LASERS Light Amplification by the Stimulated Emission of

“LASERS” Light Amplification by the Stimulated Emission of Radiation

“LASERS” …. . small Tunable Diode Laser - about 2 mm x 2 mm chip - used to measure water vapor concentration in the near-IR - used to detect low-levels of gas concentration (ppm, ppb)

“LASERS” …. . Large!!! NOVA Laser at LLNL

“LASERS” Laser Guide Stars - VLT 8. 2 m telescopes - creates an artificial star at an altitude of 90 km -yellow sodium line - part of the VLT’s Adaptive Optics system

“LASERS” Laser Cutting CO 2, Nd: YAG E ≈ 1 MW/cm 2 fbeam <. 5 mm carbon steel, stainless steel, aluminum, titanium http: //en. wikipedia. org/wiki/File: Lasercutting-video. ogg Laser Welding top: CAD model http: //en. wikipedia. org/wiki/File: Remote_Fibre_Laser_Welding_WMG_Warwick. ogg bottom: laser-cut part - 0. 5 mm thick stainless steel

“LASERS” …. . History 1917 --Albert Einstein describes the photon and points out that stimulated emission of light could occur. 1958 --Arthur Schawlow and Charles Townes publish their theoretical paper "Infrared and Optical Masers" in Physical Review, 1958. 1960 --Theodore Maiman invents the first laser, the optical version of the maser, using a man-made ruby crystal. First operated on May 16, 1960. 1961 --He. Ne gas laser is invented by Ali Javan, et al. , Bell Labs. -first laser to emit a continuous (CW) beam of light -first output was at 3. 39 microns, in the infrared -visible output at 0. 633 microns (633 nm) in 1962 -"workhorse of the laser industry“ 1963 --CO 2 gas laser is invented by Patel, Bell Labs. 1964 --Argon ion laser is invented by Bridges, Hughes Research Labs. 1966 --Organic Dye (liquid) laser is invented. 1970's--Semiconductor lasers are run at room temperature, paving the way for their practical use today.

“LASERS” …. . 2010, the 50 th Anniversary! “A solution looking for a problem. ” http: //spie. org/media/laserplayer. html http: //www. laserfest. org/

“LASERS” …. . Basic Principle Light Amplification by the Stimulated Emission of Radiation Atoms absorb energy… A population inversion is created… The atoms return to their non-energetic states by emitting radiation (“light”--UV, visible, or IR) through stimulated emission… Feedback in an optical cavity amplifies this light… Some of this light is emitted in the form of laser light!

“LASERS” …. . Stimulated Emission

“LASERS” …. . Characteristics of Laser Light

“LASERS” …. . Laser Speckle (random interference pattern)

“LASERS” …. . Fundamental Parts "How to Make a Laser" "Gain medium (to provide for population inversion)" + "Input source of energy (electricity, light, etc. )" + "Resonant cavity (provides optical feedback and sustains stimulated emission)"

“LASERS” …. . Example: The Ruby Laser The Ruby. Laser - Sapphire crystal doped with chromium ions (≈ 0. 05%) - The sapphire rod has flat, polished ends coated with gold - The chromium ions absorb the input white-light and emit the laser light - Wavelength of 694 nm (ruby-red color) - Output beam is pulsed - Needs high voltage to run the flash lamp

“LASERS” …. . Example: The Ruby Laser

“LASERS” …. . Example: He-Ne Laser

“LASERS” …. . Example: Red laser pointer

“LASERS” …. . Example: Red laser pointer Red Laser Pointer - direct output of red light from the Laser Diode (“LD”) λ = 633 nm, 650 nm, 670 nm, etc. - output is monitored by the built-in photodiode detector (“PD”) -beam expands and is collimated by the aspheric lens

“LASERS” …. . Example: Green laser pointer λ = 532 nm 5 m. W beam

“LASERS” …. . Example: Green laser pointer Diode-Pumped Solid State “DPSS laser” - 808 nm (near-infrared) pump diode laser 808 nm energy converted to 1064 nm by the Nd: YVO 4 crystal - 1064 nm energy converted to 532 nm green light by the KTP crystal - this is a non-linear process called “frequency-doubling” - the input frequency is doubled, and the output wavelength is cut in half - beam is expanded - beam is collimated - beam is filtered to block the (powerful) original IR energy at 808 nm