Time response of optical switching properties of Sb thin films under focused laser pulses

The time response of optical switching properties of Sb thin films under focused laser pulses is investigated. The results show that the response course can be divided into onset, opening, and closing stages. Formulas for their lengths are given. The onset and opening times decrease with increasing pumping light power density. The closing time is about 150 ns. For optical memory, if the power density of the readout and recording lasers changes from 5 x 10(9) to 15 x 10(9) W/m(2), the onset time changes from 2.5 to 0.30 mus, and the opening time is on the nanosecond scale. (C) 2003 Society of Photo-Optical Instrumentation Engineers.

Tunable focal depth of an apodized focusing optical system

The axial intensity distribution and focal depth of an apoclized focusing optical system are theoretically investigated with two kinds of incident light fields: a uniform-intensity-distribution beam and a Gaussian beam. Both a low-numerical-aperture and a high-numerical-aperture optical system are considered. Numerical results show that the depth of focus can be adjusted by changing the geometrical parameters and transmissivity of the apodizer in the focusing optical system. When a Gaussian beam is employed as the incident beam, the waist width also affects the depth of focus. The tunable range of the focal depth is very considerable. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

New approach for improving transverse superresolution in optical data storage

We have proposed a new confocal readout system which is based on the combination of two N-zone circular phase-only transverse superresolving pupils to improve transverse superresolution. The procedure for designing such an improved system is presented. Results of comparisons between the performance of the proposed system and the transverse superresolving pupils indicate that with the same Strehl ratio the former has much higher transverse superresolution capacity and significantly lower sidelobe intensity. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Nonlinear response and optical limiting in SrBi2Ta2O9 thin films

SrBi2Ta2O9 (SBT) thin films on quartz substrates were prepared by use of the pulsed-laser deposition technique. The nonlinear refractive indices, n(2), Of the SBT films were measured by use of z-scan techniques with picosecond pulses. Large negative nonlinear refractive indices of 3.84 and 3.58 cm(2)/GW were obtained for the wavelengths 532 nm and 1.064 mum, respectively. The two-photon absorption coefficient was determined to be 7.3 cm/GW for 532 nm. The limiting behavior of SBT thin film on a quartz substrate was investigated in an f/5 defocusing geometry by use of 38-ps-duration, 532-nm, 1.064-mum. laser excitation. (C) 2001 Optical Society of America.

Tunable focal depth of an apodized focusing optical system

The axial intensity distribution and focal depth of an apoclized focusing optical system are theoretically investigated with two kinds of incident light fields: a uniform-intensity-distribution beam and a Gaussian beam. Both a low-numerical-aperture and a high-numerical-aperture optical system are considered. Numerical results show that the depth of focus can be adjusted by changing the geometrical parameters and transmissivity of the apodizer in the focusing optical system. When a Gaussian beam is employed as the incident beam, the waist width also affects the depth of focus. The tunable range of the focal depth is very considerable. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Simulation of an apodizer's effect for high-density optical storage

The effect of an apodizer with two parallel taper refractive surfaces is theoretically investigated for high-density optical storage. The apodizer may modulate an incident Gaussian beam into an annular beam. Simulation shows that with the increasing inner radius of the modulated beam, the focal spot shrinks obviously. The depolarization effect gets strong simultaneously, which induces the circular symmetry loss of the focal spot. In this process, pattern density of the orthogonal and longitudinal diffractive fields increases remarkably.

Optical near-field simulation of Sb thin film thermal lens and its application in optical recording

Using the finite-difference-time-domain method, the near-field optical distribution and properties of Sb thin film thermal lens are calculated and simulated. The results show as follows. Within the near-field distance to the output plane of thermal lens, the spot size is approximately 100 nm, and its intensity is greatly enhanced, which is higher than that of incident light. The spot shape gradually changes from ellipse to round at the distance of more than 12 nm to the output plane. The above-simulated results are further demonstrated by the static optical recording experiment. (C) 2005 American Institute of Physics.

Gradient force pattern, focal shift, and focal switch in an apodized optical system

In this paper, the evolution of the gradient force pattern, focal shift, and focal switch induced by a three-portion pure phase-shifting apodizer is numerically investigated in detail. The results show that the proposed apodizer may induce tunable gradient force on the particles in the focal region, focal shift, and focal switch. By adjusting the geometrical parameters of the phase-shifting apodizer, multiple traps may occur with changeable distance between them, and the shape of the optical trap also evolves evidently. More interestingly, for certain geometrical parameters of the proposed apodizer, by changing the phase shift of inner annular portion, the considerable focal shift may occur with focal switch accompanying, which is discussed to show that this kind of apodizer may be a very promising method of transporting trapped particles. © 2005 Elsevier GmbH. All rights reserved.

Optical properties and structure of Sb-rich AgInSbTe phase change thin films

A new composition content quaternary-alloy-based phase change thin film, Sb-rich AgInSbTe, has been prepared by DC-magnetron sputtering on a K9 glass substrate. After the film has been subsequently annealed at 200degreesC for 30 min, it becomes a crystalline thin film. The diffraction peak of antimony (Sb) are observed by shallow (0.5 degree) x-ray diffraction in the quaternary alloy thin film. The analyses of the measurement from differential scanning calorimetry (DSC) show that the crystallization temperature of the phase change thin film is about 190degreesC and increases with the heating rate. By Kissinger plot, the activation energy for crystallization is determined to be 3.05eV. The reflectivity, refractive index and extinction coefficient of the crystalline and amorphous phase change thin films are presented. The optical absorption coefficient of the phase change thin films as a function of photon energy is obtained from the extinction coefficient. The optical band gaps of the amorphous and crystallization phase change thin films are 0.265eV and 1.127eV, respectively.

New approach for improving transverse superresolution in optical data storage

We have proposed a new confocal readout system which is based on the combination of two N-zone circular phase-only transverse superresolving pupils to improve transverse superresolution. The procedure for designing such an improved system is presented. Results of comparisons between the performance of the proposed system and the transverse superresolving pupils indicate that with the same Strehl ratio the former has much higher transverse superresolution capacity and significantly lower sidelobe intensity. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Optical recording properties of metal-azo dye as recording medium with super-resolution near-field structure

A novel metallized azo dye has been synthesized. The absorption spectra of the thin film and thermal characteristic are measured. Static optical recording properties with and without the Bi mask layer super-resolution near-field structure (Super-RENS) of the metal-azo dye are investigated. The results show that the metal-azo dye film has a broad absorbance band in the region of 450-650 nm and the maximum absorbance wavelength is located at 603 nm. It is also found that the new metallized azo dye occupies excellent thermal stability, initiatory decomposition temperature is at 270 degrees C and the mass loss is about 48% in a narrow temperature region (15 degrees C). The complex refractive index N (N = n + ik) is measured. High refractive index (n = 2.45) and low extinction coefficient (k = 0.2) at the recording wavelength 650nm are attained. Static optical recording tests with and without Super-RENS are carried out using a 650nm semiconductor diode laser with recording power of 7mW and laser pulse duration of 200ns. The AFM images show that the diameter of recording mark on the dye film with the Bi mask layer is reduced about 42%, compared to that of recorded mark on the dye film without Super-RENS. It is indicated that Bi can well performed as a mask layer of the dye recording layer and the metallized azo dye can be a promising candidate for recording media with the super-resolution near-field structure.

Optical transmission larger than 1 (T > 1) through ZnS-SiO2/AgOx/ZnS-SiO2 sandwiched thin films

Optical transmission through flat media should be smaller than 1. However, we have observed optical transmission up to T=1.18. The samples were ZnS-SiO2/AgOx/ZnS-SiO2 sandwiched thin films on glass substrate. The supertransmission could only be observed in the near field. We attribute the supertransmission to the lateral propagation relayed by the laser activated and decomposed Ag nanoparticles. (c) 2006 American Institute of Physics.

Thermal, structural and optical properties of NiOx thin films deposited by reactive dc-magnetron sputtering

The NiOx thin films were deposited by reactive dc-magnetron sputtering from a nickel metal target in Ar + O-2 with the relative O-2 content 5%. The as-deposited NiOx, thin films could represent a two-component system comprising crystalline NiO particles dispersed in an amorphous Ni2O3. Decomposition temperature of the as-deposited NiO, thin films was at about 263 degrees C. After annealed at 400 degrees C for 30 min in air, the surface morphology of the films became very rough due to the decomposition of the Ni2O3, leading to the changes of the optical properties of the NiO, thin films. The reflectivity of the films annealed at 400 degrees C was lower than that of the as-deposited one and the optical contrast was 52% at 405 nm. (c) 2006 Elsevier B.V. All rights reserved.

Thiophene-fluorene derivatives with high three-photon absorption activities and their application to optical power limiting

The three-photon absorption (3PA) properties of two thiophene-fluorene derivatives (abbreviated as MOTFTBr and ATFTBr) have been determined by using a Q-switched Nd:YAG laser pumped wish 38ps pulses at 1064nm in DMF. The measured 3PA cross-sections are 152x10(-78)cm(6)s(2) and 139x10(-78)cm(6)s(2), respectively. The optimized structures were obtained by AM1 calculations and the results indicate that these two molecules show nonplanar structures, and attaching different donors has different effects on the molecular structure. The charge density distributions during the excitation were also systematically studied by using AM1 method. In addition, an obvious optical power limiting effect induced by 3PA has been demonstrated for both derivatives.