Heat-mode optical recording

The following properties are generally required for all heat-mode optical recording applications ... 

Optical Data Storage on Write-once Media 9.13.2.3.1 Heat-mode recording... 

In addition to heat emission, radiative decay processes may also occur, in which light is emitted due to a transition from the lowest excited singlet or triplet state to the ground state (fluorescence or phosphorescence). In order to effect rapid and efficient conversion of optical energy (the laser) to heat, dyes which exhibit low fluorescence and in which excitation primarily involves the singlet states are the most suitable for heat-mode recording.196... 

The DRAW disc which offers the facility to make one recording consists of a plastic substrate such as polycarbonate (PC) or polymethylmethacrylate (PMMA) and a recording layer made in amorphous colourants. The thickness of the recording layer is approximately 30-100 nm. The principle of the optical DRAW disc memory, called heat mode system, is shown in Fig. 1. In this system, microscopic pits in the coloured recording layer of a disc are formed by thermal energy transformed from photo energy of a... 

Nematic and smectic side-chain LCP are suitable as optical data storage media. A particular technique is the heat-mode recording technique [75], By locally heating, an optical scattering center is generated. However, heat-mode recording has the disadvantages of slow response time and low resolution [19],... 

The idea to use this effect for reversible optical data storage goes back to Todorov [77,78] and Rings-dorf [79], which is now addressed as photo-mode recording. The advantage of photo-mode recording over heat-mode recording lies in superior resolution. 

Magneto-optical media An optical recording material in which marks are recorded using a thermomag-netic process. That is, the material is heated until the magnetic domains can be changed by the application of a modes magnetic field. This material is rewritable. 

The quantities a, c, f, F, r, and p are the thermal diffusivity, sound speed, heat capacity ratio, bulk viscosity coefficient, shear viscosity coefficient, and density of the sample, respectively and Eo, a, P and Cp are the energy fluence of the laser beam, the optical absorption coefficient, the volume expansion coefficient, and the isobaric heat capacity, respectively, of the fluid. Tlie first and second terms in Eq. 2 describe the time dependences of the thermal and acoustic modes of wave motion, respectively. Since the decays of the acoustic and thermal mode densities back to their ambient values take place on such different time scales (microsecond time scale for acoustic mode and millisecond time scale for thermal mode), they were recorded on the oscilloscope using different time bases. 

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