Optical Refrigerator

Abstract

An optical refrigerator comprises a laser source, a cooling crystal, a cavity for enhancing the absorption of the laser light in the cooling crystal, a thermal link which connects a cold finger to the cooling crystal and prevents the fluorescence from heating the cold finger, an absorbing chamber to remove the fluorescence and eliminate the waste heat, an a mechanical support that keeps the cooling crystal properly aligned with the laser beam and minimizes heat leakage.

What is claimed is: 
     
         1 . An optical refrigerator, comprising:
 (a) a laser source;   (b) a cooling crystal configured to receive light from the laser source;   (c) a cavity configured to enhance the absorption of the laser light in the cooling crystal;   (d) a cold finger configured to accept heat from an object to be cooled by the optical refrigerator;   (d) a thermal link mounted with the cooling crystal and in thermal communication with the cold finger and configured to discourage fluorescence from the cooling crystal from heating the cold finger;   (e) an absorbing chamber mounted to receive fluorescence light from the cooling crystal;   (f) a mechanical support configured to maintain the cooling crystal in optical alignment with the laser source.   
     
     
         2 . An optical refrigerator as in  claim 1 , wherein the thermal link comprises an element with two or more sharp bends. 
     
     
         3 . An optical refrigerator as in  claim 1 , wherein the mechanical support has a spiral shape. 
     
     
         4 . An optical refrigerator as in  claim 1 , wherein the absorbing chamber is coated with a spectrally selective coating. 
     
     
         5 . An optical refrigerator as in  claim 4 , wherein the spectrally selective coating is tarnished silver. 
     
     
         6 . An optical refrigerator as in  claim 1 , wherein the cavity comprises a plurality of mirrors, each of which is configured to reflect light onto at least one other mirror in the plurality of mirrors. 
     
     
         7 . An optical refrigerator as in  claim 6 , wherein at least one of the mirrors has a pinhole therethrough configured to accept light into the cavity. 
     
     
         8 . An optical refrigerator as in  claim 1 , wherein the absorbing chamber comprises one or more photovoltaic cells mounted with the chamber such that fluorescence light impinges on the one or more photovoltaic cells. 
     
     
         9 . An optical refrigerator as in  claim 1 , further comprising a heat sink in thermal communication with the absorption chamber. 
     
     
         10 . An optical refrigerator as in  claim 1 , wherein the thermal link comprises a material having low absorption of fluorescence and high thermal conductivity. 
     
     
         11 . An optical refrigerator as in  claim 1 , wherein the thermal link is configured such that light entering the thermal link escapes through the sides of the thermal link. 
     
     
         12 . An optical refrigerator as in  claim 1 , wherein the cooling crystal comprises a transparent host material doped with a rare earth ion. 
     
     
         13 . An optical refrigerator as in  claim 1 , wherein the absorption chamber has an interior surface with high absorption for light at the wavelength of the fluorescent radiation of the cooling crystal, and low absorption at the wavelengths corresponding to the Planck blackbody radiation at the chamber temperature. 
     
     
         14 . An optical refrigerator as in  claim 4 , wherein the spectrally selective coating is anodized nickel. 
     
     
         15 . An optical refrigerator as in  claim 1 , wherein the thermal link comprises sapphire. 
     
     
         16 . An optical refrigerator as in  claim 1 , wherein the thermal link comprises baffles connected to the absorbing chamber and coated with a selective absorbing coating. 
     
     
         17 . An optical refrigerator as in  claim 1 , wherein the cavity is defined by surfaces of the cooling crystal configured to achieve substantially total internal reflection. 
     
     
         18 . An optical refrigerator as in  claim 1 , wherein the thermal link comprises a highly reflective mirror at one end.