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LASER technology uses stimulated emission to generate a coherent beam of photons. A gain medium and a resonant optical cavity are required to create a laser. Different gain mediums produce lasers of different wavelengths. Lasers have a wide range of applications, including data storage, cutting, vision correction, and nuclear fusion. The maximum achievable laser pulse intensity has increased exponentially since the mid-1980s. Lasers could one day provide energy for the entire human race and propel solar sails into space.
LASER (Light Amplification Stimulated Emission of Radiation) is a triumph of modern optics. Using a quantum mechanical effect called stimulated emission, lasers generate a coherent, almost monochromatic beam of photons. Non-laser light sources typically generate incoherent, unfocused beams of light at a variety of wavelengths, impeding certain applications.
To create a laser, two components are required: a gain medium and a resonant optical cavity. For a gain medium, some crystals, glasses, gases, semiconductors and even colored liquids can be used. The gain medium is stimulated by an energy pump source such as an electric current or other laser. The medium absorbs the energy, exciting the states of the particles in the medium. After a certain threshold, called a population inversion, is reached, light shining through the medium causes more stimulated emission, or release of energy, than absorption.
A resonant optical cavity is a specially sized chamber with a mirror at one end and a semi-silver mirror at the other. The two reflective surfaces cause light trapped inside to reflect back and forth through the gain medium, acquiring more energy with each pass. When this effect fades, the gain is said to be saturated and the light becomes true laser light. Different means of gain give rise to lasers of different wavelengths.
Two varieties of lasers are continuous and pulsed. The continuous laser is more useful for most applications, but the energy in a pulsed laser can be very large. The degree of divergence of the beam over time varies inversely with its diameter. Small bundles diverge rapidly, while larger bundles remain coherent.
When the laser was patented by Bell Labs in 1960, it was not immediately feasible to use it, although spectrometry, interferometry, radar and nuclear fusion were discussed as potential areas of interest. Today, the laser is among the most versatile technological marvels, with applications in data storage and retrieval, laser cutting, vision correction, surveying, measurements, holography and displays, and even nuclear fusion. The maximum achievable laser pulse intensity has increased exponentially since the mid-1980s. One day, lasers could be used to generate fusion reactions that produce net energy, providing energy for the entire human race. They could also be used to propel solar sails into the depths of space.
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