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The coherent laser beams required for the technique are generally produced by splitting a primary beam into two or more sub-beams. As both beams originate from the same source, coherence is ensured as long as the subsequent optics do not disturb it. There are a variety of methods to split the primary laser beam: prisms [3] laser beam dividers [2]
The coherence time, usually designated τ, is calculated by dividing the coherence length by the phase velocity of light in a medium; approximately given by = where λ is the central wavelength of the source, Δν and Δλ is the spectral width of the source in units of frequency and wavelength respectively, and c is the speed of light in vacuum.
Laser linewidth from high-power high-gain pulsed laser oscillators, comprising line narrowing optics, is a function of the geometrical and dispersive features of the laser cavity. [29] To a first approximation the laser linewidth, in an optimized cavity, is directly proportional to the beam divergence of the emission multiplied by the inverse ...
Multimode helium–neon lasers have a typical coherence length on the order of centimeters, while the coherence length of longitudinally single-mode lasers can exceed 1 km. Semiconductor lasers can reach some 100 m, but small, inexpensive semiconductor lasers have shorter lengths, with one source [4] claiming 20 cm. Singlemode fiber lasers with linewidths of a few kHz can have coherence ...
Coherent control is a quantum mechanics-based method for controlling dynamic processes by light.The basic principle is to control quantum interference phenomena, typically by shaping the phase of laser pulses.
Photon detections as a function of time for a) antibunching (e.g. light emitted from a single atom), b) random (e.g. a coherent state, laser beam), and c) bunching (chaotic light). τ c is the coherence time (the time scale of photon or intensity fluctuations).
The first optical parametric oscillator was demonstrated by Joseph A. Giordmaine and Robert C. Miller in 1965, [2] five years after the invention of the laser, at Bell Labs. Optical parametric oscillators are used as coherent light sources for various scientific purposes, and to generate squeezed light for quantum mechanics research. A Soviet ...
A laser or synchrotron beam are also often used directly without additional collimation. The spatial coherence guarantees a uniform wavefront prior to beam splitting. Second, it is preferred to use a monochromatic or temporally coherent light source. This is readily achieved with a laser but broadband sources would require a filter.