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Semiconductor Laser Physics. Wide-gap semiconductor. Narrow-gap semiconductor. Wide-gap semiconductor. E g2. E g1. z. Double Heterojunction. z. E g2. E g1. E g2. Conduction band edge. Valence band edge. Type II. Type I. E c. E c. E g2. E g1. E g2. E g1. E v. E v. Type III. - PowerPoint PPT Presentation
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Semiconductor Laser Physics
Double HeterojunctionzEg2Eg2Eg1Valence band edgeConduction band edge
EcEvEg1Eg2Type IEcEvEg1Eg2EcEvType IIType IIIEg1Eg2EvEc
Evolution of the threshold current of the semiconductor lasers
Basov: Nobel prize 1964 (with Prokhorov and Townes)
Basov, Vul, Popov, Krokhin: 1957 first semiconductor laser proposal and development1961 first injection laser proposal (also Dumke 1962)
Zhores I. Alferov Herbert Kroemer The Nobel Prize in Physics 2000"for developing semiconductor heterostructures used in high-speed- and opto-electronics"
III-V semiconductor grown on Ge
Lattice-matched InGaAs/AlInAs
Molecular Beam EpitaxyNeeds UHV 10-11 Torr , high-purity elemental materials, right temperatureA. Cho, Bell Labs
Growth rate 1 m/hr or 1 atomic layer in 1 sec
Reflection High-Energy Electron Diffraction (RHEED)
Metal-Organic Chemical Vapor Deposition (MOCVD)
Growth rate 2-4 m/hr
Materials for semiconductor lasers
GaAs/AlxGa1-xAs; GaxIn1-xAsyP1-y/AlxIn1-xAs on InP; InAs1-xSb/AlGa1-xSb on GaSb
Visible-UV range
Laser Diode
Laser waveguidesVertical confinementLateral confinementGain-guidedIndex guided: ridges, ribsBuried heterostructure lasers
Ridge laser
H-field of the TM00 mode at 8.85 mumIn QCLs you can cut the ridge through the active region: strong guiding
H-field of the TM02 mode at 8.85 mum
Modes: longitudinal and transverse
Buried heterostructure laser
2743 B ridge
3032 C device 250K
DFB lasers
Vertical Cavity Surface-Emitting Laser
Large distance between cavity modes: single-mode laser Circular beam shape Low threshold and power consumption 2D laser arrays Wafer-scale testing Ultrafast modulation
Edge-emitting laserVCSEL
For long wavelength laser based on InGaAsP/InP: index contrast is too low, need too many layers, the device is too resistive as a result
Current spreading, many transverse modes -> need confinement for current and for the EM field
Oxidized aperture VCSEL
Oxide apertureHuffaker et al. APL 1994Problems: different thermal expansion coefficient, strain, bad control, non-planar technology
Phase-shifting mesaLu et al., APL2004
Oxide aperture and phase-shifting mesaAhn et al. APL 2005
From bulk materials to heterostructuresAdd slowly varying perturbation U(r) to the bulk Hamiltonian H0
(b) Seek the solution as a product zf(z) slowly varying envelope function(c) Assume that un0(r) and kx,y are the same in each layer(d) Replace kz with and solve the resulting differential matrix equation for the column-vector f(z)Advantage of the method: everything is expressed in terms of several parameters that can be measured: Eg, SO, meff(k = 0)