Ultrasensitive Polarization-Resolved Probing of Transient Dynamics in MoS$_2$ on Silicon Nitride Microresonators

TL;DR

This paper introduces an ultrasensitive, polarization-resolved technique to probe transient optical dynamics in MoS₂ on silicon nitride microresonators, revealing both rapid and slow optoelectronic effects with high sensitivity.

Contribution

The study develops a novel polarization-sensitive pump-probe method that captures transient signals in 2D materials integrated with microresonators, surpassing traditional techniques in sensitivity and temporal resolution.

Findings

Detected rapid carrier-induced nonlinear optical shifts.

Observed slower thermo-optic transients.

Enabled polarization-dependent transient measurements.

Abstract

We present an ultrasensitive technique for probing transient optical changes in atomically thin molybdenum disulfide (MoS$_2$) layers integrated onto silicon nitride (Si$_3$N$_4$) ring resonators. The MoS$_2$ is illuminated by a femtosecond laser, while a tunable near-infrared (NIR) continuous-wave laser probes the microresonator resonance. The NIR light polarization can be adjusted to either transverse electric (TE, parallel to the 2D material) or transverse magnetic (TM, perpendicular), a configuration that is impossible to achieve with conventional normal-incidence pump-probe techniques. By capturing the transmitted signal on a fast oscilloscope, we detect transient optical shifts with unprecedented sensitivity, observing phenomena over time scales ranging from picoseconds to microseconds. Our results reveal both a rapid, carrier-induced nonlinear optical shift in the resonance, and a slower thermo-optic transient. The ability to simultaneously measure these fast and slow dynamics offers new insight into the complex optoelectronic behavior of 2D materials when integrated with microresonators. This method provides a significant advance over traditional pump-probe approaches, enabling the detection of exceedingly small transient signals and opening new avenues for exploring the optical properties of atomically thin materials. Our findings highlight the potential of this approach for investigating polarization-dependent nonlinear effects, with applications in photonics, sensing, and optoelectronics.