, 2018
Summary
This study shows tungsten diselenide (WSe2) exhibits strong reverse saturable absorption (RSA) with femtosecond lasers. This semiconductor offers a new material for optical limiters, protecting against laser damage.
Area of Science:
- Materials Science
- Optics
- Condensed Matter Physics
Background:
- Reverse saturable absorption (RSA) materials decrease transmittance under intense laser irradiation, useful for optical limiting.
- Current RSA research focuses on carbon-based nanomaterials for nanosecond lasers.
- Semiconductors typically show saturable absorption (SA) at laser energies above their band gap.
Purpose of the Study:
- To investigate the RSA properties of indirect gap semiconductor WSe2.
- To explore WSe2 as a potential optical limiter for femtosecond lasers.
- To understand the underlying mechanism of RSA in WSe2.
Main Methods:
- Experimental investigation of WSe2 under femtosecond laser irradiation.
- Near band gap excitation with laser energy (E_laser) greater than the band gap (E_B).
- Analysis of optical transmittance changes with increasing laser intensity.
Main Results:
- WSe2 exhibits significant RSA under femtosecond laser exposure.
- The observed RSA is attributed to longitudinal optical phonon-assisted anti-Stokes transitions.
- A low optical limiting threshold of approximately 21.6 mJ cm^-2 was measured for femtosecond lasers at 800 nm.
Conclusions:
- Indirect gap WSe2 demonstrates high RSA performance with femtosecond lasers.
- WSe2 is a promising candidate for advanced optical limiting applications.
- The phonon-assisted transition mechanism provides insight into RSA in semiconductors.
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