Overview of First Presentation Laser Types of Laser Quantum DL Basic Components of QDL Types of QDL Theory of QDL Application

 Non-traditional semiconductor  Crystals composed of periodic groups of II-VI, III-V, or IV-VI materials  Range from 2-10 nanometres (10-50 atoms) in diameter  An electromagnetic radiation emitter with an easily tunable band gap  0 degrees of freedom

Number of free dimensions StructureQuantum Confinement 3BulkNone 2Quantum Well 1 1Quantum Wire 2 0Quantum Dot 3 Structures and energy levels in quantum confined systems

 There are three main ways to confine excitons in semiconductors: ◦ Lithography ◦ Colloidal synthesis ◦ Epitaxy:  Patterned Growth  Self-Organized Growth 4 2. Fabrication of Quantum Dots

 Light Amplification by Stimulated Emission of Radiation.  Laser light is monochromatic, coherent, and moves in the same direction.

Lasers are commonly designated by the type of lasing material employed:  Gas lasers: The most important are CO2 and excimer lasers (derived from “excited dimer”: ArF, KrF, XeCl). Moreover, there are also the heliumneon and argon-ion lasers.  Liquid lasers: The medium is a dye solution, as a result of which the colour of the laser light can be varied over a wide range.

 Solid-state type lasers: The most important one is the neodymium-YAG laser. The medium in this case is a synthetically produced monocrystal, yttrium-aluminium- garnet, in which some yttrium ions have been replaced by neodymium ions.  Semi-conductor/diode lasers: After quantum dot laser, The latest laser types which generate light effectively from the smallest space

 A quantum dot laser is a semiconductor laser that uses quantum dots as the active laser medium in its light emitting region. ◦ Due to the tight confinement of charge carriers in quantum dots, they exhibit an electronic structure similar to atoms.

DEVELOPMENT OF QDL

 An ideal QDL consists of a 3D-array of dots with equal size and shape  Surrounded by a higher band-gap material ◦ confines the injected carriers.  Embedded in an optical waveguide ◦ Consists lower and upper cladding layers (n-doped and p-doped shields)

 Wavelength of light determined by the energy levels not by bandgap energy:  improved performance & increased flexibility to adjust the wavelength  Maximum material gain

 Low threshold  High output power  Large modulation bandwidth  Superior temperature stability

 High speed quantum dot lasers Directly modulated quantum dot lasers Mode-Locked Quantum Dot Lasers InP Based Quantum Dot Lasers

 High power Quantum Dot lasers QD lasers for Coolerless Pump Sources Single Mode Tapered Lasers

High speed quantum dot lasers Advantages Directly Modulated Quantum Dot Lasers Datacom application Rate of 10Gb/s Mode-Locked Quantum Dot Lasers Short optical pulses Narrow spectral width Broad gain spectrum InP Based Quantum Dot Lasers Low emission wavelength Wide temperature range Used for data transmission

High power Quantum Dot lasers Advantages QD lasers for Coolerless Pump Sources Size reduced quantum dot Single Mode Tapered Lasers Small wave length shift Temperature insensitivity

The potential energy region defined by

 Inside the well Schrödinger equation is identical that of free particle and reduces to =0=0

 more precisely to three independent equation of the form  The most general solution of x equation is given by

 The boundary condition so that X(x) is given by for

 The additional boundary condition is applied x=L gives Implying that, which finally gives

 The solution has the same form each independent coordinate giving for with Or

QD Lasers Microwave/Millimeter wave transmission with optical fibers Datacom network Telecom network Optics

25  Photovoltaic devices: solar cells  Biology : biosensors, imaging  Light emitting diodes: LEDs  Quantum computation  Flat-panel displays  Memory elements  Photodetectors 25 Applications

 Gerald B. Stringfellow (1999). Organometallic Vapor-Phase Epitaxy: Theory and Practice (2nd ed.). Academic Press  Betul Arda, Huizi Diwu. Department of Electrical and Computer Engineering University of Rochester    H. Goronkin, P. Allmen, R. Tsui, T. Zhu, “Functional Nanoscale Devices”, ch.5.  N. N. Ledentsov, “Quantum Dot Heterostructures: Fabrication, Properties, Lasers”  D. Bimberg, G. Fiol, M. kuntz et al. “High speed nanophotonic devices based on quantum dots.”phys  D. Bimberg, M. Grundmann, N. Ledenstov, “Quantum Dot Heterostructures”  Particle in a box figures, Retrieved in