Abstract
Low-loss depressed cladding waveguide architecture is highly attractive for improving the laser performance of waveguide lasers. We report on the design and fabrication of the "ear-like" waveguide structures formed by a set of parallel tracks in neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal via femtosecond laser writing. The obtained "ear-like" waveguides are with more symmetric mode profiles and lower losses by systematically comparing the guiding properties of two kinds of normal cladding waveguide. Efficient waveguide lasers are realized based on the designed structure in both continuous wave and pulsed regimes. Combined the high-gain from cladding waveguide and special "ear-like" structure, a passively fundamentally Q-switched laser with the narrow pulse width and the high repetition rate has been obtained by using tin diselenide (SnSe2) as saturable absorber.
Highlights
Optical waveguides are far more than merely connecting elements between integrated optical components
This design is an evolved scheme of the solution firstly presented by Okhrimchuk et al [22], the present approach being based on a smart combination of the standard Femtosecond laser direct writing (FsLDW) double-line and depressed cladding waveguides
The crystal wafer is placed on a motorized XYZ micro-positioning stage which allows for precise translation of the sample at a constant velocity (0.5 mm/s in this work to minimize the stress effect induced by laser pulses) with respect to the incident laser beam
Summary
Optical waveguides are far more than merely connecting elements between integrated optical components. Femtosecond laser direct writing (FsLDW), which is a rapidly evolving technology, exploits tightly focused femtosecond laser pulses to modify the optical properties of a small volume inside a transparent material, inducing localized and controllable refractive index modification in a direct procedure without using any patterned masking [11] Such a technology allows monolithic and sophisticated waveguide fabrication in a very flexible manner [12]. In this work we investigate the properties of depressed-cladding waveguide geometry with an “ear-like” structure, in order to enhance the optical confinement of light field This design is an evolved scheme of the solution firstly presented by Okhrimchuk et al [22], the present approach being based on a smart combination of the standard FsLDW double-line and depressed cladding waveguides. To the best of our knowledge, this pulse duration is the shortest ever reported for passive Q-switched bulk lasers based on SnSe2 SA
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