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101.
We develop a theory of the photoacoustic effect of semiconductor quantum wells. Assuming a multilayer system of optically uniaxial media with dissipation we describe the generation of heat and the conduction of the heat through the system by a generalized transfer-matrix method. It is shown by applying this theory to a semiconductor quantum well that the photoacoustic signal is very sensitive on the quantum-size effect and the longitudinal and transverse relaxation times. Our theory predicts that photoacoustics should be a profitable method for the investigation of semiconductor micro- and nanostructures. 相似文献
102.
K. Yamasaki S. Juodkazis T. Lippert M. Watanabe S. Matsuo H. Misawa 《Applied Physics A: Materials Science & Processing》2003,76(3):325-329
We report the reversible micro-structuring of a synthetic rubber polymer (cis1,4-polybutadiene (PB)) by femtosecond laser
illumination. Visco-elastic relaxation of the optically damaged region was observed. The recovery time, typically 102–104 ms, can be varied by changing the irradiation pulse energy. Multi-shot-induced damage recovers on the much longer scale of
101–102 s. It was found that the doping of PB by 4 wt. % of pentazadiene ([4-NO2]–phenyl–N=N–N(C3H7)–N=N–phenyl–[4-NO2]) reduces the threshold of light-induced photo-modification by 20%. This is explained by photo-induced (homolytic) cleavage
of the pentazadiene bonds and formation of gaseous N2, which facilitates material failure at the irradiated spot.
The recovery of optical transmission can be applied to optical memory, optical and micro-mechanical applications. The underlying
mechanism of the phenomenon is discussed in terms of anelastic α- and β-relaxation (polymer backbone and chains/coils relaxation,
respectively).
Received: 11 October 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +81-88/656-7598, E-mail: misawa@eco.tokushima-u.ac.jp 相似文献
103.
Noritaka Kawasegi Noboru Morita Shigeru Yamada Noboru Takano Tatsuo Oyama Sadao Momota Jun Taniguchi Iwao Miyamoto 《Applied Surface Science》2007,253(6):3284-3291
Ion beam lithography of a silicon surface using an Ar ion beam with an ion energy in the order of hundreds of keV is demonstrated in this study. A specially designed ion irradiation facility was employed that enabled generation and irradiation with a highly accelerated and highly charged Ar ion beam. An ion-beam-induced amorphous layer on a silicon substrate can be selectively etched in hydrofluoric acid, whereas, a non-irradiated area is scarcely etched and, consequently, a concave structure can be fabricated on the irradiated area. To control the depth of the structure, parameters for dependence of the depth on ion irradiation were investigated. As a result, the depth of irradiated area can be controlled by the ion energy that is adjusted by the acceleration voltage and the ion charge. In addition, the etch resistance of the irradiated area increases with an increase in ion energy due to the crystalline layer formed on the surface. Simulation results reveal that the depth is strongly related to the defect distribution induced by ion irradiation. These results indicate the potential use of this method for novel three-dimensional lithography. 相似文献
104.
Ferrite-piezoelectric composites are magnetoelectric (ME) due to the interaction between magnetic and electrical subsystems through mechanical forces. A theory for the low-frequency Maxwell-Wagner relaxation in ME coefficients is discussed for bulk composites of nickel or cobalt ferrite and lead zirconate titanate (PZT). ME coefficients versus frequency spectra show two types of relaxation, over 0.1-100 μHz and 1-1000 Hz. The relaxation frequencies and the magnitude of the ME coefficients are dependent on the electrical and composite parameters and volume fraction for the two phases. The ME coefficient αE is in the range 10−1-104 mV/cm Oe, higher in cobalt ferrite-PZT than for nickel ferrite-PZT, and is strongly dependent on PZT volume fraction v. Estimates of αE and relaxation frequencies versus v provided here are useful for engineering composites with maximum ME effects for specific frequency bands. 相似文献
105.
Kota Chaen 《Optics Communications》2007,280(1):165-172
Liquid crystal spatial light modulators, which are widely used as display devices for computer-generated holograms, have modulation characteristics that depend on spatial frequency. We describe a method for displaying a computer-generated hologram on a liquid crystal spatial light modulator with compensation of its spatial frequency response. Using this method, we demonstrate a binary phase grating with smaller dependence on the spatial frequency. We also demonstrate application of the display method to holographic femtosecond laser processing. 相似文献
106.
Feasibility of Non-Collinear TeO2 Acoustic-Optic Tunable Filters Used in the Optical Communication 下载免费PDF全文
The characteristics and the structure of TeO2 acoustic-optic tunable filter used in communication are discussed briefly based on the acoustic-optic theory and it is shown that a large optical incident angle and a long interaction length are suitable for the optical add/drop multiplexer based on the TeO2 acoustic-optic tunable filter. The distribution of acoustic energy flow in the device supports the large optical incident angle. The long interaction length depends on the change of the device structure to some degree. The measured results of the samples show that the diffraction efficiency reaches at 96% in the tuning range larger than lOOnm and the bandwidth is about 2nm. It can be found that there is a good consistency with the basic theoretical mode. The optimized design result shows that the diffraction efficiency can arrive at 100%, and the bandwidth can be less than 0.4nm. Thus, the non-collinear TeO2 acoustic-optic tunable filter can play an important role in the coming general optical network. 相似文献
107.
Massimo Marinelli F. Murtas M. G. Mecozzi U. Zammit R. Pizzoferrato F. Scudieri S. Martellucci Marco Marinelli 《Applied Physics A: Materials Science & Processing》1990,51(5):387-393
The photopyroelectric effect has been used to measure simultaneously specific heat (c), thermal conductivity (k) and thermal diffusivity () at low temperatures. A calibration procedure which allows the use of a pyroelectric transducer at low temperatures is described. Simultaneous measurements of c, k, and over a high T
c superconducting phase transition are reported. 相似文献
108.
We examine the nanosecond and femtosecond UV laser ablation of poly(methyl methacrylate) (PMMA) as a function of molecular weight (Mw). For laser ablation with nanosecond laser pulses, at the excimer wavelengths 248 nm and 193 nm, we show that high temperatures develop; yet the dynamics of material ejection differs depending on polymer Mw. The results on the nanosecond ablation of polymers are accounted within the framework of bulk photothermal model and the results of molecular dynamics simulations. Turning next to the 248 nm ablation with 500 fs laser pulses, the ablation threshold and etching rates are also found to be dependent on polymer Mw. In addition, ablation results in morphological changes of the remaining substrate. Plausible mechanisms are advanced. 相似文献
109.
Generation of Optical Vortex Using a Spiral Phase Plate Fabricated in Quartz by Direct Laser Writing and Inductively Coupled Plasma Etching 下载免费PDF全文
A simple, economical and reliable technique is proposed for fabricating a spiral phase plate (SPP) in a quartz substrate to generate optical vortex with a unit topological charge at the wavelengths of 632.8nm. The spiral phase plate is first formed in the photoresist by direct laser writing lithography and then transferred into the quartz substrate by inductively coupled plasma etching. The performance of the fabricated SPP is verified by using beam intensity distribution, which is in agreement with the theoretical calculation result. The interference measurement suggests that we have succeeded to generate optical vortex with a unit topological charge with the fabricated SPP. 相似文献
110.
J. J. Brondijk X. Li H. B. Akkerman P. W. M. Blom B. de Boer 《Applied Physics A: Materials Science & Processing》2009,95(1):1-5
By patterning a self-assembled monolayer (SAM) of thiolated molecules with opposing dipole moments on a gold anode of a polymer
light-emitting diode (PLED), the charge injection and, therefore, the light-emission of the device can be controlled with
a micrometer-scale resolution. Gold surfaces were modified with SAMs based on alkanethiols and perfluorinated alkanethiols,
applied by microcontact printing, and their work functions have been measured. The molecules form a chemisorbed monolayer
of only ∼1.5 nm on the gold surface, thereby locally changing the work function of the metal. Kelvin probe measurements show
that the local work function can be tuned from 4.3 to 5.5 eV, which implies that this anode can be used as a hole blocking
electrode or as a hole injecting electrode, respectively, in PLEDs based on poly(p-phenylene vinylene) (PPV) derivatives. By microcontact printing of SAMs with opposing dipole moments, the work function was
locally modified and the charge injection in the PLED could be controlled down to the micrometer length scale. Consequently,
the local light-emission exhibits a high contrast. Microcontact printing of SAMs is a simple and inexpensive method to pattern,
with micrometer resolution, the light-emission for low-end applications like static displays.
Both authors (J.J. Brondijk and X. Li) contributed equally. 相似文献