Optical Isolator, Shutter, Variable Optical Attenuator and Modulator Device And Method

Abstract

An integrated optical device functioning as optical isolator, shutter, variable optical attenuator, and modulator is disclosed. The device employs a Pockels cell for dynamically rotating with nanosecond speed the polarization state of incident light for attenuation and modulation. The invention provides a compact, high performance and reliable device without moving parts for use in laser systems and particularly in fiber optic telecommunication system.

What is claimed is: 
     
         1 . A method for providing a modifiable intensity output beam from an input light beam, the method comprising:
 polarizing the input light beam along a first plane of polarization;   rotating the polarized input beam by a Faraday rotator to generate a first rotated beam, wherein the first rotated beam is rotated by an angle of about 45 degrees relative to the first plane of polarization;   rotating by a Pockels cell the first rotated beam in response to an external input voltage to generate a second rotated beam, where the second rotated beam rotated by an angle between 0 and 90 degrees relative to the first rotated beam depending on the external input voltage; and   polarizing the second rotated beam to generate the modifiable intensity output beam having a maximum intensity when the second rotated beam is rotated by 0 degrees, zero or close to zero intensity when the second rotated beam is rotated by 90 degrees, and variable intensity when the second rotated beam is rotated in a range between 0 degrees and 90 degrees.   
     
     
         2 . The method of  claim 1 , wherein the input light beam is substantially linearly polarized, substantially coherent, monochromatic and collimated, and oriented with the first plane of polarization. 
     
     
         3 . The method of  claim 1 , wherein the Faraday rotator is configured for a single wavelength or within certain wavelength range to rotate the polarized input light beam by an angle of 45 degrees of the first polarization plane. 
     
     
         4 . The method of  claim 1 , wherein the Faraday rotator is selected to meet a wavelength requirement for a particular application. 
     
     
         5 . The method of  claim 1 ,
 wherein the Pockels cell includes an electric field sensitive medium;   wherein the external input voltage supplies energy for an electric field applied to the electric field sensitive medium of the Pockels cell; and   wherein the electric field applied to the Pockels cell electric field sensitive medium is either longitudinal or transverse to the light beam input to the Pockels cell.   
     
     
         6 . The method of  claim 5 , wherein the Pockels cell electric field sensitive medium is selected to meet a specific wavelength requirement for a particular application. 
     
     
         7 . The method of  claim 1 ,
 wherein the Faraday rotator and the Pockels cell have a number of facets; and   wherein all facets the Faraday rotator and the Pockels cell are coated with multiple layers of anti-reflection dielectric thin films to eliminate reflections and reduce light insertion loss.   
     
     
         8 . The method of  claim 1 ,
 wherein light beams pass respectively through the Faraday rotator and the Pockels cell; and   wherein the Faraday rotator and the Pockels cell are bonded with adhesives that are transparent to the selected optical wavelength, or bonded by adhesives without interfering with areas through which the light beam passes.