Verification and comparison of a fast fourier transform-based full diffraction method for tilted and offset planes

The recent introduction of a fast Fourier transform- (FFT-) based method for calculating the Rayleigh-Sommerfeld full diffraction integral for tilted and offset planes permits high-speed evaluation of integrated optical systems. An important part of introducing a new calculational tool is its validation and an assessment of its limitations. The validity of the new FFT-based method was determined by comparison of that method with direct integration (DI) of the Rayleigh-Sommerfeld integral, a well-established method. Points of comparison were accuracy, computational speed, memory requirements of the host computer, and applicability to various optical modeling situations. The new FFT-based method is 228 times faster, yet requires 14 times more memory, than the DI method for a 500 mum by 500 mum real computational window.

Modeling photobleached optical polymer waveguides

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.

Corneal edema recovery dynamics in diabetes: is the alloxan induced diabetic rabbit a useful model?

PURPOSE

To compare the contact lens-induced corneal edema recovery dynamics of human subjects with type 1 diabetes with those of age- and sex-matched normal human subjects; to compare the human data with previously reported data from alloxan-induced diabetic rabbit.

METHODS

Corneal edema was induced by 2 hours of closed eye wear with a thick, soft contact lens. After removal of the contact lens, central corneal thickness measurements were made at 30-minute intervals for 3 hours using optical pachometry.

RESULTS

Human subjects with type 1 diabetes demonstrated a significantly slower rate of corneal edema recovery than age- and sex-matched human controls. The rate of corneal edema recovery found in this study for human subjects with type 1 diabetes is similar to that previously reported for alloxan-induced diabetic rabbits.

CONCLUSIONS

The decreased corneal edema recovery ability of the patient with type 1 diabetes suggests that care should be taken when prescribing contact lens use in these people. The similarity between corneal edema recovery rates in the human subject with type 1 diabetes and the alloxan-induced diabetic rabbit supports the use of the alloxan-induced diabetic rabbit as an animal model for studies of corneal edema recovery dynamics in diabetes.