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LASER- Light Amplification by Stimulated Emission of Radiation


The acronym LASER stands for Light Amplification by Stimulated Emission of Radiation. It is commonly used as a word and written as “laser”. The “radiation” portion of the acronym sounds ominous, but radiation just means traveling light or other particles. Light, or photons, are electromagnetic waves including everything from X-rays to radio waves. LASER light tends to be in or near the visible portion of the electromagnetic spectrum.

How a LASER works
Normal light sources tend to emit a hodgepodge of diverse photons. The Sun and stars, incandescent light bulbs, florescent lights, fires and candles, LEDs (Light Emission Devices), and most surfaces reflecting light, are made of a variety of atomic elements that hold and emit light of different frequencies and at different polarities.

Frequency in light refers to a photon’s position in the electromagnetic spectrum. All light oscillates, waving up and down, side to side, or somewhere in between as it travels. How quickly it waves determines the frequency. The polarity of light is the direction of the oscillations. Polarized light oscillates all in one direction instead of a natural, random distribution of directions. LASERs emit light of the same frequency and polarity.

Though different types of LASERs vary greatly, there are two common components necessary to make a LASER. There must be a gain medium and there must be a resonant optical cavity, a fancy name for a mirrored chamber.

The gain medium is usually a uniform material that is stimulated to release a photon as another photon passes by. The passing photon causes an outer electron on an atom of the gain medium to fall (or rather pop) towards the nucleus. This releases a photon of the same frequency as the passing photon, and the light is amplified.

The resonant optical cavity has two mirrors. One is a fully reflective mirror, and the other is partially reflective. The released light bounces back and forth between the mirrors (resonating), bumping more electrons in the gain medium and releasing even more photons. The partially reflective mirror allows some of the light to eventually escape, creating the LASER beam.

Common Uses
It is unlikely that LASERs are being used to torture secret agents in the underground lairs of supervillians, but LASERs are found in all sorts of devices. The computer you are reading this on probably has a CDROM or DVD drive. Both use a LASER to read discs. The disc is encoded with information by a LASER that burns tiny holes into the metallic medium on the disc. The disc is later read by a similar LASER at lower energy that beams light into the metal and finds where the holes are. The different between hole and non-hole provides the information (much like the records CDs replaced).

LASERs are also used in speed detection for law enforcement, surveying in land development, satellite topography (including the mapping of Mars and Venus), vision correction (LASIK – LASER Assisted in Situ Keratomileusis), and barcode scanners.

It is generally considered that LASERs will be an integral component in successful nuclear fusion reactors. Ultimately, this may be the most valuable use of LASERs.

The term “laser” is an acronym: Light Amplification by Stimulated Emission of Radiation..Light Amplification (by) Stimulated Emission (of) Radiation Many different types:
Ruby rod laser – basically a polished rod of aluminium oxide/chromium oxide (synthetic tuby), surrounded by apowerful flashtube. – Visible Red
Nitrogen laser, co2 laser (gas lasers) fairly efficient by laser standards, inivisble output but can be strong enough to cut metal
semiconductor – both invisible and red – cheap for low power
dpss – diode pumped solid state – these lasers use a “pump” diode which is usually 808nm, tis goes into a sliver of something called vanadate which take in light at 808bm (almost invisible Infra Red) and re-emit it at 1064nM (Invisible. It is then put through a crystal of KTP which halves the wavelength (doubling the frequency) and re-emits at 532nM – bright green





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