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Contents• Historical background• Laser physics• Photobiology of Lasers• Laser safety• Types of Lasers• Clinical Applications• Medico legal considerations in Laser Surgery• Future Trends
Historical background•Albert Einstein – 1917 – Quantum theory•Theodore Maiman – 1960 – 1st Laser using Ruby crystal•Javan – 1961 – HeNe Continuous mode of laser•Johnson – 1961 – Nd:YAG Laser•Leon Goldman – 1963 – Father of modern lasers•Patel – 1964 – CO2 Laser•Anderson RR & – 1983 – Selective PhotothermolysisParrish JA
Laser physics ELECTROMAGNETIC SPECTRUM ALEXANDRITE ERBIUM-YLF KRYPYON EXCIMER Nd: YAG Ho:YAG ARGON HE NE RUBY KTP CO2 X - RAYS TV & RADIO WAVESFrequency 1020 1019 1018 1017 1016 1015 1014 1013 1012 1011 1010 109 108 107 106 105 104 103 102 101 100 3AO 3nm 3µm 3mm 3cm 3mWave length 3km MICROWAVES GAMMA WAVES ULTRAVIOLET VISIBLE LIGHT INFRARED IONISING NON - IONISING
Generation of Laser EnergyCertain laser medium or LASANT with in the resonator space is energized by internal or external energy to produce an excited population of atoms, molecules and rare gases (SPECIES). The energy with in the resonator reaches a population inversion in which the greatest cohort of species is in an excited state and in which photons are emitted and amplified within a laser cavity. The radiant energy is released as a laser beam.
The basic requirements for the laser activity are – Active medium – LASANT – Energy input – external or internal – A population inversion through quantum electronics – Some form of optical feedback or optical resonator
Laser CavityFundamental components of laser system include • Resonator cavity housing active medium • Energy input – external or internal.The cavity is bound by two mirrors • One totally reflecting • Other partially reflecting
• The mirrors are essentially parallel to each other and placed at the either end of the cylinder• The mirrors are separated by a fixed distance (d) forming a Fabry-Perot interferometer.• Principle of interference. Two or more waves simultaneously penetrate some material, forms a combied wave. Resulting a larger wave. » Constructive interference » Destructive interference