Yellow diode-pumped lasing of femtosecond-laser-written Dy,Tb:LiLuF4 waveguide

TL;DR

This paper addresses the need for compact yellow-emitting light sources by developing a Dy,Tb codoped LiLuF4 waveguide laser written with femtosecond pulses. It demonstrates direct, diode-pumped operation in the yellow spectral band (568–578 nm) using depressed-cladding waveguides and a half-ring surface geometry, achieving lasing at multiple wavelengths with appreciable slope efficiencies. The work reports a maximum output power of 86 mW at 574 nm and 100 mW at 578 nm, with a peak slope efficiency of 19%, and it validates a propagation-loss figure of around 0.07 dB/cm via Findlay–Clay analysis. Collectively, the results establish Dy-doped fluoride-based waveguide lasers as viable, scalable yellow sources and suggest pathways for further power scaling through resonant pumping and monolithic cavity integration for metrological and aerospace applications.

Abstract

In this article we report the fabrication of a diode-pumped Dy,Tb:LiLuF4 waveguide laser operating in the yellow region of the visible spectrum. The circular depressed-cladding waveguides have been fabricated by direct femtosecond laser writing, and showed propagation losses as low as 0.07 dB/cm. By employing these structures, we obtain a maximum output power of 86 mW at 574 nm from a 60 μm diameter waveguide, and a highest slope efficiency of 19% from a 80 μm diameter depressed cladding waveguide. In addition, we demonstrate lasing at 574 nm from a half-ring surface waveguide, with a maximum output power of 12 mW. Moreover, we also obtained dual wavelength operation at 568-574 nm, with a maximum output power of 15 mW, and stable lasing at 578 nm, with an output power of 100 mW. The latter wavelength corresponds to the main transition of the atomic clock based on the neutral ytterbium atom. To the best of the authors' knowledge, this is the first demonstration of a yellow waveguide laser based on Dy-doped materials.

Figures (7)

• Figure 1: Polarized absorption spectra of Dy,Tb:LLF. Resolution of 0.09nm.
• Figure 2: Microscope image of WG2 (left, 80µm diameter) and WG3 (right, 80µm diameter, half waveguide) waveguide cross sections. The crystallographic axes are common to both pictures. Scale bars correspond to 20µm.
• Figure 3: Schematics of the whole setup. DIODE is the collimated pump diode, HW are the two half-wavelength plates, PBS is the polarizing beam splitter, FL is the focusing lens, IC is the input coupler, CRYSTAL is the Dy,Tb :LLF crystal, OC is the output coupler, CLL is the collection lens, LP is the long pass dielectric filter, and DET represents the various instruments employed to analyze the laser beam.
• Figure 4: Data, best fit, and intensity profiles for the laser operation of WG1 at 574nm. The abscissa reports the pump power coupled in the waveguide.
• Figure 5: Emission spectra of the single and dual-wavelength operation of the yellow DyTb-waveguide laser. Resolution of 1nm.