# Wavelength Tunable Pulsed Lasers Enabled by a Versatile Metafiber Functioning as Both Saturable Absorber and Filter

## TL;DR

A new laser design uses a single fiber-based component to tune wavelengths and generate pulses, solving issues with traditional hybrid systems.

## Contribution

A monolithic metafiber Fabry-Perot structure enables both saturable absorption and tunable filtering in a compact laser system.

## Key findings

- The metafiber Fabry-Perot structure achieves Q-switching in the telecommunication band.
- Dynamic wavelength tuning of approximately 10 nm is enabled via temperature and refractive index modulation.
- The design reduces coupling losses and eliminates complex alignment procedures.

## Abstract

Wavelength‐tunable pulsed lasers have garnered significant research interest due to their critical role in applications requiring precise spectral matching, such as wavelength‐division multiplexing and spectroscopic analysis. Although recent hybrid architectures integrating saturable absorbers with wavelength‐selective components have enabled notable progress, these systems remain constrained by two fundamental challenges: excessive coupling losses and complex alignment procedures. Here, a compact wavelength‐tunable pulsed laser configuration is presented that employs a monolithic fiber‐based component, effectively addressing the complexity and alignment issues inherent in conventional hybrid systems. By leveraging advanced manufacturing techniques, a 2D metafiber is integrated with a 3D Fabry‐Perot interferometer at the end facet of a single‐mode optical fiber, forming a metafiber Fabry‐Perot structure that simultaneously functions as both a saturable absorber and a tunable optical filter. Exploiting the versatile optical feedback provided by the Fabry‐Perot cavity, our design achieves Q‐switching operation in the telecommunication band and enables approximately 10 nm dynamic wavelength tuning through temperature/refractive index modulation. This work circumvents the structural complexity of traditional hybrid systems while ensuring stable laser operation, demonstrating a promising pathway for high‐performance wavelength‐tunable pulsed laser applications.

Schematic diagram of wavelength‐tunable pulsed laser based on metafiber‐FP (Fabry‐Perot). The alcohol solution is filled inside the FP cavity to simultaneously form a spectral filter and a saturable absorber. By adjusting the refractive index value and temperature inside the cavity, the tunable filtering effect is introduced to realize wavelength‐tunable pulsed laser generation.