On this day in 1967 Theodore H. Malman was granted the patent for RUBY LASER SYSTEMS. U.S. Patent No. 3,353,115.
This invention relates to the generation, amplification, and utilization of electromagnetic waves in the infrared, visible and ultraviolet portion of the spectrum, and more specifically to lasers and laser systems. A laser, the term being an acronym for light amplification by stimulated emission of radiation, is a device capable of generating or amplifying coherent light. The principle of operation is similar to that of a maser and is therefore also referred to as an optical maser.
Much effort has been expended in the fields of electronics and physics in attempts to generate or amplify coherent light. Such an achievement, it was known, would make available a vast new region of the electromagnetic spectrum for a multitude of purposes including communications and metrology (measurements) applications. Such coherent light would have the properties of being monochromatic and of having its component waves prop a gating in phase with each other. Thus, as at radio or microwave frequencies, a great deal of energy could be concentrated at or extremely near to a single frequency and be utilized in methods analogous to those at radio frequencies.
Ordinary techniques of generating or amplifying electromagnetic waves, including microwave maser techniques, cannot be extended usefully into the optical frequencies because such techniques require components, such as maser cavities, for supporting wave oscillations which must have physical dimensions of the order of a wavelength. Obviously, such components can neither be manufactured nor meaningfully utilized at optical frequencies where the wavelengths are of the order of atomic dimensions. When it is attempted to use cavities which have dimensions corresponding to a large number of wavelengths, many modes are supported, coherence is degraded, and impracticably large sources of pumping power are required.
A laser has been proposed by Schawlow and Townes, see United States Patent No. 2,929,922, issued March 22, 1960, which suggests using as the negative temperature medium certain gaseous state materials such as alkali metal vapors. Such materials may be shown to have energy levels in their atomic systems corresponding to appropriate optical frequencies for absorbing optical pump energy to invert the population from the stable equilibrium state and thus provide the material with what is known as a negative temperature or excited, non equilibrium state. Then by stimulation or spontaneous relaxation the atomic system falls back to its normal equilibrium state by one or more steps emitting energy of certain optical frequencies.
Such proposed gaseous state devices are of great interest its theoretical models and represent significant academic advances, however, they have not been shown to provide it not generation or amplification of light. In addition, the structure of gaseous state systems is complex and requires the mainttenance of critical vapor pressures and temperatures. Impurities in the gas is another very serious problem. The inter-atomic spacing of the gas severely limits the efficiency of coupling between the stimulated emission and a coherent wave propagating through the medium. In addition, the frequency of operation of any given gas laser may be effectively tuned only by Stark or Zeeman effects which can provide a tuning range of only approximately 5X1011 cycles per second. Further, the construction of a gas cell is extremely critical in that the end plates must be highly reflective and perfectly parallel so that the many reflections required because of the low density gaseous material will be accomplished.
It is therefore an object. of the present invention to provide an operable, low noise. efficient laser.
It is another object to provide a laser which is mechanically stable and of noncritical construction.
It is another object to provide a laser which operates at room temperature or cryogenic temperatures for additional simplicity and even greater flexibility in design parameters.
It is another object to provide a laser which does not require critical vacuum or vapor pressure techniques and which operates in a medium of high dielectric constant.
It is another object to provide a laser capable of much higher power handling.
It is another object to provide a laser which is tunable over aproximately a 5X1011 cycles per second range.
It is another object to provide an optical radar system utilizing the advantages of a laser.
Briefly, these and other objects are achieved in accordance with the present invention in a system including a solid state negative temperature medium. In one example a segment of solid state.
