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, 08-1-30, . . KIST . Group members : Staff ; Students ; (former std, ) , , , , , , . . - PowerPoint PPT Presentation

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  • , 08-1-30, KIST

  • Group members :

    Staff ;

    Students ; (former std, ) , , , , , ,

  • ? 2-1. 2-2. 3. KIST - - LD - SLD - 4.

  • Quantum Dot ?AFM images of SAQD* SAQD(Self-Assembled Quantum dot)

  • Quantum Dot ?

  • QD growth-SK method

  • Electronic structure of QD

  • PL of QD

  • Quantum Dot ? Important for both physics and application Strong carrier confinement and high radiative efficiency Quasi-0D system in the solid state : Atom-like, artificial atom Embedded in semiconductor matrix : Many applications Strong Coulomb interaction Two level system, long coherence :good material for quantum optics Separate advantages for ensemble and single dot application Ensemble : Optical devices(LD, VCSEL, QDIP, SOA, SLD) Uniform QDs for LD, VCSEL, QDIP Non-uniform QD for SOA and SLD Single dot : Quantum information processes (quantum cryptography) Low density QD ( 1 ~ 2 QD/mm2) Focus on In(Ga)As/GaAs SAQD: Best developed

  • QD(>10000 atoms) : An artificial atomArtificial atom; 0-D degree of freedom of e- and h+ 2 allowed states (up, down) ; s orbital-like behavior (quite different from QW) ; single photon emitterNature, 405, 923(2000)

  • Coupled QD (QD molecule) for entanglements e-h pair configuration for entanglementScience, 291, 491(2001)Show coupled states at 60 K

  • Why In(Ga)As/GaAs QD ? relatively mature growing tech. & Device Tech.(ex. 1300nm QD-LD) Wavelength ~ 1500nm (optical comm.) on GaAs High Q-cavity (VCSEL, PC) possible for single photon emitter- coupled QDs supply entanglement of quantum statesScience 295, 102(2002)Electrically driven SPSMicrodisk type SPSScience 290, 2282(2000)VCSEL type SPSPRL 89, 233602(2002)Nature 432, 197(2004)In(Ga)As/GaAs QD based SPS

  • In(Ga)As/GaAs QD based SPSQD in PC-based nanocavity, Nature 432, 200(2004)

  • QD for Quantum Information Process Requirements ; Low density QD ~ 1/mm2 : for real applications Location control : for real applications Control of QD energy by shape, size and composition Determination of QD energy : Spectroscopic method Objectives of project; 1. Growing tech. of low density QD ~ 1/mm2 by MBE 2. QD growing tech. on micron-size patterned substrate for real application of quantum information processes 3. Characterization of QD state by spectroscopic method

  • gain bandwidth ECL, SOASymmetric gain profile Low chirpGain profile of QD ensemble

  • Material Gain of QD :QW : 60 A/cm2QD : ~ 20A/cm2

  • Carrier confinement of QD : - Ntr (Nth) - lateral leakage - chirping (QW 1/100) LD

  • QD LD - low Ith ~ 20 A/cm2 - Temperature stability : high T0 ~ 385 K - High differential gain ~ 10 times that of QW LD - Long wavelength operation on GaAs to 1.8 um 1.3 um is especially important because of optical comm. (VCSEL) - High frequency modulation with negligible chirp - High quantum efficiency(95%) and wall-plug efficiency(51%) even for high power laser - High power CW laser (carrier localization, low Auger process)QD-LD

  • History of LD

  • Why 1300nm LD(VCSEL) on GaAs ? Bandwidth growth will be 100-200 times over the next 4 years.Nortel, Optical Network DivisionOptical Internet working Forum(OIF) , CS 7 p691.3m VCSEL ? : - - - LAN/MAN

  • Fiber-To-The-Home(FTTH)Palo Alto FTTH PON (2001, 2002 )* FTTH (Fiber-To-The Home), PON (Passive Optical Network)

  • Why 1300nm LD(VCSEL) on GaAs ? Edge emitting LDVCSEL: Vertical Cavity Surface Emitting LaserVCSEL : - () - beam (fiber: ) - 2D array ( ) - Wafer scale test()1300nm QDLD InP LD uncooled (~100oC) ( ~ 2.5Gbps) FTTH LD

  • Why 1300nm LD(VCSEL) on GaAs ? 1.3m VCSEL: : GaAs - InP ( ) - pair GaAs/AlAs DBR mirror stack ( , ) : In(Ga)As - ( ) - ( ) - GaAs 1~1.8m ; - (>95%) - ; 100 ( , WDM) -