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Twisted Light
An optical vortex (also known as a photonic quantum vortex, screw dislocation or phase singularity) is a zero of an optical field; a point of zero intensity. The term is also used to describe a beam of light that has such a zero in it. The study of these phenomena is known as singular optics. Explanation In an optical vortex, light is twisted like a corkscrew around its axis of travel. Because of the twisting, the light waves at the axis itself cancel each other out. When projected onto a flat surface, an optical vortex looks like a ring of light, with a dark hole in the center. The vortex is given a number, called the topological charge, according to how many twists the light does in one wavelength. The number is always an integer, and can be positive or negative, depending on the direction of the twist. The higher the number of the twist, the faster the light is spinning around the axis. This spinning carries orbital angular momentum with the wave train, and will induce torqu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helix Oam
A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, and many proteins have helical substructures, known as alpha helices. The word ''helix'' comes from the Greek word ''ἕλιξ'', "twisted, curved". A "filled-in" helix – for example, a "spiral" (helical) ramp – is a surface called ''helicoid''. Properties and types The ''pitch'' of a helix is the height of one complete helix turn, measured parallel to the axis of the helix. A double helix consists of two (typically congruent) helices with the same axis, differing by a translation along the axis. A circular helix (i.e. one with constant radius) has constant band curvature and constant torsion. A '' conic helix'', also known as a ''conic spiral'', may be defined as a spiral on a conic surface, with the distance to the apex an e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holograms
Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other applications. In principle, it is possible to make a hologram for any type of wave. A hologram is made by superimposing a second wavefront (normally called the reference beam) on the wavefront of interest, thereby generating an interference pattern which is recorded on a physical medium. When only the second wavefront illuminates the interference pattern, it is diffracted to recreate the original wavefront. Holograms can also be computer-generated by modelling the two wavefronts and adding them together digitally. The resulting digital image is then printed onto a suitable mask or film and illuminated by a suitable source to reconstruct the wavefront of interest. Overview and history The Hungarian-British physicist Dennis Gabor (in Hungarian: ''Gábor Dénes'') ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birefringent
Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are often birefringent, as are plastics under mechanical stress. Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking slightly different paths. This effect was first described by Danish scientist Rasmus Bartholin in 1669, who observed it in calcite, a crystal having one of the strongest birefringences. In the 19th century Augustin-Jean Fresnel described the phenomenon in terms of polarization, understanding light as a wave with field components in transverse polari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deformable Mirror
Deformable mirrors (DM) are mirrors whose surface can be deformed, in order to achieve wavefront control and correction of optical aberrations. Deformable mirrors are used in combination with wavefront sensors and real-time control systems in adaptive optics. In 2006 they found a new use in femtosecond pulse shaping. The shape of a DM can be controlled with a speed that is appropriate for compensation of dynamic aberrations present in the optical system. In practice the DM shape should be changed much faster than the process to be corrected, as the correction process, even for a static aberration, may take several iterations. A DM usually has many degrees of freedom. Typically, these degrees of freedom are associated with the mechanical actuators and it can be roughly taken that one actuator corresponds to one degree of freedom. Deformable mirror parameters Number of actuators determines the number of degrees of freedom (wavefront inflections) the mirror can correct. It is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spatial Light Modulator
A spatial light modulator (SLM) is an object that imposes some form of spatially varying modulation on a beam of light. A simple example is an overhead projector Transparency (projection), transparency. Usually when the term SLM is used, it means that the transparency can be controlled by a computer. In the 1980s, large SLMs were placed on overhead projectors to project computer monitor contents to the screen. Since then, more modern Video projector, projectors have been developed where the SLM is built inside the projector. These are commonly used in meetings of all kinds for presentations. Usually, a SLM modulates the Intensity (physics), intensity of the light beam. However, it is also possible to produce devices that modulate the phase (waves), phase of the beam or both the intensity and the phase simultaneously. SLMs are used extensively in holographic data storage setups to encode information into a laser beam similarly to way a transparency does for an overhead projector. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermite-Gaussian Mode
In optics, a Gaussian beam is a beam of electromagnetic radiation with high monochromaticity whose amplitude envelope in the transverse plane is given by a Gaussian function; this also implies a Gaussian intensity (irradiance) profile. This fundamental (or TEM00) transverse Gaussian mode describes the intended output of most (but not all) lasers, as such a beam can be focused into the most concentrated spot. When such a beam is refocused by a lens, the transverse ''phase'' dependence is altered; this results in a ''different'' Gaussian beam. The electric and magnetic field amplitude profiles along any such circular Gaussian beam (for a given wavelength and polarization) are determined by a single parameter: the so-called waist . At any position relative to the waist (focus) along a beam having a specified , the field amplitudes and phases are thereby determinedSvelto, pp. 153–5. as detailed below. The equations below assume a beam with a circular cross-section at all val ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mode Conversion
Mode conversion is the transformation of a wave at an interface into other wave types (modes). Principle Mode conversion occurs when a wave encounters an interface between materials of different impedances and the incident angle is not normal to the interface. Thus, for example, if a longitudinal wave from a fluid (e.g., water or air) strikes a solid (e.g., steel plate), it is usually refracted and reflected as a function of the angle of incidence, but if some of the energy causes particle movement in the transverse direction, a second transverse wave is generated, which can also be refracted and reflected. Snellius' law of refraction can be formulated as: \frac = \frac = \frac = \frac This means that the incident wave is split into two different wave types at the interface. If we consider a wave incident on an interface of two different solids (e.g. aluminum and steel), the wave type of the reflected wave also splits. Besides these simple mode conversions, an incident ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blazed Grating
A blazed grating – also called echelette grating (from French ''échelle'' = ladder) – is a special type of diffraction grating. It is optimized to achieve maximum grating efficiency in a given diffraction order. For this purpose, maximum optical power is concentrated in the desired diffraction order while the residual power in the other orders (particularly the zeroth) is minimized. Since this condition can only exactly be achieved for one wavelength, it is specified for which ''blaze wavelength'' the grating is optimized (or ''blazed''). The direction in which maximum efficiency is achieved is called the ''blaze angle'' and is the third crucial characteristic of a blazed grating directly depending on blaze wavelength and diffraction order. Blaze angle Like every optical grating, a blazed grating has a constant line spacing d, determining the magnitude of the wavelength splitting caused by the grating. The grating lines possess a triangular, sawtooth-shaped cross sec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ronchi Linear Diffraction Grating
A Ronchi ruling, Ronchi grating, or Ronchi mask, named after the Italian physicist Vasco Ronchi, is a constant-interval bar and space square-wave optical target or mask. The design produces a precisely patterned light source by reflection or illumination, or a stop pattern by transmission, with precise uniformity, spatial frequency, sharp edge definition, and high contrast ratio. Manufacturing Ronchi rulings are typically manufactured through photolithographic deposition of metallic chromium on a substrate, which yields a precise, nearly 100% contrast pattern. For a reflective or illuminated type, dark stripes are printed on a diffusely reflecting or translucent substrate, such as a square of white ceramic material or opal glass. For a transmissive type, opaque stripes are printed on a transparent glass substrate. A transmissive type may be readily modified to act as an illuminated type by stacking a reflective object behind it. Applications A test target in the Ronchi patt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laguerre-Gaussian Beam
In optics, a Gaussian beam is a beam of electromagnetic radiation with high monochromaticity whose amplitude envelope in the transverse plane is given by a Gaussian function; this also implies a Gaussian intensity (irradiance) profile. This fundamental (or TEM00) transverse Gaussian mode describes the intended output of most (but not all) lasers, as such a beam can be focused into the most concentrated spot. When such a beam is refocused by a lens, the transverse ''phase'' dependence is altered; this results in a ''different'' Gaussian beam. The electric and magnetic field amplitude profiles along any such circular Gaussian beam (for a given wavelength and polarization) are determined by a single parameter: the so-called waist . At any position relative to the waist (focus) along a beam having a specified , the field amplitudes and phases are thereby determinedSvelto, pp. 153–5. as detailed below. The equations below assume a beam with a circular cross-section at all v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
