Electro-optic modulator

This is caused by forces that distort the position, orientation, or shape of the molecules constituting the material.Generally, a nonlinear optical material, such as ferroelectrics like lithium niobate (LiNbO3) or barium titanate (BaTiO3), polymers, or organic electro-optic materials, with an incident static or low frequency optical field will see a modulation of its refractive index.The simplest kind of EOM consists of a crystal, such as lithium niobate, whose refractive index is a function of the strength of the local electric field.That means that if lithium niobate is exposed to an electric field, light will travel more slowly through it.Therefore, the phase of the laser light exiting an EOM can be controlled by changing the electric field in the crystal.There is a useful identity involving Bessel functions called the Jacobi–Anger expansion which can be used to derive which gives the amplitudes of all the sidebands.This alternative technique is often used in integrated optics where the requirements of phase stability is more easily achieved.The beam splitter divides the laser light into two paths, one of which has a phase modulator as described above.Changing the electric field on the phase modulating path will then determine whether the two beams interfere constructively or destructively at the output, and thereby control the amplitude or intensity of the exiting light.Polarization modulation in electro-optic crystals can also be used as a technique for time-resolved measurement of unknown electric fields.It describes a change in the absorption spectrum due to a shift in the band gap edge when an electric field is present.