Theodore E. Batchman

Waveguide polarizers with hydrogenated amorphous silicon claddings.

We have fabricated TE- and TM-pass waveguide polarizers with polarization isolations of 42 and 35 dB, respectively. The devices were fabricated by the growth of hydrogenated amorphous silicon claddings on K(+)-Na(+) ionexchanged channel waveguides in glass. Cladding thicknesses were accurately tuned to permit optimum coupling of either a TE or a TM mode to the cladding. We have also demonstrated that a waveguide polarizer attenuation as high as 760 dB/cm can be measured by using a photothermal deflection technique.

Effect of polymer mixtures on the performance of PDLC films

Generally one type of polymer is used in the construction of polymer dispersed liquid crystal (PDLC) films. The authors tested the effect of incorporating an additional fluoropolymer in varying percentages on the electro-optic performance of PDLC films based on poly(methyl methacrylate). Compared to samples made from a single polymer, several correlations are noted, including a decrease in liquid crystal fall-time, an increase in rise-time, and an increase in the threshold voltage (Vt).

Improvement in the electro-optic response of PDLC films (Invited Paper)

We have investigated two approaches to improving the electro-optic performance of polymer dispersed liquid crystal (PDLC) films. One involves using a partially fluorinated epoxy based thermoset to serve as the PDLC binding matrix. Results indicate that this causes an enhanced phase separation of the liquid crystal which leads to significant changes in the contrast ratio and fall time of a PDLC film. The other approach involves using duel frequencies to enhance the electro-optic performance of another type of PDLC film. Studies suggest that the hysteresis effect can be minimized and the overall control of the electro-optic response can be greatly increased by adding a second high frequency component to the PDLC driving voltage.

Direct measurement of the electrogyratory effect in bismuth silicon oxide.

A direct measurement of the electrogyratory effect in bismuth silicon oxide is performed at wavelengths of 633, 543, and 442 nm. We experimentally measured the electrogyratory effect separately from the electro-optic effect. For externally applied electric fields ranging from 0 to 60 kV/cm, the contribution due to the electrogyratory effect is found to be negligible with respect to the contribution due to the electro-optic effect. Since devices employing bismuth silicon oxide typically require applied electric fields in this range, the electric field dependence of the rotary power is shown not to perturb the desired operation.

The effect of partial fluorination on the performance of epoxy based PDLC films

Abstract Changes in the electro-optic performance of polymer dispersed liquid crystal (PDLC) films caused by partial fluorination of the epoxy polymer binder have been investigated. The switching performance of the PDLC films was characterized by threshold voltage, rise time, fall time and contrast ratio. The results indicate that fluorine substitution in the polymer can cause a better phase separation, resulting in significant increases in the contrast ratio as well as large decreases in the fall time.

The effect of dual-frequency addressing on the electro-optic response of a PDLC film

Abstract The effect of using dual-frequency addressing in the reduction of the response time in polymer dispersed liquid crystal (PDLC) displays has been investigated. The utilization of a second high frequency component of the driving voltage enables an added control of the waveform not possible in a single frequency addressed system. The use of dual-frequency addressing, combined with some special driving techniques, opens up the possibility of controlling the response of PDLC displays in sweeping-mode operations.

In‐situ optimization of coupling between semiconductor claddings and dielectric waveguides

Coupling interactions between the low loss‐modes of dielectric waveguides and the high‐loss modes supported by semiconductor waveguide claddings are of prime importance in the design and fabrication of integrated optical photodetectors and polarizers. It is desirable to maximize energy transfer from dielectric waveguides to semiconductor claddings in order to achieve optimal operation of detectors and polarizers. We have experimentally verified that the intermodal coupling of light from a low‐loss dielectric guiding region to a highly absorbing semiconductor cladding region is periodic as a function of cladding thickness. Results were obtained by the in situ monitoring of output intensity during the growth and etching of hydrogenated amorphous silicon on polarization‐preserving, D‐shaped, optical fiber. Strong correlation exists between theoretical and experimental results for both TE and TM polarizations. The in situ, intensity monitoring technique allows for precise control of attenuation characteristic...

Electric‐field dependence of the photocarrier hopping mobility in bismuth silicon oxide

The photocarrier mobility of bismuth silicon oxide was measured through a time‐of‐flight technique. To determine the photocarrier transit time, a method of data analysis was applied that has been developed for transit time dispersion in amorphous solids. The universality of current shape typical of low‐mobility amorphous solids was observed and an electric‐field dependence of the photocarrier mobility in bismuth silicon oxide is now reported. In accordance with hopping conduction among localized band‐gap sites, the photocarrier mobility in bismuth silicon oxide decreases with increasing electric field.

Electro-optic performance of a PDLC film utilizing dual-frequency addressing

Several different types of polymer dispersed liquid crystal (PDLC) systems have been developed in recent years. The transmission characteristics of each type depend on the materials used, the method of construction, and the addressing technique used to drive the system. Greater control over the transmittance response as a function of time is important for many display operations. The effect of using dual-frequency addressing and pulsed mode dual frequency addressing in controlling the transmittance response of one type of PDLC film has been investigated. The results suggest that the gray scale inconsistency as well as the hysteresis effect can be reduced by utilizing the frequency dependence of the dielectric anisotropy of the liquid crystal.

Continuous mode operation of a PRIZ space-time light modulator

A conducting PRIZ device is fabricated and shown to exhibit the unique image processing features of edge detection, directional spatial filtering, and dynamic image selection. The active element is single crystal bismuth silicon oxide (Bi12SiO20 or BSO) . Auger electron spectroscopy (AES) and neutron activation analysis (NAA) techniques were applied to BSO to identify the impurities which contribute to the device operation.