M.K. Loze

Temperature distributions in semi-infinite and finite-thickness media as a result of absorption of laser light.

A time-domain method is used to derive simple expressions for temperature distributions within media heated by a moving laser beam with a Gaussian power density profile. Various medium-absorption functions are considered. The solutions are given as single integrals with respect to time of simple functions. The expressions can be applied to multilayer media consisting of layers with different optical (light-absorbing) properties, provided that the layers have similar thermal properties. A number of optical recording examples have been examined in detail, and the results compared with those obtained by use of a more general (fast-Fourier-transform-based) approach.

Temperature distributions in laser-heated semi-infinite and finite-thickness media with convective surface losses

The temperature distributions produced within semi-infinite and finite-thickness media heated by a moving laser beam with a Gaussian power-density profile are examined by use of a time-domain method. Convective losses, described by Newtons law of cooling, from the medium surfaces are included. Various medium absorption models are considered. The solutions are given as single integrals with respect to time of simple functions. The resulting expressions have been used to examine the role of surface losses in information storage and medical applications. The role of convective losses in optical recording systems is found to be insignificant. However, for medical applications, combined convective and evaporative surface losses represent an important surface-heat-loss mechanism.

Temperature distributions in laser-heated biological tissue with application to birthmark removal

The time-dependent temperature distributions produced within thermally homogeneous media heated by a moving laser beam with Gaussian and uniform power density profiles are examined using a time-domain method based on Greens functions. Regions of finite length, width, and depth within the medium having exponential power absorption are considered. The temperature distribution is written as a single integral with respect to time of simple functions and the resulting expressions have been used to model the heating of blood vessels for birthmark (port-wine stain) removal. The temperature distributions obtained are in good agreement with those produced using Monte Carlo optical and finite difference thermal models.

A comparison of various methods for characterising the head-medium interface in digital magnetic recording

A simple model for the isolated replay pulse spectrum for a digital magnetic recording channel is considered. Various methods for determining the parameters characterizing it are described. Values for these parameters, which also characterize the head-medium interface, are obtained from various types of experimental data and compared with the theoretical predictions. >

The thermal performance of the MAMMOS disk structure

The temperature distribution in the MAMMOS disk structure is modelled. It is shown that the readout layer temperature is mainly determined by the heat generated by the absorption of power directly from the laser beam. In contrast, the record layer temperature is determined mainly by heat diffusing into it from the hot readout layer. The readout layer reaches the highest temperatures. The large temperature gradients in the readout layer should aid domain expansion during readout of data. The temperature gradients in the record layer seem poor, which may hinder the recording of very small marks. Marks recorded using the light intensity modulation method may have poor boundary regularity and show a large amount of internal fragmentation due to the presence of large demagnetizing fields in the TM-rich alloys typically used for the record layer.

Optimizing the recording performance of the MAMMOS disk structure

The recording performance of MAMMOS-type disks is investigated by computational modelling, and strategies for improving written bit shape and regularity are suggested. Laser power, record layer coercivity and record field waveform are found to be important in determining shape and regularity of recorded marks. The LP-MFM method is shown to be suitable for recording short marks with accurately located edges.

A MATLAB-based read/write model for magneto-optic recording

A comprehensive computational model describing the read and write processes in magneto-optic data storage has been developed. The model has been implemented using MATLAB software on a Pentium PC. The model is capable of predicting recorded bit shapes and readout pulse waveforms under a wide range of conditions (media properties, disc structure, readout optics etc.), yet requires only moderate computing power and runs using readily available and easy-to-use commercial software (MATLAB 4.2c),.

Computer simulation tools for the design and optimization of optical disk systems

This paper describes the development and application of software models for the design and optimization of the record, readout and data recovery processes in all commonly used optical disk storage formats.