Buranasiri, Prathan

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Photorefractive effect in Pb- based relaxor ferroelectric materials
(2008-05-15)
Suttirak, S.
;
Buranasiri, P.
;
Banerjee, P. P.
;
Witthayakorn, N.
;
Neeyakorn, W.
In this work, we present a review of recent works on photorefractive effect in Pb-based relaxor ferroelectric material. The review is based on the well known Kukhtarev's model [1] and recent experimental photorefractive two beam coupling works by He et al [2] and Abe et. al. [3,4]. We also suggest the generation of higher orders and other applications such as optical correlation, phase conjugation, which may be worked well with a Pb-Based relaxor ferroelectric materials. From this work, we have seen the bright future of the research in photorefractive effect using the Pb-based relaxor ferroelectric materials.
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Single-beam holography using anisotropic self-diffraction
(2006-11-13)
Buranasiri, Prathan
;
Banerjee, Partha P.
We report a new kind of single incident beam holography. In this method, we use only one beam instead of two beams to make gratings inside photorefractive cerium doped barium titanate. The configuration of the method is based on an anisotropic self-diffraction scheme. The reflection of self-phase conjugate beam at the surface of incidence plays the role of the second beam. By using the reflection of the self-phase conjugate beam, the difficulty of alignment between two focused writing beams has been eliminated. The autocorrelation images in non-Bragg orders have been monitored in order to verify the effectiveness of this method for writing holograms.
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Combination of simple chemical and spectroscopic methods for the identification of Thai hom mali rice
(2009-09-08)
Suwansukhoa, Kajpanya
;
Sumriddetchkajorn, Sarun
;
Buranasiri, Prathan
As the Thai Dawk Mali (KDML105) rice variety is popular due to its high sensory after cook, there is an increase in mixing the KDML105 rice with other rice varieties that leads to unqualified KDML105 milled rice products for export and unqualified unmilled rice seeds for next plants. Instead of using traditional time consuming methods based on the disintegration of the rice kernel in an alkali solution and the inspection of rice cooked in boiling water, this paper proposes to analyze the milled rice powder dissolved in our alkali solution via a spectroscopic method. In our study, 0.1 g, 0.2 g, and 0.3 of milled rice powder from four Thai rice varieties, i.e., KDML105, Pathumthani1, Chainat1, and RD6, are selected. Then each milled rice sample is ground and then dissolved in a 10% potassium hydroxide (KOH) solution. At the specified minutes of dissolution, the relative optical transmission spectrum of the milled rice solution in a 500-800 nm wavelength is measured and only its first derivative is used for the identification of the KDML105 milled rice. We find that the use of 0.10 g of the milled rice powder dissolved in our KOH solution for 10 minutes provides the lowest false rejection rate of 15%, indicating that we have a faster approach with less amount of waste produced. With the 0.2-g milled rice powder, 5 minutes of dissolution is needed but with a slightly higher false rejection rate of 18.3%. © 2009 SPIE.
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Identification of Thai hom mali rice using a refractometer
(2009-09-08)
Sumriddetchkajorn, Sarun
;
Suwansukho, Kajpanya
;
Buranasiri, Prathan
Because Thai Hom Mali, also known as Thai Dawk Mali (KDML105), rice is very popular and its price is high compared to other Thai rice varieties, there is an increase in mixing KDML105 milled and unmilled rice grains with other rice varieties, leading to unqualified KDML105 milled rice products for export and unqualified KDML105 unmilled rice seeds for next plants. Instead of using traditional time- and energy- consuming procedures such as alkaline spreading value and pasting property tests, this paper proposes a fast refractometry-based method to analyze ground milled rice grains dissolved in an alkaline solution. Our idea comes from the fact that due to differences in the amount of amylose content in each rice variety, the refractive index of the milled rice powder dissolved in an alkaline solution can be used to distinguish the desired KDML105 rice from others. In our approach, only 0.1 grams of milled rice powder is ground, it is then dissolved in a 10% potassium hydroxide, and its refractive index is investigated. Our experiment using a temperature-controlled optical refractometer and four Thai rice varieties (KDML105, Pathumthani1, Chainat1, and a Thai sticky rice) shows that the milled KDML105 rice can be distinguished from the remaining three rice varieties with a total false error rate of 6.7% and the required measurement time of < 20 seconds. Key advantages include simplicity, moderate accuracy, and less waste produced. © 2009 SPIE.
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Dispersion relations for negative index materials and slow light
(2007-12-01)
Banerjee, Partha P.
;
Nehmetallah, Georges
;
Aylo, Rola
;
Buranasiri, Prathan
In this work we theoretically model continuous and pulse wave propagation using the underlying dispersion relations. We also derive the dispersion relations of the underlying wave equations based on the real and imaginary parts of the propagation constant which are related through Hubert transformation to ensure causality. Also, in this paper we show that by using a model of photorefractive two wave coupling, we can derive the dispersion relation for pulsed propagation and coupling in a diffusion dominated photorefractive material. We note that the dispersion relation we have found in photorefractive material also obeys the Hubert transform property. Finally, we show that the group velocity of light can be slowed down by means of phase coupling in the photorefractive two-wave mixing process.

Buranasiri, Prathan

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