Compact mid-ir laser

Abstract

A compact mid-IR laser device utilizes a quantum cascade laser to provide mid-IR frequencies suitable for use in molecular detection by signature absorption spectra. The compact nature of the device is obtained owing to an efficient heat transfer structure, the use of a small diameter aspheric lens and a monolithic assembly structure to hold the optical elements in a fixed position relative to one another. The compact housing size may be approximately 20 cm×20 cm×20 cm or less. Efficient heat transfer is achieved using a thermoelectric cooler TEC combined with a high thermal conductivity heat spreader onto which the quantum cascade laser is thermally coupled. The heat spreader not only serves to dissipate heat and conduct same to the TEC, but also serves as an optical platform to secure the optical elements within the housing in a fixed relationship relative on one another. A small diameter aspheric lens may have a diameter of 10 mm or less and is positioned to provided a collimated beam output from the quantum cascade laser. The housing is hermetically sealed to provide a rugged, light weight portable MIR laser source.

1 . A handheld target marker viewable by a thermal imaging system, the marker comprising:
 (a) a compact housing having an interior and an exterior;   (b) a quantum cascade laser retained in the interior of the housing for emitting a beam at a thermal infrared wavelength along a beam path, a portion of the beam path extending from the housing to a target being substantially optically direct;   (c) a driver retained within the housing and operably connected to the quantum cascade laser causing the quantum cascade laser to emit the beam along the beam path   (d) a lens located in the beam path; and   (e) an imager to capture the image of target.   
     
     
         2 . The handheld target marker of  claim 1 , wherein the wavelength of the beam is between approximately 2-30 microns. 
     
     
         3 . The handheld target marker of  claim 1 , wherein the marker is one of a designator, a pointer, and an aiming device. 
     
     
         4 . The handheld target marker of  claim 1 , further comprising a temperature controller thermally coupled to the quantum cascade laser. 
     
     
         5 . The handheld target marker of  claim 4 , wherein the temperature controller is one of a Peltier module and a Stirling module. 
     
     
         6 . The handheld target marker of  claim 1 , further comprising a diffractive optic in the beam path. 
     
     
         7 . The handheld target marker of  claim 6 , wherein the diffractive optic collimates the beam. 
     
     
         8 . The handheld target marker of  claim 6 , wherein the diffractive optic is movable relative to the beam path. 
     
     
         9 . The handheld target marker of  claim 6 , wherein the diffractive optic is fixed relative to the beam path. 
     
     
         10 . The handheld target marker of  claim 1 , wherein the power supply is operably connected to the both the quantum cascade laser and the driver. 
     
     
         11 . A method of marking a target comprising:
 (a) intersecting a thermal infrared beam from a quantum cascade laser retained in a handheld housing, a portion of a beam path extending from the housing to the target being substantially optically direct;   (b) capturing a portion of the beam; and   (c) imaging the target and at least a portion of the beam.   
     
     
         12 . The method of  claim 11 , further comprising forming the infrared beam to have a wavelength between approximately 8 microns and 30 microns. 
     
     
         13 . The method of  claim 11 , further comprising forming the infrared beam to have a wavelength between approximately 2 microns and 5 microns. 
     
     
         14 . The method of  claim 11 , further comprising sealing the quantum cascade laser in the housing. 
     
     
         15 . The method of  claim 11 , further comprising hermetically sealing the quantum cascade laser in the housing. 
     
     
         16 . A weapons-mounted target marker viewable by a thermal imaging system, the marker comprising:
 (a) a housing mounted to a firearm, the housing having an interior and an exterior;   (b) a quantum cascade laser retained in the interior of the housing for emitting a beam at a thermal infrared wavelength along a beam path;   (c) a driver retained within the housing and operably connected to the quantum cascade laser;   (d) a lens located in the beam path; and   (e) an imager.   
     
     
         17 . The weapons-mounted target marker of  claim 16 , wherein the wavelength of the beam is between approximately 2-30 microns. 
     
     
         18 . The weapons-mounted target marker of  claim 16 , wherein the marker is one of a designator, a pointer, and an aiming device. 
     
     
         19 . The weapons-mounted target marker of  claim 16 , further comprising a temperature controller thermally coupled to the quantum cascade laser. 
     
     
         20 . The weapons-mounted target marker of  claim 19 , wherein the temperature controller is one of a Peltier module and a Stirling module. 
     
     
         21 . The weapons-mounted target marker of  claim 16 , further comprising a diffractive optic in the beam path. 
     
     
         22 . The weapons-mounted target marker of  claim 21 , wherein the diffractive optic collimates the beam. 
     
     
         23 . The weapons-mounted target marker of  claim 21 , wherein the diffractive optic is movable relative to the beam path. 
     
     
         24 . The weapons-mounted target marker of  claim 21 , wherein the diffractive optic is fixed relative to the beam path.