# A Compact Millimeter-Wavelength Fourier-Transform Spectrometer

## TL;DR

This paper presents a compact, lightweight Fourier-transform spectrometer operating at millimeter wavelengths, optimized for high throughput and spectral resolution, with detailed design, simulation, and control software.

## Contribution

The paper introduces a novel, miniaturized millimeter-wave FTS with a simple design, high throughput, and detailed characterization, including simulation and software tools.

## Key findings

- Achieved spectral resolution of 4 GHz
- Constructed a compact FTS with volume 355x260x64 mm
- Validated performance through optical simulation and measurements

## Abstract

We have constructed a Fourier-transform spectrometer (FTS) operating between 50 and 330 GHz with minimum volume (355 x260 x64 mm) and weight (13 lbs) while maximizing optical throughput (100 $\mathrm{mm}^2$ sr) and optimizing the spectral resolution (4 GHz). This FTS is designed as a polarizing Martin-Puplett interferometer with unobstructed input and output in which both input polarizations undergo interference. The instrument construction is simple with mirrors milled on the box walls and one motorized stage as the single moving element. We characterize the performance of the FTS, compare the measurements to an optical simulation, and discuss features that relate to details of the FTS design. The simulation is also used to determine the tolerance of optical alignments for the required specifications. We detail the FTS mechanical design and provide the control software as well as the analysis code online.