# Single-Particle Photothermal Microscopy Using On-Chip Silicon Nitride Microring Resonators

## TL;DR

This paper explores using silicon nitride microring resonators for single-particle photothermal microscopy, demonstrating its potential through experiments and simulations.

## Contribution

The study introduces on-chip silicon nitride microring resonators for single-particle photothermal microscopy and validates their performance.

## Key findings

- Absorption cross-section per atom values for carbon nanotubes match literature values.
- Finite-element simulations reveal thermal gradients relevant to the MRR geometry.
- The planar MRR geometry's benefits and drawbacks for single-particle microscopy are discussed.

## Abstract

Optical microresonators confine light in time and space,
enabling
high sensitivity for the detection of small thermal perturbations.
We utilized these properties and investigated on-chip integrated silicon
nitride microring resonators (MRRs) for single-particle photothermal
microscopy. We calibrate the technique using individual nonphotoluminescent
carbon nanotubes and determine values for absorption cross-section
per atom that agree with literature values. Finite-element simulations
are performed to track all relevant thermal gradients. The combination
of experiment and simulation allows for discussion of the benefits
and drawbacks of the planar MRR geometry for single-particle microscopy.