One of the most efficient ways to prepare nonlinear optical polymer channel waveguides is by photobleaching. To control the index profile precisely and to design and improve the performance of active electro-optical devices, modeling of the photobleaching process is important. We report our phenomenological bleaching model, which uses a stretched exponential time dependency technique that predicts the index profile for polymer channel waveguides and present design rules for active optical switches and modulators. One way to verify the bleaching model is to calculate the effective index and compare this with our measured effective index obtained with prism-coupling techniques. The bleaching model shows good agreement with experiments.
We report studies on UV-photobleached optical channel waveguides in nonlinear optical polymer films. The nonlinear optical polymer used is poly(methyl methacrylate)/DR1 side-chain polymer. The effective indices of the channel waveguides are measured with the prism-coupling technique, along with the effective indices of bleached and unbleached polymer films. The effective-index method was used to predict the effective indices of the channel waveguides from measurements of the slab waveguides, without detailed knowledge of the index distributions in the polymer films. Some local stress-related effects on the boundaries of the channel waveguides caused by the UV-bleaching process are identified by comparison between direct channel measurement and prediction. It is found that the technique used in this study can be employed to predict the performance of channel waveguides processed such that they have no excessive internal stress distributions.
This paper on the reports design, fabrication and position monitoring of a micro electromagnetic linear actuator. The actuator consists of stator, slider, guide, sensors and affiliated jigs. Actuation is achieved through ampere force between two phase micro-coils (copper) on the stator and permanent magnets (thick NdFeB film) on the slider. During the slider’s movement in the guide slot, tunnelling magneto-resistance (TMR) sensors are utilized to sense the magnetic field to realize position monitoring. TMR is chosen because it owns advantages of small size, large sensitivity and easy integration with micro devices. Purpose of this research is to report the micro fabrication of thick magnet films and testify the possibility of using TMR as position monitoring sensors. Actuators are fabricated by micro-electro-mechanical system process (stator and guide) and precise machining (slider and jigs). Surface magnetic field generated by the slider, driving characteristics of the actuator as well as the position monitoring capabilities of TMR elements are simulated and experimented, respectively. The slider attains 60 mm s−1 speed by sinusoidal input signal at 300 Hz frequency and 0.2 A current magnitude. Actuation bandwidth is between 300 Hz and 500 Hz at open loop condition. The maximum position monitoring error in present work is 2.2% with 101 μm value for 4.5 mm stroke.
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