mid-infrared State-of-the-Art Quantum Cascade Lasers
Mattias Beck University of Neuchatel, Switzerland Collaborators: J. Faist, T. Aellen, R. Maulini, M. Giovannini, N.Hoyler (all from Uni Ne) S. Blaser (Alpes Lasers, coatings) E. Gini (ETH Zurich, MOCVD growth)
Funding: Swiss National Science Foundation, EU Projects SUPERSMILE and WANTED
Outline
a lot of different active region designs during the past 10 years:
3-QW, 4-QW, chirped superlattice (cSL), and bound-to-continuum (BtC) with high performances some parameters are few investigated, e.g. doping level, injector thickness
little knowledge about influence of growth conditions on laser performances this work: -) study of doping level for a 4-QW active region -) influence of MBE background impurity -) comparison of 3 active region designs (3-QW, 4-QW, cSL)
Influence of doping level
Influence of background impurity
Comparison of active regions
3-QW = 8m active region: C.Gmachl et al., APL 72(24), 3130 (1998).
30 periods, InP cladding, 8nm doped with 2*1017cm-3 Ppeak = 210mW, = 180mW/A, Jth = 5.5kA/cm2
4-QW = 9.1m active region: D.Hofstetter et al., APL 78(14), 1964 (2001).
35 periods, InP cladding, 10.3nm doped with 3*1017cm-3 Ppeak = = 1W, 300mW/A, Jth = 3.6kA/cm2
Chirped SL = 7.2m active region: A.Tredicucci et al., APL 73(15), 2101 (1998).
28 periods, InAlAs cladding, 14.2nm doped with 2*1017cm-3 Ppeak = 300mW, Pavg = 14mW, Jth = 5.0kA/cm2
this work: all active regions with same number of periods (35), same doping level (2*1017 cm-3), and same waveguide (InP cladding).
Active region comparison
External cavity QCL: Littrow setup
pulsed operation manually controlled grating angle: range ~10 deg laser with broad gain curve: 297cm-1 luminescence FWHM
Extreme tuning range
ECL tuning range: from 946 to 1097 cm-1 15% of free running wavelength SMSR: >20dB over 50 cm-1 >10dB over 110 cm-1 Pavg: >1mW over 100 cm-1
Time resolved spectra
R...