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A green laser pointer. Reduction of the speckle was necessary to photograph the laser's Gaussian profile, accomplished by removing all lenses and projecting it onto an opaque liquid (milk) being the only surface flat and smooth enough. Speckle is considered to be a problem in laser based display systems like the Laser TV. Speckle is usually ...
The speckle pattern seen when using a laser pointer is another diffraction phenomenon. It is a result of the superposition of many waves with different phases, which are produced when a laser beam illuminates a rough surface. They add together to give a resultant wave whose amplitude, and therefore intensity, varies randomly.
When a Gaussian laser beam is focused, the focused spot diameter is defined by d 00 = 4 λ f π D 00 {\displaystyle d_{00}={4\lambda f \over \pi D_{00}}} , (3) where d 00 is the ideal focused spot diameter, f is the focal length of the focusing lens, and D 00 is the input beam waist and is placed one focal length from the lens as shown in the ...
Laser cooling was also achieved with Ytterbium-doped yttrium lithium fluoride crystals to generate cold spots using lasers to achieve trapping with reduced photobleaching. [41] The sample temperature has also been reduced to achieve optical trapping for a significantly increased selection of particles using optothermal tweezers for drug ...
The Gaussian function has a 1/e 2 diameter (2w as used in the text) about 1.7 times the FWHM.. At a position z along the beam (measured from the focus), the spot size parameter w is given by a hyperbolic relation: [1] = + (), where [1] = is called the Rayleigh range as further discussed below, and is the refractive index of the medium.
Hence, the focal spot of a uniform circular laser beam (a flattop beam) focused by a lens will also be an Airy pattern. In a camera or imaging system an object far away gets imaged onto the film or detector plane by the objective lens, and the far field diffraction pattern is observed at the detector.
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M 2 is useful because it reflects how well a collimated laser beam can be focused to a small spot, or how well a divergent laser source can be collimated. It is a better guide to beam quality than Gaussian appearance because there are many cases in which a beam can look Gaussian, yet have an M 2 value far from unity. [1]