Ridge-width dependence of the threshold of long wavelength (λ ≈14 µm) quantum cascade lasers with sloped and vertical sidewalls

doi:10.1364/OE.20.002539

Ridge-width dependence of the threshold of long wavelength (λ ≈14 µm) quantum cascade lasers with sloped and vertical sidewalls

Xue Huang, Yenting Chiu, William O. Charles, and Claire Gmachl »View Author Affiliations

Optics Express, Vol. 20, Issue 3, pp. 2539-2547 (2012)
http://dx.doi.org/10.1364/OE.20.002539

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Abstract

We investigate the ridge-width dependence of the threshold of Quantum Cascade lasers fabricated by wet and dry etching, respectively. The sloped sidewalls resulting from wet etching affect the threshold in two ways as the ridge gets narrower. First, the transverse modes are deeper in the substrate, hence reducing the optical confinement factor. Second, more important, a non-negligible field exists in the lossy SiO₂ insulation layer, as a result of transverse magnetic mode coupling to the surface plamon mode at the insulator/metal surface, which increases the waveguide loss. By contrast, dry etching is anisotropic and leads to waveguides with vertical sidewalls, which avoids the shift of the modes to the substrate layer and coupling to the surface plasmons, resulting in improved threshold compared with wet-etched lasers, e.g., for narrow ridge widths below 20 µm, the threshold of a 14 µm wide λ ≈14 µm laser by dry etching is ~60% lower than that of a wet-etched laser of the same width, at 80 K.

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

ToC Category:
Lasers and Laser Optics

History
Original Manuscript: December 1, 2011
Revised Manuscript: January 1, 2012
Manuscript Accepted: January 9, 2012
Published: January 19, 2012

Citation
Xue Huang, Yenting Chiu, William O. Charles, and Claire Gmachl, "Ridge-width dependence of the threshold of long wavelength (λ ≈14 µm) quantum cascade lasers with sloped and vertical sidewalls," Opt. Express 20, 2539-2547 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-3-2539

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References

M. Troccoli, X. Wang, and J. Fan, “Quantum cascade lasers: high-power emission and single-mode operation in the long-wave infrared (λ > 6 µm),” Opt. Eng.49(11), 111106 (2010). [CrossRef]
N. Bandyopadhyay, Y. Bai, B. Gokden, A. Myzaferi, S. Tsao, S. Slivken, and M. Razeghi, “Watt level performance of quantum cascade lasers in room temperature continuous wave operation at λ ~ 3.76 µm,” Appl. Phys. Lett.97(13), 131117 (2010). [CrossRef]
S. Slivken, A. Evans, W. Zhang, and M. Razeghi, “High-power, continuous-operation intersubband laser for wavelengths greater than 10 µm,” Appl. Phys. Lett.90(15), 151115 (2007). [CrossRef]
K. Fujita, M. Yamanishi, T. Edamura, A. Sugiyama, and S. Furuta, “Extremely high T0 values (– 450) of long wavelength (–5 µm), low-threshold-current-density quantum cascade lasers based on the indirect pump scheme,” Appl. Phys. Lett.97(20), 201109 (2010). [CrossRef]
X. Huang, W. O. Charles, and C. Gmachl, “Temperature-insensitive long-wavelength (λ ≈14 µm) Quantum Cascade lasers with low threshold,” Opt. Express19(9), 8297–8302 (2011). [CrossRef] [PubMed]
P. Fuchs, J. Semmel, J. Friedl, S. Höfling, J. Koeth, L. Worschech, and A. Forchel, “Distributed feedback quantum cascade lasers at 13.8 µm on indium phosphide,” Appl. Phys. Lett.98(21), 211118 (2011). [CrossRef]
S. Slivken, J. S. Yu, A. Evans, J. David, L. Doris, and M. Razeghi, “Ridge-width dependence on high-temperature continuous-wave quantum-cascade laser operation,” IEEE Photon. Technol. Lett.16(3), 744–746 (2004). [CrossRef]
W. Bewley, C. Canedy, C. S. Kim, M. Kim, J. R. Lindle, J. Abell, I. Vurgaftman, and J. Meyer, “Ridge-width dependence of midinfrared interband cascade laser characteristics,” Opt. Eng.49(11), 111116 (2010). [CrossRef]
R. P. Leavitt, J. L. Bradshaw, K. M. Lascola, G. P. Meissner, F. Micalizzi, F. J. Towner, and J. T. Pham, “High-performance quantum cascade lasers in the 7.3- to 7.8-µm wavelength band using strained active regions,” Opt. Eng.49(11), 111109 (2010). [CrossRef]
C. Gmachl, F. Capasso, A. Tredicucci, D. L. Sivco, A. L. Hutchinson, and A. Y. Cho, “Long wavelength (λ ≃ 13 µm) quantum cascade lasers,” Electron. Lett.34(11), 1103–1104 (1998). [CrossRef]
A. Tredicucci, C. Gmachl, F. Capasso, D. L. Sivco, A. L. Hutchinson, and A. Y. Cho, “Long wavelength superlattice quantum cascade lasers at λ ≃ 17 μm,” Appl. Phys. Lett.74(5), 638–640 (1999). [CrossRef]
R. Kitamura, L. Pilon, and M. Jonasz, “Optical constants of silica glass from extreme ultraviolet to far infrared at near room temperature,” Appl. Opt.46(33), 8118–8133 (2007). [CrossRef] [PubMed]
S. A. Maier, Plasmonics: Fundamentals and Applications (Springer, 2007).
F. Toor, D. L. Sivco, H. E. Liu, and C. F. Gmachl, “Effect of waveguide sidewall roughness on the threshold current density and slope efficiency of quantum cascade lasers,” Appl. Phys. Lett.93(3), 031104 (2008). [CrossRef]
Z. Liu, “Room-temperature, continuous-wave Quantum Cascade lasers in the first and second atmospheric windows,” Ph.D. dissertation (Princeton University, 2008)

Abell, J.
Bai, Y.
Bandyopadhyay, N.
Bewley, W.
Bradshaw, J. L.
Canedy, C.
Capasso, F.
Charles, W. O.
Cho, A. Y.
David, J.
Doris, L.
Edamura, T.
Evans, A.
Fan, J.
Forchel, A.
Friedl, J.
Fuchs, P.
Fujita, K.
Furuta, S.
Gmachl, C.
Gmachl, C. F.
Gokden, B.
Höfling, S.
Huang, X.
Hutchinson, A. L.
Jonasz, M.
Kim, C. S.
Kim, M.
Kitamura, R.
Koeth, J.
Lascola, K. M.
Leavitt, R. P.
Lindle, J. R.
Liu, H. E.
Meissner, G. P.
Meyer, J.
Micalizzi, F.
Myzaferi, A.
Pham, J. T.
Pilon, L.
Razeghi, M.
Semmel, J.
Sivco, D. L.
Slivken, S.
Sugiyama, A.
Toor, F.
Towner, F. J.
Tredicucci, A.
Troccoli, M.
Tsao, S.
Vurgaftman, I.
Wang, X.
Worschech, L.
Yamanishi, M.
Yu, J. S.
Zhang, W.

Appl. Opt.

R. Kitamura, L. Pilon, and M. Jonasz, “Optical constants of silica glass from extreme ultraviolet to far infrared at near room temperature,” Appl. Opt.46(33), 8118–8133 (2007). [CrossRef] [PubMed]

Appl. Phys. Lett.

F. Toor, D. L. Sivco, H. E. Liu, and C. F. Gmachl, “Effect of waveguide sidewall roughness on the threshold current density and slope efficiency of quantum cascade lasers,” Appl. Phys. Lett.93(3), 031104 (2008). [CrossRef]
A. Tredicucci, C. Gmachl, F. Capasso, D. L. Sivco, A. L. Hutchinson, and A. Y. Cho, “Long wavelength superlattice quantum cascade lasers at λ ≃ 17 μm,” Appl. Phys. Lett.74(5), 638–640 (1999). [CrossRef]
N. Bandyopadhyay, Y. Bai, B. Gokden, A. Myzaferi, S. Tsao, S. Slivken, and M. Razeghi, “Watt level performance of quantum cascade lasers in room temperature continuous wave operation at λ ~ 3.76 µm,” Appl. Phys. Lett.97(13), 131117 (2010). [CrossRef]
S. Slivken, A. Evans, W. Zhang, and M. Razeghi, “High-power, continuous-operation intersubband laser for wavelengths greater than 10 µm,” Appl. Phys. Lett.90(15), 151115 (2007). [CrossRef]
K. Fujita, M. Yamanishi, T. Edamura, A. Sugiyama, and S. Furuta, “Extremely high T0 values (– 450) of long wavelength (–5 µm), low-threshold-current-density quantum cascade lasers based on the indirect pump scheme,” Appl. Phys. Lett.97(20), 201109 (2010). [CrossRef]
P. Fuchs, J. Semmel, J. Friedl, S. Höfling, J. Koeth, L. Worschech, and A. Forchel, “Distributed feedback quantum cascade lasers at 13.8 µm on indium phosphide,” Appl. Phys. Lett.98(21), 211118 (2011). [CrossRef]

Electron. Lett.

C. Gmachl, F. Capasso, A. Tredicucci, D. L. Sivco, A. L. Hutchinson, and A. Y. Cho, “Long wavelength (λ ≃ 13 µm) quantum cascade lasers,” Electron. Lett.34(11), 1103–1104 (1998). [CrossRef]

IEEE Photon. Technol. Lett.

S. Slivken, J. S. Yu, A. Evans, J. David, L. Doris, and M. Razeghi, “Ridge-width dependence on high-temperature continuous-wave quantum-cascade laser operation,” IEEE Photon. Technol. Lett.16(3), 744–746 (2004). [CrossRef]

Opt. Eng.

W. Bewley, C. Canedy, C. S. Kim, M. Kim, J. R. Lindle, J. Abell, I. Vurgaftman, and J. Meyer, “Ridge-width dependence of midinfrared interband cascade laser characteristics,” Opt. Eng.49(11), 111116 (2010). [CrossRef]
R. P. Leavitt, J. L. Bradshaw, K. M. Lascola, G. P. Meissner, F. Micalizzi, F. J. Towner, and J. T. Pham, “High-performance quantum cascade lasers in the 7.3- to 7.8-µm wavelength band using strained active regions,” Opt. Eng.49(11), 111109 (2010). [CrossRef]
M. Troccoli, X. Wang, and J. Fan, “Quantum cascade lasers: high-power emission and single-mode operation in the long-wave infrared (λ > 6 µm),” Opt. Eng.49(11), 111106 (2010). [CrossRef]

Opt. Express

X. Huang, W. O. Charles, and C. Gmachl, “Temperature-insensitive long-wavelength (λ ≈14 µm) Quantum Cascade lasers with low threshold,” Opt. Express19(9), 8297–8302 (2011). [CrossRef] [PubMed]

Other

S. A. Maier, Plasmonics: Fundamentals and Applications (Springer, 2007).
Z. Liu, “Room-temperature, continuous-wave Quantum Cascade lasers in the first and second atmospheric windows,” Ph.D. dissertation (Princeton University, 2008)

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