A detailed investigation of surface acoustic wave (SAW) propagating in x-cut y propagation lithium niobate (LiNbO<sub>3</sub>) for integrated acousto-optic tunable filters (IAOTF) is reported in this paper. With getting curves of velocities, the walk-off angular (the angular between the power-flux vector and the propagation direction) can be obtained by the cubic spline interpolation method. The electromechanical coupling constant curve is given. Now, an optimal configuration of IAOTF has been designed, in which the direction of interdigital transducer should be inclined about 4.18°.
A numerical approach based on the finite element - artificial transmitting boundary method is newly formulated for suppressing the sidelobe of integrated acousto-optic tunable filters with weighted coupling on a piezoelectric substrate. We use cosine and Gaussian weighting functions and obtained relevant response curves of TE-TM mode conversion efficiency. The result shows that the sidelobe can be efficiently suppressed by transforming the weighting function. Conversion of Gaussian weighting function is better than the one of cosine weighting function. The result is agreed with other references.
Based on the coupled-mode theory, Cherenkov second harmonic generation (CSHG) from a channel waveguide has been analyzed and discussed in detail. The conversion efficiency with only conversion depletion and the conversion efficiency with conversion depletion and propagation loss are obtained respectively, the results show that for the case of low conversion efficiency the conversion depletion can be neglected, but for the case of high conversion efficiency we must take conversion depletion into account, and the propagation loss must be taken into accounted for the both. Furthermore, the nonlinear phase shift (NPS) of the fundamental beam can be maximized by choosing appropriate grating period and appropriate waveguide thickness, which makes the configuration have a promising potential to realize all-optical switches.
Surface Acoustic Waves (SAW) propagating in a semi-infinite, anisotropic medium Lithium niobate(LiNbO<sub>3</sub>) are discussed. Integrated Acousto-Optical Tunable Filters (AOTF) have demonstrated wide application in various fields of laser technology, spectroscopy, optoelectronics and optical signal processing as well as wavelength division multiplexed (WDM) networks. We fabricated practical quasi-collinear integrated AOTF.
In an earlier approach, the 2-D acoustical field profiles on the substrate region are often calculated with BPM. In this
paper, we present a new approach based on the finite element - artificial transmitting boundary method and calculate the
2-D acoustical field on the substrate region.
In an earlier approach, the 2-D acoustical field profiles on the substrate region are often calculated with BPM. In this paper, we present a new approach based on the finite element - artificial transmitting boundary method and calculate the 2-D acoustical field on the substrate region.
An intersecting wave guide has a high extinction ratio, low loss, and wavelength independent characteristics for an acousto-optic tunable filters (AOTF). An oxide film-loaded surface acoustical wave guide (SAWG) has a strong confinement, excellent filter characteristics, and provide high design flexibility. In this paper we present a numerical method for an oxide film-loaded SAWG on a substrate. The result is agreed with the experiment.
The structure parameters and the Ti-diffusion parameters of the Integrated Optical Polarization Splitter (IOPS) affect the performance of the device greatly. By discussing these two factors quantificationally and comprehensively, we obtain a series of theoretical conclusions, which are important guidance to fabricate high-performance splitters. In particular, because of the limitation of the lithophotographical technique, there must be a flat at the end of the V-shape between the branch waveguides of the IOPS. The flat has crucial effect on the optimization procedure of the structure parameters. We have analyzed the interaction between the width of the flat and other parameters in an IOPS, which is not discussed in previous papers. Technological parameters' affection on the structure optimization is also discussed. In addition, we have fabricated a series of splitters, which have optimized TE and TM splitting ratios of 28dB and 25dB. Through experimental measurements, we have validatedthe theoretical calculations.
Integrated Acoustooptical Tunable Filters (AOTF) have great potential application in WDM optical networks because of some advanced properties, especially the unique property of simultaneous multiwavelength filtering. In this paper, we have developed time-dependent coupling mode equations with multiple acoustic waves travelling simultaneously. Take four acoustic waves as an example, we have shown some numerical results of conversion characteristics based on the developed coupling mode equations. We have also analyzed the fluctuation of the main peak, the center wavelength and the full width of half-maximum (FWHM) with respect to time. After discussing the drawbacks of the collinear AOTF in multiwavelength operation, especially the serious distort of conversion characteristics and the high crosstalk for narrow channel spacing, we propose for the first time that the conversion characteristics of AOTF can be improved by using quasi-collinear acoustooptical filters.