• Korean Journal of Crystallography
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• v.3 no.1
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• pp.37-43
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• 1992

KTiOP04 is a nonlinear optical crystal which is most widely used for frequency doubling of the radiation of Nd : YAG laser. In the experiment, sin ale crystals of KTiOP04 were grown by TSSG technique using 3K2W04·P2O5 flux. Low temperature gradient furnace suitable for KTP single crystal growth was used. Seed crystal was placed at the surface of the solution for the purpose of better observation of the growing crystals and the possibility of diameter control. Solution included 66.7mol% KTiOP04 for all experiments and its saturation temperature was 1020℃. The conditions of single crystal growth were as follows: cooling rate 0.2℃/h, crystal rotation rate 50rpm, c -axis seed. Using these conditions, single crystals up to 23 ×25×25mm3 have been groan from about 100cc solution. We have also observed a change in the crystal growth habit which resulted in the formation of large (201) faces and small (100) faces. And some crystals have (101) faces.

• ETRI Journal
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• v.16 no.4
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• pp.13-25
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• 1995

We have derived a nonlinear spatiotemporal differential equation for space-charge fields from Kukhtarev’s material equations in a moving coordinate system and obtained the spatial subharmonic instability boundaries by using linear stability analysis. It is also found that there is an analogy between the temporal subharmonic and the spatial subharmonc instabilities in the sense that the governing differential equations describing the instability boundaries are formally identical. The experiments for generating spatial subharmonic waves are performed in a photorefractive $Bi_{12}SiO_{20}$ crystal by using conventional moving grating technique. The threshold detunings are experimentally determined and the results are compared with the theory.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.92-93
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• 2000

1961년에 비선형 광학이 시작된$^{(1)}$ 이후로 비선형 광학의 큰 응용 잠재성 때문에 많은 비선형 광학 결정이 개발되어 왔고, 현재도 많은 연구실에서 제조 및 연구되고 있다. 일단 결정이 만들어지면 결정축(X,Y,Z축)이 파악되어야 모든 연구나 응용이 가능하다. 이러한 결정축의 측정은 X선, 중성자, 또는 전자를 이용하는 회절 방법을 통하여 가능하며, 이 중 X선회절 장비가 가장 많이 쓰인다.$^{(2 4)}$ 그러나 이러한 장비들은 값이 워낙 비싸서, 결정축 측정외에 그다지 쓸모가 없는 비선형 광학 물질 제조 연구실이나 광학 연구실에서는 이 장비를 구입하기가 다소 어려운 것이 현실이다. 더구나 이 방법은 해석이 복잡하다는 단점이 있다. (중략)

• Journal of the Optical Society of Korea
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• v.3 no.1
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• pp.27-31
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• 1999

The two-photon absorption of a SiC photodiode was utilized to obtain autocorrelation signals of the pulses from a mode-locked Rh6G dye laser. The autocorrelation signals were in good agreement with those obtained by a conventional autocorrelator using a second harmonic crystal and photomultiplier tube. The sensitivity of the autocorrelator with the SiC photodiode was about $4{\times}10^3 {(mW)}^2$ . From these results it was demonstrated that the SiC photodiode is suitable as a nonlinear device for an autocorrelation measurement in the visible range.

• Current Optics and Photonics
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• v.3 no.4
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• pp.342-349
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• 2019

We present a theoretical research concerning terahertz (THz) wave generation with $KTiOPO_4$ (KTP) by collinear phase matching (CPM) stimulated polariton scattering (SPS). Both CPM and corresponding nonzero nonlinear coefficients can be simultaneously realized with $s{\rightarrow}f+f$ in yz plane, $s{\rightarrow}f+s$ with ${\theta}$ < ${\Omega}$ in xz plane and $s{\rightarrow}f+f$ with ${\theta}$ < ${\Omega}$ in xz plane. The effective nonlinear coefficients including electronic nonlinearities and ionic nonlinearities are calculated. Based on the parameter values of refractive indices, absorption coefficients and effective nonlinear coefficients, we simulate THz wave intensities generated with CPM SPS by solving coupled wave equations and give the relationship among the maximum THz wave intensity, optimal crystal length and the angle ${\theta}$. The calculation results demonstrate that CPM SPS with KTP can generate THz waves with high intensities and quantum conversion efficiencies.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.85-91
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• 2003

Intracavity frequency doubling of a single-mode Nd:YAG laser by using a nonplanar ring cavity is demonstrated. The nonplanar ring cavity consists of a Brewster-angled Nd:YAG crystal placed in a magnetic field, a KTP crystal, and two spherical mirrors. In this design the Nd:YAG block acts as both a nonreciprocal polarization rotator and a partial polarizer, and the nonplanar portion of the ring cavity, which is formed by a relative twist angle between the Brewster-angled end surfaces of the Nd:YAG block, serves as a reciprocal polarization rotator. An eigenpolarization theory for the cavity configuration is presented and suitable values of the relative twist angle for unidirectional operation are estimated. A single-mode output power of 22 ㎽ at 532 nm and an optical to optical conversion efficiency of 1.8% are obtained with a 1.2 W diode laser at 809 nm.

• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.268-274
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• 1992

An attempt to improve the second harmonic generation (SHG) efficiency of MAP (methyl (2,4-dinitrophenyl)aminopropanoate) by modifying the substituents on the amino group of MAP is described. Several MAP analogues have been prepared using optically active amino acids alanine, phenylalanine and serine, and their SHG efficiencies measured. None of the MAP analogues exhibited SHG efficiencies as high as that of MAP. X-ray crystal structures of three MAP analogues have been determined. In the crystal structures of two of them, which were the derivatives of phenylalanine, two crystallographically-independent molecules existing in the asymmetric unit are aligned almost antiparallel. These structures are consistent with the very low SHG efficiencies of these compounds. On the other hand, the crystal structure of a serine derivative reveals substantial alignment of the dinitroaniline chromophore along the polar axis. However, the angle of 86.2° between the molecular charge tranfer axis and the polar axis of the crystal is still far away from the optimum value of 54.74° for the phase-matchable SHG. The structure is consistent with the SHG efficiency of this compound which is much higher than those of the phenylalanine derivatives but still lower than that of MAP. This study demonstrates the importance of the orientation of molecules in the crystal lattice in determining secod-order nonlinear optical properties of crystalline materials.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.794-798
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• 1992

We present an optical Voltage and current sensor using $BSO(Bi_{12}SiO_{20})$ monocrystal. The voltage and current sensor consist of PBS(Polarizing Beam Splitter), 1/4 wavelength plate, ZnSe, Selfoc lens, LED, and PIN-PD etc. Magnetic core was made using permalloy for applying magnetic field to current sensor effectively. Current was measured from 100 to 1,600 ampere and accuracy was about ${\pm}$5%. The accuracy could be improved to ${\pm}$l% after reducing the nonlinear property of BSO crystal using our own program in PC (IBM286). We noticed that these data were not influenced by 154,000 voltage at all. Applied voltage was reduced to 1/20 using capacitors. And experiment was carried out up to 450V of the reduced voltage. The data fran optical voltage sensor was similar to that from conventional voltage sensor. The accuracy of the data was within about ${\pm}$1%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.3
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• pp.223-232
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• 1995

Abstract Urea($(NH_2)_2CO$) and THAMP (Tris(hydroxymethyl) aminomethane phosphate) are new organic nonlinear optical materials (NLO) for the device application such as the frequency conversion of laser radiation. The single crystals of urea and THAMP have been grown by the falling temperature method and the temperature difference method. The crystal growth parameters were presented associated with the molphology of the grown crystals. Based on the solubility measurements, methanol was a suitable solvent for the growth of urea. The solubilities of urea have a positive temperature coefficient and the heat of solution of urea was estimated to be -2.58 kcal/mol. The grown crystals of urea have the preferential growth habit in the z-axis. Additives such as $NH_4_H_2PO_4$, KCL, $H_3PO_4$, $CaCl_2{\cdot}2H_2O$, $C_2H_5OH$ were used for the favourable growth in the x - and y-axis and the preventive growth in the z-axis. The moleratio of THAM and H3P04 for the solution of THAMP was 1 : 1. The solubilities of THAMP have a positive temperature coefficient. The heat of solution was estimated to be - 1.70 kcal/ mol.

• Current Optics and Photonics
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• v.5 no.4
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• pp.458-465
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• 2021

Borate nonlinear optical crystals have been used as frequency conversion devices in many fields due to their unique transparency and nonlinearity from ultraviolet to visible spectral range. In this study, we theoretically and numerically investigate the properties of broadband second harmonic generation (SHG) in the recently reported Pna2₁-Ba₃Mg₃(BO₃)₃F₃ (BMBF) crystal. The technique is based on the simultaneous achievement of birefringence phase matching and group velocity matching between interacting waves. We discussed all factors required for broadband SHG in the BMBF in terms of two types of phase matching and group velocity matching conditions, the beam propagation direction and the corresponding effective nonlinearity and spatial walk-off, and the spectral responses. The results show that bandwidths calculated in the broadband SHG scheme are 220.90 nm (for Type I) and 165.85 nm (for Type II) in full-width-half-maximum (FWHM). The central wavelength in each case is 2047.76 nm for Type I and 1828.66 nm for Type II at room temperature. The results were compared with the non-broadband scheme at the telecom C-band.