To suppress spatial hole burning, a direction related polarizer is adopted in Er-doped fiber ring laser gyroscope. To decrease the frequency drift caused by fluctuation of environment temperature, the polarization maintaining (PM) fiber is substituted for single mode fiber in the ring cavity. To obtain better reciprocity, two 90-deg rotations of PM fiber are introduced. Through the manners, the stable single-mode continuous wave lasers are observed simultaneously in both output directions. At last, better performance of the ring laser gyroscope based on Er-doped fiber is achieved.
Oxidizing thick porous silicon layer into silicon dioxide is a timesaving and low-cost process for producing thick silicon dioxide layer used in silicon-based optical waveguide devices. The solution of H<sub>2</sub>O<sub>2</sub> is proposed to post-treat thick porous silicon (PS) films. The prepared PS layer as the cathode is applied about 10mA/cm<sup>2</sup> current in mixture of ethanol, HF, and H<sub>2</sub>O<sub>2</sub> solutions, in order to improve the stability and the smoothness of the surface. With the low-temperature dry-O<sub>2</sub> pre-oxidizations and high-temperature wet O<sub>2</sub> oxidizations process, a high-quality SiO<sub>2</sub> 30 <i>μm</i> thickness layer that fit for the optical waveguide device was prepared. The SEM images show significant improved smoothness on the surface of oxidized PS thick films, the SiO<sub>2</sub> film has a stable and uniformity reflex index that measured by the prism coupler, the uniformity of the reflex index in different place of the wafer is about 0.0003.
The transfer matrix method combined with the effective index method is adopted to model the silica-based channel waveguide patterned by UV writing. The effective indexes of the graded index channel waveguides with different dimension are calculated. The maximal error of the effective index is less than 3×10-5. By this method, the number of the guided mode and the dimension range to guide certain modes can be obtained easily. Finally, the dimension range to guide a single mode is presented.
The effective index method (EIM) was adopted to model the channel waveguide patterned by the UV in photosensitive silica film. The effective indexes of the different dimension symmetrical and asymmetrical channel waveguides were calculated, and the resource of the error of the method was pointed out. At last, the dimension rang to propagate single mode was presented.
The combination of the effective index method and the transfer matrix method is adopted to calculate the indices of quasi-TE and quasi-TM modes in a UV-written channel waveguide, and the difference between the indices is used to characterize its birefringence. The dimensions, the ratio of width to thickness, the original index of the core layer, the index of the cladding, and the index profile are all taken into account. The simulation results indicate that the birefringence decreases with increasing dimensions, ratio of width to thickness, and indices of the cladding; on the contrary, increases of the original index of the core layer and of the vertical index gradient intensified the birefringence.
A 32-channel 50-GHz spaced arrayed-waveguide grating with our innovative configuration has been designed and fabricated. The performance of the device has been fully tested by using a tunable laser light source, optical power meter, and polarization controller. The insertion loss (IS) of the device is 4.2~7.4 dB. The crosstalk is about –28 dB. The IS uniformity is less than 3.2 dB. With our configuration, the performance of the device has been enhanced effectively and the difficulty in alignment process has been decreased obviously.