Lecture 11 – Quantum ConfinementEECS 598-002 Winter 2006Nanophotonics and Nano-scale FabricationP.C.Ku2EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuSchedule for the rest of the semester Introduction to light-matter interaction (1/26): How to determine ε(r)?  The relationship to basic excitations. Basic excitations and measurement of ε(r). (1/31) Structure dependence of ε(r) overview (2/2) Surface effects (2/7): Surface EM wave Surface polaritons Size dependence Case studies (2/9 – 2/16): Quantum wells, wires, and dots Nanophotonics in microscopy Nanophotonics in plasmonics Dispersion engineering (2/21 – 3/7): Material dispersion Waveguide dispersion (photonic crystals)3EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuQuantum confinement reviewg(E) = Density of statesEgEg(E)EgEg(E)EgEg(E)EgEg(E)bulksheetwiredot3D 2D 1D 0D4EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuQuantum wells and double heterostructuresNPRecombination of electron and hole pairsgenerate radiation.5EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuQuantum well lasers>100λ~3λννννGainFree Spectral Range6EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuDFB v.s. DBR structuresDistributed Feedback Distributed Bragg ReflectorDFB DBRn1n2n3wΛ7EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuCross section of DFB Lasers8EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuSemiconductor superlatticeRef: Prasad, chapter 4, figures 10 and 11.9EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuIntersubband transition Intersubband transition can be used to generate or detect mid-infrared radiation (~ 10 µm).Ref: H. Page et al., Appl. Phys. Lett., 78 (2001) 3529.10EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuQuantum confined Stark effect (QCSE)Ref: J. S. Weiner et al., Appl. Phys. Lett., 47 (1985) 1148.11EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku2D plasmons realizationRef: S. J. Allen et al., Phys. Rev. Lett., 38 (1977) 980.12EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuIncrease of quantum confinement in indirect semiconductors Confinement of electrons and holes in a small volume increase the possibly allowed ∆k and therefore enhances the emission efficiency of an indirect semiconductor, e.g. silicon.Ref: W. D. Kirkey et al., MRS Symp. 789 (2004) N15.30.1.13EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuQuantum dot lasers Reduction of threshold current Reduction of temperature dependence Æ uncooledoperation Increase in differential gain Smaller linewidth enhancement factorBetter high-speedperformanceM. Asada et al, J. Quantum Elec., 22 (1986) 1915.Y. Arakawa and H. Sakaki, Appl. Phys. Lett., 40(1982) 939.14EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Kuα – linewidth enhancement factor Change of carrier density (e.g. due to amplitude modulation) Æ change in absorption/gain Æ change in refractive index (via Kramers-Kronig relation)Re /Im /NNεαε∂∂≡∂∂Ref: J. Oksanen and J. Tulkki, J. Appl. Phys., 94 (2003) 1983.15EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuQuantum optics in semiconductor QD’s Rabi oscillation:Ref: T. H. Stievater et al., Phys. Rev. Lett., 87 (2001) 133603.16EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuQuantum dot biosensorsFRET = fluorescenceenergy transferRef: C. Y. Zhang et al., Nature Mat., 4 (2005) 826.17EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.KuNonlinear optical properties in semiconductors Plasmon screening Exciton ionization Bandfilling Æ blue shift Bandgap renormalization Æ red shift Thermal nonlinearities Æ red shift for most of materialsExciton signature