掺半导体玻璃波导的导波功率限制

首次利用阳极氧化法在掺半导体玻璃上制备了两端带有抛物耦合喇叭的4微米条宽沟道波导,用光栅耦合器将波长0.532微米的YAG倍频激光耦合进波导中,实现了输出光的功率限制.

POWER LIMIT OF GUIDED WAVE ON SEMICONDUCTOR-DOPED GLASS WAVEGUIDE

The channel waveguides with parabolic coupling horns(length of 1 cm and width of 4μm)were fabricated on semiconductor-doped glasses to get aperture match between the laser beam and the channel waveguide to decrease scattering loss of guided wave.The input photoresist grating couplers(period of 0.34μm)were made near the wider ends of parabolic-shaped horns.A top view of the device is shown in Fig.1.The fabrication processes of the sample used in this report weie as follows.1)Sputtering Al on the surface of semiconductor-doped glass;2)Spincoating Shipley AZ 1350 B photoresist on the Al thin film;3)4um width photoresist streak pattern mask with parabolic horns was produced on the Al thin film by means of standard photolithography;4)Except photoresist mask area,Al thin film was oxidized to become γ-Al2O3;5)Moving photoresist streak mask,Al surface of the Streak and both parabolic horns were exposed;6)The sample was immersed in phosphoric acid,then Al streak pattern with parabolic hoins was etched.As a result the streak pattern with parabolic horns was reproduced on the plane of semiconductor-doped glass,on the other hand,γ-Al2O3 was remained on the surface of glass as a thin film mask;7)Channel waveguide with parabolic coupling hoins of semicoductor-doped glass was fabricated with the aid of K+ ion exchange.8)Photoresist grating couplers were formed by writing holographic gratings in photoiesist.YAG laser pulses(with duration of 100 ps and frequency of 10 Hz)were coupled into the channel waveguide by grating coupler.The experimental Set-up is shown in Fig.2.The relation between output and input energy is shown in Fig.3.When YAG laser beam leached to channel waveguide through the coupling horn,the energy was obviously lost due to lower efficiency of grating nonlinear coupler and absorbing and scattering loss of the coupling horn.But the power density of guided wave entered the channel waveguide substantially grewn up to the two-dimension limitation of channel waveguide geometry.Power limit effect of device was mainly caused by both the dis-match of phase of input grating nonlinear coupling and the self-defocusing(n2<0)of channel waveguide.So the turning point of energy curve shown in Fig.2.might be shifted to lower threshold compared with planner waveguide.