Abstract

An alternative pump scheme, named indirect pump one is proposed to clarify its own feasibility. The high device performances of 8 µm quantum cascade lasers with cavity lengths of 4 mm and 1.5 mm are demonstrated: low threshold current densities of 2.7 and 3.3 kA/cm2 and maximum output powers of 362 and 50 mW at room temperature, and high T0-values of 243 and 303 K around room temperature. The higher T0-value, 303 K is the highest record ever reported with quantum cascade lasers. The high stability for temperature changes is interpreted in terms of the indirect pumping model.

© 2008 Optical Society of America

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  1. A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
    [CrossRef]
  2. M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
    [CrossRef] [PubMed]
  3. K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
    [CrossRef]
  4. J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho "Quantum cascade laser," Science 264, 553-556 (1994).
    [CrossRef] [PubMed]
  5. C. Sirtori, F. Capasso, J. Faist, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "Resonant tunneling in quantum cascade lasers," IEEE J-QE 34, 1722-1729 (1998).
    [CrossRef]
  6. G. Scamarcio, M. Troccoli, F. Capasso, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "High peak power (2.2 W) superlattice quantum cascade laser," Electron. Lett. 37, 295-296 (2001).
    [CrossRef]
  7. H. Callebaut and Q. Hu, "Importance of coherence for electron transport in teraherz quantum cascade lasers," J. Appl. Phys. 98,104505 (2005).
    [CrossRef]
  8. M. Yamanishi, T. Edamura, K. Fujita, N. Akikusa, and H. Kan, "Theory of the intrinsic linewidth of quantum cascade lasers: hidden reason for the narrow linewidth and line-broadening by thermal photons," IEEE J-QE 44, 12-29 (2008).
    [CrossRef]
  9. A. Wittmann, T. Gresch, E. Gini, L. Hovzdara, N. Hoyler, M. Giovannini, and J. Faist, "High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications," IEEE J-QE 44, 36-40 (2008).
    [CrossRef]
  10. Q. J. Wang, C. Pfluegl, L. Diehl, F. Capasso, S. Furuta, and H. Kan, "High-power long-wavelength room-temperature MOVPE-grown quantum cascade lasers with air-semiconductor waveguide," Electron. Lett. 44, 525-526 (2008).
    [CrossRef]
  11. J. Faist, "Wall-plug efficiency of quantum cascade lasers: critical parameters and fundamental limits," Appl. Phys. Lett. 90,253512 (2007).
    [CrossRef]
  12. B. S. Williams, "Terahertz quantum-cascade lasers," Nat. Photonics 1,517-525 (2007).
    [CrossRef]

2008 (3)

M. Yamanishi, T. Edamura, K. Fujita, N. Akikusa, and H. Kan, "Theory of the intrinsic linewidth of quantum cascade lasers: hidden reason for the narrow linewidth and line-broadening by thermal photons," IEEE J-QE 44, 12-29 (2008).
[CrossRef]

A. Wittmann, T. Gresch, E. Gini, L. Hovzdara, N. Hoyler, M. Giovannini, and J. Faist, "High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications," IEEE J-QE 44, 36-40 (2008).
[CrossRef]

Q. J. Wang, C. Pfluegl, L. Diehl, F. Capasso, S. Furuta, and H. Kan, "High-power long-wavelength room-temperature MOVPE-grown quantum cascade lasers with air-semiconductor waveguide," Electron. Lett. 44, 525-526 (2008).
[CrossRef]

2007 (3)

J. Faist, "Wall-plug efficiency of quantum cascade lasers: critical parameters and fundamental limits," Appl. Phys. Lett. 90,253512 (2007).
[CrossRef]

B. S. Williams, "Terahertz quantum-cascade lasers," Nat. Photonics 1,517-525 (2007).
[CrossRef]

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

2006 (1)

A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
[CrossRef]

2005 (1)

H. Callebaut and Q. Hu, "Importance of coherence for electron transport in teraherz quantum cascade lasers," J. Appl. Phys. 98,104505 (2005).
[CrossRef]

2002 (1)

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

2001 (1)

G. Scamarcio, M. Troccoli, F. Capasso, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "High peak power (2.2 W) superlattice quantum cascade laser," Electron. Lett. 37, 295-296 (2001).
[CrossRef]

1998 (1)

C. Sirtori, F. Capasso, J. Faist, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "Resonant tunneling in quantum cascade lasers," IEEE J-QE 34, 1722-1729 (1998).
[CrossRef]

1994 (1)

J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho "Quantum cascade laser," Science 264, 553-556 (1994).
[CrossRef] [PubMed]

Aellen, T.

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

Akikusa, N.

M. Yamanishi, T. Edamura, K. Fujita, N. Akikusa, and H. Kan, "Theory of the intrinsic linewidth of quantum cascade lasers: hidden reason for the narrow linewidth and line-broadening by thermal photons," IEEE J-QE 44, 12-29 (2008).
[CrossRef]

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

Beck, M.

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

Blaser, S.

A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
[CrossRef]

Callebaut, H.

H. Callebaut and Q. Hu, "Importance of coherence for electron transport in teraherz quantum cascade lasers," J. Appl. Phys. 98,104505 (2005).
[CrossRef]

Capasso, F.

Q. J. Wang, C. Pfluegl, L. Diehl, F. Capasso, S. Furuta, and H. Kan, "High-power long-wavelength room-temperature MOVPE-grown quantum cascade lasers with air-semiconductor waveguide," Electron. Lett. 44, 525-526 (2008).
[CrossRef]

G. Scamarcio, M. Troccoli, F. Capasso, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "High peak power (2.2 W) superlattice quantum cascade laser," Electron. Lett. 37, 295-296 (2001).
[CrossRef]

C. Sirtori, F. Capasso, J. Faist, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "Resonant tunneling in quantum cascade lasers," IEEE J-QE 34, 1722-1729 (1998).
[CrossRef]

J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho "Quantum cascade laser," Science 264, 553-556 (1994).
[CrossRef] [PubMed]

Cho, A. Y.

G. Scamarcio, M. Troccoli, F. Capasso, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "High peak power (2.2 W) superlattice quantum cascade laser," Electron. Lett. 37, 295-296 (2001).
[CrossRef]

C. Sirtori, F. Capasso, J. Faist, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "Resonant tunneling in quantum cascade lasers," IEEE J-QE 34, 1722-1729 (1998).
[CrossRef]

J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho "Quantum cascade laser," Science 264, 553-556 (1994).
[CrossRef] [PubMed]

Diehl, L.

Q. J. Wang, C. Pfluegl, L. Diehl, F. Capasso, S. Furuta, and H. Kan, "High-power long-wavelength room-temperature MOVPE-grown quantum cascade lasers with air-semiconductor waveguide," Electron. Lett. 44, 525-526 (2008).
[CrossRef]

Edamura, T.

M. Yamanishi, T. Edamura, K. Fujita, N. Akikusa, and H. Kan, "Theory of the intrinsic linewidth of quantum cascade lasers: hidden reason for the narrow linewidth and line-broadening by thermal photons," IEEE J-QE 44, 12-29 (2008).
[CrossRef]

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

Faist, J.

A. Wittmann, T. Gresch, E. Gini, L. Hovzdara, N. Hoyler, M. Giovannini, and J. Faist, "High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications," IEEE J-QE 44, 36-40 (2008).
[CrossRef]

J. Faist, "Wall-plug efficiency of quantum cascade lasers: critical parameters and fundamental limits," Appl. Phys. Lett. 90,253512 (2007).
[CrossRef]

A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
[CrossRef]

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

C. Sirtori, F. Capasso, J. Faist, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "Resonant tunneling in quantum cascade lasers," IEEE J-QE 34, 1722-1729 (1998).
[CrossRef]

J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho "Quantum cascade laser," Science 264, 553-556 (1994).
[CrossRef] [PubMed]

Fujita, K.

M. Yamanishi, T. Edamura, K. Fujita, N. Akikusa, and H. Kan, "Theory of the intrinsic linewidth of quantum cascade lasers: hidden reason for the narrow linewidth and line-broadening by thermal photons," IEEE J-QE 44, 12-29 (2008).
[CrossRef]

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

Furuta, S.

Q. J. Wang, C. Pfluegl, L. Diehl, F. Capasso, S. Furuta, and H. Kan, "High-power long-wavelength room-temperature MOVPE-grown quantum cascade lasers with air-semiconductor waveguide," Electron. Lett. 44, 525-526 (2008).
[CrossRef]

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

Gini, E.

A. Wittmann, T. Gresch, E. Gini, L. Hovzdara, N. Hoyler, M. Giovannini, and J. Faist, "High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications," IEEE J-QE 44, 36-40 (2008).
[CrossRef]

A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
[CrossRef]

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

Giovannini, M.

A. Wittmann, T. Gresch, E. Gini, L. Hovzdara, N. Hoyler, M. Giovannini, and J. Faist, "High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications," IEEE J-QE 44, 36-40 (2008).
[CrossRef]

A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
[CrossRef]

Gresch, T.

A. Wittmann, T. Gresch, E. Gini, L. Hovzdara, N. Hoyler, M. Giovannini, and J. Faist, "High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications," IEEE J-QE 44, 36-40 (2008).
[CrossRef]

Hofstetter, D.

A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
[CrossRef]

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

Hovzdara, L.

A. Wittmann, T. Gresch, E. Gini, L. Hovzdara, N. Hoyler, M. Giovannini, and J. Faist, "High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications," IEEE J-QE 44, 36-40 (2008).
[CrossRef]

Hoyler, N.

A. Wittmann, T. Gresch, E. Gini, L. Hovzdara, N. Hoyler, M. Giovannini, and J. Faist, "High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications," IEEE J-QE 44, 36-40 (2008).
[CrossRef]

Hu, Q.

H. Callebaut and Q. Hu, "Importance of coherence for electron transport in teraherz quantum cascade lasers," J. Appl. Phys. 98,104505 (2005).
[CrossRef]

Hutchinson, A. L.

G. Scamarcio, M. Troccoli, F. Capasso, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "High peak power (2.2 W) superlattice quantum cascade laser," Electron. Lett. 37, 295-296 (2001).
[CrossRef]

C. Sirtori, F. Capasso, J. Faist, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "Resonant tunneling in quantum cascade lasers," IEEE J-QE 34, 1722-1729 (1998).
[CrossRef]

J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho "Quantum cascade laser," Science 264, 553-556 (1994).
[CrossRef] [PubMed]

Hvozdara, L.

A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
[CrossRef]

Ilegems, M.

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

Kan, H.

M. Yamanishi, T. Edamura, K. Fujita, N. Akikusa, and H. Kan, "Theory of the intrinsic linewidth of quantum cascade lasers: hidden reason for the narrow linewidth and line-broadening by thermal photons," IEEE J-QE 44, 12-29 (2008).
[CrossRef]

Q. J. Wang, C. Pfluegl, L. Diehl, F. Capasso, S. Furuta, and H. Kan, "High-power long-wavelength room-temperature MOVPE-grown quantum cascade lasers with air-semiconductor waveguide," Electron. Lett. 44, 525-526 (2008).
[CrossRef]

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

Melcher, H.

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

Ochiai, T.

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

Oesterle, U.

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, and H. Melcher, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

Pfluegl, C.

Q. J. Wang, C. Pfluegl, L. Diehl, F. Capasso, S. Furuta, and H. Kan, "High-power long-wavelength room-temperature MOVPE-grown quantum cascade lasers with air-semiconductor waveguide," Electron. Lett. 44, 525-526 (2008).
[CrossRef]

Scamarcio, G.

G. Scamarcio, M. Troccoli, F. Capasso, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "High peak power (2.2 W) superlattice quantum cascade laser," Electron. Lett. 37, 295-296 (2001).
[CrossRef]

Sirtori, C.

C. Sirtori, F. Capasso, J. Faist, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "Resonant tunneling in quantum cascade lasers," IEEE J-QE 34, 1722-1729 (1998).
[CrossRef]

J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho "Quantum cascade laser," Science 264, 553-556 (1994).
[CrossRef] [PubMed]

Sivco, D. L.

G. Scamarcio, M. Troccoli, F. Capasso, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "High peak power (2.2 W) superlattice quantum cascade laser," Electron. Lett. 37, 295-296 (2001).
[CrossRef]

C. Sirtori, F. Capasso, J. Faist, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "Resonant tunneling in quantum cascade lasers," IEEE J-QE 34, 1722-1729 (1998).
[CrossRef]

J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho "Quantum cascade laser," Science 264, 553-556 (1994).
[CrossRef] [PubMed]

Sugiyama, A.

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

Troccoli, M.

G. Scamarcio, M. Troccoli, F. Capasso, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "High peak power (2.2 W) superlattice quantum cascade laser," Electron. Lett. 37, 295-296 (2001).
[CrossRef]

Wang, Q. J.

Q. J. Wang, C. Pfluegl, L. Diehl, F. Capasso, S. Furuta, and H. Kan, "High-power long-wavelength room-temperature MOVPE-grown quantum cascade lasers with air-semiconductor waveguide," Electron. Lett. 44, 525-526 (2008).
[CrossRef]

Williams, B. S.

B. S. Williams, "Terahertz quantum-cascade lasers," Nat. Photonics 1,517-525 (2007).
[CrossRef]

Wittmann, A.

A. Wittmann, T. Gresch, E. Gini, L. Hovzdara, N. Hoyler, M. Giovannini, and J. Faist, "High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications," IEEE J-QE 44, 36-40 (2008).
[CrossRef]

A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
[CrossRef]

Yamanishi, M.

M. Yamanishi, T. Edamura, K. Fujita, N. Akikusa, and H. Kan, "Theory of the intrinsic linewidth of quantum cascade lasers: hidden reason for the narrow linewidth and line-broadening by thermal photons," IEEE J-QE 44, 12-29 (2008).
[CrossRef]

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

Appl. Phys. Lett. (3)

A. Wittmann, M. Giovannini, J. Faist, L. Hvozdara, S. Blaser, D. Hofstetter, and E. Gini, "Room temperature, continuous wave operation of distributed feedback quantum cascade lasers with widely spaced operation frequencies," Appl. Phys. Lett. 89, 141116 (2006).
[CrossRef]

K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, "Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy," Appl. Phys. Lett. 91, 141121 (2007).
[CrossRef]

J. Faist, "Wall-plug efficiency of quantum cascade lasers: critical parameters and fundamental limits," Appl. Phys. Lett. 90,253512 (2007).
[CrossRef]

Electron. Lett. (2)

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Figures (6)

Fig. 1.
Fig. 1.

Schematic illustration of the proposed IDP scheme.

Fig. 2.
Fig. 2.

(a). Normalized electron populations in an IDP laser, computed with Eq. (3) using the parameters: n sp=1.4, τ 21/τ 12=0.2, τ 43/τ 34+τ 43/τ 3=0.4, and normalized maximum current density computed with Eq. (2) using τ tunn/τ 3=0.18 and η pump=0.8. These parameter values are very close to room temperature ones actually used in the computation of the threshold current density of the test devices. (b) Normalized electron populations in a DP laser, computed by using the corresponding parameters: n sp=1.3, τ 21/τ 12=0.2 and τ tunn/τ 3=0.18. The quality factor, (n 3n 2)/n 1 in the IDP case is also plotted. The vertical dashed lines indicate maximum normalized currents, commonly in Figs. (a) and (b).

Fig. 3.
Fig. 3.

Conduction band diagram and moduli squared of the relevant wavefunctions in the designed active region of the IDP QC laser. The lattice-matched In0.53Ga0.47As/In0.52Al0.48As layer sequence of one period of the active layers, in angstroms, starting from the injection barrier (toward the right side) is as follows: 45/24/21/69/10/60/17/46/21/40/20/37/22/34/24/31/30/29/33/27/35/25 where In0.52Al0.48As barrier layers are in bold, In0.53Ga0.47As QW layers in roman, and doped layers (Si, ~1017 cm-3) are red-colored. (a) The bias field is assumed to be strong, 34.5 kV/cm enough to align the ground state of the injector to the level 4. (b) The bias field is assumed to be weak, 18 kV/cm, corresponding to a current turn-on voltage. The injector state 1′ is already located to be higher than the upper laser states, level 3. The structure is designed to avoid couplings of the injector states with the adjacent upper laser states, level 3 under any bias fields.

Fig. 4.
Fig. 4.

(a). Current-light output characteristics of an IDP QC laser with a cavity length of 4 mm at different temperatures, 77 k~380 K. The current-voltage characteristics as well as the lasing spectrum at 300 K are also shown. (b) Current-light output and current-voltage characteristics of another IDP QC laser with a cavity length of 1.5 mm at different temperatures, 77 k~330 K, together with lasing spectrum at 300 K.

Fig. 5.
Fig. 5.

(a). Plots of the threshold current densities of the 4-mm and 1.5-mm long lasers as functions of device temperature. Note that the vertical scales for two devices are shifted for a clear view. The straight lines represent fits, showing empirical T 0-values. The dashed curves labeled “Ks ” are theoretical ones taking account of the suppression of the electron population in the injector. The dashed curves labeled “Ks =0” are obtained by assuming Ks =0 and ones labeled “Ks /2” are done with the half values for Ks . Note that the current range of both the curves is reasonably limited to be below the maximum current density. In Eq. (2), the uses of the injector doping ninj =5×1010 1/cm2 together with the estimated value of τrelax=1.73 ps (given by τ332320/[(1+δ) Nphonon +1]=0.823 ps, n sp=1.42, τ2112=0.65, τ4334=0.295, and τ433=0.212) at T=380 K (weak-lasing temperature), and the tunneling time τtunn=0.175 ps (given by ħ Ω 1′4=7 meV and τdeph=100 fs) lead to a maximum current density of 3.96 kA/cm2, shown by the horizontal arrows, which is fairly close to the observed current densities, ~4.0 kA/cm2, for maximum output powers at high temperatures (Figs. 4(a) and 4(b)), caused by the complete alignment of the injector states with the intermediate state, level 4. (b) Plots of the slope djth/d(1/L) of the threshold current-density jth-versus-the inverse of cavity length 1/L as a function of device temperature. The experimental data of the jth-(1/L) characteristics for different temperatures, 100 K~330 K are shown in the inset. The curve labeled “Ks ” are theoretical one taking account of the suppression of the electron population in the injector. The curve labeled “Ks =0” are obtained by assuming Ks =0.

Fig. 6.
Fig. 6.

(a). Gain cross section gc and key parameter Ks as functions of device temperature. The gain cross sections identified at three temperatures, 100 K, 150 K and 200 K are fitted by the curve represented by gc =Gc /(aT-bT2-1) with Gc =1.19×10-10 cm, a=0.021 1/K and b=2.16×10-5 1/K2 for the temperature range, 100 K~400 K. (b) Computed electron population n1th/ninj in the injector and population-inversion (n 3n 2)th/ninj of the 4-mm long QC lasers at threshold conditions, and ratio Mgc 2112)/(α (0) inj/ninj ) as functions of device temperature.

Equations (7)

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j = e ( n 1 n 4 ) [ 1 + ( E 41 ' ) 2 τ deph 2 ] τ tunn ,
j = en inj { ( 1 + τ 21 τ 12 ) [ 1 + ( E 41 ' ) 2 τ deph 2 ] τ tunn + τ relax } ,
n 1 n inj = [ 1 ( 1 + τ 21 τ 12 ) ] [ 1 ( 2 1 n sp + τ 43 τ 34 + τ 43 τ 34 ) ( η pump j τ 3 en inj ) ] , n 2 n inj = ( τ 21 τ 12 ) ( n 1 n inj ) + ( 1 1 n sp ) ( τ pump j τ 3 en inj ) , n 3 n inj = ( η pump j τ 3 en inj ) = [ 1 ( τ 43 τ 34 + τ 43 τ 3 ) ] ( n 4 n inj ) . }
j th = ( en sp η pump τ 3 ) { [ α c + ( 1 L ) ln ( 1 R ) ] Mg c + [ α inj ( 0 ) Mg c ( τ 21 τ 12 ) n inj ] ( 1 + τ 21 τ 12 ) } ( 1 + K s ) ,
K s = n sp ( 2 1 n sp + τ 43 τ 34 + τ 43 τ 3 ) [ α inj ( 0 ) + ( τ 21 τ 12 ) ( n inj Mg c ) ] ( 1 + τ 21 τ 12 ) ( n inj Mg c ) .
j th 0 d j th d ( 1 L ) = { α c + [ α inj ( 0 ) + ( τ 21 τ 12 ) n inj Mg c ] ( 1 + τ 21 τ 12 ) } ln ( 1 R ) ,
η ext = ( 1 2 ) [ M η pump n sp ( 1 + τ 21 τ 31 ) ] { ( 1 L ) ln ( 1 R ) [ α c + ( 1 L ) ln ( 1 R ) + ( α inj ( 0 ) n inj ) n 1 th ] } .

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