Laser stabilization with an actively controlled fabry-perot resonance cavity

Abstract

Tuning of an optical resonator, e.g., a Fabry-Perot resonant etalon, is carried out. The length of the resonator is actively controlled through the frequency of an identical length microwave resonant cavity. The length is tunable over a several micron range with the precision and stability of the microwave source frequency.

What is claimed is: 
     
         1 . A device comprising:
 a resonator structure having a first optical resonator and a second microwave resonator housed therein, where said first and second resonators are coplanar, wherein said structure having a first end of the resonator structure, and a second end of the resonator structure, and lengths of both a first resonator and said second resonator are identical, both defined by a distance between said first and second ends of the resonator structure, a first microwave control loop, connected to inject a microwave signal into said microwave resonator, said first control loop creating an error signal indicative of a frequency difference between said microwave signal and a resonant frequency of said second microwave resonator,   an actuator, connected to said second end of the resonator, and operating based on an applied control signal that this based on said error signal, to change said distance between said first and second ends of the resonator structure,   and thereby controlling the resonant frequency of the optical resonator; and   a second, optical control loop, including a laser, and operating to maintain an output of the laser locked to the resonance of the optical resonator.   
     
     
         2 . The device as in  claim 1 , wherein the output of the laser is the input to the first optical resonator. 
     
     
         3 . The device as in  claim 1 , wherein the optical resonator is a Fabry-Perot etalon. 
     
     
         4 . The device as in  claim 3  wherein the optical control circuit is an optical Pound-Drever-Hall lock. 
     
     
         5 . The device as in  claim 1 , wherein the microwave control loop includes a microwave source and a stabilization for the microwave source. 
     
     
         6 . The device as in  claim 5 , wherein the stabilization for the microwave source includes a rubidium clock. 
     
     
         7 . The device as in  claim 3 , wherein the optical control circuit is a control circuit using serrodyne modulation. 
     
     
         8 . The device as in  claim 2 , wherein the optical resonator includes first and second optical reflectors at first and second ends, and where the light from the laser is injected through said first optical reflector into the optical resonator. 
     
     
         9 . The device as in  claim 1 , wherein the microwave resonator and the optical resonator are coaxial with one another. 
     
     
         10 . An optical control device, comprising:
 a coaxial resonator, having a microwave resonator and an optical resonator coaxial with one another;   a stabilized microwave source, injecting microwave into the microwave resonator;   an error signal detector for detecting an error value between the microwave that is injected and a resonant value of the microwave resonator and producing an output error signal indicative thereof;
 a resonator control part, which changes a length simultaneously of both the microwave resonator and the optical resonator, said resonator control part being operated by said output error signal, 
   thereby changing an optical resonant value of the optical resonator based on a stability of the microwave source.   
     
     
         11 . The device as in  claim 10 , wherein the stabilized microwave source includes a microwave stabilized with a stabilized clock. 
     
     
         12 . The device as in  claim 10 , further comprising an optical control circuit, and a laser, producing its output injected into the optical resonator via said optical control circuit, said optical control circuit forming an optical loop with said laser that maintains a value of said laser output locked with a resonant value of the optical resonator,
 and where said output from said laser is injected into the optical resonator and output from the optical resonator's output as an output of said device.   
     
     
         13 . The device as in  claim 10 , wherein said optical resonator is a Fabry Perot etalon. 
     
     
         14 . The device as in  claim 12 , wherein the laser is injected through a first mirror at a first end of the coaxial resonator and output through a second mirror at a second end of the coaxial resonator. 
     
     
         15 . The device as in  claim 10 , wherein the resonator control part includes a piezoelectric actuator which changes the length of the coaxial resonator to change lengths of both the optical resonator and the microwave resonator. 
     
     
         16 . A method of stabilizing an optical source using microwave stabilization, comprising:
 stabilizing the microwave source, to produce a stabilized programmable frequency microwave output;   injecting the stabilized microwave output into a parallel resonator, which has first and second resonator parts, both of which have the same outer walls, and the same overall length;   using a control circuit to match a frequency of the microwave resonator to a resonant frequency of the stabilized microwave, by changing a length between said outer walls in order to maintain the resonant frequency of the microwave resonator at said frequency of the stabilized microwave; and   using the second control loop to stabilize an output of the laser by maintaining the output of the laser as resonant with the resonant frequency of the optical resonator.   
     
     
         17 . The method as in  claim 16 , wherein said parallel resonator is a coaxial resonator having one resonator inside the other resonator and where said changing the length changes a position of one of the walls of the coaxial resonator. 
     
     
         18 . The method as in  claim 16 , wherein said optical resonator is a Fabry-Perot etalon. 
     
     
         19 . The method as in  claim 18 , wherein said walls have mirrors at their ends in an area of the optical resonator, and the laser output is injected through one mirror, and output through the other mirror.