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Germanium diselenide (GeSe 2), a layered IV-VI semiconductor, has an in-plane anisotropic structure and a wide band gap, exhibiting unique optical, electrical, and thermal properties. In this paper, polarization axis Raman spectrum and linear absorption spectrum are used to characterize the crystal axis orientation and energy band characteristics of GeSe 2flake, respectively. Based on the results, a micro-domain I scan system is used to study the optical nonlinear absorption mechanism of GeSe 2near the resonance band. The results show that the nonlinear absorption mechanism in GeSe 2is a superposition of saturation absorption and excited state absorption, and is strongly dependent on the polarization and wavelength of incident light. Under near-resonance excitation (450 nm), the excited state absorption is more greatly dependent on polarization. With different polarizations of incident light, the modulation depth can be changed from 4.6% to 9.9%; for non-resonant excitation (400 nm), the modulation depth only changes from 7.0% to 9.7%. At the same time, compared with saturation absorption, the polarization-dependent excited state absorption is greatly affected by the distance away from the resonance excitation wavelength.
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Keywords:
- anisotropy/
- excited state absorption/
- micro-domain I-scan
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Polarization/(°) α0/cm–1 β0/cm·GW–1 I1,s/GW·cm–2 I2,s/GW·cm–2 δT/% 0 31559 508 15947 41 7.0 30 33593 559 7962 38 7.5 60 36579 606 972 35 8.2 90 38790 663 349 34 9.7 120 36972 599 1394 36 8.1 150 34029 543 6629 39 7.3 180 31062 496 17082 41 7.0 Polarization/(°) α0/cm–1 β0/cm·GW–1 I1,s/GW·cm–2 I2,s/GW·cm–2 δT/% 0 43909 175 9390 63 4.6 30 49631 157 1258 69 5.6 60 60289 65 409 75 7.1 90 67501 22 188 79 9.9 120 57266 81 469 76 6.8 150 48345 158 2333 68 5.0 180 43173 176 10483 62 4.6 -
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