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Growth, characterization and optical properties of potassium iodide (KI) doped potassium hydrogen phthalate (KHP) single crystals for optoelectronic applications

Raju R. K., Beena P., Jayanna H. S.

Materials Science Poland

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2019

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Vol. 37, No. 3

510--516

EN

Potassium iodide (KI) doped potassium hydrogen phthalate (KHP) single crystals were grown by slow evaporation technique using millipore water as a solvent. The grown single crystals were analyzed by powder X-ray diffraction and the analysis confirmed that KI-doped KHP crystallizes in orthorhombic system with space group Pca21. The functional groups were identified by FT-IR technique which showed slight shift in vibrational frequencies, indicating inclusion of dopant into the crystal lattice. The UV-Vis spectral studies revealed the optical transparency of the doped crystals in the entire visible region. The optical band gap values were estimated from Tauc plots. Kurtz-Perry powder test was employed for second harmonic generation efficiency studies of the grown crystals.

2

Study of the effect of director fluctuations on liquid-crystalline molecular reorientation

Sierakowski M. W.

Opto-Electronics Review

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2014

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Vol. 22, No. 2

109-112

EN

Initial phase of field-induced molecular reorientation in threshold geometry of a liquid-crystalline structure is essentially influenced by thermal orientational fluctuations. Still not quite clear is the way in which the reorientation starts and how it runs over an LC-structure in its initial phase. Fluctuations are stochastic events in time and also in space. This feature suggests, that the reorientation process may be induced by director fluctuations locally in a particular part of the LC-structure. In this work we have studied the impact of fluctuations on the molecular reorientation in nematics involving optical nonlinear interaction. The restricted area of a nematic layer was excited by light beam that amplified director fluctuations locally. By manipulation of optical excitation we were able to affect the dynamics of the effect. Since the threshold-type configuration of nematics is used in a number of optical devices, the obtained results may have practical aspect contributing to a new way of controlling the field-induced transition.

3

Development of wide range displacement sensors based on polarized light detecting technology

Lu X., Li W., Lin Y.

Optica Applicata

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2011

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Vol. 41, nr 1

97--108

EN

A series of novel wide range displacement sensors based on polarized light detecting technology is presented. The sensors include a displacement-current comparator and a servo comparison displacement sensor. Special structures and technologies are introduced to the sensor systems to solve the optical problems, such as the nonlinearity, the light source drift etc., and realize wide range measurement. The designing, assembling, and testing results of the prototypes of sensors are described. The testing results of the prototypes show that the novel sensors based on polarized light detecting technology have good linearity, and wide range measuring ability.

4

Dependence of nonlinear refractive index of ZnSe on Be and Mg content

Derkowska B., Firszt F., Marasek A., Sahraoui B.

Opto-Electronics Review

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2010

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Vol. 18, No. 4

384-387

EN

The values of the nonlinear refractive index n₂ and the two-photon absorption coefficient ß of ternary and quaternary ZnSe-based mixed crystals were extracted from the standard backward degenerate four wave mixing (DFWM) and nonlinear transmission measurements at 532 nm, respectively. Studied crystals were grown by the modified high-pressure Bridgman method. We found that the value of the nonlinear refractive index n2 for Zn0.79Be0.21Se is higher than that for Zn0.80Mg0.20Se. However, the opposite behaviour was found in the case of two-photon absorption coefficient ß for these compounds. We also found that the values of the nonlinear refractive index n2 and the two-photon absorption coefficient ß for Zn0.83Be0.04Mg0.13Se are about five times lower and three times higher than that for Zn0.80Mg0.13Se, respectively. In the case of ternary ZnSe-based crystals we noticed that the value of the nonlinear refractive index n2 decreases with increasing Mg or Be content. However, the value of the two-photon absorption coefficient ß increases with increasing Mg or Be content.

5

Study of the third order nonlinear optical properties of Zn1-xMgxSe and Cd1-xMgxSe crystals

Derkowska B., Firszt F., Sahraoui B., Marasek A., Kujawa M.

Opto-Electronics Review

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2008

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Vol. 16, No. 1

8-11

EN

Third order nonlinear optical susceptibilities χ³ of ternary Zn₁-xMgxSe and Cd₁-xMgxSe crystals have been measured using standard degenerate four-wave mixing (DFWM) method at 532 nm. The nonlinear transmission technique has been applied to check if our crystals exhibit two-photon absorption. The studied Zn₁-xMgxSe and Cd₁-xMgxSe solid solutions were grown from the melt by the modified high-pressure Bridgman method. For both crystals the energy gap increases with increasing Mg content. In the case of Zn₁-xMgxSe, it was found that the value of third order nonlinear optical susceptibility χ³ decreases with increasing Mg content. An explanation of this behaviour results from the dependence of optical nonlinearities on the energy band gap Eg of the studied crystals. In the case of Cd₁₋xMgxSe with low content of Mg, no response was observed for the studied wavelength since the energy gap in such crystals is smaller than the photon energy of the used laser radiation. It was also found that the value of third order nonlinear optical susceptibility χ³ for Cd₀.₇₀Mg₀.₃₃ is higher than for Zn₀.₆₇Mg₀.₃₃Se. This behaviour can be understood if one take into consideration that the free carrier concentration in Cd₁₋xMgxSe samples is about four orders of magnitude higher than that in Zn₁₋x MgxSe ones with comparable Mg content respectively. It is commonly known that when the electric conductivity increases, the values of nonlinear optical properties increase. From the performed measurements one can conclude that the incorporation of Mg as constituent into ZnSe and CdSe crystals leads to a change of the third order nonlinear optical susceptibilities.

6

Dye-enhanced nonlinearity threshold measurements in liquid crystals

Sierakowski M., Waga Ł.

Opto-Electronics Review

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2005

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Vol. 13, No. 2

151-155

EN

Since early eighties it is well known, that optical field can interact with liquid crystalline structures inducing molecular motion in similar way to quasi-electrostatic fields. This nonlinear optical effect (NOE) causes changes of refractive index distribution in the structure and in this way leads to several optical phenomena, like self-diffraction of the propagating beam, harmonic generation, four-wave mixing, nonlinear wave-guiding, etc. At first, NOE was observed in nematics for relatively high optical power densities. In the middle of nineties, Istvan Janossy discovered, that small addition of specific dopants to LC-material can significantly reduce the light power required for NOE. At present, NOE can be induced in certain LC-materials by sub-miliwatt laser beams. This achievement opened a way to many applications of the accompanied optical phenomena. Mechanism of the Janossy effect is still not quite clear. NOE is generally a threshold effect, which means that it starts after a certain threshold value of the optical power. In this work we examine the threshold of the self-diffraction of light in doped nematics in selected conditions, trying to understand its nature. Final goal of the work is examination of NOE in chiral liquidcrystal structures (cholesterics).

7

Nieliniowość optyczna w światłowodowych siatkach dyfrakcyjnych

Ciosmak J.

Elektronika : konstrukcje, technologie, zastosowania

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2003

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Vol. 44, nr 5-6

21-22

PL

Rozważa się wpływ nieliniowości optycznej w światłowodowych siatkach dyfrakcyjnych. Bazując na wybranej metodzie analizy struktur dyfrakcyjnych - metodzie linii, analizowano wpływ nieliniowości optycznej na propagowane fale w siatce światłowodowej. Przyjmując nieliniowe załamanie jako główny składnik nieliniowości optycznej zaobserwowano wzrost wartości odbicia pasma podstawowego przy jednoczesnym zmniejszeniu szerokości połówkowej. Charakterystyka odbicia ulega przesunięciu w kierunku fal dłuższych wprost proporcjonalnie do przyłożonej mocy optycznej.

EN

The influence of optical nonlinearity of fiber grating was considered in the paper. The method of lines provided the basis for the analysis of the impact of optical nonlinearity on the wave propagation in fiber gratig. Assuming the nonlinear refraction to be the main component of nonlinearity, it was observed that the main band reflection value increased, at the same time fuli width half maximum (FWHM) decreased. The reflection characteristics is shifted towards longer waves, directly proportional to the applied optical power.