# Off-axis parabolic mirror optics for polarized Raman spectroscopy at low temperature

## TL;DR

This paper introduces a novel low-temperature Raman spectroscopy detection system using an off-axis parabolic mirror that enables high numerical aperture, polarization control, and integration with scanning probe microscopy for advanced nanoscale analysis.

## Contribution

The paper presents a new optical setup based on a parabolic mirror for low-temperature Raman spectroscopy, combining high collection efficiency with compatibility for near-field and tip-enhanced techniques.

## Key findings

- Achieves a numerical aperture of approximately 0.85.
- Maintains polarization within 80-90% in far-field measurements.
- Allows integration with AFM/STM with less than 10% aperture loss.

## Abstract

We report the development of a detection optics for the integration of Raman scattering and scanning probe microscopy at low temperature based on a parabolic mirror. In our set-up half of the paraboloid mirror covers a solid angle of $\pi$ corresponding to a numerical aperture of N.A.\,$\approx 0.85$. The optical system can be used for far- and near-field spectroscopy. In the far field the polarizations can be maintained to within 80-90\%. In combination with a scanning microscope (AFM/STM), tunneling or near-field experiments are possible with less than 10\% loss of aperture. Our set-up provides ideal conditions for the future development of tip-enhanced Raman spectroscopy (TERS) at low temperature.