12/29/2023 0 Comments Coherence time![]() G(\tau)=\frac$ ( $\approx37\%$) of its initial value gives you your coherence time. A more sophisticated evaluation of the coherence time can be carried out by calculating the temporal coherence function: A monochromatic laser is also not perfectly monochromatic and has a distribution of frequencies with some width $\Delta\nu$ which gives rise to a coherence time $\Delta\tau=1/\Delta\nu$. In long-distance transmission systems, the coherence time may be reduced by propagation factors such as dispersion, scattering, and diffraction. The origin of such coherence measures is simply due to uncertainty. For an electromagnetic wave, the coherence time is the time over which a propagating wave (especially a laser or maser beam) may be considered coherent, meaning that its phase is, on average, predictable. Lasers tend to have a high degree of coherence with single-mode He-Ne lasers having coherence lengths of about ~100 meters! Similarly, you can also define a coherence length ( $L=c\tau$) which is the distance covered by the beam until it can be considered to be in-phase with itself. It essentially tells you if a traveling beam remains 'in-phase' with itself after a certain time. Because wavelets provide local information about data in time and scale (frequency), wavelet-based coherence allows you to measure time-varying correlation. ![]() Environmental disruptions cause a quantum. This lifetime may be limited by inelastic collisions, possibly enhanced by the formation of long-lived molecular complexes ( 31 ), or by trapping light-induced collisions. Coherence time ( $\tau$) is a measure of the correlation between phases of a wave at two different instances of time. The sphere surrounded by a bubble represents an isolated quantum state. The eventual coherence limit for bulk gases will be the trap lifetime, on the order of several seconds for our chemically stable NaK molecules ( 17 ).
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