Erasure Characteristics Research Articles

Thermal poling and ultraviolet erasure characteristics of type-III ultraviolet-grade fused silica and application to periodic poling on planar substrates

A periodically poled structure on type-III ultraviolet (UV)-grade planar fused silica was realized by periodic UV erasure of second-order nonlinearity of the thermally poled fused silica plate. Poling and UV-erasure characteristics are given. The second-order nonlinearity profile of thermally poled fused silica was found to correlate with a buried Gaussian function. The nonlinear depth, calculated by curve fitting Maker fringes assuming a step-like nonlinear profile, corresponded to the location of the 1/e peak in the buried Gaussian function. The etching rate in hydrofluoric acid of the UV-bleached thermally poled fused silica was found to be the same as that of unpoled fused silica along the direction of the poling field but was larger along the direction perpendicular to the poling field.

Parallel optical logic processor and bit slice-full adder using a single electron trapping device

A new method is proposed for implementing logic operations by using a single electron trapping (ET) device. Based on the storage and erasure characteristics of the device, each Boolean logic operation can be performed by the corresponding programming. The encoding method is efficient, since each bit is spatially encoded by a single pixel. The system is simple and the optical elements can be stacked together, so the structure is compact. Furthermore, the logic operations involving three or even more variables can be realized easily with the suggested architecture. All the operations are executed in parallel. As an example, a triple-in binary logic processor is demonstrated to perform bit-slice full additions. Experimental results are given.

Erasure of high-energy magnetic tape recording media

The erasure characteristics of CrO 2, Co−γ-Fe 2O 3, Ba ferrite, metal-evaporated and metal particle tapes were examined. It was found that the Ba ferrite sample was the hardest to erase, and the CrO 2 the easiest. For all the media studied, except Ba ferrite, longitudinal ac fields yield higher degrees of erasure than dc fields. Time domain measurements indicated that particle orientation dispersion plays an important role in the erasure process.

Erasing magnetic recording media

The erasure characteristics of longitudinal magnetic recording media have been explored by correlating measurements and the results of a magnetic recording simulation. The two-dimensional simulation uses the standard self-consistent method with a vector Preisach hysteresis model. Writing NRZI-All-1 patterns with a ferrite head at 1 MHz generates the unerased magnetization pattern. The simulated unerased voltage pulse shapes agree well with experiment. The Fourier harmonics of the readback waveform characterize the recorded signal, and are observed as a function of longitudinally applied dc and decaying ac erase fields. Results from experiment and simulation indicate that dc erase fields, of strength near Hc, enhance even Fourier harmonics of the NRZI waveform by destroying the antisymmetric relationship between successive pulses. The measured superiority of ac erasure is explained by both more rapid approach to demagnetization, and broadening of the transition.

Erasure of signals on magnetic recording media

This paper explores some aspects of the erasure of signals from magnetic recording media. The first part gives the erasure characteristics for several different types of materials in current use for magnetic recording. A novel method of displaying the results shows that γ-Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> and Cobaloy metal alloy particles behave substantially the same, while CrO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and Co-doped gamma ferric oxide are different from them and from each other. The second part explores anomalous signal recurrence after complete erasure. It is shown that under certain conditions of storage a non-magnetic memory of the signal is left on the tape. This signal can be converted back to the magnetic form and measured, although its level is quite low. It is subsequently posible on most tapes to remove the non-magnetic signal. The plausibility of the "non-magnetic signal" hypothesis is supported by calculations of the expected level which are of the same order of magnitude as the levels actually measured.

Mechanism of Curie-Point Writing in Thin Films of Manganese Bismuth

This paper presents the first detailed calculation of the demagnetizing field using the measured temperature dependence of the magnetization of manganese bismuth films and assuming realistic time-dependent temperature distributions. It yields calculated demagnetizing fields that are in good agreement with the measured values of field required to erase written spots in manganese bismuth in either of its two phases. Based on the agreement between measured erasure field and calculated demagnetizing field, we conclude that the demagnetizing field model of Curie-point writing is justifiable. The results can be used to explain the previously reported partial erasure characteristics of this material.