Accurate measurements of the electro-optic coefficients and birefringence changes using an external modulation signal

Abstract

We propose a new method to measure within a high accuracy both the electro-optic properties and the birefringence changes in bulk crystals. This technique is based upon the frequency doubling electro-optic modulation (FDEOM) method in which an external modulator is inserted in the experimental Sénarmont setup. We present a complete analysis of the optical response of a Sénarmont setup within Jones formulation. The FDEOM method possesses as main advantages a high accuracy and sensitivity in the measurements due to a direct determination of the electric field-induced phase retardation in the crystal under study. The measurements are recorded with an adjustment of the shape of the output beam at a frequency double the frequency of the ac applied voltage. The external modulation version of this method allows us to perform measurements with a higher modulation depth and to avoid any additional dynamical perturbation in the electro-optic crystal under study. Therefore, even small values of the electro-optic coefficients can be accurately measured. Moreover, the new method is able to measure with a high accuracy the variations of the birefringence in any crystal, even if it does not present an electro-optic effect. Some significative results in LiNbO3 point out the large advantages of the method.

Precise Measurements of the Quadratic Electro-Optic Effect in KH2PO4 Crystals Using a Sénarmont-Type System

“…For such materials, the configuration, described by Equation (4), is traditionally used with a quarter-wave plate (γ = 90°), which is added to obtain an almost linear relationship between the intensity of the transmitted light and small field-induced changes in Γ. This approach has been used in many electro-optic measurements performed for various uniaxial crystals, with a light beam along the optical axis, including LiNbO 3 , GaAS, KDP-type crystals, and others [ 4 , 5 , 6 , 7 , 8 ]. There are also known measurements of the Kerr effect in dispersions of nanoparticles [ 9 ] and in various liquids, such as mineral oils [ 10 ].…”

“…There are several known variations of measurement methods using the Sénarmont-type arrangement [ 4 , 5 ], but it is typically assumed that only one of the two specific operating points on the I (Γ) characteristic is used. The first option is to use the most linear part of the characteristic (5), which can be achieved by setting the analyzer at β = −Γ(0)/2, where Γ(0) is the field-free value of Γ.…”

All-optical technique to measure the pyroelectric coefficient in electro-optic crystals

“…The probe-beam passes through the sample whose birefringence is to analyze. At the exit, the phase shift ⌫ between its ordinary and extraordinary polarization components is proportional to the birefringence ⌬n: [11][12][13]…”

“…where p is the wavelength of the laser beam and L is the length of the sample. If ␤ is the angle of the analyzer ͑A͒ with respect to ĉ axis, in the configuration described above, the transmission function ͑⌫ , ␤͒ is given by 12 =…”

Precise Method for Measuring the Quadratic Electro-Optic Effect in Noncentrosymmetric Crystals in the Presence of Natural Birefringence

“…A typical order of magnitude of LEOE is 10 −11 -10 −12 mV −1 . An extensive description of the measurement techniques used in the LEOE studies was presented by Aillerie et al [6,7]. Some of the methods described therein, which use the initial natural birefringence compensation, can be used to measure LEOE in the presence of birefringence.…”