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Lasers

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Observations About Lasers

They produce narrow beams of intense light
They often have pure colors
They are dangerous to eyes
Reflected laser light has a funny speckled look

Stimulated Emission

Excited atoms can be stimulated into duplicating passing light
Photons are correlated and identical
Coherent light

Laser Oscillation


Laser medium in a resonator produces oscillator
A spontaneous photon is duplicated over and over
Duplicated photons leak from semitransparent mirror
Photons from oscillator are identical

Properties of Laser Light

Coherent – identical photons
Controllable wavelength/frequency – nice colors
Controllable spatial structure – narrow beams
Controllable temporal structure – short pulses
Energy storage and retrieval – intense pulses
Giant interference effects
Apart from these issues, laser light is just light

Types of Lasers

Gas (HeNe, CO2, Argon, Krypton)
Powered by electricity
Solid state (Ruby, Nd:YAG, Ti:Sapphire, Diode)
Powered by electricity or light
Liquid (Dye, Jello)
Powered by light
Chemical (HF)
Nuclear