Abstract

3R-MoS2, a MoS₂ polytype with broken inversion symmetry, enables unique light-matter interactions and is promising for linear and nonlinear integrated photonics beyond the monolayer limit. Yet, systematic studies of its thickness-dependent reflectivity and its impact on harmonic generation are still lacking. Here, we introduce a non-destructive optical method to determine the thickness of 3R-MoS₂ flakes from reflectivity measurements, offering AFM-like precision with a mean bias of less than 2 nm, while being much faster and applicable to non-solid substrates such as PDMS, in the 3-200 nm range. Nonlinear characterization further reveals distinct thickness-dependent maxima in second- and third-harmonic generation (SHG / THG), with the first clear peak at ~200 nm. These maxima arise from Fabry-Pérot-type phase matching conditions mediated by the film thickness and can further be shaped by absorption.

Abstract

3R-MoS2, a MoS₂ polytype with broken inversion symmetry, enables unique light-matter interactions and is promising for linear and nonlinear integrated photonics beyond the monolayer limit. Yet, systematic studies of its thickness-dependent reflectivity and its impact on harmonic generation are still lacking. Here, we introduce a non-destructive optical method to determine the thickness of 3R-MoS₂ flakes from reflectivity measurements, offering AFM-like precision with a mean bias of less than 2 nm, while being much faster and applicable to non-solid substrates such as PDMS, in the 3-200 nm range. Nonlinear characterization further reveals distinct thickness-dependent maxima in second- and third-harmonic generation (SHG / THG), with the first clear peak at ~200 nm. These maxima arise from Fabry-Pérot-type phase matching conditions mediated by the film thickness and can further be shaped by absorption.

Abstract

3R-MoS2, a MoS₂ polytype with broken inversion symmetry, enables unique light-matter interactions and is promising for linear and nonlinear integrated photonics beyond the monolayer limit. Yet, systematic studies of its thickness-dependent reflectivity and its impact on harmonic generation are still lacking. Here, we introduce a non-destructive optical method to determine the thickness of 3R-MoS₂ flakes from reflectivity measurements, offering AFM-like precision with a mean bias of less than 2 nm, while being much faster and applicable to non-solid substrates such as PDMS, in the 3-200 nm range. Nonlinear characterization further reveals distinct thickness-dependent maxima in second- and third-harmonic generation (SHG / THG), with the first clear peak at ~200 nm. These maxima arise from Fabry-Pérot-type phase matching conditions mediated by the film thickness and can further be shaped by absorption.

Abstract

3R-MoS2, a MoS₂ polytype with broken inversion symmetry, enables unique light-matter interactions and is promising for linear and nonlinear integrated photonics beyond the monolayer limit. Yet, systematic studies of its thickness-dependent reflectivity and its impact on harmonic generation are still lacking. Here, we introduce a non-destructive optical method to determine the thickness of 3R-MoS₂ flakes from reflectivity measurements, offering AFM-like precision with a mean bias of less than 2 nm, while being much faster and applicable to non-solid substrates such as PDMS, in the 3-200 nm range. Nonlinear characterization further reveals distinct thickness-dependent maxima in second- and third-harmonic generation (SHG / THG), with the first clear peak at ~200 nm. These maxima arise from Fabry-Pérot-type phase matching conditions mediated by the film thickness and can further be shaped by absorption.