飞秒激光在铽镓石榴石中的光刻光波导

Inscription of Waveguides in Terbium Gallium Garnet Using Femtosecond Laser

飞秒激光光刻是一种灵活的三维光子器件制作方法。由于铽镓石榴石具有法拉第效应,具有广泛的应用,利用中心波长为800nm,重复频率为1kHz的飞秒激光,在磁致旋光晶体铽镓石榴石中刻写了双线型和压低圆包层两种光波导,重构了激光诱导折射率改变的分布和测试了光波导的传输损耗。双线型波导具有偏振依赖的导光特性,圆包层波导则不存在偏振依赖的导光特性。对于双线型波导,横电(TE)模和横磁(TM)模相位完全失配,在外加磁场下,导模的偏振面不会发生旋转,光刻的圆包层波导的导模的偏振面能够发生磁致旋转。铽镓石榴石中的双线型和圆包层波导可以作为波导偏振器和磁旋光器件,在集成光学上有潜在的应用价值。

Femtosecond-laser-photolithography is a flexible avenue to fabricate three-dimensional photonic devices in transparent materials. Terbium gallium garnet is widely used because of its Faraday rotation. Femtosecond laser operated at 1 kHz with a central wavelength of 800 nm is used to write double line waveguide and circular depressed-cladding waveguide in terbium gallium garnet. The distributions of refractive index change are reconstructed，and propagation losses of the waveguides are measured. Only the double line waveguide shows polarization dependent optical guiding. The magneto-optic response of the waveguides is determined. The rotation of plane of polarization cannot be occurred in double line waveguide under externally applied magnetic field ascribed to the phase mismatch of transvers electric （TE） mode and transverse magnetic （TM） mode. For the circular depressed-cladding waveguide, the plane of polarization is rotated under applied magnetic field. The inscribed double line and circular depressed-cladding waveguide in terbium gallium garnet are candidates for waveguide polarizer and magneto-optic device respectively, which are valuable for integrated optics.