Chiral smectic liquid crystal multipass optical filters including a variable retarder (and a variable isotropic spacer)
First Claim
1. A tunable optical filter for receiving linearly polarized input light and for transmitting light of a selected design wavelength, comprising:
- a front and a back reflector positioned to form a multipass cavity;
an exit polarizer positioned on the opposite side of said back reflector from said front reflector and oriented at angle θ
with respect to the polarization of the input light;
a variable retarder positioned between said front and back reflectors and oriented at angle ρ
with respect to the polarization of the input light, said variable retarder being a half- or full-wave retarder at the design wavelength;
a first quarter-wave retarder positioned between said front reflector and said variable retarder and oriented parallel or perpendicular to the polarization of the input light; and
a second quarter-wave retarder positioned between said back reflector and said variable retarder and oriented parallel or perpendicular to the polarization of the input light;
wherein said variable retarder is a multiple-element retarder comprising a planar-aligned chiral smectic liquid crystal half-wave retarder, the optic axis of which is rotatable by application of an electric field parallel to the smectic layers, said variable retarder further comprising third and fourth quarter-wave retarders positioned in series with and on first and second sides, respectively, of said liquid crystal half-wave retarder, wherein said third and fourth quarter-wave retarders are oriented parallel or perpendicular to each other and at an angle of ρ
±
45°
with respect to the polarization of the input light.
1 Assignment
0 Petitions
Accused Products
Abstract
This invention provides a multipass Solc filter which utilizes liquid crystal variable retarders to provide high resolution and tunability. The Solc polarization-interference effects are used synergistically with the Fabry-Perot cavity resonances. The cavity comprises a central retarder, two quarter wave plates, and an optional isotropic spacer. The central retarder or the isotropic spacer can include liquid crystal cells to provide tuning of the Solc envelope or the cavity resonances respectively. In one embodiment the variable retarder is a three element quarter-half-quarter device with a liquid crystal electro-optically rotatable half-wave plate. Reflection mode configurations are introduced wherein, because of the bilateral symmetry of the Solc filter, it is possible to use only half of the intracavity elements. Criteria for designing filter parameters to meet resolution, out-of-band discrimination, and tuning range requirements are provided.
-
Citations
23 Claims
-
1. A tunable optical filter for receiving linearly polarized input light and for transmitting light of a selected design wavelength, comprising:
-
a front and a back reflector positioned to form a multipass cavity; an exit polarizer positioned on the opposite side of said back reflector from said front reflector and oriented at angle θ
with respect to the polarization of the input light;a variable retarder positioned between said front and back reflectors and oriented at angle ρ
with respect to the polarization of the input light, said variable retarder being a half- or full-wave retarder at the design wavelength;a first quarter-wave retarder positioned between said front reflector and said variable retarder and oriented parallel or perpendicular to the polarization of the input light; and a second quarter-wave retarder positioned between said back reflector and said variable retarder and oriented parallel or perpendicular to the polarization of the input light; wherein said variable retarder is a multiple-element retarder comprising a planar-aligned chiral smectic liquid crystal half-wave retarder, the optic axis of which is rotatable by application of an electric field parallel to the smectic layers, said variable retarder further comprising third and fourth quarter-wave retarders positioned in series with and on first and second sides, respectively, of said liquid crystal half-wave retarder, wherein said third and fourth quarter-wave retarders are oriented parallel or perpendicular to each other and at an angle of ρ
±
45°
with respect to the polarization of the input light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
-
Specification