Technische Physik, Universität Würzburg (jpr\powerpoint\2004\2004_ESLW\QCL_talk) fo il 1 Nanostructured Quantum Cascade Lasers for Longitudinal Single Mode Control • Motivation and structure of quantum cascade (QC) lasers • Ultra-Short QC Microlaser • Two segment distributed feedback (DFB) lasers J.P. Reithmaier 1,3 , S. Höfling 1 , J. Seufert 2 , M. Fischer 2 , J. Koeth 2 , A. Forchel 1 1 Technische Physik, Universität Würzburg, Germany 2 nanoplus, Nanosystems and Technology GmbH, Germany 3 present address: Technische Physik, Universität Kassel, Germany
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Technische Physik, Universität Würzburg (jpr\powerpoint\2004\2004_ESLW\QCL_talk) foil 1 Nanostructured Quantum Cascade Lasers for Longitudinal Single Mode.
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Technische Physik, Universität Würzburg (jpr\powerpoint\2004\2004_ESLW\QCL_talk) foil 1
Nanostructured Quantum Cascade Lasers for Longitudinal Single Mode Control
Nanostructured Quantum Cascade Lasers for Longitudinal Single Mode Control
• Motivation and structure of quantum cascade (QC) lasers
• Ultra-Short QC Microlaser
• Two segment distributed feedback (DFB) lasers
J.P. Reithmaier1,3, S. Höfling1, J. Seufert2, M. Fischer2, J. Koeth2, A. Forchel1
1 Technische Physik, Universität Würzburg, Germany
2 nanoplus, Nanosystems and Technology GmbH, Germany
3 present address: Technische Physik, Universität Kassel, Germany
Technische Physik, Universität Würzburg (jpr\powerpoint\2004\2004_ESLW\QCL_talk) foil 2
MotivationMotivation• Many important gases have
their fundamental absorptionin the mid-infrared spectralregion (e.g NH3, O3, CO2)
• Quantum cascade lasers (QCLs) are reliable mid-infrared laserscapable of room temperature operation
Single mode emission is requestedfor gas sensing applications
• Detection of NH3 demonstrated with single mode distributed feedback lasers in cooperation with:
Technische Physik, Universität Würzburg (jpr\powerpoint\2004\2004_ESLW\QCL_talk) foil 3
Active Region DesignsActive Region Designs
321
Page et al., Appl. Phys. Lett. 78(22) (2001)
Three quantum
well design
• Resonant tunneling between lowest injector state and upper laser level 3
• Fast depopulation of lower laser level 2 by interminibandscattering processes
Pflügl et al., Appl. Phys. Lett. 83(23) (2003)
bound-to-continuum design
• Resonant tunneling between lowest injector state and upper laser level 3
• Fast depopulation of lower laserlevel 2 by LO-phonon resonancewith ground state 1
Technische Physik, Universität Würzburg (jpr\powerpoint\2004\2004_ESLW\QCL_talk) foil 4
Advantages of micro-lasers: • Increased device density compared to conventional ridge waveguide lasers by approximately a factor 10 is possible• Low threshold currents• Short cavity devices can exhibit single mode emission due to limited gain bandwidth and large mode spacing
[Höfling et al, Electr. Lett. 40, 120 (2004)]
Wavelength tuning should be possible by controling the cavity length
Use of highly reflective deeply etched semiconductor-air Bragg mirrors
allows the fabrication of ultra-short ridge waveguide micro-lasers:
Why Micro-LasersWhy Micro-Lasers
LngFP 2
1~/1
Ln
m
gFP 2
~
Technische Physik, Universität Würzburg (jpr\powerpoint\2004\2004_ESLW\QCL_talk) foil 5
Fabrication ProcessFabrication Process
Monolithically integrated: ridge waveguide and Bragg-mirror fabrication