Yuechen Jia

Femtosecond laser inscribed cladding waveguides in Nd:YAG ceramics: Fabrication, fluorescence imaging and laser performance

We report on the fabrication of depressed cladding waveguide lasers in Nd:YAG (neodymium doped yttrium aluminum garnet, Nd:Y3Al5O12) ceramics microstructured by femtosecond laser pulses. Full control over the confined light spatial distribution is demonstrated by the fabrication of high contrast waveguides with hexagonal, circular and trapezoidal configurations. The confocal fluorescence measurements of the waveguides reveal that the original luminescence features of Nd3+ ions are well-preserved in the waveguide regions. Under optical pump at 808 nm, cladding waveguides showed continuous wave efficient laser oscillation. The maximum output power obtained at 1064.5 nm is ~181 mW with a slope efficiency as high as 44%, which suggests that the fabricated Nd:YAG ceramic waveguides are promising candidates for efficient integrated laser sources.

Femtosecond laser micromachining of lithium niobate depressed cladding waveguides

We report on the fabrication and characterization of femtosecond laser micromachined depressed cladding waveguides in lithium niobate crystal. The cladding structures support two-dimensional guidance of light from the visible to the mid-infrared spectral regimes. Particularly, single-mode propagation of light at a wavelength of 4 μm has been achieved for the waveguides with diameter of 50 μm. It is also found that the thermal annealing treatment reduces the propagation loss lower than 0.5 dB/cm at 1.064 μm, exhibiting good transmission properties for photonic applications.

Monolithic crystalline cladding microstructures for efficient light guiding and beam manipulation in passive and active regimes

Miniature laser sources with on-demand beam features are desirable devices for a broad range of photonic applications. Lasing based on direct-pump of miniaturized waveguiding active structures offers a low-cost but intriguing solution for compact light-emitting devices. In this work, we demonstrate a novel family of three dimensional (3D) photonic microstructures monolithically integrated in a Nd:YAG laser crystal wafer. They are produced by the femtosecond laser writing, capable of simultaneous light waveguiding and beam manipulation. In these guiding systems, tailoring of laser modes by both passive/active beam splitting and ring-shaped transformation are achieved by an appropriate design of refractive index patterns. Integration of graphene thin-layer as saturable absorber in the 3D laser structures allows for efficient passive Q-switching of tailored laser radiations which may enable miniature waveguiding lasers for broader applications. Our results pave a way to construct complex integrated passive and active laser circuits in dielectric crystals by using femtosecond laser written monolithic photonic chips.

Ridge waveguide lasers in Nd:YAG crystals produced by combining swift heavy ion irradiation and precise diamond blade dicing

Ridge waveguides have been fabricated in Nd:YAG crystals by using ion irradiation and precise diamond blade dicing. Continuous-wave lasers at ~1064 nm have been realized in the ridge waveguides through optical pumping at 808 nm at room temperature. The ridge guiding structure shows superior lasing performance with respect to the planar counterpart with a slope efficiency of 43% and a maximum output power of 84 mW.

Efficient continuous-wave laser operation at 1064 nm in Nd:YVO 4 cladding waveguides produced by femtosecond laser inscription

Cladding waveguides have been produced in Nd:YVO4 crystals by using femtosecond laser inscription. Such structures are fabricated with circular cross sections and diameters of ~100-120 μm, supporting multi-mode guidance in the two orthogonal polarizations. At room temperature continuous wave laser oscillations at wavelength of ~1064 nm have been realized through the optical pump at 808 nm with slope efficiency as high as 65% and a maximum output power of 335 mW.

Ridge waveguide lasers in Nd:GGG crystals produced by swift carbon ion irradiation and femtosecond laser ablation.

We report on the fabrication of ridge waveguide in Nd:GGG crystal by using swift C(5+) ion irradiation and femtosecond laser ablation. At room temperature continuous wave laser oscillation at wavelength of ~1063 nm has been realized through the optical pump at 808 nm with a slope efficiency of 41.8% and the pump threshold is 71.6 mW.

Continuous wave ridge waveguide lasers in femtosecond laser micromachined ion irradiated Nd:YAG single crystals

Ridge waveguides have been fabricated in Nd:YAG single crystal by using femtosecond laser micromachining in an oxygen ion irradiated planar waveguide. The microphotoluminescence features have been found well preserved in the waveguide structures. Continuous wave lasers have been realized at 1.06 µm at room temperature in the ridge waveguide system with a lasing threshold of ~39 mW and a slope efficiency of 35%, which show superior performance to the planar waveguide.

Femtosecond-Laser-Inscribed BiB3O6 Nonlinear Cladding Waveguide for Second-Harmonic Generation

We report on the fabrication of a nonlinear cladding waveguide in BiB3O6 crystal by using femtosecond laser inscription. The waveguide (with a nearly circular cross section of 150 µm diameter) shows good guiding properties in two transverse polarizations. The guided-wave second-harmonic generation (SHG) at 532 nm green light has been realized under CW and pulsed wave pump at 1064 nm, based on the Type I birefringent phase matching configuration. The conversion efficiencies for CW and pulsed green laser SHG are 0.083 and 25%, respectively.

Simultaneous dual-wavelength lasers at 1064 and 1342 nm in femtosecond-laser-written Nd:YVO 4 channel waveguides

Dual-wavelength waveguide lasing at 1064 and 1342 nm corresponding to the 4F3/2→4I11/2 and 4F3/2→4I13/2 Nd transitions has been demonstrated in a femtosecond-laser-inscribed Nd:YVO4 channel waveguide. Under 808 nm optical pumping, the obtained laser thresholds at 1064 and 1342 nm were 180 and 210 mW, respectively. The laser slope efficiencies at 1064 and 1342 nm were found to be 15.6% and 1.7%, respectively.

Mid-infrared waveguides in zinc sulfide crystal

Depressed cladding optical waveguides have been fabricated in a zinc sulfide (ZnS) crystal by femtosecond laser inscription. The structures support single- or multi-mode guidance at the mid-infrared wavelength of ~4 μm. The two-dimensional refractive index profiles of the single-mode waveguides have been reconstructed, and the modal profiles of TE and TM modes were calculated numerically, that show very good agreement with the measured near-field modal profiles. The minimum propagation losses of the multimode cladding waveguides at 4 μm were ~1.1 dB/cm for the TE polarization and ~1.3 dB/cm for the TM polarization.