# Camera detection and modal fingerprinting of photonic crystal nanobeam resonances

## TL;DR

This paper introduces a method to identify and distinguish resonance modes in photonic crystal nanobeam cavities using far-field scattering profiles, improving detection accuracy and signal-to-noise ratio in nanophotonic device characterization.

## Contribution

It demonstrates the use of resonance scattering as a fingerprint for mode identification and enhances detection SNR by spatially isolating emission near the cavity.

## Key findings

- Resonance scattering profiles can identify mode order.
- SNR improved by approximately 19 dB.
- Method applicable to nanophotonic device characterization.

## Abstract

We demonstrate in simulation and experiment that the out-of-plane, far-field scattering profile of resonance modes in photonic crystal nanobeam (PCN) cavities can be used to identify resonance mode order. Through detection of resonantly scattered light with an infrared camera, the overlap between optical resonance modes and the leaky region of k-space can be measured experimentally. Mode order dependent overlap with the leaky region enables usage of resonance scattering as a "fingerprint" by which resonant modes in nanophotonic structures can be identified via detection in the far-field. By selectively observing emission near the PCN cavity region, the resonant scattering profile of the device can be spatially isolated and the signal noise introduced by other elements in the transmission line can be significantly reduced, consequently improving the signal to noise ratio (SNR) of resonance detection. This work demonstrates an increase in SNR of ~19 dB in out-of-plane scattering measurements over in-plane transmission measurements. The capabilities demonstrated here may be applied to improve characterization across nanophotonic devices with mode-dependent spatial field profiles and enhance the utility of these devices across a variety of applications.