Feng Chen

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.

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.

Swift carbon ion irradiated Nd:YAG ceramic optical waveguide amplifier

A high-gain optical waveguide amplifier has been realized in a channel waveguide platform of Nd:YAG ceramic produced by swift carbon ion irradiation with metal masking. The waveguide is single mode at wavelength of 810 and 1064 nm, and with the enhanced fluorescence intensity at around 1064 nm due to the Nd(3+) ion emissions. In conjunction with the low propagation loss of the waveguide, about 26.3 dB/cm of the small signal gain at 1064 nm is achieved with an 18 ns pulse laser as the seeder under the 810-nm laser excitation. This work suggests the carbon ion irradiated Nd:YAG waveguides could serve as efficient integrated amplifiers for the signal amplification.

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.

Femtosecond-laser inscribed double-cladding waveguides in Nd:YAG crystal: a promising prototype for integrated lasers

We report on the design and implementation of a prototype of optical waveguides fabricated in Nd:YAG crystals by using femtosecond-laser irradiation. In this prototype, two concentric tubular structures with nearly circular cross sections of different diameters have been inscribed in the Nd:YAG crystals, generating double-cladding waveguides. Under 808 nm optical pumping, waveguide lasers have been realized in the double-cladding structures. Compared with single-cladding waveguides, the concentric tubular structures, benefiting from the large pump area of the outermost cladding, possess both superior laser performance and nearly single-mode beam profile in the inner cladding. Double-cladding waveguides of the same size were fabricated and coated by a thin optical film, and a maximum output power of 384 mW and a slope efficiency of 46.1% were obtained. Since the large diameters of the outer claddings are comparable with those of the optical fibers, this prototype paves a way to construct an integrated single-mode laser system with a direct fiber-waveguide configuration.

Q-switched pulse laser generation from double-cladding Nd:YAG ceramics waveguides

This work reports on the Q-switched pulsed laser generation from double-cladding Nd:YAG ceramic waveguides. Double-cladding waveguides with different combination of diameters were inscribed into a sample of Nd:YAG ceramic. With an additional semiconductor saturable absorber, stable pulsed laser emission at the wavelength of 1064 nm was achieved with pulses of 21 ns temporal duration and ~14 μJ pulse energy at a repetition rate of 3.65 MHz.

Channel waveguide lasers in Nd:LGS crystals

Optical channel waveguides have been produced in Nd:LGS laser crystals by using ultrafast laser inscription with a depressed cladding configuration. The cross sectional shape of the cladding waveguides is circular, surrounded by low refractive index tracks, which makes the channel waveguides as three-dimensional tubular structures. Under optical pump of 810 nm light, continuous-wave waveguide lasers at 1068 nm have been achieved at room temperature, with minimum lasing threshold of 54 mW, a maximum slope efficiency of 24% and a maximum output power of 16 mW.

Efficient waveguide lasers in femtosecond laser inscribed double-cladding waveguides of Yb:YAG ceramics

We report on the fabrication of depressed double-cladding waveguides in Yb:YAG ceramics by using femtosecond (fs) laser inscription. The double-cladding structures consist of tubular central structures with 30 μm diameter and concentric larger size tubular claddings with diameters of 100-200 μm. Continuous wave laser oscillations at wavelength of 1030 nm have been realized at room temperature through optical pump at 946 nm. The obtained maximum output power of the double-cladding waveguide lasers is ~80.2 mW with a slope efficiency as high as 62.9%.

Near-infrared lasers and self-frequency-doubling in Nd:YCOB cladding waveguides

A design of cladding waveguides in Nd:YCOB nonlinear crystals is demonstrated in this work. Compact Fabry-Perot oscillation cavities are employed for waveguide laser generation at 1062 nm and self-frequency-doubling at 531 nm, under optical pump at 810 nm. The waveguide laser shows slope efficiency as high as 55% at 1062 nm. The SFD green waveguide laser emits at 531 nm with a maximum power of 100 μW.

Continuous wave laser operation in Nd:GGG depressed tubular cladding waveguides produced by inscription of femtosecond laser pulses

Depressed tubular cladding waveguides have been produced in Nd:GGG crystals by using multiple inscription with femtosecond (fs) laser pulses. The guiding cores are located inside the tubular regions with cross-section diameters of 90-150 μm, which are surrounded by fs-laser induced low-refractive-index tracks. At room temperature continuous wave (cw) laser oscillations at wavelength of ~1063 nm have been realized through the optical pump at 808 nm. The slope efficiency of the cladding waveguide lasers is as high as 44.4% and the maximum output power at 1063 nm is 209 mW, which shows superior laser performance to the Type II stress induced Nd:GGG waveguides.