semiconductor laser physics
DESCRIPTION
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 PresentationTRANSCRIPT
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Semiconductor Laser Physics
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Double HeterojunctionzEg2Eg2Eg1Valence band edgeConduction band edge
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EcEvEg1Eg2Type IEcEvEg1Eg2EcEvType IIType IIIEg1Eg2EvEc
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Evolution of the threshold current of the semiconductor lasers
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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)
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Zhores I. Alferov Herbert Kroemer The Nobel Prize in Physics 2000"for developing semiconductor heterostructures used in high-speed- and opto-electronics"
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III-V semiconductor grown on Ge
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Lattice-matched InGaAs/AlInAs
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Molecular Beam EpitaxyNeeds UHV 10-11 Torr , high-purity elemental materials, right temperatureA. Cho, Bell Labs
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Growth rate 1 m/hr or 1 atomic layer in 1 sec
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Reflection High-Energy Electron Diffraction (RHEED)
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Metal-Organic Chemical Vapor Deposition (MOCVD)
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Growth rate 2-4 m/hr
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Materials for semiconductor lasers
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GaAs/AlxGa1-xAs; GaxIn1-xAsyP1-y/AlxIn1-xAs on InP; InAs1-xSb/AlGa1-xSb on GaSb
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Visible-UV range
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Laser Diode
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Laser waveguidesVertical confinementLateral confinementGain-guidedIndex guided: ridges, ribsBuried heterostructure lasers
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Ridge laser
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H-field of the TM00 mode at 8.85 mumIn QCLs you can cut the ridge through the active region: strong guiding
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H-field of the TM02 mode at 8.85 mum
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Modes: longitudinal and transverse
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Buried heterostructure laser
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2743 B ridge
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3032 C device 250K
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DFB lasers
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Vertical Cavity Surface-Emitting Laser
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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
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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
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Oxidized aperture VCSEL
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Oxide apertureHuffaker et al. APL 1994Problems: different thermal expansion coefficient, strain, bad control, non-planar technology
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Phase-shifting mesaLu et al., APL2004
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Oxide aperture and phase-shifting mesaAhn et al. APL 2005
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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)