Light modulator and exposure head

摘要

A first electro-optic crystal substrate and a second electro-optic crystal substrate are provided as an electro-optic crystal substrate. The first electro-optic crystal substrate comprises a first periodic polarization reversal structure in which first polarization pairs, in each of which the directions of polarization in response to electric fields are opposite to each other, are arranged in a first period along a first arrangement direction which is orthogonal or inclined with respect to the direction of propagation, and light passes through the first periodic polarization reversal structure. The second electro-optic crystal substrate comprises a second periodic polarization reversal structure in which second polarization pairs, in each of which the directions of polarization in response to electric fields are opposite to each other, are arranged in a second period along a second arrangement direction which is orthogonal or inclined with respect to the direction of propagation, and light outstanding from the first electro-optic crystal substrate passes through the second periodic polarization reversal structure. At least one of a first condition and a second condition is satisfied. The first condition is that the first and the second periods are different from each other and a second condition is that the first arrangement direction and the second arrangement direction are different from each other.

主权项

1. A light modulator which modulates light propagating in a propagation direction, comprising:
a first electro-optic crystal substrate having a first periodic polarization reversal structure including a plurality of first and second polarization sections alternately arranged in a first period along a first arrangement direction orthogonal to the propagation direction to allow the light to propagate through the first periodic polarization reversal structure, directions of polarization developed in each first polarization section and each second polarization section in response to electric fields being opposite to each other; a second electro-optic crystal substrate having a second periodic polarization reversal structure including a plurality of third and fourth polarization sections alternately arranged in a second period along a second arrangement direction orthogonal to the propagation direction to allow outgoing light from the first electro-optic crystal substrate to propagate through the second periodic polarization reversal structure, directions of polarization developed in each third polarization section and each fourth polarization section in response to electric fields being opposite to each other; and a driver that applies a voltage upon the first electro-optic crystal substrate and the second electro-optic crystal substrate to create diffraction gratings inside the first periodic polarization reversal structure and the second periodic polarization reversal structure, thereby modulating the light, wherein the first period and the second period are different from each other.