laser predavanje
TRANSCRIPT
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LASERSTIMULISANA EMISIJA
FOTONA
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• Light Amplification by Stimulated Emision of Radiation.
• Otkriven 1960 godine, Theodore Maiman.
• 1917. A. Einstein teorija o “laseru” pod nazivom- stimulirana emisija.
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• Laserski zrak- proizvodi se stimulisanom emisijom fotona.
Uslovi:
1. Bohrov uslov: razlika energetskih nivoa, nekog laserskog medija = energiji emitovanog fotona.
2. Većina atoma (molekula) u pobuđenom stanju.
3. Metastabilni(dugoživeći nivo)
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• INVERZNA NASELJENOST
br. atoma u pobuđenom stanju > br. atoma u osnovnom stanju
• Tada nastaje:– Koherentni snop laserskog zračenja
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• Najčešće dolazi do:– apsorpcije– spontane emisije zračenja.
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SREDSTVO
• Laserska emisija se odvija u aktivnoj sredini– različite vrste gasova– čvrste supstance– tečne supstance.
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Laserska sredina
• Smeštena između dva paralelna ogledala.
• Zraci svetla koje prolaze kroz ta ogledala tstvaraju- stojeće talase.
• Lasersko zračenje se višestruko reflektuje, te se pojačava.
• Nakon niza refleksija lasersko zračenje izlazi kroz delomično propusno ogledalo.
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TIPOVI LASERA
• Gasni laseri (aktivno sredstvo gas)– Helijum-neonski laser, argonski laser,CO2
• Laseri s čvrstom aktivnom sredinom– Rubinski laser,staklo sa neodijumom
• Laseri s tečnom aktivnom sredinom– Laseri za koje se koriste organske boje.
• Hemijski laser.• Poluprovodnički laser.
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PRIMENA
• Industrija
• Medicina
• Ekologija
• Informacione tehnologije
• Elektrotehnika, mašinstvo, tekstilna ind.
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LASER U MEDICINI
• Prvo korišten u oftalmologiji i dermatologiji– rubin, tek onda argonski laser
• Koristi se u:– neurohirurgiji– ortopediji– estetskoj hirurgiji…
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• Laserski zrak upijaju pigmenti(hromofor), supstance kroz koju prolaze pri čemu se oslobađa energija koja različito deluje na tkivo:– stimulisanje
– mehaničko uništenje…
• Hromofor-u ljudskom telu postoje 3 vrste:– voda
– melanin (pigment)
– hemoglobin .