An iterative algorithm for band structure of lossy 2D photonic crystal is presented in this paper. This iterative algorithm is effective and the real part of the eigenvalue converges fast and accurately when the dielectric function is complex (ε(f)=ε1 + i•ε2(f)) and dependent on frequency in lossy cases with ε2(f)≈0.1ε1. Effects of the frequency dependent dielectric function on band structure of a particular 2D photonic crystal is discussed.
The intersubband electron transition rates assisted by interface-longitudinal-optical-phonon emission in a quantum cascade laser with a four quantum-well active region are evaluated using Femi’s golden rule. The electron energy and wavefunction of nonparabolic conduction band are calculated using an eight-band k•p method with the axial approximation. The energy dispersions of interface-longitudinal-optical-phonon modes and associated electrostatic potentials are studied within the framework of macroscopic dielectric continuum model. The numerical results show that AlAs-like interface phonon modes give larger contribution to intersubband transition rates between lower energy states than other interface phonon modes.
LO-phonons in the active region of interband cascade lasers based on type-II multi-quantum well are investigated in detail. The dispersion relation and phonon potential for interface LO-phonon modes are calculated by the macroscopic dielectric continuum model. The expression of electron- phonon overlap with multiband k*p approximation is obtained and energy separations of hole subbands for fast LO-phonon assisted depopulations of the lower lasing state are proposed.
The electronic structures of (InAs)m/(GaSb)n short- period superlattices are investigated by the empirical pseudo potential method and multiband kp envelope function approximation with the same underlying bulk band structures. The calculated result are compared to each other and with experiment. Generally, the results of the empirical pseudo potential method are in better agreement with the experimental measurement. The superlattice active region of an optically-pumped type-II laser are investigated by the empirical pseudo potential method. The calculated result predict that its lasing wavelength is about 3.5 micrometers at 80K and internal losses due to intervalence absorption have been suppressed.
The active region of a type-II mid-IR quantum cascade laser with improved high-temperature performance is investigated by multiband k(DOT)p methods. The calculated results show that internal losses due to intervalence absorption have been suppressed successfully in this active region. A fourteen-band k(DOT)p approach is used and results for short period type-II InAs/GaSb superlattices are compared with an eight-band k(DOT)p method and a plane wave pseudopotential method.
We report the recent progress of interband cascade (IC) lasers based on InAs/Ga(In)Sb/AlSb type-II quantum wells. For the 4.5-micrometers IC lasers, the internal loss was 11.6 cm-1 and the internal quantum efficiency was 460% at 90 K. When mounted epi-side down on diamond, cw operation was observed with an external quantum efficiency (EQE) of 193%, a cw output power over 500 mW, and a threshold current density as low as 35 A/cm2 at 80 K. Dual-wavelength IC laser was also demonstrated. The device lased simultaneously at 4.482 and 4.568 micrometers . At 110 K, a peak output power of 150 mW per facet was achieved with 5-microsecond(s) pulses at 1-KHz repetition rate. The threshold current density, average EQE, and peak output power of a 0.4-mm long device were 119 A/cm2, 278%, and 150 mW per facet, respectively.
A new type of cascade laser, the so-called interband cascade laser based on type-II quantum well staircase structures, has been demonstrated recently. Here, we will discuss the design and modeling of the interband cascade lasers in connection with device performance. Normalized excess voltage and current will be introduced to evaluate how efficiently the input power is converted into the optical output power in the sense of the utilization of both injection current and applied voltage. Our modeling is based on Kane's eight-band k(DOT)p theory with envelope wave-function approximation and strain effects included. The calculated threshold current density, which includes contributions of radiative current, direct tunneling and Auger recombination, is significantly smaller than the experimentally observed value. This indicates that there are additional current leaking channels, which may be related to interface scattering and material defects, suggesting significant room for improvement. Our modeling also found that the device performance could vary substantially with temperature. Implications of our analyses and the modeling results will be interpreted in terms of carrier transport, optical gain and loss, as well as power efficiency.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.