【文章內(nèi)容簡介】
, highly stable, singlefrequency sine wave, exactly like the signal generated by a highly stable electronic oscillator in any other frequency range. ? The term coherence necessarily refers not to one property of a signal at a single point in space and time, but to a relationship, or a family of relationships, between one signal at one point in space and time, and the same or another signal at other points in space and time. ? More colloquially, a signal is called “temporally coherent” if there is strong correlation in some sense between the amplitude and/or phase of the signal at any time and at earlier or later time. ? Both the amplitude and the phase of a goodquality laser oscillator will in fact change only slowly with time, so that the amplitude and the phase of the output sine wave from the laser at any one time will be strongly correlated with the amplitudes and phases at considerably earlier or later times. A goo