1. LASERs Light Amplification by Stimulated Emission of Radiation

2. Function Produce an intense beam of light at a very narrow bandwidth (0.01 nm) that is highly coherent Useful in spectroscopy –Specificity –High sensitivity –Small detection window

3. Components Power Supply Pumping Source Laser media Mirrors

4. Mechanism of Action Power Supply turns on the pumping source Pumping Source emits radiation that is absorbed by laser media Intensity of pumping source produces a population inversion Stimulated emission becomes the dominant process

5. continued Stimulated emission – one photon is “absorbed” by excited electron and two coherent photons are emitted. Coherent photons that happen to travel along the horizontal path between the two mirrors are selectively amplified (photon traveling at different angles deviate from the path between the two mirrors and are lost

6. 3 and 4 level systems are most common because it is easier to reach a population inversion E0E0 EnEn EyEy EnEn EyEy ExEx E0E0 Non-radiative NR (fast) NR (fast)

7. Types Solid State –Nd:YAG laser; 1064 nm (freq doubled) Gas lasers –He/Ne, CO 2, N 2, eximer (ArF + ) Dye Laser –Fluorescent dye solutions, tunable (20-50 nm) –Organic compounds capable of fluorescing in the UV, visible, and IR regions Semiconductor Diode Lasers –LEDs; Not used much in spectroscopy, as of yet.