Lasers? Ah, one of the early lasers was He-Ne gas in a narrow tube, a radio transmitter antenna wrapped around the tube (or some such), and mirrors at both ends of the tube. So, photons would go back and forth between the mirrors, a tiny fraction would leak out of a mirror as the laser light, and the rest would stay in tube and help generate more photons from the radio and He-Ne interactions (laser, light amplification via stimulated emission of radiation).
So, right, just thinking from the OP, between mirrors there was some highly favorable line of amplification, and that line meant that the beam out of the laser would be an extension of that line and form a "narrow" beam!!!
Right, if use some voltage on some piezoelectric crystal to make tiny adjustments in the distance between the mirrors, then will make small changes in the frequency of the light, i.e., there is a highly favorable wavelength that fits a whole number of times between the mirrors or some such.
The changes in frequency of the light still have to correspond to the thermally moving gas atoms generating the light. Right, if have the favorable frequency in the middle of the feasable range, will get slightly less power in the beam, a dip, called the Lamb dip. Could that dip be used as a length standard? First job, worked on that, physicist, NIST, then the NBS, US National Bureau of Standards.
That is, at the end of the laser we have a tiny light source that puts out a very narrow beam. How? As above and not from antenna theory.
So, right, just thinking from the OP, between mirrors there was some highly favorable line of amplification, and that line meant that the beam out of the laser would be an extension of that line and form a "narrow" beam!!!
Right, if use some voltage on some piezoelectric crystal to make tiny adjustments in the distance between the mirrors, then will make small changes in the frequency of the light, i.e., there is a highly favorable wavelength that fits a whole number of times between the mirrors or some such.
The changes in frequency of the light still have to correspond to the thermally moving gas atoms generating the light. Right, if have the favorable frequency in the middle of the feasable range, will get slightly less power in the beam, a dip, called the Lamb dip. Could that dip be used as a length standard? First job, worked on that, physicist, NIST, then the NBS, US National Bureau of Standards.
That is, at the end of the laser we have a tiny light source that puts out a very narrow beam. How? As above and not from antenna theory.