# Investigating the use of the hydrogen cyanide (HCN) as an absorption media for laser spectroscopy

## TL;DR

This paper explores hydrogen cyanide (HCN) as a cost-effective alternative to acetylene for laser spectroscopy in the 1.55 μm band, aiming to expand frequency coverage and improve traceable optical standards.

## Contribution

It investigates HCN's potential as a new absorption medium for laser spectroscopy, comparing it with acetylene and outlining its advantages for frequency standards.

## Key findings

- HCN offers a wider frequency span than acetylene.
- HCN is cost-efficient and readily available.
- Potential for HCN data to be included in traceable standards.

## Abstract

The laser spectroscopy is a fundamental approach for the realisation of traceable optical frequency standards. In the $1.55\,\mu$m wavelength band, widely used in telecommunications, the acetylene is the typical and the most widespread absorption media. We present our investigation of using the hydrogen cyanide (HCN) as a cost-efficient and readily available alternative, that also provides a wider frequency span (from $1527\,$nm to $1563\,$nm). We have compared the practical aspects of using new absorption media in comparison to existing experience with the acetylene with an outlook to carry out an independent measurement of the entire spectra. The results should contribute to the future inclusion of the HCN spectroscopic data into the Mise en pratique, thus allowing for the use of HCN as a reference for the realisation of traceable laser standards.