Second-harmonic generation to green using ultrafast fibre source and femtosecond written periodically poled waveguide

Optical waveguides in crystalline dielectric materials produced by femtosecond‐laser micromachining

“…The fs‐laser inscription has been applied to birefriengent KTP with Type II dual‐line approach as well as Type III cladding configuration . In PPKTP, only Type II structures have been fabricated . The Type II waveguides in KTP have a propagation loss around 0.8 dB/cm, supporting both TE‐ and TM‐polarization modes .…”

“…For the QPM SHG, in Type II PPLN waveguides a high value of η = 58% has been achieved, with 59 W output peak power of 532‐nm light . For PPKTP, η reached a maximum value as high as 47.4% and a peak power of green light of 252 W was generated . In addition, the SHG of near‐IR light under pulsed laser pump has been realized in a PPLN Type II waveguide .…”

“…In waveguides, the second‐harmonic or higher‐order generation may be realized with enhanced efficiencies with respect to the bulks. For fs‐laser inscribed waveguides, most of the work focuses on the second‐harmonic generation . The conversion efficiency, however, depends not only on the bulk nonlinear features but also on the guiding properties of the structures.…”

“…The fs‐laser micromachined waveguides have been used to realize SHG of light in a wavelength region from ∼400 to 790 nm . Table summarizes the results obtained from the literature for SHG in fs‐laser micromachined crystal waveguides.…”

Ultrafast Laser Microprocessing of Transparent Dielectrics. New Schemes for the Fabrication of Photonic Devices

“…Waveguides based in Type II modifications have important characteristics, for example, the core is located in regions between the damaged tracks, therefore the material of the core is not significantly affected, as a consequence, the luminescence and nonlinear properties of the material in that zone are well preserved. These characteristics make of this waveguides the most used for the fabrication of active devices such as waveguide lasers [88][89][90][91][92][93][94][95] and frequency converters in both CW and pulsed laser regimes [96][97][98][99][100]. It should be to pointed it out that in this case the mechanisms responsible for the change in the refractive index are well understood [88] in comparison with waveguides based in Type I modifications.…”