Search

Optical detection of pressure has the advantage of direct and dynamic indication of the pressure distribution with a high spatial resolution. In this study, microcrystal (µ-crystal) light-emitting ...

We succeeded in hydrogen evolution using InGaN photocatalysts grown on conductive Ga2O3 substrates. These photocatalysts exhibited a conversion efficiency of 0.8% from incident light energy to stored H2 chemical energy. Their quantum efficiency was determined to be more than 1% at 404 nm by incident photon-to-current conversion efficiency (IPCE) measurement. We found that the wavelength response of the InGaN structure can be extended to the visible region. These results indicate that the conductive Ga2O3 substrates are suitable for the photocatalysts.

The magnetic spacing of both longitudinal and perpendicular Ba-ferrite particulate tapes was evaluated in comparison with that of metal particulate tapes. First, the effective spacing, which is the sum of the magnetic spacing and the transition parameter, was determined by fitting the wavelength response to Wallace's equation. Next, the transition parameter was obtained from a magnetic force microscopy image. Finally, the magnetic spacing was calculated as the difference between the effective spacing and the transition parameter. Both the transition parameter and the magnetic spacing of both longitudinal and perpendicular Ba-ferrite particulate tapes were much smaller than those of metal particulate tapes. These results indicate that Ba-ferrite particulate media have a considerable advantage over metal particulate media in high-density recording.

We propose and demonstrate a 1times2 thermooptic digital optical switch with variable optical attenuators that are integrated with the S-bend waveguides connecting the output of the Y-switch with a standard fiber array. With a total heating power of 140 mW applied to the switch, we have achieved less than -42-dB optical crosstalk. The wavelength response of the switch is flat across the entire C-band. The average polarization-dependent loss of the switch is about 0.49 dB

A novel Frequency Selective Surface (FSS) conflguration is proposed for the design of polarization-insensitive metamaterial absorbers operating below 1GHz, where the flrst resonances of small commercial enclosures appear. The novel FSS shows a strong sub- wavelength response, enhanced by the dielectric substrate, which allows the design of compact planar absorbers with excellent angular and polarization stability.

It has been reported that high-density and wide-bandwidth characteristics may be obtained by using a ring head with obliquely oriented metal evaporated magnetic recording tape. We therefore developed new equipment for the preparation of obliquely oriented tapes based on ?-Fe 2 O 3 particles, and examined the morphology, magnetic properties, and wavelength response of the tapes. The experimental results showed that tape with an oblique orientation of 30° has the highest output and widest bandwidth characteristics.

The effect of filter characteristics on the output performance of actively mode-locked fiber ring lasers has been studied experimentally and numerically, with the same 3-dB bandwidth, the filter that has a flatter wavelength response tends to generate narrower soliton-like pulses.

A rapid, non-destructive optical method for detecting the perpendicular orientation at the surface of metal LIPS tape is described. This technique uses reflection anisotropy due to the depolarization coefficient anisotropy of the acicular metal particles. A tape sample with low anisotropy according to this method of evaluation exhibited higher density wavelength response characteristics.

Ring resonators are coupled in parallel in order to obtain a second order type of wavelength response. The phase relationship between the rings determines the details of the spectral response. The rings used in the experiment have radii of 25 /spl mu/m and are fabricated from compound glass having an index of 1.539. Several resonances are observed to have double peaked box-like response.

In 1953 Westmijze found analytic solutions for the fields and wavelength responses of ring-type-head models with zero and infinite gap depths and demonstrated that the wavelength responses for these two extreme cases are substantially different. A model two-dimensional electromagnet that is equivalent to a more general ring-type-head model that takes into consideration a final gap-depth value is considered. It is shown that the Westmijze head models are actually two specific cases of this more general model. Using the theory of complex analytic functions, the gap between the two Westmijze models is bridged and an analytic solution for the wavelength response of a ring-type head with an arbitrary gap depth is derived. Graphs of the responses calculated for several gap depths are presented. These graphs illustrate that the gap depth has no practical effect on wavelength response as long as the ratio of pole thickness to gap size exceeds 0.5. However, further decrease of this ratio causes considerable changes in wavelength responses. >

A four-channel phased-array wavelength demultiplexer with a flattened wavelength response has been realised for the first time in InP/InGaAsP at 1.54 mu m by employing multimode output waveguides. The device has 2 nm channel spacing and a flat response (within 1 dB) of 17 nm. >

A new method for the fabrication of a singlemode fibre wavelength independent Y-junction is described; through asymmetrically tapering a pre-assembled Y-junction precursor, the splice point is drawn into the waist region of the device and low-loss is ensured. The lowest loss and flattest wavelength response for such a device is reported.

Results of calculations are presented which illustrate the effect of the location of an ideal winding on the wavelength response of probe heads from a perpendicular recording medium with a permeable underlayer. Calculated wavelength responses represent the theoretical limits for the response of practical probe heads with practical windings. A numerical estimate of possible improvement of readback response of probe heads is presented.

The readback response of a perpendicular recording system utilizing a medium with a soft magnetic underlayer (SMUL) had been investigated using rigorous two-dimensional theory. The results are as follows. 1) Changes in the medium thickness (with a SMUL) effect radical changes in the wavelength response of the heads. 2) For a thin medium, the effective gap of a ring head becomes twice its geometrical gap. 3) The combination of probe head and medium with SMUL has adequate resolution only if the recording medium thickness is an order of magnitude less than probe thickness. 4) The foregoing combination has a potential advantage over longitudinal recording on conventional thin media with respect to the absolute value of readback output.

Recently developed 3-5 compound semiconductor photocathodes show promise of substantial advantages over conventional photocathodes in increased yield and longer wavelength response. This paper reviews the physical principles of operation, preparation, and activation of these new types of photocathode. Also discussed are current fabrication techniques, problem areas, practical difficulties, and operating characteristics of experimental cathodes.

A LIPS tape of CrO 2 particles was prepared through the follwing steps: 1) a perpendicular orientation over the entire thickness by the previous "VAST" method (Vertical magnetic orientation-AC demagnetization-Smoothing period -Train), 2) a short radiation heating only in the shallow surface layer and 3) a magnetic reorientation to the longitudinal direction only in the inside layer, still in a low viscosity state. Their magnetic data show that the thickness of the perpendicular surface layer can be controlled to any suitable thin value by the heating condition. Their wavelength response shows both high density and wide band characters.

Barium-ferrite fine-particle-coated perpendicular magnetic recording tapes have been experimentally fabricated. Typical tapes have M s = 120 - 130 emu/cc, H c = 600 - 1500 Oe and perpendicular squareness ratio M_{r\perp}/M_{s} larger than 0.9. Tape recording performances were measured with a perpendicular head as well as With a ring-shaped head. A good short wavelength response, D 50 = 76k FRPI, which has never been attained by longitudinally oriented particulate tapes, was obtained; The relationship between perpendicular squareness ratio and output was also investigated to show the importance of perpendicular orientation for attaining a higher recording density.

Achieving both high resolution and high read/write efficiency has been tried with a rather thick single-pole-head film core having the sensitive (ordinary) trailing edge and the less sensitive leading edge in the neighborhood of which a degradation of the magnetic flux density (Bs) is made. The degradation is made by laminating several sputtered layers of different alloy constitution of Co 1-x Zr x (x = 0.17-0.32). The whole film core consists of this degradation region of 4.2 μm thick and high permeability Co 0.85 Zr 0.03 Nb 0.12 region of 5.0 μm thick. Observed shallowing of the reproduce nulls in the wavelength response with the rather thick core shows a possible compatibility of the resolution and the efficiency.

Output response of thin film heads was analyzed using wavelength response to determine the optimum pole tip length for both low peak shift and high resolution. From the analytical analysis, thin film heads were designed and fabricated. The experimental results very much agree with the theoretical results. We conclude that by selecting the trailing pole to be thicker than the leading pole we can achieve optimum results for certain linear density requirements. We also observe that heads with thin poles provide better results at both low frequency and high frequency, while heads with thick poles work better at mid range frequency.

The fabrication and performance of a stable single-mode transmissive 8×8 star coupler is described. The device exhibits very low excess loss (0.13 dB), good coupling uniformity (0.73 dB) and low near-end crosstalk (>64 dB). The star coupler is fabricated from eight lengths of single-mode fibre, by forming 3 dB fused coupling regions between appropriate fibre pairs. A Table of insertion loss measurements is presented, together with graphs showing the wavelength response between 1.2 and 1.7 μm.

A short review of bias methods for the magnetoresistive head (MRH), all based on the rotation of the magnetization, is given, and the properties of the various methods are discussed. A novel bias method is proposed which avoids many disadvantages of the former since it is based on the rotation of the current with the aid of slanted conductors, covering the MRH. Measured and calculated static curves are given for this new configuration, for which the name "Barber Pole" is proposed. The Barber Pole turns out to be more linear than a field-biassed MRH. The wavelength response of a Barber Pole is calculated and found to be very similar to that of a normal MRH; this is confirmed by measurements. A two terminal track sensing head, based on the new biassing principle is described.

The perpendicular recording mode is still a candidate for obtaining higher densities. Best recording results on a double-layer (DL) medium must be expected from using a probe head (PH). This contribution provides an analysis of the write-read performance of one-sided PHs that do not use an auxiliary pole on the back of the medium. Analytical as well as numerical models were used to calculate the effects of saturation and medium thickness on the write fields. Experimental verification of the modeling results was obtained by measuring the wavelength response of many W-shaped PHs on DL media. Combining this with the calculated response, we obtained a semi-empirical relation between the pole nulls, pole thickness and the pole-to-backlayer distance. It reveals a PH behaviour very different from a ring head (RH). The pole thickness calculated from the measured pole-null wavelengths showed a very close agreement with the optically determined value. The calculated head efficiencies are very small, as was confirmed experimentally, and need improvement before the PH has an output comparable with a RH.

The wavelength response of a reproducing head can be estimated quantitatively by the superposition of isolated pulses in perpendicular magnetic recording, because recording demagnetization does not occur. In this paper, the resolution of reproduction of a single-pole head is theoretically investigated for various thicknesses of the main-pole and compared with the experimental results. It is also shown that the 50 % down density D 50 is influenced by the virtual spacing, which depends on the thickness of the Co-Cr layer of a double-layered medium. To realize the high resolution of a single-pole head, the main-pole of 0.15 μm in thickness has been made of a Co-Zr-Nb amorphous film. The 50 % down density D 50 of 135 kFRPI could be reached by combining this head with the double-layered medium having a thinner Co-Cr layer of 0.25 μm.

The wavelength dependence of the ac biased recording sensitivity is calculated utilizing a model in which both longitudinal and vertical record fields are considered. Even though the effects of demagnetization fields and spreads in particle switching fields are neglected, the calculation yields excellent quantitative agreement with measurements on extremely well-oriented CrO 2 and γFe 2 O 3 magnetic tapes.

The twisting of an asymmetric fused tapered single-mode fibre coupler is found to decrease the maximum coupled power, in addition to the usual shift in the wavelength response. This effect can be used to optimise a wavelength-flattened coupler's performance during or after coupler elongation.

Summary form only given, as follows. The author reviews device technologies that may benefit from the use of photorefractive materials. These include optical data storage, associative memory, neural networks, optical crossbars, and optical defect inspection. For these technologies, the author defines the properties desired of photorefractive materials. Photorefractive materials exhibit a broad range of properties. These properties determine the utility of the material in any particular device application. Materials with a property of special appeal to an application may be deficient in another important property. It is therefore essential to understand the properties demanded by certain applications, and to mount a research program to determine the ability to alter the properties of the base materials with which one can work. As a result of this activity, a great deal can be learned about the accuracy of the solid-state models used to project the capabilities of these materials. A research program on photorefractive materials is described that addresses such properties as retention time, diffraction efficiency, speed, and wavelength response. The effect of doping on these parameters is demonstrated, and some fundamental shortcomings in the classical band transport model are noted. >