Second harmonic coefficient

Table I. Second-Harmonic Coefficients 33) and Temporal Decay Data for NPP-Functionalized Poly(2,6-Dimethyl-1,4-Phenylene Oxide)...

Figure 1. (A) Time dependence of the second harmonic coefficient of a PPO-NPP film (1.4 NPP moieties per polymer repeat unit) contact-poled at 1.2 MV/cm. Decay data taken at 25°C. The data points are shown as filled triangles. The two curves describing the biexponential fit to equation 1 are shown separately, with the open triangles representing data points dominating the short-term decay. (B) Time dependence of the second harmonic coefficient of a corona-poled PPO-NPP film (1.4 NPP moieties per repeat unit). Decay data taken at 25°C. The data points are shown as filled triangles. The two curves describing the biexponential fit to equation 1 are shown separately, with the open triangles representing data points dominating the short-term decay.

Table II. Second-Harmonic Coefficients ( 33) and Temporal Decay Parameters for Corona-Poled, NPP-Functionalized Poly(p-hydroxystyrene) Films as a Function of Thermal Cross-Linking a...

Figure 3. Time dependence of the second harmonic coefficient, d33, for corona-poled (PS)O-NPP films. A. Simultaneously poled (180°C) and cross-linked with 0.50 equiv. 1,2,7,8-diepoxyoctane/phenol OH B. Poled at 180°C C. Poled at 150°C. The solid lines are least-squares fits to equation 1, yielding the decay parameters in Table II.

Second harmonic coefficients of the poled films were measured at... 

Figure 5. Time dependence at room temperature of the second harmonic coefficient, d33 of epoxy films containing Disperse Orange 1 (4) after simultaneously poling and curing at 150°C.

The nonlinear optical properties of thin films of the polymers were investigated through measurement of second-harmonic generation, and exhibit second-harmonic coefficients, d33, in the range 4.1-34 pm/V. 

The values of the second-harmonic coefficient, d33, for samples 5-9 are listed in Table II. The values of d33 were obtained using the analysis of Jerphagnon and Kurtz (25), and were calculated under the assumption that the degree of alignment of the nonlinear optical chromophores can be described using the isotropic model. Hence, we assumed d33=3d31 (4). 

B. F. Levine, L. G. Bethea, C. D. Thurmond, R. T. Lynch, and J. L. Bernstein, An organic crystal with an exceptionally large optical second-harmonic coefficient 2-methyl-4-nitroaniline, /. Appl. Phys. 50 2523 (1979). 

The odd order susceptibilities are nonzero in all materials. However, owing to the fact that x is a third rank tensor, the second order susceptibility is nonzero only in noncentrosym-metric materials, that is, materials possessing no center of symmetry. The focus of this paper is on second order processes, and the relationships between the bulk susceptibility, second harmonic generation, and the linear electro-optic effect. For second harmonic generation, Xijl is symmetric in ij, leading to the relationship between the second harmonic coefficient dijk and the bulk second order susceptibility x 2)[i2l... 

TABLE 2. Potential second harmonic coefficient for various molecular dopants in poled poly (methyl methacrylate) (PMMA) using Eqs. (6) and (7) with... 

It has been established experimentally that the origin of the electro-optic effect in organic materials is largely electronic. This implies that the linear electro-optic coefficient can be estimated from the second harmonic coefficient. By properly accounting for the dispersion (using a two level model), the electronic contribution to the electro-optic coefficient is calculated to be r5 3 - 2.4 0.6 x 10 m/V at X-O.S m. Measured values of the electro-optic coefficient are in agreement within experimental uncertainty. These values compare favorably with that of GaAs (r4i - 1.2 x 10 m/V). 

Figure 6. Temporal behavior of the second harmonic coefficient of the IPN at different temperatures. 

Ashwell, et al., have shown that small molecules with large molecular hypeipolarizabilities can be used to build up relatively thick NLO films which have large second harmonic coefficients ( ). Penner, et al, demonstrated that 0.5-micron thick NLO films of high optical quality could be fabricated by LBK heterolayer deposition of side chain polymers (9). Recentiy, Lindsay, et al., reported the use of two mainchain chromophoric polymers to fabricate LBK heterolayer NLO films (10). 

Walba et a/. synthesized a low molar mass ferroelectric liquid crystal specially designed for second-order nonlinear optics that showed a second harmonic coefficient 1X22) of 0.6 0.3 pmA in the chiral smectic C (SC ) phase. The nonlinear optics-chromophores aligned in the direction of the polarization, perpendicular to the long axis of the molecules were later successfully varied. This can be illustrated as follows ... 

Figure 3. Time dependence of effective second harmonic coefficient during poling process for polymers 50P (a), and SOP (b), respectively (T-Tg = 0 ( ), 5 (A), 10 (0), and 15 °C (O)).

Figure 5. Temporal characteristic of effective second harmonic coefficient at room temperature for polymers 30P-100P.

Tablell. The thickness, refraction indices, and second harmonic coefficient (d33).

Fig. 26.9 Temporal stability of the effective second harmonic coefficients of two samples monitored at 100°C. BPAZO/APAN represents a poled/cured polymer film that was prepared from an APAN-doped BPAZO polymer solution. For comparison, a poled/cured BPAZO sample was investigated concurrently.

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