Optical switch attenuator

• US 4,410,238 A
• Filed: 09/03/1981
• Issued: 10/18/1983
• Est. Priority Date: 09/03/1981
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Hanson, Eric G.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Gallivan, Richard F.
• Application Number:
  US06/298,986
• Time in Patent Office: 775 Days
• Field of Search: 350/330, 350/331 R, 350/347 E, 350/353, 350/355, 350/356
• US Class Current: 349/196
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence
• CPC Class Codes: Y10S 359/90 Methods

Abstract

An optical switch having low insertion loss and low crosstalk is provided by two slabs of birefringent material having a polarization rotator as a control element interposed therebetween. By controlling the polarization rotator electrically, a selectable ratio of transmitted-to-displaced output optical power is realized. The optical switch therefore can function as an attenuator to a light beam traversing through it. In the preferred embodiment calcite crystals are used for the slabs, and a liquid crystal cell for the polarization rotator.

Claims

1. An apparatus for selectively attenuating the power of an unpolarized input light beam, the apparatus comprising:

a first transmission medium of birefringent calcite for receiving the input light beam and for splitting said input light beam into ordinary and extraordinary beams having orthogonal polarizations;

a liquid crystal cell having a first surface adjacent to said first transmission medium for receiving said ordinary and extraordinary beams and for selectively rotating the polarization of a portion of each of said beams by 90 degrees; and

,

a second transmission medium of birefringent calcite adjacent to a second surface of the liquid crystal cell, said second transmission medium being operative for receiving the rotated ordinary and extraordinary beams and for splitting said rotated ordinary beam into first and second beams having orthogonal polarizations and for splitting said rotated extraordinary beam into third and fourth beams having orthogonal polarizations such that an unpolarized output light beam is formed from a combination of the second and third beams and the power of said output light beam is variable from substantially zero to substantially the power of the input light beam.

2. A method for selectively attenuating the power of an unpolarized input light beam, the method comprising the steps of:

displacing the input light beam in a calcite slab to form ordinary and extraordinary light beams;

receiving said ordinary and extraordinary light beams in a liquid crystal cell and rotating therein a selected portion of the ordinary and extraordinary light beams by 90 degrees;

splitting said ordinary light beam in another calcite slab to form first and second beams having orthogonal polarizations;

splitting said extraordinary light beam in the other calcite slab to form third and fourth beams having orthogonal polarizations;

combining said second and third beams into an unpolarized output light beam;

selecting the portion of the ordinary and extraordinary light beams which are rotated such that a ratio of the power of the output light beam to the power of the input light beam is variable from substantially zero to substantially unity.