Novel procedure for the simultaneous determination of the Debye length and electro-optic coefficient for an optically active photorefractive Bi12SiO20 crystal

Gómez, Jorge; Gómez, Héctor Lorduy; Salazar, Ángel

doi:10.1016/j.optcom.2010.09.030

Cited by 5 publications

(9 citation statements)

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“…5(b) in Ref. [1], due to the oscillatory behavior of the coupling factor L Γ as a function of L, a low optical activity does not necessarily means high gain for a given L. It must be noticed, however, that the position of the maximum does not appear to be affected by optical activity. It is coherent with the fact that the Debye screening length and optical power are physically independent photorefractive parameters.…”

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confidence: 88%

“…[1]) prevent that the term multiplying the derivative of |Δn x | is zero. Therefore, it follows that ∂|Δn x |/∂K=0.…”

Section: Differentiating This Expression With Respect To the Magnitudmentioning

confidence: 99%

“…In particular, a two-beam coupling constitutes a suitable technique for material characterization. Direct holographic techniques and phase modulation techniques for self-stabilized recording and fringe-locked holograms have been used to measure some of the most important parameters [1]- [21]. Recently, in Ref.…”

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confidence: 99%

“…Recently, in Ref. [1], a procedure for the simultaneous determination of the screening Debye length and the electro-optic coefficient for an optically active Bi 12 SiO 20 (BSO) crystal, has been presented. For the computation of these material parameters, experimental data of gain vs. grating spacing have been obtained by a two-beam arrangement.…”

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confidence: 99%

“…Figure 5(b) in Ref. [1] shows the graphs for the coupling factors ΓL and L Γ [2] as functions of the crystal thickness, with and without optical activity, respectively. The curves show that coupling factors coincide for thin crystals (L≤1mm), where the effect of optical activity is negligible.…”

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confidence: 99%

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Formal demonstration of the independence on the optical activity of the maximum gain position in a two-wave coupling experiment

Gómez

Salazar

2010

Photon. Lett. Poland

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Abstract-The two-beam coupling method has been a useful procedure to estimate the screening Debye length in a photorefractive crystal. The position and value of the maximum gain value as a function of the photorefractive spacing grating is used to obtain the Debye length value. This position and not the maximum value of the gain, appears to be evidently independent of the optical activity of the material. However, a formal treatment to this effect is not found in the specialized literature. In this paper, we present such formal treatment.Holographic techniques using photorefractive crystals have been demonstrated to be appropriated for the characterization of crystals themselves. In particular, a two-beam coupling constitutes a suitable technique for material characterization. Direct holographic techniques and phase modulation techniques for self-stabilized recording and fringe-locked holograms have been used to measure some of the most important parameters [1]- [21]. Recently, in Ref.[1], a procedure for the simultaneous determination of the screening Debye length and the electro-optic coefficient for an optically active Bi 12 SiO 20 (BSO) crystal, has been presented. For the computation of these material parameters, experimental data of gain vs. grating spacing have been obtained by a two-beam arrangement. A general expression for the diffraction efficiency in the presence of self-diffraction was considered. The fitting of the experimental data to the predicted theoretical behavior was achieved by finding the closest theoretical curve to a set of data sampled from a spline-smoothed curve of the experimental data. Both the Debye screening length l s and the electro-optic coefficient r 41 were used as fitting parameters. By searching in wide intervals for each one of the parameters, the estimation of their values was obtained in a reliable and direct way from only one experiment. Calculations were performed in the diffusion regimen and the procedure led to l s =0.22µm and r 41 =4.5•10 -12 m/V. Because the optical activity can alter the maximum gain value, and self-diffraction effects influence the energy exchange, the procedure turned out to be physically appropriated for the simultaneous determination of these * E-mail: jagomez@elpoli.edu.co physical parameters when thick photorefractive crystals with high optical activity were used (in our experimental set up, the crystal depth was L=10mm). The result of the fitting was shown in Fig. 4(b) of Ref. [1]. The effect of the optical activity is to reduce the gain. (L≤1mm), where the effect of optical activity is negligible. However, for thick crystals (L>1mm), the difference is notable. The error in the calculation of the theoretical gain would considerably increase for an optically active thick crystal if its effect is not taken into account. Figure 1 shows the theoretical curves of gain using our treatment for a 10mm BSO crystal, maintaining the obtained parameters l s =0.22µm and r 41 =4.5•10 -12 m/V fixed, but modifying the optical activity from its value ρ=37...

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mentioning

confidence: 88%

“…[1]) prevent that the term multiplying the derivative of |Δn x | is zero. Therefore, it follows that ∂|Δn x |/∂K=0.…”

Section: Differentiating This Expression With Respect To the Magnitudmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%