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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 14, Iss. 1 — Jan. 9, 2006
  • pp: 171–181

Continuous wave operation of a superlattic quantum cascade laser emitting at 2 THz

Chris Worrall, Jesse Alton, Mark Houghton, Stefano Barbieri, Harvey E. Beere, David Ritchie, and Carlo Sirtori  »View Author Affiliations

Optics Express, Vol. 14, Issue 1, pp. 171-181 (2006)

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We report the operation of a 2 THz quantum cascade laser based on a GaAs/Al0.1Ga0.9As heterostructure. The laser transition is between an isolated subband and the upper state of a 14 meV wide miniband. Lasing action takes place on a high order vertical mode of a 200 μm thick double-metallic waveguide. In pulsed mode operation, with a 3.16mm long device, we report a threshold current density of 115 A/cm2 at T = 4K, with a maximum measured peak power of 50 mW. The device shows lasing action in continuous wave up to 47K, with a maximum power in excess of 15 mW at T = 4K.

© 2006 Optical Society of America

OCIS Codes
(140.3070) Lasers and laser optics : Infrared and far-infrared lasers
(140.5960) Lasers and laser optics : Semiconductor lasers
(230.5590) Optical devices : Quantum-well, -wire and -dot devices

ToC Category:
Lasers and Laser Optics

Chris Worrall, Jesse Alton, Mark Houghton, Stefano Barbieri, Harvey E. Beere, David Ritchie, and Carlo Sirtori, "Continuous wave operation of a superlattice quantum cascade laser emitting at 2 THz," Opt. Express 14, 171-181 (2006)

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  1. R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, A. G. Davies, D. A. Ritchie, R. C. Iotti, and F. Rossi, "Terahertz semiconductor-heterostructure laser," Nature 417, 156 (2002) [CrossRef] [PubMed]
  2. B. S. Williams, S. Kumar, and Q. Hu, "Operation of THz Quantum cascade lasers at 164K in pulsed mode and at 117K in continuous-wave mode," Opt. Express 13, 3331 (2005) [CrossRef] [PubMed]
  3. B. S. Williams, S. Kumar, Q. Hu, and J.L. Reno "Resonant-phonon terahertz quantum cascade laser operating at 2.1 THz (λ= 141 µm)," Electron. Lett. 40, 431 (2004) [CrossRef]
  4. G. Scalari, S. Blaser, J. Faist, H. Beere, E. Linfield, D. Ritchie, and G. Davies, "Terahertz emission from quantum cascade lasers in the quantum Hall regime: evidence for many-body resonances and localization effects," Phys. Rev. Lett. 93, 237403-1 (2004) [CrossRef]
  5. G. Scalari, L. Sirigu, C. Walther, J. Faist, M. Sadowski, H. Beere, and D. Ritchie, "Lasing down to 1.45 THz in strong magnetic fields," 8th International Conference on Intersubband transitions in Quantum Wells, ITQW 2005, Cape Cod, MA, Abstract book (2005).
  6. H. Willenberg, G. H. Döhler, and J. Faist, "Intersubband gain in a Bloch oscillator and quantum cascade laser," Phys. Rev. B 67, 085315 (2003). [CrossRef]
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  11. S. Barbieri, J. Alton, H. E. Beere, J. Fowler, E. H. Linfield, and D. A. Ritchie, "2.9 THz quantum cascade laser operating up to 70K in continuous wave," Appl. Phys. Lett. 85, 1674 (2004) [CrossRef]
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  13. . J. Alton, S. Barbieri, H. E. Beere, J. Fowler, E. H. Linfield, and D. A. Ritchie, "Optimum resonant tunnelling injection and influence of doping density on the performance of bound-to-continuum THz quantum cascade lasers," Proc. SPIE Int. Soc. Opt. Eng. 5727, 65 (2005)
  14. The etch-stop layer beneath the active region is not relevant for this work, and was grown in order to allow the fabrication of a double metal waveguide. See for example: S. S. Dhillon, J. Alton, S. Barbieri, C. Sirtori, A. de Rossi, M. Calligaro, H. E. Beere, and D. A. Ritchie, "Ultra-low threshold current quantum cascade lasers based on double-metal buried strip waveguides," Appl. Phys. Lett. 87, 071107 (2005) [CrossRef]
  15. The dielectric constants of the doped GaAs layers were computed on the basis of the classical Drude model of the conductivity, with a scattering time of 1 ps in the AR, and of 0.1 ps elsewhere.
  16. C. Sirtori, F. Capasso, J. Faist, A. L. Hutchinson, D. L. Sivco, and A. Y. Cho, "Resonant tunnelling in quantum cascade lasers," IEEE J. Quantum Electron. 34, 1722 (1998) [CrossRef]
  17. More realistic calculations of the reflectivity are under way. See C. M. Herzinger, C. C. Lu, T. A. DeTemple, and W. C. Chew, IEEE J. Quantum Electron. 29, 2273 (1993). [CrossRef]
  18. Recently, we observed laser emission at 1.94 THz with devices processed from a nominally identical growth of the present QCL.
  19. These findings were confirmed by magneto transport measurements at low biases. At constant voltage we observed periodic oscillations of the current density as a function of 1/B, where B is the intensity of a magnetic field applied parallel to the growth axis. At any voltage, and down to 0.5V, we measured a constant periodicity, from which we derived a transition energy of 8.3 meV. C. Worral et al., unpublished data. For a description of the technique see: J. Alton, S. Barbieri, J. Fowler, J. Muscat, H. E. Beere, E. H. Linfield, A. G. Davies, D. A . Ritchie, R. Khöler, and A. Tredicucci, "Magnetic-field in-plane quantization and tuning of population inversion in a THz superlattice quantum cascade laser," Phys. Rev. B 68, 081303R (2003). [CrossRef]
  20. M. F. Pereira, Jr., S. -C. Lee, and A. Wacker, "Controlling many-body effects in the midinfrared gain and terahertz absorption of quantum cascade structures," Phys. Rev. B. 69, 205310 (2004). [CrossRef]
  21. M. S. Vitiello, G. Scamarcio, V. Spagnolo, B. S. Williams, S. Kumar, Q. Hu, and J. L. Reno, "Measurement of subband electronic temperatures and population inversion in THz quantum-cascade lasers," Appl. Phys. Lett. 86, 111115 (2005). [CrossRef]
  22. The pulsed mode Jth vs T curves of Fig. 5 are representative of several devices with different cavity lengths.

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