Compact mid-IR laser

{
  "publication_number": "US2007291804A1",
  "country": "US",
  "kind": "A1",
  "title": "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.",
  "claims": [
    "1. A mid-IR (MIR) laser device comprising: a housing; a thermo electric cooling (TEC) device contained within said housing; a heat spreader mounted within said housing (1) above a top surface of said TEC or (2) above an intermediate plate positioned between said top surface of said TEC and said heat spreader; a quantum cascade laser contained within said housing and fixedly coupled to said heat spreader; an optical lens contained within said housing and fixedly mounted to said heat spreader for collimating light output from said quantum cascade laser to an exterior of said housing; said heat spreader serving to distribute heat to said TEC and also serving as an optical platform to fixedly position said quantum cascade laser and said optical lens relative to one another. 2. The MIR laser device as recited in claim 1 wherein said housing has dimensions of approximately 20 cm×20 cm×20 cm or less. 3. The MIR laser device as recited in claim 1 wherein said housing has dimensions of approximately 3 cm×4 cm×6 cm. 4. The MIR laser device as recited in claim 1 wherein said optical lens has a diameter of approximately 10 mm or less. 5. The MIR laser device as recited in claim 2 wherein said optical lens has a diameter of approximately 10 mm or less. 6. The MIR laser device as recited in claim 3 wherein said optical lens has a diameter of approximately 10 mm or less. 7. The MIR laser device as recited in claim 1 wherein said optical lens has a diameter of approximately 5 mm or less. 8. The MIR laser device as recited in claim 1 wherein said heat spreader have a thermal conductivity approximately 150-400 W/mK. 9. The MIR laser device as recited in claim 1 wherein said heat spreader comprises CuW. 10. The MIR laser device as recited in claim 1 further comprising a high thermal conductivity sub-mount interposed between said quantum cascade laser and said heat spreader, said sub-mount comprising at least diamond. 11. The MIR laser device as recited in claim 1 further comprising a high thermal conductivity sub-mount interposed between said quantum cascade laser and said substrate said high thermal conductivity sub-mount having a thermal conductivity of approximately 500-2000 W/mK. 12. The MIR laser device as recited in claim 1 further comprising an electronics sub-assembly comprising: a switch contained within said housing; an summing node, contained within said housing; an RF input port for inputting an RF modulating signal; a drive current input terminal electrically connected to said quantum cascade laser for inputting drive current to said quantum cascade laser; a switching control signal input terminal for inputting a switching control signal for switching said switch between a first and second state; said switch electrically connected to said quantum cascade laser and operative in a first state to turn said quantum cascade laser on and in a second state operative to turn said quantum cascade laser off; said summing node interposed in an electrical path between said drive current input terminal and said quantum cascade laser to add said RF modulating signal to said drive current. 13. A mid IR (MIR) laser device comprising: a housing; a quantum cascade laser contained within said housing; an optical lens contained within said housing and mounted for collimating light output from said quantum cascade laser; said optical lens having a diameter of approximately 10 mm or less. 14. The MIR laser device as recited in claim 13 wherein said housing forms a rectangular structure having dimensions of approximately 20 cm×20 cm×20 cm or less. 15. The MIR laser device as recited in claim 13 further comprising a window contained within an aperture of said housing for permitting light from said quantum cascade laser to pass therethrough, and said housing being hermetically sealed. 16. The MIR laser device as recited in claim 13 wherein said optical lens has a diameter of approximately 5 mm or less. 17. The MIR laser device as recited in claim 13 further comprising an electronics sub-assembly comprising: a switch contained within said housing; an summing node, contained within said housing; an RF input port for inputting an RF modulating signal; a drive current input terminal electrically connected to said quantum cascade laser for inputting drive current to said quantum cascade laser; a switching control signal input terminal for inputting a switching control signal for switching said switch between a first and second state; said switch electrically connected to said quantum cascade laser and operative in a first state to turn said quantum cascade laser on and in a second state operative to turn said quantum cascade laser off; said summing node interposed in an electrical path between said drive current input terminal and said quantum cascade laser to add said RF modulating signal to said drive current. 18. The MIR laser device as recited in claim 13 further comprising: a cooling device contained within said housing; a heat spreader mounted within said housing (1) above a top surface of said cooling device or (2) above an intermediate plate positioned between said top surface of said cooling device and said heat spreader; said quantum cascade laser fixedly coupled to said heat spreader; said optical lens contained within said housing and fixedly mounted to said-heat spreader for collimating light output from said quantum cascade laser to an exterior of said housing; said heat spreader serving to distribute heat to said cooling device and also serving as an optical platform to fixedly position said quantum cascade laser and said optical lens relative to one another. 19. A mid IR (MIR) laser device comprising: a housing; a quantum cascade laser contained within said housing; an optical lens contained within said housing and mounted for collimating light output from said quantum cascade laser; said housing have a dimensions of approximately 20 cm×20 cm×20 cm or less. 20. The MIR laser device as recited in claim 19 wherein the dimensions of said housing are approximately 3 cm×4 cm×6 cm. 21. The MIR laser device as recited in claim 19 further comprising a window contained within an aperture of said housing for permitting light from said quantum cascade laser to pass therethrough, and said housing being hermetically sealed. 22. The MIR laser device as recited in claim 19 further comprising an electronics sub-assembly comprising: a switch contained within said housing; an summing node, contained within said housing; an RF input port for inputting an RF modulating signal; a drive current input terminal electrically connected to said quantum cascade laser for inputting drive current to said quantum cascade laser; a switching control signal input terminal for inputting a switching control signal for switching said switch between a first and second state; said switch electrically connected to said quantum cascade laser and operative in a first state to turn said quantum cascade laser on and in a second state operative to turn said quantum cascade laser off; said summing node interposed in an electrical path between said drive current input terminal and said quantum cascade laser to add said RF modulating signal to said drive current. 23. The MIR laser device as recited in claim 19 further comprising: a high thermal conductivity mount contained within said housing and directly thermally coupled to said quantum cascade laser; a heat spreader contained within said housing and directly coupled for thermal communication to said high thermal conductivity mount; a thermo electric cooling (TEC) device contained within said housing and in conductive thermal communication with said heat spreader; whereby heat from said quantum cascade laser is dissipated by said high thermal conductivity mount and said heat spreader and transferred remote from said quantum cascade laser by said TEC device. 24. The MIR laser device as recited in claim 23 wherein said high thermal conductivity mount comprises diamond. 25. The MIR laser device as recited in claim 23 wherein said high thermal conductivity mount having a thermal conductivity of approximately 500-2000 W/mK; said heat spreader have a thermal conductivity approximately 150-400 W/mK. 26. The MIR laser device as recited in claim 19 further comprising: a heat spreader contained within said housing and directly coupled for thermal communication to said quantum cascade laser; a cooling device contained within said housing and in conductive thermal communication with said heat spreader; whereby heat from said quantum cascade laser is dissipated by said heat spreader and transferred remote from said quantum cascade laser by said cooling device."
  ],
  "description_excerpt": "1. Field of the Invention\n\nEmbodiments of the invention relate to a compact Mid-Infrared (MIR) laser which finds applications in many fields such as, molecular detection and imaging instruments for use in medical diagnostics, pollution monitoring, leak detection, analytical instruments, homeland security and industrial process control. Embodiments of the invention are also directed more specifically to the detection of molecules found in human breath, since such molecules correlate to existing health problems such as asthma, kidney disorders and renal failure.\n\n2. Description of Related Art\n\nMIR lasers of interest herein may be defined as, lasers having a laser output wavelength in the range of approximately 3-12 arm (3333-833 cm −1). More broadly, however, “MIR” may be defined as wavelengths within a range of 3-30 μm. The far-IR is generally considered 30 300 μm, whereas the near IR is generally considered 0.8 to 3.0 μm. Such lasers are particularly advantageous for use in absorption spectroscopy applications since many gases of interest have their fundamental vibrational modes in the mid-infrared and thus present strong, unique absorption signatures within the MIR range.\n\nVarious proposed applications of MIR lasers have been demonstrated in laboratories on bench top apparatuses. Actual application of MIR lasers has been more limited and hampered by bulky size and cost of these devices.\n\nOne laser gain medium particularly useful for MIR lasers is the quantum cascade laser (QCL).",
  "cpc": [
    "H01S 5/02216",
    "B82Y 20/00",
    "G02B 3/00",
    "G02B 7/023",
    "H01S 5/005",
    "H01S 5/02325",
    "H01S 5/02415",
    "H01S 5/02492",
    "H01S 5/0427",
    "H01S 5/06226",
    "H01S 5/3401"
  ],
  "ipc": [
    "H01S 3/04",
    "H01S 3/08",
    "H01S 3/30"
  ],
  "inventors": [
    "Timothy Day",
    "David Arnone"
  ],
  "filing_date": "2005-06-15",
  "publication_date": "2007-12-20",
  "priority_date": "2005-06-15",
  "application_number": "US-15426405-A",
  "family_id": "37679005",
  "cited_by_count": 67,
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}