PROPERTIES OF LASER
First, let’s discuss the properties of laser light and then we will go into how is is created. Laser light is monochromatic, directional, and coherent. Monochromatic
The light emitted from a laser is monochromatic, that is, it is of one wavelength (color). In contrast, ordinary white light is a combination of many different wavelengths (colors). Directional
Lasers emit light that is highly directional. Laser light is emitted as a relatively narrow beam in a specific direction. Ordinary light, such as coming from the sun, a light bulb, or a candle, is emitted in many directions away from the source.
The light from a laser is said to be coherent, which means the wavelengths of the laser light are in phase in space and time.
These three properties of laser light are what make it more of a hazard than ordinary light. Laser light can deposit a great deal of energy within a very small area – as James Bond nearly found out in Goldfinger!
BENEFITS OF LASER
Some of the world’s most powerful and complex arrangements of multiple lasers and optical amplifiers are used to produce extremely high intensity pulses of light of extremely short duration. These pulses are arranged such that they impact pellets of tritium-deuterium simultaneously from all directions, hoping that the squeezing effect of the impacts will induce atomic fusion in the pellets. This technique, known as “inertial confinement fusion”, so far has not been able to achieve “breakeven”, that is, so far the fusion reaction generates less power than is used to power the lasers, but research
Confocal laser scanning microscopy and Two-photon excitation microscopy make use of lasers to obtain blur-free images of thick specimens at various depths. Laser capture microdissection use lasers to procure specific cell populations from a tissue section under microscopic visualization. Additional laser microscopy techniques include harmonic microscopy, four-wave mixing microscopy and interferometric microscopy. Military
Military uses of lasers include applications such as target designation and ranging, defensive countermeasures, communications and directed energy weapons.
Directly as an energy weapon
Directed energy weapons are being developed, such as Boeing’s Airborne Laser which was constructed inside a Boeing 747. Designated the YAL-1, it is intended to kill short- and intermediate-range ballistic missiles in their boost phase.
Defensive countermeasure applications can range from compact, low power infrared countermeasures to high power, airborne laser systems. IR countermeasure systems use lasers to confuse the seeker heads on heat-seeking anti-aircraft missiles. High power boost-phase intercept laser systems use a complex system of lasers to find, track and destroy intercontinental ballistic missiles (ICBM). In this type of system a chemical laser, one in which the laser operation is powered by an energetic chemical reaction, is used as the main weapon beam (see Airborne Laser). The Mobile Tactical High-Energy Laser (MTHEL) is another defensive laser system under development; this is envisioned as a field-deployable weapon system able to track incoming artilleryprojectiles and cruise missiles by radar and destroy them with a powerful deuterium fluoride laser. Another example of direct use of a laser as a defensive weapon was researched for the Strategic Defense Initiative (SDI, nicknamed “Star Wars”), and its successor programs.
This project would use ground-based or space-based laser systems to destroy incoming intercontinental ballistic missiles (ICBMs). The practical problems of using and aiming these systems were many; particularly the problem of destroying ICBMs at the most opportune moment, the boost phase just after launch. This would involve directing a laser through a large distance in the atmosphere, which, due to optical scattering and refraction, would bend and distort the laser beam, complicating the aiming of the laser and reducing its efficiency. Another idea from the SDI project was the nuclear-pumped X-ray laser. This was essentially an orbiting atomic bomb, surrounded by laser media in the form of glass rods; when the bomb exploded, the rods would be bombarded with highly-energetic gamma-ray photons, causing spontaneous and stimulated emission of X-ray photons in the atoms making up the rods. This would lead to optical amplification of the X-ray photons, producing an X-ray laser beam that would be minimally affected by atmospheric distortion and capable of destroying ICBMs in flight. The X-ray laser would be a strictly one-shot device, destroying itself on activation. Some initial tests of this concept were performed with underground nuclear testing; however, the results were not encouraging. Research into this approach to missile defense was discontinued after the SDI program was cancelled. Disorientation
Some weapons simply use a laser to disorient a person. One such weapon is the Thales Green Laser Optical Warner.
* Cosmetic surgery (removing tattoos, scars, stretch marks, sunspots, wrinkles, birthmarks, and hairs): see laser hair removal. Laser types used indermatology include ruby (694 nm), alexandrite (755 nm), pulsed diode array (810 nm), Nd:YAG (1064 nm), Ho:YAG (2090 nm), and Er:YAG (2940 nm). * Eye surgery and refractive surgery
* Soft tissue surgery: CO2, Er:YAG laser
* Laser scalpel (General surgery, gynecological, urology, laparoscopic) * Photobiomodulation (i.e. laser therapy)
* “No-Touch” removal of tumors, especially of the brain and spinal cord. * In dentistry for caries removal, endodontic/periodontic procedures, tooth
whitening, and oral surgery