# Swept-wavelength mid-infrared fiber laser for real-time ammonia gas sensing

## TL;DR

This paper introduces a swept-wavelength mid-infrared fiber laser that enables real-time ammonia gas sensing with high sensitivity and fast acquisition, leveraging broadband dysprosium emission and acousto-optic tuning.

## Contribution

The paper presents a novel swept-wavelength mid-IR fiber laser using dysprosium and acousto-optic tuning for rapid, high-resolution gas sensing applications.

## Key findings

- Achieved electronically controlled wavelength sweep from 2.89 to 3.25 μm.
- Demonstrated ammonia absorption spectroscopy with 0.3 nm resolution.
- Real-time sensing with 40 ms acquisition time.

## Abstract

The mid-infrared (mid-IR) spectral region holds great promise for new laser-based sensing technologies, based on measuring strong mid-IR molecular absorption features. Practical applications have been limited to date, however, by current low-brightness broadband mid-IR light sources and slow acquisition-time detection systems. Here, we report a new approach by developing a swept-wavelength mid-infrared fiber laser, exploiting the broad emission of dysprosium and using an acousto-optic tunable filter to achieve electronically controlled swept-wavelength operation from 2.89 to 3.25 {\mu}m (3070-3460 cm^-1). Ammonia (NH3) absorption spectroscopy is demonstrated using this swept source with a simple room-temperature single-pixel detector, with 0.3 nm resolution and 40 ms acquisition time. This creates new opportunities for real-time high-sensitivity remote sensing using simple, compact mid-IR fiber-based technologies.