Autocorrelator light pulses
(57) Abstract:Autocorrelator light pulses contains a light beam splitter, line variable optical delay, the node combining beams, optically coupled to the node registration. The light beam splitter, line variable optical delay and the node combining beams is made in the form of a beamsplitter cube with a beam-splitting layer, made on its diagonal, and the input and output faces is planar and orthogonal to each other, and the other two are made so that the difference of various parts of the wave front has changed by a certain precisely known to the law, and also applied reflective coating, while multi-element photodetector aligned and optically coupled with the output side of the cube. The technical result - the creation of stable autocorrelator light pulses. 4 C.p. f-crystals, 6 ill. The invention relates to a device for measuring one of the main characteristics of optical radiation is the autocorrelation function of the light wave in time.A device for implementing the method of measuring the optical thickness of the plane-parallel transparent objects, prozrachnoe flat mirror, covering the plane-parallel transparent object, biprism Fresnel (in one embodiment of the invention) and spatial-sensitive multi-element photodetector.The disadvantages of this device is the lack of stability for use in portable devices, field conditions, moving objects, in systems designed for operation in conditions of high vibration. Two reasons cause a decrease in its resistance to vibration and sensitivity. The first is due to the large distance between the lens and the photodetector. The second is associated with insufficient quantity of the light flux, which is caused by the requirement of high spatial coherence of the beam and, accordingly, the use of a narrow slit in the collimator beam. In addition, the device has a small range of change of the difference of the stroke, due to conflicting requirements between the angle of the prism at the top and the dimensions of the prism, or the resolution of the spatial-sensitive photodetector.Known autocorrelator light pulses containing the light beam splitter, line variable optical delay, the node combining direct and delayed the ohms specified autocorrelator is its low stability and difficulty settings due to the presence of a large number of degrees of freedom structural elements.The basis of the invention is the creation of stable autocorrelator light pulses by executing divider light pulses, a delay line pulse, the node combining beams and registration system in a single beam-splitting cube and the placement of a sensor directly on the output surface of the cube.Achieving the above technical result is ensured by the fact that in the known autocorrelator light pulses containing the light beam splitter, line variable optical delay, the node combining beams, optically coupled to a node in the Desk, and a radiation receiver, the recording power of the waves, the light beam splitter, line variable optical delay and the node combining beams is made in the form of a beamsplitter cube with a beam-splitting layer, placed on the diagonal of the cube, and the input and output faces of the cube is planar and orthogonal to each other, while the other two made so to the difference of various parts of the wave front has changed by a certain precisely known to the law, and n is n and optically coupled with the output side of the cube.The implementation of all parts of autocorrelator into a single beam-splitting cube allows you to maximize the stability of the device.The invention is illustrated in Fig.1. In Fig.1 light source 1 having a low degree of coherence in time, lights using achromatic condenser 2, which may be a lens, mirror, small diaphragm 3, the dimensions of which are selected from conditions provide sufficient spatial coherence for radiation of all measured frequencies. Aperture 3 is placed in the front focal plane of the collimator 4, which can be combined with the input surface of the cube, creating a parallel light beam 5. The parallel beam is directed to a beam splitter 6, inside the beam-splitting cube 7, made of a substance that is transparent throughout the required range of wavelengths. The cube has two faces - the input 8 and output 9 is flat and orthogonal to each other, and the other two are 10, 11 is made so that the difference of various parts of the wave front parallel beams is changed by a specific and precisely known to the law, in particular, Fig.1 the difference varies linearly along one of the coordinates, the PE the spine). In the latter case, the surface of the cube are planes normal to which is inclined relative to the axis of the beam. On the verge 10, 11 is applied reflective coating with high refractive index throughout the working spectral region, guiding the reflected beams back to the beam splitter. Passed through the beam splitter, the beam reflected from the faces 10, and the beam reflected from the faces 11 and then reflected from the beam splitter 6, adding to the space behind the beam splitter, form in space arrangements beams, shown in Fig.1 hatch, an interference pattern which is recorded using the spatial-sensitive sensor 12 directly behind the beam-splitting cube. It can also be projected on the photodetector using the additional optical system. The operation of the photodetector is controlled by the electronic system 13. The signal of the photodetector is processed either the same electronic system, or a specialized 14.The device can be used beamsplitter cubes made with polished at a given angle edges, and faces orthogonal, having deposited on the surfaces of wedge-shaped layers of transparent videolina, placed on the flat surfaces of the cube, is made orthogonal to the optical axis. The number, size and thickness of the layers are selected in accordance with the desired set of values of the differences of the stroke and with consideration of the influence of diffraction. You can also use wavefronts with a surface curved in exactly the known law (e.g., spherical).For approval of resolution multi-element photodetector with the structure of the interference pattern between the photodetector and the output face of the cube can accommodate optical system for forming a real image of the interference pattern on the surface of the photodetector, including a variable focal length (zoom).The work of autocorrelator can be explained as follows.In this invention, when receiving the interference pattern to measure the autocorrelation function instead of dividing the wave front method of dividing the light wave amplitude. With this purpose, create a collimated light beam and directing it to the translucent mirror, forming two coherent beam, fully match the distribution of the amplitude volnyichya orthogonal polarization States (two plane-polarized waves, or two waves oppositely directed circular polarization). Impose a delay between different areas of the wavefronts, and various known accurately for different sections of the front. Then using the same, or the second special semi-transparent mirror or a polarizing prism keep these two beams so that a respective different region of wave fronts were kept in the same order as they were in the original beam. Due to the interference amplitude plots of the wave front, which experienced a different delay will be different. Measure the spatial distribution of light intensity of the interference field using spatial-sensitive photodetector and share the light on constant and variable field components. Allocate a variable component, and find its dependence on well-known difference of course between the beams. The obtained dependence is a function of the autocorrelation of the light flux, with accuracy up to a constant factor, which depends on the integral brightness of the light source and the geometry of the optical system.To study the autocorrelation function of the light flux from the light source with a different geometry of the light beam in oostergo image source and homogeneous filling of the collimator light.In the correlator shown in Fig.1, the interference pattern has a one-dimensional character shown in Fig.2: the illumination of the photodetector standing on one of the coordinates (y) changes with orthogonal axes (x). The use of two-dimensional spatial-sensitive photodetector in this case leads to unnecessary overestimation of requirements, that is accompanied by an increase in the noise power. The contradiction is resolved in the apparatus shown in Fig.3, which shows the diagram of a device operating on the above principle, supplemented by a cylindrical lens 15, is installed on the output cube. The lens can be combined with the output surface of the cube, instead of lenses can be used cylindrical or toroidal mirror. Focusing is performed in the direction (y) orthogonal to the direction of measurement of the difference of the stroke of the beams. Instead of a two-dimensional matrix of a sensor in this case is linear, oriented along the direction (x), which leads to reduction of the area of the photodetector and reduce noise level. Due to this increase the accuracy of the measurement of the autocorrelation function and increase the sensitivity, but also extends the range of possible fotopro the fronts on the amplitude and on the front. With this aim, the inclined outer faces of the cube 10, 11 is applied to a system of strips of transparent substances of the same width, oriented in the direction of the change in the difference between progress and manufactured so that each further has an optical thickness less than the previous by an amount equal to the difference between the optical thickness of the cube in the extreme points of the interference pattern. A simplified form of the beam-splitting cube shown in Fig.4. As a result of this interference field is consisting of a system of parallel strips. In each of the bands of the difference varies linearly, and the difference in one of the bands differs from the next by a constant amount equal to the full change in the difference of the operation in this band. Processing the light distribution in the interference pattern through the device 14, the end of the distribution for one of the bands mathematically "sew" with the beginning of another. A complete change of the difference of the operation in the interference pattern is equal to the sum of the changes in the difference of course all the bands.Between the output face of the described complex beam-splitting cube, shown in Fig. 4, and space-sensitive photodetector can be installed additional optyka. Such a system may consist of a linear raster formed by parallel cylindrical lenses oriented its generatrix direction parallel to the sweep direction of the interference pattern. The narrowing of the images of the illuminated strips allows the use of a photodetector smaller effective area, thereby increasing the signal to noise in registered autocorrelation function. A raster is made in the form of a system of parallel PLANO-convex cylindrical lens, may be its flat surface is mechanically combined with the output surface of the cube.The use of multi-element photodetectors with a discrete set of elements (pixels) leads to the sampling of the interferogram to change the difference of course. This fact allows the use of the interference of the cube, creating a discrete set of difference values of a course consisting of N values. The number and magnitude of the difference of a course chosen from the same conditions as used for the FTIR with selectable scan. To this end, the cube mentally divided into N independent "elementary blocks", each of which corresponds to the specified value times the RMS-parallel transparent layers of material, the area of each of which corresponds to one or more elements (pixels) of the photodetector, and the optical thickness corresponds to the set for this "elementary cube" the difference of course. A simplified structure of such a cube is shown in Fig.5 for N = 4. The image element of the interference pattern is recorded by using one element of a sensor, or some combination of elements, you can use an additional optical system for forming a real image of the interference pattern on the surface of the photodetector, including raster.Much of the information about the nature of the wave process regular type if known, the average frequency spectrum can be obtained from the shape of the envelope of the autocorrelation function. As an example of the device for measuring film thickness sufficient to determine the position of the maxima of the envelope system of lateral interference fringes. In this case, the resolution of the multi-element photodetector can be much smaller than the period of oscillations in the autocorrelation function. A simple reduction in resolution leads to a smoothing of interferents. In order to ensure the ability to measure low-frequency characteristics while neglecting high frequency, you can enter into the gap between the output side of the cube and the photodetector environment with non-linear characteristics of the transmission or use of nonlinear photodetector. The following variants are possible nonlinear registration device interference pattern.In any area between the photodetector and the output face of the cube is placed Wednesday, with the threshold characteristics of the transmission, such as high transmittance for radiation of high power have filters made of glass type NA or a substance having the property of nonlinear luminescence in the multiphoton absorption, or used when solving problems of up-conversion of radiation (e.g., nonlinear glass and crystals). Under the action of a sufficiently powerful illumination of the investigated radiation, or a combination of auxiliary and studied radiation, there is a partial enlightenment nonlinear filter in the areas of the surface where the field strength of the light wave in the interference pattern maximum, or in the same places occurs induced by multiphoton absorption luminescente nature of the interference pattern illustrated in Fig.6. Her example shows the autocorrelation function of radiation "almost white" source. Fig.2,and shows the response of a linear system, and Fig. 2, b-threshold, and the threshold value shown in Fig.2,and the dotted line. The deterioration of the resolution of the photodetector to the width of one strip in the first case will lead to the fact that it will show a constant illumination, equal to the average signal level and the second will reproduce approximately the shape of the envelope.To reduce the threshold is preferably non-linear optical elements near the plane of focus coming out of the cube radiation, applying the use of luminescence additional optical system projecting the field of luminescence on the surface of the photodetector.The use of nonlinear photodetector, in particular, with adjustable sensitivity threshold is preferred because it provides greater sensitivity, efficiency, and ease of device management. 1. Autocorrelator light pulses containing the light beam splitter, line variable optical delay, the node combining beams, optically coupled to the node registration, characterized in that the divider snogo cube with beam-splitting layer, executed on its diagonal, and the input and output faces is planar and orthogonal to each other, and the other two are made so that the difference of various parts of the wave front has changed by a certain precisely known to the law, and also applied reflective coating, while multi-element photodetector aligned and optically coupled with the output side of the cube.2. Autocorrelator under item 1, characterized in that the two other faces are tilted with respect to the axis of the beam.3. Autocorrelator under item 1, characterized in that the inclined faces of the cube put a system of strips of transparent substances of the same width, oriented in the direction of the change in the difference between progress and manufactured so that each further has an optical thickness less than the previous by an amount equal to the difference between the optical thickness of the cube in the extreme points of the interference pattern.4. Autocorrelator under item 1, characterized in that between the output face of the described complex beam-splitting cube and a photodetector installed additional optical system including a linear raster formed by parallel cylindrical lenses, orientation is">5. Autocorrelator under item 1, characterized in that between the output face of the cube and the photodetector entered Wednesday with a non-linear or nonlinear characteristics of the photodetector.
FIELD: optical electronics, in particular, engineering of devices for transforming pulse optical emission to pulse electric signal of appropriate duration and shape, possible utilization for generating single or series of ultra-short electric pulses, registration of optical radiation pulse shape, measuring power of optical radiation.
SUBSTANCE: optic-electronic device for generation of ultra-short electric pulses and registration of shape of optical radiation pulses has light source of ultra-short pulses, transformer of light to electric signal, two electrodes positioned on the surface of light transformer and having electrical contact with same. Light transformer is made in form of film of carbon material having optical rectification property. Surface of film is positioned in inclined manner relatively to falling beam from light source. Optic-electronic device additionally includes device for measuring amplitude, shape and duration of electric voltage pulses. Light transformer may be realized in form of film, applied to substrate with electric conductivity being substantially lower than electric conductivity of film material. Electrodes can be made in form of linear electric conductors, positioned in parallel to each other and perpendicularly to light falling plane, in particular between carbon film and substrate. Also possible is adding of optical device to device for transformation of ultra-short pulse source to linearly polarized radiation in plane, perpendicular to film plane, and positioned between light source and light transformer, and beam expander, positioned between ultra-short pulse source and light transformer.
EFFECT: simplified construction of device, improved transformation efficiency.
6 cl, 6 dwg
SUBSTANCE: impulse detector with synchronized detection matrix contains collimated light beam lighting a Bragg cell, excited by input signal, containing impulses of varying modulation, aforementioned cell spatially modulating collimated light beam. Binary optical plate multiplies image of Bragg cell on non-transparent plate, containing multiple slits, each one of which has set length. Optical system of lenses forms spatial Fourier light distribution transformation, as a result of which light intensiveness in focal plane of optical system of lenses is proportional to energetic spectral density of light distribution in slits of non-transparent plate. Detector/processor of focal plane, containing detector matrix, responds to intensiveness of light detected by detector matrix, processes analog output signals and transforms them to initial adjustment commands for detecting and determining impulse characteristics in input signal and generates output signals.
EFFECT: realization of algorithm of synchronized detection matrix with usage of hybrid optical-electrical analog and digital processor.
5 cl, 10 dwg
FIELD: optics; nonlinear optics.
SUBSTANCE: method can be used for measuring field of ultra short light pulses. Two copies of tested pulses are created first. Copies are directed onto non-linear crystal, which provides simultaneous generation of radiation of second harmonic of one pulse and radiations of total frequency of both copies. Intensity distribution, arising at interference of tested pulse's second harmonic and of pulse total frequency are registered. Single-dimension distribution of intensity is measured and pulse field time dependence is determined by means of iteration algorithms which algorithms have visual zero approach, which gives the chance of watching pulse field in oscillograph mode at minimal load of computational system.
EFFECT: improved precision of measurement.
2 cl, 7 dwg
FIELD: physics, optics.
SUBSTANCE: invention concerns optics and can be used for measuring of peak-phase structure of supershort light impulses of a femtosecond pulse, both radiated by lasers, and any other nature. Method consists that integrated spatial distributions on time register not less, than in two planes of the spectroscopic device which are on various distances from plane of formation of spectrum. Then spend processing of the gained data, consisting that in the allocations gained out of plane of formation of spectrum, eliminate the greasing arising owing to motion of light stain, having the restricted sizes, in a variance direction on plane of recording during impulse existence. As a result in corresponding plane gain the instantaneous allocation of intensity on which spot spatial peak-phase structure of the gained spatial distribution of signal strength in a plane of formation of a spectrum.
EFFECT: simplification of hardware embodying.
2 cl, 6 dwg
SUBSTANCE: invention can be used for recording of pulse shape of optical radiation and measuring of its power, and also for reception single or series of ultrashort electrical impulses. Photodetector consists of substrate, nanographite film executed from graphite nanocrystals which base planes are canted to the surface of substrate and are preferentially undirectional, and two parallel electrodes having electrical link with it. The electrodes can be located parallelly preferred direction of edges of dihedral angles formed by plane of substrate and base planes of crystal grains.
EFFECT: increase of operational performances of device.
2 cl, 2 dwg
FIELD: electrical engineering.
SUBSTANCE: invention relates to opto-electronics, in particular to devices designed to convert pulsed optical radiation into pulsed electric signal and can be used recording optical radiation and designing angle-measurement devices. Proposed opto-electric converter consists of a substrate, conducting film and two parallel conducting electrodes in contact with aforesaid film. It differs from known designs in that the said conducting film represents a thick-film silver- and palladium-based resistor.
EFFECT: higher resistance of converter to mechanical and optical effects.
SUBSTANCE: metre of radiation intensity in pulse optical quantum oscillators comprises double-beam interferometre by Rozhdestvenskiy with two dead and two semi-transparent mirrors. In its first optical branch - signal one - magnetooptical cell of Cotton-Mouton and crossed nicol are serially installed, and in the second one - reference one - there are the following components serially installed - phase plate, photometric wedge and half-wave plate. To inlet of interferometre by Rozhdestvenskiy via Polaroid there is a single-frequency single-mode optical quantum oscillator of continuous action connected. Radiation of measured pulse optical quantum oscillator via quarter-wave plate and diaphragm radiates magnetooptical cell of Cotton-Mouton in direction perpendicular to distribution of laser radiation in it from single-frequency single-mode optical quantum oscillator of continuous action. Outlet of interferometre by Rozhdestvenskiy is connected to inlet of homodyne photodetector based on compound "cadmium-mercury-tellurium" cooled by liquid nitrogen, electric outlet of which is connected to inlet of spectrum analyser.
EFFECT: provision of linear assessment of intensity of ultra-short and powerful pulses of laser radiation of optical quantum oscillators that operate in modes with modulated Q value or synchronisation of modes.
SUBSTANCE: measurements are continuously taken relative each wall and roof of a building and recorded every 5-10 seconds during the entire period of observation, and solar radiation energy is determined using the formula: q=1000*V*K, where V is pyranometer voltage, mV; K is the coefficient of said pyranometer, W/(m2*mV). Values of solar radiation energy on each wall and roof of the building are added and the value of solar radiation energy falling on the entire building is obtained. The device is in form of a cross comprising 6 tubes attached at the centre at an angle of 90° relative each other, wherein four tubes lie in the horizontal plane with pyranometers attached at their ends, and the fifth tube with a pyranometer at its end is vertical.
EFFECT: invention increases accuracy of measuring solar radiation energy falling on a building.
2 cl, 2 dwg
SUBSTANCE: pulsed radiation sources can be any fast natural or artificial processes accompanied by a light flash. The apparatus, along with an electrooptical camera, consisting of an objective, an electrooptical converter having slit-type image scanning and an image processing and recording system, has a so called calibration channel comprising a system for picking up single pulses and a Fabry-Perot interferometer for generating a train of equidistant optical pulses, lying along the optical axis of the pulsed laser. The image recording system is a solid-state matrix image receiver connected to a computer, having a program for correcting the scanning coefficient of the electrooptical camera, based on comparison thereof with duration of time intervals between pulses in the train.
EFFECT: invention enables to take high-precision measurements of time characteristics of pulsed optical radiation in the nano-picosecond range.
FIELD: measurement equipment.
SUBSTANCE: device for measurement of a physical value with local resolution, comprising facilities for generation of the first electric signal (6) with the first frequency and the second electric signal (7) with the second frequency, differing from the first one by the value of differential frequency, a source of optical radiation for generation of an optical signal, which is modulated by the first frequency and may interact with the object of measurement, as a result of which the following may be modified: a mixer (11), which may mix the electric signal (10) produced on the basis of the optical signal with the second signal (7), a digital-to-analogue converter (13) to digitise at least one mixed signal (12) and in particular the facilities for generation of the third electric signal (8) with the third frequency made in the form of a DDS system (3), besides, the third frequency corresponds to the differential frequency or exceeds it several times, at the same time the digital-to-analogue converter (13) may scan the mixed signal (12) for its digitisation with the third frequency.
EFFECT: measurement of a physical value with local resolution.
10 cl, 4 dwg
SUBSTANCE: device has circular metallic plate, in which a periodic matrix of rectangular slits is cut. Plate is positioned in such a way, that a falling beam of millimeter-long waves falls at an angle of 45° relatively to plate surface. Polarization of falling beam is parallel to plate surface. When direction of plate is such, that electric field is perpendicular to slits (i.e. electric field is directed transversely to lesser dimension of slits), plate transfers almost 100% of falling power. If the plate rotates around its axis for 90° (while keeping angle between falling beam and plate equal to 45°) in such a way, that falling electric field is parallel to slits, then plate transfers 0% and reflects almost 100% of falling power at an angle of 90° relatively to falling beam. By changing rotation angle between 0° and 90° both reflected and passed power can be continuously varied between values 0% and 100% from falling power. Light divider has cooling device for taking heat, absorbed from magnetic waves, away from edge of metallic plate.
EFFECT: continuous variation of reflected and passed power.
11 cl, 15 dwg
FIELD: image generation devices - displays.
SUBSTANCE: claimed device contains a light source, liquid-crystalline panel, and also redirecting film and stack of optical wave conductors positioned between the first two parts, where optical wave conductors are made in form of films, first ends of which are oriented towards the light source, and second ends are extended relatively to one another with creation of toothed surface, which is connected to first toothed surface of redirecting film, second surface of which is connected to liquid-crystalline panel, where the teeth of both connected surfaces have to faces.
EFFECT: increased brightness of image.
6 cl, 2 dwg
SUBSTANCE: light conducting optical element, which includes at least one light supplying base, which is equipped with at least two surfaces located parallel to each other; optical means that are used for entering light beams into the base by total internal reflection so that the light would strike one of the above surfaces, set of one or more partially reflecting surfaces located inside of the base, the surfaces of which are not parallel to the above base surfaces; the partially reflecting surfaces being flat surfaces selectively reflecting at an angle, which are crossed by part of beams several times before exiting the base in the required direction.
EFFECT: provision of wide field of view and increase of eye movement area with device fixed.
44 cl, 36 dwg
SUBSTANCE: optical substrate contains three-dimensional surface preset by the first function of surface pattern, modulated second function of surface pattern. The first function of surface pattern can be described by length, width and vertex angle with optical characteristics for formation of, at least, one output mirror component. The second function of surface pattern can be described by geometry with, at least, pseudorandom characteristic for modulation of the first function of surface pattern, at least, by phase along length of the first function of surface pattern. At that the phase presents horizontal position of peak along width. The surface of optical substrate creates mirror and scattered light from input light beam. The three-dimensional surface can have value of correlation function which is less than approximately 37 percent of initial throughout the length of correlation about 1 cm or less.
EFFECT: brightness increase is provided.
46 cl, 41 dwg