Supervised ByDr.Zafar Ali ShahPresented ByNouman Ali Bajwa(120817)Design & Simulation of Microchip laser choas Communication System

Table of ContentLaser IntroductionLaser Basic PrincipalLaser Basic ComponentsLaser TypesCHOAS Microchip LASERBasic Concept

LASER - IntroductionLasers are devices that produce intense beams of light which is

MonochromaticCoherentHighly colimatedHigh output power (amplification)

The wavelength(color) of laser light is extremely pure (monochromatic) when compared to other sources of light, and all of the photons (energy) that make up the laser beam have a fixed phase relationship (coherence)with respect to one another Laser light can deposit a lot of energy within a small area

LASER Basic PrincipalAbsorption: An atom in the ground state might absorb a photon emitted by another atom, thus making a transition to an excited state.Spontaneous Emission: Random emission of a photon, which enables the atom to relax to the ground state.Stimulated Emission: An atom in an excited state might be stimulated to emit a photon by another incident photon.

LASER - Basic Principal

LASER Basic ComponentsActive Medium The active medium may be solid crystals such as ruby or Nd:YAG, liquid dyes, gases like CO2 or Helium/Neon, or semiconductors such as GaAs. Active mediums contain atoms whose electrons may be excited to a metastable energy level by an energy source. Excitation Mechanism Excitation mechanisms pump energy into the active medium by one or more of three basic methods; optical, electrical or chemical. High Reflectance Mirror A mirror which reflects essentially 100% of the laser light. Partially Transmissive Mirror A mirror which reflects less than 100% of the laser light and transmits the remainder.

LASER Basic ComponentsGas lasers consist of a gas filled tube placed in the laser cavity. A voltage (the external pump source) is applied to the tube to excite the atoms in the gas to a population inversion. The light emitted from this type of laser is normally continuous wave (CW).

LASER- Matlab ModelThe parameter values used in the calculations are [2] z, = 3 ns, zp = 1 ps, No = 1 x ioz4 m-3, GN = 1 x lo-'' m3 s-', J b = 1.4 Jrk, and f, = 0.866f, ( N 2.25 GHz). m = 1.4 (J, = 0.56 Jfh

LASER- Matlab Model

Chaos Highly sensitive to initial conditionsNonlinear COUPLED systemAt least three degrees of freedomChaotic signal have several properties Wideband SpectrumWaveform does not accurately repeats itselfRandom-like appearanceRelatively simple analog hardware implementation

Types of chaotic waveformPulsedContinuous

Types Of LASERSolid state lasersGas lasersExcimer lasersDye lasersSemiconductor lasersMicrochip lasers

MICROCHIP LASERS MICROCHIP LASERS are among the world's smallest and least expensive solid state lasers. At the same time, they have extremely desirable operating characteristics that are difficult to obtain with more conventional designs. For example, microchip lasers are linearly polarized, single-frequency devices that operate in the fundamental transverse mode [1, 2] and can be tuned continuously over the gain bandwidth of the lasing transition [2-4]. The combination of high performance and low cost makes microchip lasers attractive for a wide variety of applications, including fiber-optic communications, optical storage, and medicine.

Basic Concepts Microchip lasers are typically fabricated by polishing a wafer of solid state gain medium so that two sides of the wafer are flat and parallelThe thickness of the wafer corresponds to the length of the laser cavity.The polished surfaces are dielectrically coated to form the mirrors of a two-mirror standing-wave laser cavity.The wafer is then diced into small pieces, typically1mm square; each piece is a complete microchip laser

Microchip Nd:YVO4 Laser With Feedback

Research AreasThe study of microchip lasers and their applications has been in focus now a days. Much interesting and important research still needs to be conducted. Areas that are currently under exploration include electro-optic tuning and Q-switching, nonlinear frequency conversion, and high-power operation.Areas of interest includeuse of new gain media,Different wavelengths of operation frequency locking for an ultra stable frequency reference.