Deep-red planar waveguide laser operation of Eu³⁺:KY(WO₄)₂ layers

Area of Science:

• Photonics and Laser Technology
• Materials Science
• Solid-State Physics

Background:

• Development of efficient solid-state lasers operating in the deep-red spectrum is crucial for various photonic applications.
• Europium-doped materials offer potential for red emission due to their characteristic luminescence properties.

Purpose of the Study:

• To report the first deep-red europium planar waveguide laser.
• To investigate the performance and properties of Eu:KY(WO4)2 epitaxial layers for laser applications.

Main Methods:

• Epitaxial growth of 30-µm thick, heavily-doped 11.5 at.% Eu:KY(WO4)2 layers on undoped substrates using liquid phase epitaxy with K2W2O7 solvent.
• Characterization of morphology, vibronic, and spectroscopic properties of the grown layers.
• Optical pumping of the waveguide laser with a 532 nm green laser to evaluate output power, slope efficiency, and threshold.

Main Results:

• Achieved a maximum output power of 7 mW at 704.7 nm with a slope efficiency of 9.5% and a laser threshold of 21 mW.
• Demonstrated low waveguide propagation losses of 0.05 dB/cm.
• Measured a stimulated-emission cross-section of 1.76 × 10^-20 cm^2 for the 5D0 → 7F4 transition and a luminescence lifetime of 472 µs.

Conclusions:

• Successfully fabricated and demonstrated the first deep-red europium planar waveguide laser.
• The Eu:KY(WO4)2 epitaxial layers exhibit promising optical properties for efficient deep-red laser operation.
• Low propagation losses and high stimulated-emission cross-section indicate potential for integrated optics and advanced laser systems.