Phumin Jindajitawat

Optical parametric amplification in one-dimensional photonic bandgap structures.

In this paper, optical parametric amplification based on the degenerate four-wave mixing principle in a one-dimensional photonic bandgap (PBG) structure has been numerically studied. First, the multiple scale method was introduced to derive a complete set of nonlinear coupled-mode equations for a finite structure with different inhomogeneous nonlinear coefficients than those used in previous works. This finite structure is composed of 680 dielectric layers, which are alternating half-wave/eight-wave films. The wavelengths of the pump, signal, and idler pulses have been determined from the transmission spectrum, which was illustrated by using the transfer matrix method. The parametric interaction of the pump, signal, and idler pulses inside PBG structure has been numerically simulated by using the split-step Fourier transform method. The results of the simulation have shown that the intensities of the signal and idler have exponential growth with respect to the number of layers in the medium. Meanwhile, pump wavevector detuning directly affects the intensities of both pulses due to a band-edge phase-matching condition that might be achieved from only one optimal detuning parameter. Moreover, both the amplification gain and the conversion efficiency of the idler pulse have been shown to be dependent on the bandwidth of the pump pulse spectrum. A very narrow pulse, with a bandwidth much less than the relevant transmission peak, enables the highest amplification and conversion efficiency in this medium because the most efficient phase-matched condition occurs in this situation. Finally, the conversion efficiency grows exponentially with input pump intensity for several input signal intensities. Furthermore, the maximum conversion efficiencies directly vary with input signal intensity.

Preparation, Characterization and Finite Element Computation of Cu(Al1/2Fe1/2)O2 Delafossite-Oxide Themoelectric Generator Module

The CuAl1/2Fe1/2O2 delafossite oxide has been synthesized by solid state reaction method for studying thermoelectric properties and measuring thermoelectric generator output electric power. The Finite Element technique was used to compute the output voltage of thermoelectric generator in applying temperature difference on a single bar and a module model with compared to the measurement results. The measurement results of positive sign Seebeck coefficient confirm the p-type conductor of the sample. The properties of Seebeck coefficient, electrical conductivity, and thermal conductivity are range from 260 to 310μV/K, from 7 to16 S/cm and from 2.5 to 3.5 W/cm-K,respectively, in the temperature range of 300 to 960 K. The output voltage of the single bar in dimension 4.2 × 2.5 × 20 mm3 obtained 0.5 to 3 mV on applying temperature difference from 1 to 10 K closely to the Finite Element result. The computing results of the thermoelectric single bar and module in high temperature reveal the output electric voltage of CuAl1/2Fe1/2O2 oxide raises with the temperature and the number of thermoelectric leg increase. In important results, the high value of electric voltage is obtained 0.2 and 0.4 V for the single bar and the module at 950 K.

A Computational Investigation of Third-harmonic Generation in One-dimensional Photonic Band-gap Materials with Multiple-Scale Method

In this paper, we present a numerical investigation of third-harmonic (TH) generation in a one-dimensional photonic band-gap material that is doped with a nonlinear χ(3)medium. For modeling harmonic generation phenomena, a multiple-scale method has been introduced to perturb the nonlinear wave equation by a small factor with appropriate scale. So, we obtain coupled-mode equations (CMEs) with different from the conventional CMEs for this phenomenon. Then, we have solved these CMEs numerically to obtain the output amplitudes of TH waves in both forward- and backward-directions, and the conversion efficiencies. Finally, the solutions show that this photonic band-gap material can generate the TH waves whose amplitudes and the conversion efficiencies may be larger than the TH wave and the efficiency produced by an equivalent length of a phase-matched, bulk medium.

Optical and electronic transport properties of p-type CuCoO2 transparent conductive oxide

The CuCoO2 sample has been synthesized by a conventional solid-state reaction method to investigate electronic transport and optical properties for p-type transparent conducting oxide materials. The crystal structure was characterized by XRD. The Seebeck coefficient and electrical conductivity were measured in the high temperature. The UV-VIS-NIR and FTIR spectra were analyzed at room temperature. The XRD peaks confirm the samples forming the delafossite structure phase. The Seebeck coefficient sign confirms the samples displays the p-type conducting. The electronic transport energy for activating free carrier production and conduction contain 0.276 eV and 0.131 eV, respectively. The optical direct gap is 3.65 eV which is a visible-transparent oxide material. These results support that the CuCoO2 oxide compound is p-type transparent conducting oxide materials.

Fingerprint verification by using low coherence digital holography

In this paper, we have proposed the novel prototype of the portable fingerprint scanner. Using this method, the low coherence digital holography technique has been used to verify fingerprints. In our experiment, the Michelson’s interferometer has been setup first for determining the coherence length of a laser diode with wave length of 635 nm. In our model, the light transmission and reflection properties of the glass slide have been applied. Then, the glass slide has been used as a beam splitter for separating the light to two beams, which are the reference beam and fingerprint image bearing beam. The results show fingerprint pattern, which are reconstructed with numerical method.

Thermoelectric Properties of Sn2+-Substituted CuFeO2 Delafossite-Oxide

This study aims to investigate the effect of the Sn2+-substituted into the CuFeO2 delafossite on thermoelectric properties in the Sn content of x = 0.03, 0.05. The CuFe1−xSnxO2 samples were synthesized by solid state reaction. The crystal structure was characterized by XRD, TGA, XPS and the thermoelectric properties were measured in the range of 300 to 960 K. The Seebeck coefficient display positive sign in all temperature range and the XPS show the stable Sn+2 state as confirming the Sn-doped CuFeO2 playing p-type conductor. The Sn2+-substituted supports the mixed valency Fe3+/Fe4+ state in transition octahedral oxide of FeO6 layer enhancing Seebeck coefficient. The high Seebeck are appeared in content of x=0.03 which are 280 to 340 µV/K in the range of 300 to 800 K. The experimental Seebeck corresponds to the prediction formula at high temperature. Totally, the maximum Power Factor is 2.30×10−4 W/mK2 occurring in the CuFe0.95Sn0.05O2 at 860 K which is higher than that value of the undoped-CuFeO2 in 4 times. These support that the Sn-substituted CuFeO2 delafossite enhancing thermoelectric properties.

High temperature thermoelectric properties of delafossite CuBO 2

CuBO₂ is prepared by a solid-state reaction method to investigate thermoelectric properties in high temperature. The XRD result confirms the CuBO₂ compound existing in this method. The Seebeck reveals the compound displays p-type thermoelectric material. The experimental results of electrical resistivity exhibited results of 0.004 S/cm to 0.038 S/cm with the temperature range of 650 to 830 K. The Seebeck value is in the range of 450 μV/K to 950 μV/K, and the thermal conductivity is in the range of 1.4 × 10^-5 to 5.3 × 10^-5 W/m-K² with the same temperature. The maximum PF and ZT is 5.3 × 10^-5 W/m-K² and 0.0016, respectively, at 960 K. This work demonstrates that the CuBO₂ delafossite-oxide compound displays the p-type thermoelectric materials.

The Direct Measurement of the Photorefractive Grating on Anisotropic Self Diffraction Using Digital Holography

In this paper, the measurement of grating period in photorefractive anisotropic self diffraction by using digital holography technique is proposed. In our experimental setup, He –Ne laser beam with wavelength of 632.8 nm has been separated and then incident on photorefractive cerium doped barium titanate crystal to produce photorefractive index grating. The transmitted probe beam, which contains phase and amplitude has been expanded and recorded on digital camera. To explore the grating periods, both phase and amplitude of the images are reconstructed by numerical process using computer. Then the grating periods in photorefractive anisotropic self diffraction have been measured. The results show grating periods, holograms and their reconstruction.

Efficient third-harmonic generation in one-dimensional photonic crystals

In this paper, we have solved nonlinear coupled-mode equations valid for light propagation in a one-dimensional photonic crystal by using numerical expression. Moreover, the medium in this problem has been considered as a nonlinear x (3) material. The numerical results have been used to calculate the conversion efficiency in nondepleted-pump limit. The results have been shown us that the maximum conversion efficiency of third-harmonic generation could be occurred when the fundamental field has been tuned near the lower band-edge of photonic band-gap that band-edge phase matched condition has been satisfied.

The generation of optical phase conjugation from cerium doped barium titanate at wavelength of 632.8 nm

In this paper, optical phase conjugate beam with the using of different resonator configurations has been investigate. Two types of SPPC resonators were selected to use, the first one is linear resonators formed by crystal surface and the other one is linear resonators formed by single mirror and a photorefractive crystal. In our experiment, cerium doped barium titanate crystal (BaTiO3 : Ce) and He-Ne laser with wavelength of 632.8 nm have been used. From the results of both cases, the angle of the incident beams is optimum at 37.95° respect to the normal line of the surface that parallel to the c-axis of the crystal. The generating time of OPC beam are 150 seconds and 330 seconds for the first and second type resonators, respectively. The reflection ratios are equal to 8.75% and 5% for the first and second type resonators, respectively (the first type resonators could provide better reflection ratio).