Second harmonic generation in nanoscale films of transition metal dichalcogenide: Accounting for multipath interference

Abstract

The transfer matrix method has been widely used to calculate wave propagation through the layered structures consisting entirely of either linear or nonlinear optical materials. In the present work, we develop the transfer matrix method for structures consisting of alternating layers of linear and nonlinear optical materials. The result is presented in a form that allows one to directly substitute the values of material constants, refractive index and absorption coefficient, into the expressions describing the second harmonic generation (SHG) field. The model is applied to the calculation of second harmonic (SH) field generated in nano-thin layers of transition metal dichalcogenides exfoliated on top of silicon oxide/silicon Fabry-Perot cavity. These structures are intensively studied both in view of their unique properties and perspective applications. A good agreement between experimental and numerical results can be achieved by small modification of optical constants, which may arise in an experiment due to a strong electric field of an incident focused pump laser beam. By considering the SHG effect, this paper completes the series of works describing the role of Fabry-Perot cavity in different optical effects (optical reflection, photoluminescence and Raman scattering) in 2D semiconductors that is extremely important for characterization of these unique materials.

Characterization of Few-Layer 1T′ MoTe2 by Polarization-Resolved Second Harmonic Generation and Raman Scattering

“…Since the excitation wavelengths used are far off the resonance for BBO, the wavelength dependence of d 22 for BBO can be calculated using the Miller rule, which indicates that d 22 for BBO is nearly wavelength independent since the refractive index is approximately constant. While our samples were prepared on SiO 2 /Si, the cavity effect from this substrate has been shown to result in a small correction to the SHG signal. , The impact of this effect was also verified by comparing SHG measurements of monolayer MoS 2 on a glass and an Si/SiO 2 substrate (see Supporting Information). Figure a shows the wavelength dependence of d s for 1T′ MoTe 2 (blue circles) and monolayer MoS 2 (black squares).…”

“…While our samples were prepared on SiO 2 /Si, the cavity effect from this substrate has been shown to result in a small correction to the SHG signal. 30,54 The impact of this effect was also verified by comparing SHG measurements of monolayer MoS 2 on a glass and an Si/SiO 2 substrate (see Supporting Information). Figure 5a 5b.…”

Strong near band-edge excited second-harmonic generation from multilayer 2H Tin diselenide

“…The nonlinear wave propagation model implemented in COMSOL Multiphysics software 29 is described in the "Methods" section. SnSe 2 possess a large refractive index (close to 3) 12,30 at the wavelengths of interest in this work, resulting in the SHG process being strongly influenced by Fabry-Perot effects in addition to the expected dependence on phase mismatch and optical absorption 19,31,32 . The nonlinear wave-propagation model inherently considers these effects when solving for the field profiles and detected nonlinear signal.…”

Высокочувствительный фотодетектор на основе атомарно-тонкого MoS-=SUB=-2-=/SUB=-

“…В качестве основы для создаваемого устройства использовалась сильно легированная кремниевая подложка (удельное сопротивление 0.001−0.005 Ом • см) с предварительно созданным поверхностным термическим оксидом SiO 2 толщиной 90 нм. Оксид данной толщины за счет интерференционных эффектов позволяет эффективно визуализировать отдельные кристаллиты ДПМ как в режиме конфокальной оптической микроскопии, так и при использовании методик микроскопии второй оптической гармоники [13,14].…”