Two-dimensional finite-difference time-domain simulation for rewritable optical disk surface structure design.

A novel two-dimensional finite-difference time-domain simulation for treating the interaction of a focused beam with a rewritable optical disk is detailed and experimentally validated. In this simulation, the real material properties of the rewritable multilayer stack and the aperiodic nature of the disk topography are considered. Excellent agreement is obtained between calculated and measured push-pull tracking servosignals for magneto-optical disks with pregrooves and infinite-length preformat pits. To demonstrate the utility of the simulation as a design tool, the design process for a 0.9-µm track pitch, continuous, composite servoformat magneto-optical disk is given.

All-optical switching in long-period fiber gratings.

Nonlinear pulse propagation in long-period fiber gratings is studied with a mode-locked Q -switched laser pulse approximately 80ps in duration at a wavelength of 1.05 microm . Optical switching, pulse reshaping, and optical limiting are found at intensities in the range of 1-20 GW/cm(2).

Heating mechanisms in a near-field optical system.

A finite-difference-time-domain and two finite-difference-thermal models are used to study various heating mechanisms in a near-field optical system. It is shown that the dominant mechanism of sample heating occurs from optical power that is transferred from the probe to a metallic thin-film sample. The optical power is absorbed in the sample and converted to heat. The effects of thermal radiation from the probe 's coating and thermal conduction between the probe and the sample are found to be negligible. In a two-dimensional waveguide with TE polarization, most of the optical power is transferred directly from the aperture to the sample. In a two-dimensional waveguide with TM polarization, there is significant optical power transfer between the probe 's aluminum coating and the sample. The power transfer results in a wider thermal distribution with TM polarization than with TE polarization. Using computed temperature distributions in a Co -Pt film, we predict the relative size of thermally written marks in a three-dimensional geometry. The predicted mark size shows a 30 % asymmetry that is due to polarization effects.

Long-period fiber-grating-based gain equalizers.

Long-period fiber gratings are used to f latten the gain spectrum of erbium-doped fiber amplifiers. A broadband amplifier with <0.2-dB gain variation over 30 nm is presented. We also show that a chain of amplifiers can be equalized, leading to a bandwidth enhancement by a factor of 3.