Femtosecond laser writing of waveguides in zinc oxide crystals: fabrication and mode modulation

Abstract

We report for the first time on optical waveguides in zinc oxide (ZnO) crystals fabricated by femtosecond laser direct writing. The confocal Raman microscopy under 488 nm laser excitation is used to investigate the micro-modifications of the laser irradiation, and guiding properties are studied via the end-face coupling at 632.8 nm. The mode modulation has been achieved by the adjustment of laser writing parameters. A minimum propagation loss of ∼6 dB/cm is obtained for the double-line waveguide structures. A Y-branch waveguide beam splitter is also fabricated, reaching a splitting ratio of nearly 1:1. The original optical properties in the guiding region have been well preserved, according to the confocal Raman investigation, which suggests potential applications of the ZnO waveguides for integrated photonics and nonlinear optics.

Femtosecond Laser Writing of Photonic Crystal in LiNbO3 Crystal

“…Such losses result from the material absorption caused by the fs-laser, as well as the scattering losses resulting from the cladding tracks' imperfections (non-smoothness), as well as the imperfect locating of the tracks due to enhancing the mode leakage from the guiding region. The results are somewhat close to the references [9,21,24] despite different construction and engineering parameters, as well as, extending up to the wavelengths above 1.55μm for optimization; this indicates the validity of the performance. The numerical results presented in Fig.…”

Femtosecond Laser Writing of Photonic Crystal Fiber in LiNbO3 Crystal

“…Such losses result from the material absorption caused by the fs-laser, as well as the scattering losses resulting from the cladding tracks' imperfections (nonsmoothness), as well as the imperfect locating of the tracks due to enhancing the mode leakage from the guiding region. The results are somewhat close to the refs [9,21,24] despite different construction and engineering parameters, as well as, extending up to the wavelengths above 1.55μm for optimization; this indicates the validity of the performance.…”