Thermal fiber modification doubles low-noise white laser range

A team at the Technical University of Denmark has demonstrated a method to double the usable wavelength range of an ultra-low-noise supercontinuum laser, often called a white laser because it emits a broad, continuous spectrum. Published in Optica, the study shows a single-fiber system spanning from 0.86 to 2.90 micrometers, nearly twice the spectral range previously achieved by comparable low-noise sources.

Supercontinuum sources are used in medical imaging, environmental gas detection, and spectroscopy, but their utility has been limited by a trade-off: broader spectra typically come with higher noise fluctuations that reduce sensitivity. The DTU researchers bypassed this limitation using what they call thermal dispersion engineering.

Instead of splicing different fiber types together to shape and compress light pulses — a process that can introduce losses and complexity — the team heated a short section of a single optical fiber. The thermal exposure altered the fiber's internal properties, enlarging the core and reversing the dispersion in that segment.

This modification compressed the light pulses as they passed through, producing shorter, more intense pulses that generated a much broader spectrum while keeping noise at an exceptionally low level. Postdoc and first author Andrea Arduin described the approach as letting the fiber do the work in a clean, controlled way.

The extended reach into the infrared, where many molecules have strong spectral signatures, could improve the speed and sensitivity of gas sensing and spectroscopic analysis. In medical imaging, steadier light may yield clearer images and shorter scan times.

The researchers view the work as a demonstration of a broader design principle: incorporating functions directly into the fiber rather than building increasingly complex external systems. They are now exploring whether the same thermal engineering approach can be applied to other wavelengths and fiber platforms.

The study, titled "Doubling the bandwidth of low-noise supercontinuum through fiber-integrated linear pulse compression," appears in Optica (2026) with DOI 10.1364/optica.595939.