Optical crystal

The nonlinear optical teclmiques of up- and down-conversion are based on mixing optical beams in a suitable crystal (BBO, LiNbO, KDP, etc) witli tire generation of new optical frequencies tire physical principle is as follows. If two beams having optical frequencies cOp CO2 and wavevectors k, are mixed in a nonlinear optical crystal at tire appropriate angle, a new optical frequency co can be coherently generated witli tire following conditions satisfied ... 

Dmitriev V G, Gurzadyan G G and Nikogosyan D N 1997 Handbook of Nonlinear Optical Crystals 2nd edn, ed H K V Lotsoh (Berlin Springer)... 

Optical counters Optical crystals Optical data storage Optical device Optical devices... 

Optical crystals of high purity lithium fluoride are grown by use of the Stockbarger process (10) in sizes to 25 cm dia x 25 cm high (14). Typical commercial material contains 99.2% LiF typical impurities include Li CO and Fe202 at <0.1% levels, and and heavy metals as Pb at <0.01%... 

Harshaw Optical Crystals Harshaw Chemical Co., Solon, Ohio, 1967, pp. 32—33. 

Magnesium fluoride optical crystals are made by hot-pressing (14) high quaUty MgF2 powder. The optical quaUty powder is made by the NH4HF2... 

The relatively simple study of fluorescence and phosphorescence (based on the action of colour centres) has nowadays extended to nonlinear optical crystals, in which the refractive index is sensitive to the light intensity or (in the photorefractive variety (Agullo-Lopez 1994) also to its spatial variation) a range of crystals, the stereotype of which is lithium niobate, is now used. 

Currently used nonlinear optical crystals are potassium dihydrogen phosphate (KDP) and barium borate (BBO). Compared to KDP, the advantages of BBO are its transparency in the UV and its larger quantum efficiency of up-conversion by a factor of 4—6. For a given position of the crystal, only a narrow band of the fluorescence spectrum is up-converted. Therefore, if the full fluorescence spectrum is of interest, the crystal must be rotated at a series of angles. An example of experimental set-up is presented in Figure 11.2. The fwhm of the response is 210 fs. 

In modeling the SHG performanee of the bulk nonlinear optical crystals, we have assumed the incident fundamental pulses are characterized by a hyperbolic secant temporal profile, and therefore r = rg (FWHM)/l.76. For the case of KNhOs, the maximum optical-to-optical SHG efficiency achieved was 30%. The corresponding value of L/L, under these conditions, with a GVM parameter, 1.2 ps/mm, is L/L = 30. The values of beam... 

G.G. Gurzadian, V.G. Dmitriev, and D.N. Nikogosyan, Handbook of nonlinear optical crystals (3ed), (Springer Verlag, New York, 1999). 

Figure 10. Schematic of the upconversion A/2, halfwave plate BS, dichroic beamsplitter POl, polarizer M, monochromator P, photomultiplier and K.DP, potassium dihydrogen phosphate, nonlinear optical crystal.

Investigations into the influence of composition on hardness play an especially important role in mixed crystal synthesis processes. Subramanian and Bansigir (1980) synthesized a series of mixed optical crystals KCl-KBr (Fig. 5.17). They demonstrated a definite influence of mole composition on crystal hardness and the absence of a strict correlation between hardness and dislocation density in the crystals obtained in the process. The maximum number of dislocations involved pure crystals of both compounds, each exhibiting minimum hardness. 

OPTICAL CRYSTAL. A comparatively large crystal, either natural or synthetic, used for infrared and ultraviolet optics, piezoelectric effects, and shortwave radiation detection. Examples are sodium chloride, potassium iodide, silver chloride, calcium tluonde, and (for scintillation counters) such organic materials as anthracene, naphthalene, shlbene, and lerphenyl. 

Fedders and Muller (213) have derived an estimate of the solid-inter-action parameter from another point of view, which ascribes the mixing enthalpy to bond distortions associated with the alloy formation and relates these distortions to the macroscopic elastic properties of the crystal. They concluded that the results based on elastic-crystal parameters yield a similar form for the thermodynamic properties as those estimated by DLP model based on optical-crystal parameters. 

Development of New Nonlinear Optical Crystals in the Borate Series... 

We have seen that a bulk transparent electro-optic crystal changes its index by a small amount, if an electric field is applied. Figure 4.9 shows a phase modulator for transverse geometry. Let us look at some numbers for LiNb03 d = 1 mm, L = 10 mm, r33 = 30.9 pm/V, ne = 2.2, U = 180 V, and A0 = 0.6 ptm. We find... 

Figure 4.12 Longitudinal Pockels cell. The kdp electro-optic crystal between two crossed polarizers makes an intensity modulator.

FIGURE 7.4 The acousto-optical detection system. Deflection of the incident laser beam by the acousto-optic crystal. Deflection angle is determined by the frequency of the acoustic wave [683]. Reprinted with permission from John Wiley Sons. 

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