The nature of light is studied by comparison between the real and digital worlds. Combining the theoretical results obtained from a relative quantum mechanical equation which is suited for a particle with zero rest mass, spin quantum number 1/2 with experiments analysis results, we discuss the possibility that a photon could have structure. A possible photon model with internal structure is proposed and discussed. A photon could consist of a pair particles named particle x+ and antiparticle x-. x+ and x- both have zero rest masses, and spin quantum number 1/2. x+ and x- oscillate in opposite directions but spin in the same direction, which means there is an internal oscillation. The frequency of light is the frequency of the oscillation. The model can be used to explain not only all of the experiment phenomena, but also the wave particle dualism of light. It can provide clear pictures of both polarization and coherency of light. It can also explain that there are two spin states of 1 and -1. The possible experiments that could be used to prove the model are addressed too.
Thin films properties of amorphous TbFeCo were studied to determine its suitability for use in all optical
magnetic recording. Ellipsometric techniques have been used to determine the optical properties of the
films in the wavelength range of 350 to 800 nm. The effects of film thickness, Ar flow rate and presence of
Ag under layer on magnetic properties were also investigated.
This work presents a thermal analysis that explains experimental observation in all-optical magnetic recording (AOMR).
An integrated model is used to describe thermal processes at different time scales in AOMR. The formation of magnetic
marks is discussed and implemented by developing a simulator based on 3-dimensional finite element method (FEM).
The simulator is able to carry out thermal analysis of the thin film media and is a useful tool for design of AOMR media
structure, especially for the thermal sink layer.
Laser interference lithography is applied to fabricate large-area plasmonic nanostructures. This approach has the
advantages of being non-contact process in air and able to achieve large-area and maskless nanolithography at a high
speed with low system investment. Single layer Au or Ag noble metallic thin film and Ag/Au, Ag/Ni or Au/Ni bimetallic
layer thin films are patterned into nano-dot, nano-rod and nano-nut arrays by laser interference lithography. Plasmonic
effects of the fabricated metallic nanostructures are studied. Tunable and multi-peak surface plasmon resonances of these
nanostructures can be obtained, which have potential applications in solar cells, bio-sensing and photonic circuits.
An integrated analysis tool of optical system and media which combines system with media analysis of the discs is
developed in this project. This software has been used to study the influence of disc tilt, cover layer thickness and
scratches on high density recording, which show that it provides a powerful tool in practical applications.
Super-resolution near-field optical disk is one of the solutions to overcome diffraction limit and achieve high
density optical recording. In this paper, a structure of super-resolution near-field phase-change optical disk with
a thin thermal shield layer behind the recording layer is proposed. The optical disks with the new structure were
studied theoretically and experimentally. Thermal simulation shows that the thermal shield layer can reduce the
phase change layer temperature, thus improve the thermal stability of the disks. The disks with this structure
were fabricated and characterized. The experiment results are in good agreement with the simulation results.
Different definitions of spot size and depth of focus in optical data storage systems are analyzed and compared numerically. It appears that the differences between the definitions become more significant as the numerical aperture of the optical system increases. The relationship between spherical aberration and axial intensity is studied, and a general definition of the depth of focus based on this analysis is proposed.
Two structures super-resolution near-field phase-change optical disks with masks Sb2 Te3 layer and a
thermal shield layer in front of the mask layer on Blu-ray substrates were studied theoretically and
experimentally. Optical simulation was conducted and the modulation transfer function (MTF) was calculated.
MTF calculation results has revealed that the super-RENS optical disk exhibited the maximum response when
nearly half of the laser spot was covered by the mask. The thermal simulation was used to find the optimum
condition meaning that half of the laser beam is covered by the aperture on the mask layer. The recording signal
and thermal stability on different structures were measured and analyzed. The simulation results are in good
agreement with the experiment results.
A novel direct-write glass metallization based on laser induced plasma assisted ablation (LIPAA) was investigated. Laser is passed through a glass substrate and irradiated onto a metal target placed beneath the substrate. By tuning laser fluence above target ablation threshold, target ablation and plasma generation occur. The plasma flies towards the glass at a high speed and deposits metal materials onto glass backside surface. Metal films were fabricated and their sheet resistances were measured by a four-point probe. It was found that sheet resistances of the metal films vary with processing parameters. Experimental results reveal that low resistivity metal film (< 0.3 Ω/∠) can be obtained at an optimal laser scanning speed and pulse repetition rate. When target-to-substrate distance increases, film resistance also increases. Optimal design of overlap schemes among metal tracks provides a lower film resistance. Meanwhile, thin film and bulk metal targets were used to study their difference on film resistance. It was discovered that deposition using thin film target is more efficient. Laser annealing technique was also applied to activate the deposited metal materials to get higher quality glass surface metallization.
Phase transformations of 100nm Ge1Sb4Te7 films induced by single 130fs pulse at 800nm have been investigated with time-resolved microscope. With an average fluence of 30mJ/cm2, a reflective intensity increase was observed within 1ps in 100nm as-deposited Ge1Sb4Te7 films after excitation by intense femtosecond pulse, which was consistent to an electronically induced non-thermal phase transformation. XRD measurement confirmed that single femtosecond pulse could induce crystalline marks in 100nm as-deposited Ge1Sb4Te7 films. Our results indicated that single femtosecond pulse could trigger both crystalline and amorphous phase in 100nm Ge1Sb4Te7 films. The fluence for crystallization was higher than that for amorphization.
A method of high-density optical disk structure design using computational electromagnetic FDTD analysis is proposed. A staircase method is used to simulate the realistic sidewall geometrical structure of the land-groove of phase-change optical disk. The phase-change materials appear as different optical characteristics under irradiation of different frequency laser beam. Materials models in the FDTD scheme have been studied to solve the computational instability. Using this FDTD method, the structures of the phase-change optical disk with blue laser and high-NA system are investigated.
Ultrafast phase transitions triggered by single femtosecond laser pulse in Ge1Sb2Te4 films were investigated. By proper control of the film thickness, ultrafast crystalline and amorphous phase transformations have been achieved in Ge1Sb2Te4 films. These utlrafast phase transitions were confirmed by reflectivity change and x-ray diffraction measurement.
The Sb film is proposed as new absorption control layer for high-density phase-change optical disk. The computer simulation results show an absorption control layer in a phase-change optical disk can improve the thermal balance and direct overwriting properties of disk, and Sb film as an absorption control layer is better than Si and Ge films. The experiment results show Sb is a good absorption control layer of high-density phase-change optical disk.
Multi-level recording on rewritable phase change optical disk was studied using a simulation and experiments. The possibility of using multi-level reflection effects to increase the storage capacity was considered using a computer simulation software called phase change optical disk design. Optical and thermal simulations were carried out on disks with phase change material GeSbTe to study its performance. Using a suitable disk structure, the mark shapes of various sizes that give rise to multi-level reflection effects were written on the disk and examined. In order to solve the problem of the difference in the absorption between the crystalline and amorphous states, a thermal compensation layer of Sb was used. Simulation and experiment results have shown that the effect of the difference can be significantly reduced by the thermal compensation layer.
Phase change (PC) optical disk is one important type of rewritable optical disk available currently. In PC optical recording, a bit of information is written by using a laser beam to heat the disk which has been initialized to the crystalline state.
The data density of the optical recording disk is mainly dependent on the light beam spot size. In conventional optical recording system, the beam spot size, which is limited by the optical diffraction limit, can be reduced by using a shorter wavelength light source or objective lens with larger NA. Recently, near-field optical techniques have been developed to overcome the diffraction limit. In particular, Betzig et al have applied the scanning near-field optical microscope (SNOM) optics, which as a tapered fiber prove with sub-micron aperture, for use in the recording of magneto-optical (MO) media. However, the low optical coupling efficiency ofthis fiber prove need further improvement before it is practical for application in data storage. Terris et al have developed another near-field optical recording optics using the solid immersion lens that has been developed as the optics for a microscope by Mansfield and Kino. They have demonstrated the recording of the 350nm diameter mark on MO media by using the truncated spherical shaped Solid Immersion Lens (SIL).
The phase-change media, such as GeSbTe and AglnSbTe, are widely applied in rewritable DVD-RAM, CD-RW, and PD optical disks. Before information can be recorded on these disks, the initialization process that changes phase-change media from as-deposited amorphous state to crystalline state must be completed.
The development of phase change recording is spurred by the demand of high capacity, low cost and rewritable optical data storage. In phase change optical disk, recording and erasing are achieved by laser heating that induces the crystallographic structural changes in the media. The difference in reflectivities of crystalline and amorphous states determines the information stored. Hence the dependence of optical and thermal effects arising from the laser irradiation on the disk needs to be thoroughly investigated. In today’s competitive marketplace, companies are looking into ways of producing better product at lower cost and shorter development time. Thus the capability of performing interactive computer modeling and analyses of the optical disk becomes inevitable to achieve these ends.
A new thermal model to study the laser induced temperature profile of a multilayered phase change optical recording disk is proposed. The new model considers the thermal effect generated by both the transmission and reflection light. The calculation formulae are listed. The model is used to simulate the Ge2Sb2Te5 phase change optical disks with five layers structure. In order to study the differences between the new and existing models, simulations are carried out using both models and the differences are compared. The differences get larger as the phase change layer becomes thinner. It is also revealed that the differences get larger as the wavelength becomes shorter. The idea proposed in this paper is also suitable for the analysis of magneto-optical disks as well as for improved accuracy in the measurement of thermal parameters.
Crystal growth of KTiOPO4(KTP) family with flux method has been summarized. The results of defect observation with synchrotron radiation topography and other methods have been reported. It is shown that KTP crystal is of high-quality and there exist different kinds of defect such as growth striations, multiple domains in doped KTP and KTA crystals. The observation and discussion about the bicrystal of KTP family crystal have been mentioned in the paper. SHG and SFG measurements indicated that KTP family crystals investigated have excellent nonlinear optical properties.