Abstract

Nonlinear frequency conversion provides essential tools for light generation, photon entanglement, and manipulation. Transition metal dichalcogenides (TMDs) possess huge nonlinear susceptibilities and 3R-stacked TMD crystals further combine broken inversion symmetry and aligned layering, representing ideal candidates to boost the nonlinear optical gain with minimal footprint. Here, we report on the efficient frequency conversion of 3R-MoS2, revealing the evolution of its exceptional second-order nonlinear processes along the ordinary (in-plane) and extraordinary (out-of-plane) directions. Along the ordinary axis, by measuring difference frequency and second harmonic generation (SHG) of 3R-MoS₂ with various thickness - from monolayer (∼0.65 nm) to bulk (∼1 µm) - we present the first measurement of the SHG coherence length (∼530 nm) at 1520 nm and achieve record nonlinear optical enhancement from a van der Waals material, > 104 stronger than a monolayer. It is found that 3R-MoS₂ slabs exhibit similar conversion efficiencies of lithium niobate, but within propagation lengths that are more than 100-fold shorter at telecom wavelengths. Furthermore, along the extraordinary axis, we achieve broadly tunable SHG from 3R-MoS₂ in a waveguide geometry, revealing the coherence length in such structure for the first time. We characterize the full refractive index spectrum and quantify both birefringence components in anisotropic 3R-MoS₂ crystals with near-field nano-imaging. Empowered with these data we assess the intrinsic limits of the conversion efficiency and nonlinear optical processes in 3R-MoS₂ attainable in waveguide geometries.

Abstract

Nonlinear frequency conversion provides essential tools for light generation, photon entanglement, and manipulation. Transition metal dichalcogenides (TMDs) possess huge nonlinear susceptibilities and 3R-stacked TMD crystals further combine broken inversion symmetry and aligned layering, representing ideal candidates to boost the nonlinear optical gain with minimal footprint. Here, we report on the efficient frequency conversion of 3R-MoS2, revealing the evolution of its exceptional second-order nonlinear processes along the ordinary (in-plane) and extraordinary (out-of-plane) directions. Along the ordinary axis, by measuring difference frequency and second harmonic generation (SHG) of 3R-MoS₂ with various thickness - from monolayer (∼0.65 nm) to bulk (∼1 µm) - we present the first measurement of the SHG coherence length (∼530 nm) at 1520 nm and achieve record nonlinear optical enhancement from a van der Waals material, > 104 stronger than a monolayer. It is found that 3R-MoS₂ slabs exhibit similar conversion efficiencies of lithium niobate, but within propagation lengths that are more than 100-fold shorter at telecom wavelengths. Furthermore, along the extraordinary axis, we achieve broadly tunable SHG from 3R-MoS₂ in a waveguide geometry, revealing the coherence length in such structure for the first time. We characterize the full refractive index spectrum and quantify both birefringence components in anisotropic 3R-MoS₂ crystals with near-field nano-imaging. Empowered with these data we assess the intrinsic limits of the conversion efficiency and nonlinear optical processes in 3R-MoS₂ attainable in waveguide geometries.

Abstract

Nonlinear frequency conversion provides essential tools for light generation, photon entanglement, and manipulation. Transition metal dichalcogenides (TMDs) possess huge nonlinear susceptibilities and 3R-stacked TMD crystals further combine broken inversion symmetry and aligned layering, representing ideal candidates to boost the nonlinear optical gain with minimal footprint. Here, we report on the efficient frequency conversion of 3R-MoS2, revealing the evolution of its exceptional second-order nonlinear processes along the ordinary (in-plane) and extraordinary (out-of-plane) directions. Along the ordinary axis, by measuring difference frequency and second harmonic generation (SHG) of 3R-MoS₂ with various thickness - from monolayer (∼0.65 nm) to bulk (∼1 µm) - we present the first measurement of the SHG coherence length (∼530 nm) at 1520 nm and achieve record nonlinear optical enhancement from a van der Waals material, > 104 stronger than a monolayer. It is found that 3R-MoS₂ slabs exhibit similar conversion efficiencies of lithium niobate, but within propagation lengths that are more than 100-fold shorter at telecom wavelengths. Furthermore, along the extraordinary axis, we achieve broadly tunable SHG from 3R-MoS₂ in a waveguide geometry, revealing the coherence length in such structure for the first time. We characterize the full refractive index spectrum and quantify both birefringence components in anisotropic 3R-MoS₂ crystals with near-field nano-imaging. Empowered with these data we assess the intrinsic limits of the conversion efficiency and nonlinear optical processes in 3R-MoS₂ attainable in waveguide geometries.

Abstract

Nonlinear frequency conversion provides essential tools for light generation, photon entanglement, and manipulation. Transition metal dichalcogenides (TMDs) possess huge nonlinear susceptibilities and 3R-stacked TMD crystals further combine broken inversion symmetry and aligned layering, representing ideal candidates to boost the nonlinear optical gain with minimal footprint. Here, we report on the efficient frequency conversion of 3R-MoS2, revealing the evolution of its exceptional second-order nonlinear processes along the ordinary (in-plane) and extraordinary (out-of-plane) directions. Along the ordinary axis, by measuring difference frequency and second harmonic generation (SHG) of 3R-MoS₂ with various thickness - from monolayer (∼0.65 nm) to bulk (∼1 µm) - we present the first measurement of the SHG coherence length (∼530 nm) at 1520 nm and achieve record nonlinear optical enhancement from a van der Waals material, > 104 stronger than a monolayer. It is found that 3R-MoS₂ slabs exhibit similar conversion efficiencies of lithium niobate, but within propagation lengths that are more than 100-fold shorter at telecom wavelengths. Furthermore, along the extraordinary axis, we achieve broadly tunable SHG from 3R-MoS₂ in a waveguide geometry, revealing the coherence length in such structure for the first time. We characterize the full refractive index spectrum and quantify both birefringence components in anisotropic 3R-MoS₂ crystals with near-field nano-imaging. Empowered with these data we assess the intrinsic limits of the conversion efficiency and nonlinear optical processes in 3R-MoS₂ attainable in waveguide geometries.