Gain coefficient

Raman gain coefficient, whose maximum occurs at exact resonance, - oig = For a Lorentzian lineshape, the maximum gain coefficient is given by... 

International Energy Conservation Code 1998 All Buildings Simplified commercial provisions added as Chapter 7 and low-rise residential Solar Heat Gain Coefficient reguirement. 

Some low-molecular dyes also have been investigated in inactive polymer matrices. For stilbene compounds in polystyrene, peak wavelengths in the green spectral region are obtained, with net optical gain coefficients of g = 15-20 cm-1 [187],... 

In highly resistive photoconductors l/2nxr, at low light intensity, may be less than unity. This means that photoconductors with a high gain coefficient will have a very slow response time. 

Figure 5. Photorefractive two-beam coupling gain coefficient of undoped and doped BaTi03 crystals. Curves are theoretical fits to the data. Experimental conditions X = 515 nm, I = 3-5 W/cm2, beam ratio > 200, s-polarization, grating wave vector parallel to c-axis Concentrations refer to dopant atoms per BaTi03 formula unit in the melt.

Stability is guaranteed if the feedback matrix A is chosen to be the product of a unitary matrix and a gain coefficient g, where g <1. They suggest the matrix ... 

In Sect. II, a brief review of the fundamentals of the PR effect is provided. The energy transfer and light diffraction of the wave mixings in a PR medium is introduced, and the optical gain coefficient and diffraction efficiency are defined. The process of light-induced refractive index modulation is considered, and the main results of Kukhtarev s PR model (commonly used in inorganic and organic materials) are presented. 

The two-beam coupling gain coefficient can be derived from Eqs. (5) for Beam 2 (the gain beam) ... 

A systematic study on the effect of plasticization on the PR properties is reported by Bolink et al. [58], It is shown that ECZ can be used as an efficient plasticizer, leading to a large increase in the gain coefficient and the diffraction efficiency, which arises solely due to an improvement in the orientational mobility of the dispersed NLO molecules. 

A similar approach is utilized to prepare a PR composite based on isomeric mixtures of the chromophore NPADVBB [64], The composition is NPADVBB PVK ECZ TNF = 39 39 20 2 wt%, whereas NPADVBB is a mixture of four regioisomers, with vinyl groups in positions (3,3 ), (3,4 ), (4,3 ) and (4,4 ). Although it is claimed that this composite exhibited an improved shelf-life by two orders of magnitude, the gain coefficient achieved is significantly smaller than that obtained for a similar DMNPAA-based sample. 

Another approach is to use better engineered chromophores with added side groups that improve compatibility. Cox et al. have incorporated a racemic ethylhexyl group into the azo chromophore (l-(2/-ethylhexyloxy)-2,5-dimethyl-4-(4 -nitrophenylazo)-benzene, EHDNPB) (Scheme 3g) to increase the solubility of the dye in PVK, inhibiting crystallization and, at the same time, acting as a plasticizer [65], A 60% device diffraction efficiency and gain coefficient of 120 cm-1 are achieved with 55 wt% chromophore. 

Grunnet-Jepsen et al. have reported a PVK composite material consisting of 35 wt% chromophore, 4-piperidinobenzylidene-malononitrile (PDCST) (Scheme 3h), 15 wt% liquid plasticizer, butyl benzyl phthalate (BBP) (Scheme 4d), and 1 wt% of C6o [66,67], These crystallization-resistant samples exhibit a gain coefficient of 200 cm-1, a rise time of 50 ms, and a sensitivity of 3 cm3/kJ at E = 100 V/ i m. It is suggested that the improvement in stability is due to the use of a liquid plasticizer BBP instead of the crystalline ECZ. 

Polyimides carrying NLO chromophores are synthesized. The materials exhibit high Tg ( 220°C). The photoconductivity of polyimide Vin (Scheme 7) is determined to be 1.1 x 10-12 cm/(f2W) under an external field of 150 V/p,m at X = 690 nm and I = 5.9 mW/cm2. After the sample is corona poled, an optical gain coefficient of 22.2 cm-1 under zero field conditions is detected. Polyimide IX exhibits an optical gain of 15 cm-1, which is very close to the optical loss (17.6 cm-1). 

Figure 7 Gain coefficient of PR material of compound 1 as a function of grating spacing measured at an applied field of 66 V/ xm. The circles are the experimental measurements. The solid line is a theoretical fitting using Eqs. (4), (19), (20), (38), and (39), with Eq = 102.6 V/ xm. (Reprinted from Ref. 27. Copyright 2000 The American Physical Society.)...

Figure 14 shows the dependence of the gain coefficients on the external field for samples made of compounds 8 and 9. Large gain values of 117.7 and 221.4 cm-1 were observed for materials of 8 and 9, respectively, at an external... 

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