Laser Principles PDF

Laser Principles Lec.1 Dr.Jumana Al-Musawi 1. Introduction: Laser is a device that stimulates atoms or molecules to emit light at particular wavelengths and amplifies that light, typically producing a very narrow beam of radiation. The emission generally c...

Laser Principles Lec.1 Dr.Jumana Al-Musawi 1. Introduction: Laser is a device that stimulates atoms or molecules to emit light at particular wavelengths and amplifies that light, typically producing a very narrow beam of radiation. The emission generally covers an extremely limited range of visible, infrared, or ultraviolet wavelengths. Many different types of lasers have been developed, with highly varied characteristics. Laser is an acronym for “Light Amplification by the Stimulated Emission of Radiation.” 2. History The laser is an outgrowth of a suggestion made by Albert Einstein in 1916 that under the proper circumstances atoms could release excess energy as light either spontaneously or when stimulated by light. German physicist Rudolf Walther Ladenburg first observed stimulated emission in 1928, although at the time it seemed to have no practical use. 3. Work principle Light travels in waves, and the distance between the peaks of a wave is called the wavelength. Fig.(1) : Shows Wavelengths. 1 Laser Principles Lec.1 Dr.Jumana Al-Musawi Each color of light has a different wavelength. For example, blue light has a shorter wavelength than red light. Sunlight and the typical light from a lightbulb is made up of light with many different wavelengths. Our eyes see this mixture of wavelengths as white light. Fig.(2) :This animation shows a representation of the different wavelengths present in sunlight. When all of the different wavelengths (colors) come together, you get white light. A laser is different. Lasers do not occur in nature. However, we have figured ways to artificially create this special type of light. Lasers produce a narrow beam of light in which all of the light waves have very similar wavelengths. The laser’s light waves travel together with their peaks all lined up, or in phase. This is why laser beams are very narrow, very bright, and can be focused into a very tiny spot. 2 Laser Principles Lec.1 Dr.Jumana Al-Musawi Fig.(3) :This animation is a representation of in phase laser light waves. Because laser light stays focused and does not spread out much (like a flashlight would), laser beams can travel very long distances. They can also concentrate a lot of energy on a very small area. Fig.(4) :This animation shows how a laser can focus all of its light into one small point. 3 Laser Principles Lec.1 Dr.Jumana Al-Musawi Lasers have many uses. They are used in precision tools and can cut through diamonds or thick metal. They can also be designed to help in delicate surgeries. Lasers are used for recording and retrieving information. They are used in communications and in carrying TV and internet signals. We also find them in laser printers, bar code scanners, and DVD players. They also help to make parts for computers and other electronics. Lasers are also used in instruments called spectrometers. Spectrometers can help scientists figure out what things are made of. For example, the Curiosity rover uses a laser spectrometer to see what kinds of chemicals are in certain rocks on Mars. Fig.(5) :This is a picture of Martian soil before (left) and after (right) it was zapped by the Curiosity rover’s laser instrument called ChemCam. By zapping tiny holes in Martian soil and rock, ChemCam can determine what the material is made of. 4