Light amplification by stimulated emission of radiation
Light Amplification by Stimulated Emission of Radiation - acronym LASER - is generally credited to have been first demonstrated 50 years ago (1960) this Sunday, "anniversary of the first demonstration of a ruby laser at the Hughes Research Labs," as marked in the interesting article online "Lasers scan future possibilities" at
http://news.bbc.co.uk/2/hi/science/nature/8675972.stm This was done by wrapping a ruby crystal with a flashlamp that pumps light energy into the ruby's outer electrons, and having reflective surfaces in two directions bouncing light back and forth between them while having the ruby in between them, so as to coordinate the timing of those pumped-higher electrons dropping back down into their lower energy state and emitting a photon of light while doing so. The use of helium-neon lasers for continuous lasing came shortly afterwords, enabling the continuous emission of coherent light; in contrast to the brief ruby crystal laser light burst due to the brief flash of the flashlamp.
Yet the phenomenon had existed long before that, available to be demonstrated, and most likely can be done right now in your home. Find some appliance, such as many of the outlet strips that are used in one's computer setup, and find one that has the little orange light that is flickering a bit. The aging pilot light on it is a little bulb containing the gas neon; it has a resistor in series with it and is across the AC power line, to indicate that there is power applied to the outlets in the extension strip. When the voltage across the lamp goes above 45 volts, in either direction, the neon enables current flow through it, limited by the 47K ohm resistor. As the voltage cycle goes up then down below 45 volts, the neon light goes out, and restarts again when the voltage again reaches 45 volts in the other direction. When the little neon bulb ages, the quality of the gas inside deteriorates and it starts flickering. So if one dims the ambient light on the neon pilot light, it flickers more, having a harder time getting started emitting light - which is the clue to lasing, that need for adding ambient light - so do an experiment and shine a small flashlight on the neon pilot light, and it will then glow steadily, no longer flickering; its emission is being stimulated by the added light. Very weak "light amplification by stimulated emission of radiation" yet indeed it is that, although not being reinforced by mirrors bouncing the light back and forth through the gas, necessary to provide a narrow directed beam of coherent light, going through a partially silvered mirror at one end. I recall experimenting with the little neon bulbs in the early 1950's - the most embarrassingly memorable of which was when, at age about 17 and lacking awareness of the need for the 47K current limiting resistor, holding the glass neon-filled bulb carefully I inserted its two leads into an AC socket, which produced a brief brilliant blast of light, not so much from the neon in the bulb but instead from the vaporization of the leads of the bulb due to the huge current going through them - so they have been around since before that; this was before the heralded discovery of lasing in 1960.
Lasers have been important to me in the years since then - such as a R&D job I had in the mid-1960's which sometimes involved use of a 5 mW helium-neon laser - and the pocket laser pointers I used when giving my presentations of my transportation concepts at space technical conferences - but the point here is that there may be phenomena in our everyday lives that only seem a bit odd, yet are potential demonstrators of principles that could be explored - instead of just being ignored - and maybe lead to some very useful devices and their applications.
http://news.bbc.co.uk/2/hi/science/nature/8675972.stm This was done by wrapping a ruby crystal with a flashlamp that pumps light energy into the ruby's outer electrons, and having reflective surfaces in two directions bouncing light back and forth between them while having the ruby in between them, so as to coordinate the timing of those pumped-higher electrons dropping back down into their lower energy state and emitting a photon of light while doing so. The use of helium-neon lasers for continuous lasing came shortly afterwords, enabling the continuous emission of coherent light; in contrast to the brief ruby crystal laser light burst due to the brief flash of the flashlamp.
Yet the phenomenon had existed long before that, available to be demonstrated, and most likely can be done right now in your home. Find some appliance, such as many of the outlet strips that are used in one's computer setup, and find one that has the little orange light that is flickering a bit. The aging pilot light on it is a little bulb containing the gas neon; it has a resistor in series with it and is across the AC power line, to indicate that there is power applied to the outlets in the extension strip. When the voltage across the lamp goes above 45 volts, in either direction, the neon enables current flow through it, limited by the 47K ohm resistor. As the voltage cycle goes up then down below 45 volts, the neon light goes out, and restarts again when the voltage again reaches 45 volts in the other direction. When the little neon bulb ages, the quality of the gas inside deteriorates and it starts flickering. So if one dims the ambient light on the neon pilot light, it flickers more, having a harder time getting started emitting light - which is the clue to lasing, that need for adding ambient light - so do an experiment and shine a small flashlight on the neon pilot light, and it will then glow steadily, no longer flickering; its emission is being stimulated by the added light. Very weak "light amplification by stimulated emission of radiation" yet indeed it is that, although not being reinforced by mirrors bouncing the light back and forth through the gas, necessary to provide a narrow directed beam of coherent light, going through a partially silvered mirror at one end. I recall experimenting with the little neon bulbs in the early 1950's - the most embarrassingly memorable of which was when, at age about 17 and lacking awareness of the need for the 47K current limiting resistor, holding the glass neon-filled bulb carefully I inserted its two leads into an AC socket, which produced a brief brilliant blast of light, not so much from the neon in the bulb but instead from the vaporization of the leads of the bulb due to the huge current going through them - so they have been around since before that; this was before the heralded discovery of lasing in 1960.
Lasers have been important to me in the years since then - such as a R&D job I had in the mid-1960's which sometimes involved use of a 5 mW helium-neon laser - and the pocket laser pointers I used when giving my presentations of my transportation concepts at space technical conferences - but the point here is that there may be phenomena in our everyday lives that only seem a bit odd, yet are potential demonstrators of principles that could be explored - instead of just being ignored - and maybe lead to some very useful devices and their applications.
posted by Unknown at
07:42
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