# Room-Temperature Continuous-Wave Frequency-Referenced Spectrometer up to 7.5 THz

## TL;DR

This paper introduces a room-temperature, continuous-wave THz spectrometer covering 1-7.5 THz, enabling high-precision molecular spectroscopy with broad tunability and narrow linewidth, using a novel Cherenkov phase-matching scheme in a nonlinear crystal.

## Contribution

It presents a new, robust THz spectrometer technology that combines broad spectral coverage and high accuracy at room temperature, advancing molecular spectroscopy capabilities.

## Key findings

- Achieved continuous-wave THz generation up to 7.5 THz at room temperature.
- Demonstrated high-resolution spectroscopy with 10^-9 accuracy.
- Implemented Cherenkov phase-matching in a channel waveguide for THz generation.

## Abstract

The lack of coherent room-temperature sources in the whole terahertz spectral window (0.3-10 THz) has significantly hampered the growth of scientific and technological applications in this range. Among them, high-precision frequency measurements of molecular transitions play a central role but remain an open challenge. Here, room-temperature generation and detection of continuous-wave, broadly tunable, narrow-linewidth THz radiation are presented, and their application to high-resolution spectroscopy in the broad 1-7.5 THz spectral range is demonstrated. This result has been achieved by implementing a Cherenkov phase-matching scheme into a channel waveguide in a nonlinear crystal. This simple approach, entirely based on robust telecom technology, unprecedently merges in a single source an ultra-broad continuous-wave spectral coverage and a state-of-the-art accuracy (approximately 10-9) in molecular-transition-center determination.