Pockel’s effect

Pockel s effect Pocket calculators POC13 Podates POD fibers... 

Materials for Electrooptic Modulation. The fundamental phenomenon of Pockel s effect is a phase change, A( ), of a light beam in response to a low frequency electric field of voltage, V. Relevant relationships for coUinear electrical and optical field propagation are as foUows (1 6) ... 

The dynamic Kerr effect (DKE) is the third-order analogue of the second-order Pockel s effect. DKE also gives rise to phase shifts given by... 

Pockel s effect -for electrooptic materials [CERAMICS - NONLINEAR OPTICAL AND ELECTROOPTIC CERAMICS] (V ol 5) - [NONLINEAROPTICAL MATERIALS] (Vol 17)... 

The Pockel s effect [3] refers to an electro-optical process wherein the application of large electric fields onto crystals lacking a center of symmetry can lead to nonlinear polarization effects and optical rotation. Pockel cells can be used in place of photoelastic modulators and can achieve very high modulation frequencies but often have the undesirable property of a nonzero birefringence in the absence of an applied field. 

Dipolar chromophores must be assembled into a noncentrosymmetric lattice to translate molecular optical nonlinearity to maaoscopic electro-optic (EO) aaivity, which is one example of second-order NLO properties. The EO coefficient in units of pmV , rs3, is the principal element of the linear Pockel s EO effect tensor and denotes the magnitude of refractive index shift (Ai ) obtained for an applied low-frequency electric field. This... 

A second type of behavior existing in the PLZT s is the linear (Pockels) effect which is generally found in high coercive field, tetragonal materials (composition 3), This effect is so named because of the linear relationship between An and electric field. The truly linear, nonhysteretic character of this effect has been found to be intrinsic to the material and not due to domain reorientation processes which occur in the quadratic and memory materials. The linear materials possess permanent remanent polarization however, in this case the material is switched to its saturation remanence, and it remains in that state. Optical information is extracted from the ceramic by the action of an electric field which causes linear changes in the birefringence, but in no case is there polarization reversal in the material. 

PAP cycle at room temperature the inset shows the same experiment for a DRl/PMMA guest host system. Details of ATR EO modulation experiments can be found elsewhere.Briefly, the EO coefficients of polymer films are determined by applying an ac voltage (ViCosQt) between two metallic layers that sandwich the polymer film, and by recording the modulation of the reflectivity at Q, for the Pockels effect, and at 2Q, for the Kerr effect. A computer program evaluates the amplitudes of modulation of the film s thickness, and the refractive indices, , (i = x, y, 2 which represent the principal axes of the film), from which the Pockels, e.g., and Kerr, e.g., s y, EG coefficients are obtained. These are given by... 

Photonics is playing an ever-increasing role in our modern information society. Photon is gradually replacing the electron, the elementary particle in electronics. Several hooks and reviews have appeared dealing with the theory of nonlinear optics and the structural characteristics and applications of nonlinear optical molecules and materials [1—18]. Tlie earliest nonlinear optical (NLO) effect discovered was the electro-optic (EO) effect. The linear EO coefficient defines the Pockel effect, discovered in 1906, while the quadratic (nonlinear) EO coefficient s,i relates to the Kerr effect, discovered 31 years later (1875). Truly, all-optical NLO effects were not discovered until the discovery of lasers. Second harmonic generation (SHG) was first observed in a single crystal of quartz by Franken et al. [1] in 1961. They frequency doubled the output of a ruby laser (694.3 nm) into the 383... 

As shown in previous sections of this chapter, when an external perturbation is applied to the polymer film (such as irradiation), the ATR guided modes shift their angular positions and the reflectivity is modulated (Fig. 31b). These angular shifts are very small in the case of electrooptic experiments they correspond to refractive index variations of the order of 10 . One has then to modulate the measuring electric field at a low frequency Q( = cos fit) and to detect the modulated signal with lock-in amplifiers. The lock-in signals detected at the modulation frequency and its second harmonic give, respectively, the linear (or Pockels) and the quadratic (or Kerr) electrooptic effects. The amplitude of the modulation of the thickness and the refractive indices is evaluated by a computer fit, and allows the determination of Pockels (r) and Kerr (s) coefficients (Eqs. 28) ... 

Technical applications based on the Pockels effect require systems that are non-centrosymmetric on a macroscopic level. This relates particularly to polymeric systems containing physically admixed or chemically incorporated components with permanent dipoles. In such cases, macroscopic second-order nonlinearity can be accomplished by poling, i.e. by aligning the permanent dipole moments of the components with the aid of an external electric field that is applied at temperatures in the vicinity of the polymer s glass transition temperature, Tg. The order thus obtained is frozen-in by cooling to a low temperature T Tg. The refractive... 

Narasimhamurty, T. S. (1981). Kerr quadratic electro-optic effect Pockels phenomenological theory, in Photoelastic and Electro-Optic Properties of CrystalsAnonymous, pp. 359-362, Plenum Press, New York. 

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