1 / 11

Introduction to Lasers

Introduction to Lasers. 자연과학부 나종훈. LASER 의 시초 Atomic Structure Transitions between Laser states Population Inversion Pulsed Operation Power and Energy The elements for Lasers Transverse & Longitudinal Modes. 목 차.

phuc
Download Presentation

Introduction to Lasers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Introduction to Lasers 자연과학부 나종훈

  2. LASER의 시초 Atomic Structure Transitions between Laser states Population Inversion Pulsed Operation Power and Energy The elements for Lasers Transverse & Longitudinal Modes 목 차

  3. Microwave Amplification by the Stimulated Emission of Radiation -1954, 24-GHz ammonia device Light Amplification by Stimulated Emission of Radiation -1957, First idea of LASER(using Fabary Perot cavity as part of LASER) The Beginning of LASER

  4. ATOMIC STRUCTURE

  5. Spontaneous · Stimulated Emission E=hν=E2-E1 h: Planck’s constant ν: frequency of the laser light Ideal laser light are at exactly the same frequency (wavelength) & all the photons are in phase.

  6. N2/N1=Exp-(E2-E1)kBT Population Inversion Population ratio between two states N2: population in the upper state N1: population in the lower state kB: Boltzman’s constant T: temperature (K) Gain 달성 조건: Population in the upper laser state is greater than the population in the lower state. A pulse of light, an electrical spark or a chemical reaction can all be used to populate the upper laser state. → pumping

  7. Q-swicthing To concentrate the laser energy into the pulse Mode locking To shorten the width of the pulse in time Pulsed Operation Effective for reducing the laser’s heating (cf: semiconductor diode lasers)

  8. Average Power : The power of a continuous wave laser Pavg=Epulse*Rreprate Peak power : Epulse/tpulse Average energy density : The energy(J) per unit area Average power density : The energy power per unit area Peak power density : The peak power per unit area Power and Energy

  9. Monochromaticity & Coherency • Monochromaticity • A group of photons at exactly one frequency • Coherency - A group of photons with the same relative phase

  10. Gain Materialsolid(Nd:YAG,Ruby,GGG,GSGG,alexandrite,emerald,Cr:Sapphire,Ti:Sapphire,AlGaAs) Liquid(dye,chelate) Gas(Krypton,argon,nitrogen,helium-neon,CO2,KrF,XeCl) Plasma(X-ray,free-electron) Pumping source To provide the energy to set up the energy states so that stimulated emission can occur optically to be pumped using other lasers(most solid-state lasers) electrically to be pumped using a pn-junction(semiconductor diodes) Resonant cavity physically shorten the laser tailor the profile of the electromagnetic mode The elements for Lasers

  11. Transverse & Longitudinal Modes • TEM(transverse electromagnetic mode) • The frequencies of Longitudinal electromagnetic modes of the cavity(v=p*c0/2nL) • A laser can only lase at those wavelengths(longitudinal mode) for which an integral multiple of wavelengths fit into the cavity.

More Related