Femtosecond laser written stress-induced Nd:Y3Al5O12 (Nd:YAG) channel waveguide laser

Abstract

Single tracks and pairs of tracks were written into undoped and Nd-doped YAG crystals using a commercial femtosecond laser system delivering pulses with pulse duration of 140 fs and pulse energies up to 10 mu J. The pulses were focused by a 50x microscope objective below the surface of the crystals. Due to the elasto-optical effect, stress-induced birefringence was observed in domains surrounding the single tracks and between the pairs of tracks. Waveguiding was demonstrated in certain channels in these domains. To investigate the underlying guiding mechanism highly selective chemical etching of the modified material was performed with etching rates up to 5 mu m/h. Pumped at 808 nm, laser operation at a wavelength of 1064 nm was achieved. The maximum output power was 25.5 mW at 261 mW of launched pump power with a slope efficiency of 23%

Femtosecond Fabrication of Waveguides in Ion-Doped Laser Crystals

“…Refractive index profile of the waveguide recorded by QPm technique (http://www.iatia.com.au) under observation in the direction of femtosecond laser beam propagation is shown in Fig.3. The 1 kHz Ti:Sapphire laser always produces a negative PRICE in YAG single crystals (Okhrimchuk, 2005(Okhrimchuk, -a, 2005Siebenmorgen, 2009). It was reported that in the ceramic YAG doped with 2 at.% of Nd 3+ ions PRICE is negative too (Torchia, 2008).…”

“…It was reported that in the ceramic YAG doped with 2 at.% of Nd 3+ ions PRICE is negative too (Torchia, 2008). However there is refractive index increase in the area closely adjacent to a track (Dubov, 2004;Siebenmorgen, 2009) that is due to elasto-optical effect. The waveguide is produced due to this phenomenon in these works.…”

“…Although PRICE is negative inside tracks, mechanical stress induced between them provides positive PRICE. This way a single mode waveguide with almost circle mode profile was manufactured both in single crystal and in ceramic YAG (Torchia, 2008;Siebenmorgen, 2009). In this design waveguide core is the stressed area which is not exposed by the femtosecond beam.…”

“…Thus a waveguide is usually created in the area adjacent to tracks written by femtosecond beam. Since in this case waveguiding is due to an indirect effect accompanying femtosecond modification of crystal lattice, magnitude of refractive index change in the waveguide is not so high as in glass waveguides and does not exceed 1*10 -3 (Nejadmalayeri, 2005;Torchia, 2008;Siebenmorgen, 2009;Silva, 2010;Bookey, 2007;. This value is not enough to build compact waveguide lasers with diode pumping.…”

Raman and fluorescence correlative microscopy in polarized light to probe local femtosecond laser-induced amorphization of the doped monoclinic crystal LYB:Eu

“…Since the LYB:Eu is a potential laser crystal [10], these observations are of strong interest when considering possibilities to tune both structural and optical properties of this material by direct laser writing, especially for weaker crystal modifications related to waveguide writing for laser amplification applications [11][12][13][14][15]. Moreover, since such crystal is a low symmetry crystal, intensity thresholds for laser-induced modifications should significantly depend on the considered crystal orientation [16].…”