Light modulator and exposure head

Patent metadata

Field	Value
Publication number	US-9575389-B2
Application number	US-201414478982-A
Country	US
Kind code	B2
Filing date	Sep 5, 2014
Priority date	Sep 6, 2013
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

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.

First claim

What is claimed is:

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.

2. The light modulator according to claim 1 , wherein
one of the first period and the second period is twice or a larger integer multiple of the other.

3. The light modulator according to claim 1 , wherein
the driver gives rise to Raman-Nath diffraction by the diffraction grating created inside the first periodic polarization reversal structure and gives rise to Raman-Nath diffraction by the diffraction grating created inside the second periodic polarization reversal structure.

4. The light modulator according to claim 1 , wherein
the driver gives rise to Bragg diffraction by the diffraction grating created inside the first periodic polarization reversal structure and gives rise to Raman-Nath diffraction by the diffraction grating created inside the second periodic polarization reversal structure.

5. The light modulator according to claim 4 , wherein the first period is shorter than the second period.

6. The light modulator according to claim 1 , wherein
the driver gives rise to Bragg diffraction by the diffraction grating created inside the first periodic polarization reversal structure and gives rise to Bragg diffraction by the diffraction grating created inside the second periodic polarization reversal structure.

7. The light modulator according to claim 1 , further comprising a first electrode and a second electrode, wherein
each one of the first electro-optic crystal substrate and the second electro-optic crystal substrate is shaped like a flat plate whose principal surfaces are parallel to each other,
the first electrode is disposed extending on one principal surface of the first electro-optic crystal substrate and one principal surface of the second electro-optic crystal substrate,
the second electrode is disposed extending on the other principal surface of the first electro-optic crystal substrate and the other principal surface of the second electro-optic crystal substrate, and
the driver creates an electric potential difference between the first electrode and the second electrode and develops the diffraction gratings.

8. The light modulator according to claim 7 , wherein
in the orthogonal direction to the propagation direction, the width of the first electrode is wider than the width of the first polarization section and the second polarization section and the width of the third polarization section and the fourth polarization section.

9. The light modulator according to claim 7 , further comprising
a holder which is adhered to the other principal surface of the first electro-optic crystal substrate and the other principal surface of the second electro-optic crystal substrate via the second electrode, and holds the first electro-optic crystal substrate and the second electro-optic crystal substrate.

10. The light modulator according to claim 1 , further comprising a plurality of first electrodes and a second electrode, wherein
each one of the first electro-optic crystal substrate and the second electro-optic crystal substrate is shaped like a flat plate whose principal surfaces are parallel to each other,
the first electrodes are disposed on one principal surface of the first electro-optic crystal substrate and one principal surface of the second electro-optic crystal substrate such that the first electrodes extend parallel to the propagation direction and are separated from each other in the orthogonal direction to the propagation direction,
the second electrode is disposed extending on the other principal surface of the first electro-optic crystal substrate and the other principal surface of the second electro-optic crystal substrate, and
the driver creates an electric potential difference between each one of the first electrodes and the second electrode and develops the diffraction gratings between the first electrodes and the second electrode corresponding to every first electrode.

11. The light modulator according to claim 1 , further comprising
a third electro-optic crystal substrate that has a third periodic polarization reversal structure and lets the light through the third periodic polarization reversal structure in which third polarization pairs, in each of which the directions of polarization developing in response to electric fields are opposite to each other, are arranged in a third period along a third arrangement direction which is orthogonal or inclined with respect to the propagation direction, wherein
the driver applies a voltage upon the third electro-optic crystal substrate to create a diffraction grating inside the third periodic polarization reversal structure, thereby modulating the light, and
at least one of a first condition and a second condition is satisfied, the first condition being that the third period is different from the second period, the second condition being that the third arrangement direction is different from the second arrangement direction.

12. The light modulator according to claim 11 , wherein
the first condition is satisfied, and
the first period, the second period and the third period are integer multiple of the shortest one of the first period, the second period and the third period.

13. The light modulator according to claim 12 , wherein
the first period, the second period and the third period are integer multiple of each other.

14. An exposure head, comprising:
an illumination optical system which irradiates light from a light source in a propagation direction;
a light modulator which modulates the light irradiated from the illumination optical system; and
a projection optical system which projects the modulated light from the modulator upon an area-to-be-exposed,
wherein the light modulator comprises:
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

Assignees

• Dainippon Screen Mfg
• Univ Osaka
• Screen Holdings Co Ltd

Inventors

• Okazaki Masahide
• Suhara Toshiaki

Classifications

• G03F7/70191

  Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like · CPC title

• G02F2201/16

  series; tandem · CPC title

• G02F2001/311

  Physics · mapped topic

• G02F2201/307

  Reflective grating, i.e. Bragg grating · CPC title

• G02F2201/305

  diffraction grating · CPC title