Low-loss fs-laser-written surface waveguide lasers at >2  µm in monoclinic Tm³⁺:MgWO₄

Abstract

Surface channel waveguides (WGs) based on a half-ring (40–60-µm-diameter) depressed-index cladding (type III) geometry are fabricated in monoclinic Tm 3 + : MgWO 4 by femtosecond (fs) laser writing at a repetition rate of 1 kHz. The WGs are characterized by confocal laser microscopy and μ -Raman spectroscopy. A Tm 3 + : MgWO 4 WG laser generates 320 mW at ∼ 2.02 µ m with a slope efficiency of 64.4%. The WG emits a transverse single-mode and linear polarization ( E | | N m ). A remarkable low loss of &lt;<!-- 0.1 dB / cm is measured for the WG. Vibronic laser emission at ∼ 2.08 µ m is also achieved.

Femtosecond laser-inscribed optical waveguides in dielectric crystals: a concise review and recent advances

“…207 In addition, their group has demonstrated a low-loss (<0.1 dB∕cm) waveguide laser in a Tm 3þ ∶MgWO 4 crystal at ∼2.02 μm with a slope efficiency of 64.4%. 211 Also, in the multi-GHz operation regime, 5.9-and 7.8-GHz QML waveguide lasers at ∼2 μm have been successfully achieved in Ho 3þ ∶YAG 212 and Tm : YAG, 209 respectively. Cr:ZnS is another host medium for MIR laser generation.…”

Femtosecond Laser-Fabricated Photonic Chips for Optical Communications: A Review

“…One is that the optical density in the waveguide is much greater than that of the bulk material, which enhances the laser characteristics and nonlinear characteristics of the material itself. Hence, better laser performance (low threshold, high gain and oblique efficiency) and more efficient nonlinear frequency conversion efficiency [6][7][8] can be achieved. The other is that the optical waveguide can guide the light wave to carry out long-distance diffraction-free propagation in the medium, forming and connecting optical elements to build a highly compact integrated optical path device [9].…”