All-optical polarization and amplitude modulation of second-harmonic generation in atomically thin semiconductors

Abstract

Second-harmonic generation is of paramount importance in several fields of science and technology, including frequency conversion, self-referencing of frequency combs, nonlinear spectroscopy and pulse characterization. Advanced functionalities are enabled by modulation of the harmonic generation efficiency, which can be achieved with electrical or all-optical triggers. Electrical control of the harmonic generation efficiency offers large modulation depth at the cost of low switching speed, by contrast to all-optical nonlinear devices, which provide high speed and low modulation depth. Here we demonstrate all-optical modulation of second-harmonic generation in MoS2 with a modulation depth of close to 100% and speed limited only by the fundamental pulse duration. This result arises from a combination of D3h crystal symmetry and the deep subwavelength thickness of the sample, it can therefore be extended to the whole family of transition metal dichalcogenides to provide great flexibility in the design of advanced nonlinear optical devices such as high-speed integrated frequency converters, broadband autocorrelators for ultrashort pulse characterization, and tunable nanoscale holograms.

Fabrication Technologies for the On‐Chip Integration of 2D Materials

“…By using an ionic liquid gate, reversible tuning of the carrier density (up to ≈30%) in bilayer NbSe 2 was achieved. [ 436 ] Gate‐tunable NLO responses, such as FWM, [ 125,437 ] harmonic generation, [ 438,439 ] difference frequency generation, [ 440,441 ] and nonlinear optical absorption, [ 442 ] have also been demonstrated. Figure a‐i shows a schematic strategy to tune the third‐harmonic generation (THG) and FWM in graphene via ion gel gate tuning of its doping level and resonant conditions.…”

Tuning exciton recombination rates in doped transition metal dichalcogenides

“…Besides the fundamental studies on the photophysics of excitons and related quasi-particles (charged excitons/trions, biexcitons, charged biexcitons/quintons etc.) in ultra-clean 2D quantum confined systems [3], TMDs also provide new exciting solutions for optoelectronic [4], valleytronic [5] and nonlinear optical [6,7] applications. In particular, the giant enhancement of the photoluminescence (PL) quantum yield (QY) in the monolayer limit [1] holds great promise for integrated, flexible and high-speed light emitting devices [8].…”

Superior Nonlinear Optical Response in Non‐Centrosymmetric Stacking Edge‐Rich Spiral MoTe2 Nanopyramids

“…Nonlinear optics, the key branch of optics, has been widely used in ultrafast lasers, optical modulators, imaging, pulse characterization, etc. [1][2][3][4][5][6][7][8][9][10] However, the current widely adopted nonlinear optical (NLO) materials are bulk crystals, such as beta barium borate (BBO), lithium niobate (LiNbO 3 ), and potassium titanyl phosphate (KTP), which can hardly satisfy the growing demands for miniaturization and integration of NLO devices on chips. Transition metal dichalcogenides (TMDs) are considerably attractive for fundamental optical studies at atomic scale, ranging from linear and nonlinear optics to nano-photonics due to their strong light-matter interaction, unique exciton effects, and tunable band gap.…”