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Shearing Interferometer
The shearing interferometer is an extremely simple means to observe interference and to use this phenomenon to test the collimation of light beams, especially from laser sources which have a coherence length which is usually significantly longer than the thickness of the shear plate (see graphics) so that the basic condition for interference is fulfilled. Function The testing device consists of a high-quality optical glass, like N-BK7, with extremely flat optical surfaces that are usually at a slight angle to each other. When a plane wave is incident at an angle of 45°, which gives maximum sensitivity, it is reflected two times. The two reflections are laterally separated due to the finite thickness of the plate and by the wedge. This separation is referred to as the ''shear'' and has given the instrument its name. The shear can also be produced by gratings, see ''External Links'' below. Parallel-sided shear plates are sometimes used, but the interpretation of the interfere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interference (optics)
In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive interference result from the interaction of waves that are correlated or coherence (physics), coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, Light wave, light, Radio wave, radio, sound wave, acoustic, surface wave, surface water waves, gravity waves, or matter waves. Etymology The word ''interference'' is derived from the Latin words ''inter'' which means "between" and ''fere'' which means "hit or strike", and was coined by Thomas Young (scientist), Thomas Young in 1801. Mechanisms The superposition principle#Wave interference, principle of superposition of waves states that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collimated
A collimated beam of light or other electromagnetic radiation has parallel rays, and therefore will spread minimally as it propagates. A perfectly collimated light beam, with no divergence, would not disperse with distance. However, diffraction prevents the creation of any such beam. Light can be approximately collimated by a number of processes, for instance by means of a collimator. Perfectly collimated light is sometimes said to be ''focused at infinity''. Thus, as the distance from a point source increases, the spherical wavefronts become flatter and closer to plane waves, which are perfectly collimated. Other forms of electromagnetic radiation can also be collimated. In radiology, X-rays are collimated to reduce the volume of the patient's tissue that is irradiated, and to remove stray photons that reduce the quality of the x-ray image ("film fog"). In scintigraphy, a gamma ray collimator is used in front of a detector to allow only photons perpendicular to the surface to be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light which is ''coherent''. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Alternatively, temporal coherence can be used to produce ultrashort pulses of ligh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence Length
In physics, coherence length is the propagation distance over which a coherent wave (e.g. an electromagnetic wave) maintains a specified degree of coherence. Wave interference is strong when the paths taken by all of the interfering waves differ by less than the coherence length. A wave with a longer coherence length is closer to a perfect sinusoidal wave. Coherence length is important in holography and telecommunications engineering. This article focuses on the coherence of classical electromagnetic fields. In quantum mechanics, there is a mathematically analogous concept of the quantum coherence length of a wave function. Formulas In radio-band systems, the coherence length is approximated by :L = \frac \approx \frac ~, where \, c \, is the speed of light in a vacuum, \, n \, is the refractive index of the medium, and \, \mathrm f \, is the bandwidth of the source or \, \lambda \, is the signal wavelength and \, \Delta \lambda \, is the width of the range of wavelengths i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffraction Grating
In optics, a diffraction grating is an optical component with a periodic structure that diffracts light into several beams travelling in different directions (i.e., different diffraction angles). The emerging coloration is a form of structural coloration. The directions or diffraction angles of these beams depend on the wave (light) incident angle to the diffraction grating, the spacing or distance between adjacent diffracting elements (e.g., parallel slits for a transmission grating) on the grating, and the wavelength of the incident light. The grating acts as a dispersive element. Because of this, diffraction gratings are commonly used in monochromators and spectrometers, but other applications are also possible such as optical encoders for high precision motion control and wavefront measurement. For typical applications, a reflective grating has ridges or ''rulings'' on its surface while a transmissive grating has transmissive or hollow slits on its surface. Such a grating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter ''lambda'' (λ). The term ''wavelength'' is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. Wavelength depends on the medium (for example, vacuum, air, or water) that a wav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refractive Index
In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or refracted, when entering a material. This is described by Snell's law of refraction, , where ''θ''1 and ''θ''2 are the angle of incidence and angle of refraction, respectively, of a ray crossing the interface between two media with refractive indices ''n''1 and ''n''2. The refractive indices also determine the amount of light that is reflected when reaching the interface, as well as the critical angle for total internal reflection, their intensity ( Fresnel's equations) and Brewster's angle. The refractive index can be seen as the factor by which the speed and the wavelength of the radiation are reduced with respect to their vacuum values: the speed of light in a medium is , and similarly the wavelength in that medium is , where ''Π... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Types Of Interferometers
An interferometer is a device for extracting information from the superposition of multiple waves. Field and linear interferometers *Air-wedge shearing interferometer *Astronomical interferometer / Michelson stellar interferometer * Classical interference microscopy *Bath interferometer (common path) * Cyclic interferometer * Diffraction-grating interferometer (white light) * Double-slit interferometer *Dual-polarization interferometry *Fabry–Pérot interferometer *Fizeau interferometer * Fourier-transform interferometer *Fresnel interferometer (e.g. Fresnel biprism, Fresnel mirror or Lloyd's mirror) *Fringes of Equal Chromatic Order interferometer (FECO) * Gabor hologram *Gires–Tournois etalon * Heterodyne interferometer (see heterodyne) * Holographic interferometer *Jamin interferometer *Laser Doppler vibrometer *Linnik interferometer (microscopy) * LUPI variant of Michelson *Lummer–Gehrcke interferometer *Mach–Zehnder interferometer *Martin–Puplett interferometer *M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air-wedge Shearing Interferometer
The air-wedge shearing interferometer is probably the simplest type of interferometer designed to visualize the disturbance of the wavefront after propagation through a test object. This interferometer is based on utilizing a thin wedged air-gap between two optical glass surfaces and can be used with virtually any light source even with non-coherent white light. Setup An air-wedge shearing interferometer is described inG.S. Sarkisov, ''Shearing interferometer with an air wedge for electron density diagnostics in a dense plasma'', Instruments and Experimental Techniques, vol.39, No.5, pp.727-731 (1996). and was employed in set of experiments described in.S.V. Granov, V.I. Konov, A.A. Malyutin, O.G. Tsarkova, I.S. Yatskovsky, F. Dausinger, High resolution interferometric diagnostics of plasmas produced by ultrashot laser pulses, Laser Physics, 13, 3, pp.386-396 (2003). This interferometer consists of two optical glass wedges (~2-5deg), pushed together and then slightly separated fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
