Showing papers on "Beam splitter published in 1991"

Experimental evidence for a photon anticorrelation effect on a beam splitter : a new light on single-photon interferences

Abstract: We report on two experiments using an atomic cascade as a light source, and a triggered detection scheme for the second photon of the cascade. The first experiment shows a strong anticorrelation between the triggered detections on both sides of a beam splitter. This result is in contradiction with any classical wave model of light, but in agreement with a quantum description involving single-photon states. The same source and detection scheme were used in a second experiment, where we have observed interferences with a visibility over 98%. During the past fifteen years, nonclassical effects in the statistical properties of light have been extensively studied from a theoretical point of view (l), and some have been experimentally demonstrated (2-71. All are related to second-order coherence properties, via measurements of intensity correlation functions or of statistical moments. However, there has still been no test of the conceptually very simple situation dealing with single- photon states of the light impinging on a beam splitter. In this case, quantum mechanics predicts a perfect anticorrelation for photodetections on both sides of the beam splitter (a single-photon can only be detected once!), while any description involving classical fields would predict some amount of coincidences. In the first part of this letter, we report on an experiment close to this ideal situation, since we have found a coincidence rate, on both sides of a beam splitter, five times smaller than the classical lower limit. When it comes to single-photon states of light, it is tempting to revisit the famous historical .single-photon interference experiments. (8). One then finds that, in spite of their

Optical glucose sensor apparatus and method

Abstract: An optically based apparatus for non-invasively determining the concentration of optically active substances in a specimen comprises, a source of a beam of spatially coherent light (10) which is acted upon to produce a rotating linear polarized vector therein. A beam splitter (24) splits the beam into a reference beam (26) and a detector beam (30) for passage through the specimen. The detector beam (30) is received upon exiting the specimen and compared with the reference beam (26) to determine the amount of phase shift produced by passage through the specimen. This amount of phase shift is converted into concentration of the optically active substance in the specimen.

Optical device with an illuminating grid and detector grid arranged confocally to an object

Abstract: A device is described for three-dimensional examination with a confocal beam path, in which an illumination grid (12; 22; 31; 83) is imaged in a focal plane (13f; 87), said plane being located on or in the vicinity of surface (14o) of object (14). The radiation reflected in the focal plane is imaged directly by a beam splitter onto the receiving surface of a CCD receiver (17; 91). The illumination grid (12; 22; 31; 83) is then imaged on the receiver surface either by the photosensitive areas of the receiver acting as confocal diaphragms or by signals from the detector elements which only receive light scattered outside focal plane (13f; 87) not being taken into account in the evaluation or being taken into account separately. The illumination grid size generated in focal plane (13f; 87) can be either fixed or variable. A variable illumination grid size can be produced for example by an LED array. The device also makes examinations in transmitted light possible.

Observation of a nonclassical Berry's phase for the photon.

Abstract: Coincidence detection of photon pairs produced in parametric fluorescence, in conjunction with a Michelson interferometer in which one member of each pair acquired a geometrical phase due to a cycle in polarization states, has allowed the first observation of Berry's phase at the single-photon level. We have verified that each interfering photon was essentially in an n=1 Fock state, by means of a beam splitter following the interferometer combined with a triple-coincidence technique. The results can be interpreted in terms of a nonlocal collapse of the wave function.

High-isolation polarization-independent quasi-optical circulator

Abstract: A high-isolation polarization-independent optical circulator is reported. The circulator structure can sharply reduce isolation dependency on both the rotation error of a rotator and on extinction ratio of a polarizing beam splitter. As a result, the circulator has high isolation over a wide wavelength and temperature range. A 4-port circulator coupled with single-mode fibers was fabricated. Its measured insertion loss and isolation were 31.5 dB, respectively. Consequently, a loss ratio of over 29.7 dB has been realized. The isolation (which is free from reflections) was measured to be >45.1 dB. It is confirmed that the wavelength range for this kind of isolation over 40-dB is very wide. The measured range was wider than the measurement system limit of 90 nm. >

Interferometric modulator for optical signal processing

Abstract: An interferometric modulator uses a beamsplitter to produce deflected and transmitted light beams onto mirrored surfaces of a piezoelectric crystal pair, one piezoelectric crystal being driven by a modulating voltage signal, whereupon the light beams are reflected back to the beamsplitter to produce a modulated optical output signal, with the modulator being especially adaptable for use as an digital photonic clock, as a pulse width/amplitude modulator, and as a bistable optical memory cell.

Spectral division of reflected light in complex optical diagnostic and therapeutic systems

Abstract: A diagnostic system for support of laser ocular surgery, for example, solves a problem of competition for light which is often encountered when a series of different detectors are used to receive and detect features of a target reflecting an illuminating light beam. The intensity of an illuminating beam, particularly in eye surgery, is limited to a level above which damage to the eye can occur. In a system wherein a plurality of successive beam splitters are used, each reflecting a portion of the light intensity and transmitting the remaining light intensity, the series of detecting devices compete for adequate light intensity for the particular functions being served. The system of the invention solves this problem and increases the effective quantity of light useful from a given input intensity by dividing the light spectrally after its reflection from the eye, thereby making use of a different spectral range of the light at each of the plurality of different detecting devices.

Performance limits of stationary Fourier spectrometers

Abstract: Theoretical performance limits of stationary Fourier spectrometers without mechanical scanning are analyzed and compared with the performance of a scanning Fourier spectrometer. Spectrometers employing uncollimated light are most favorable. In amplitude-splitting interferometers the reduction in fringe visibility brought about by the extended source can be avoided and leads to high optical throughput in the corresponding spectrometer. In a stationary wave-front-splittirig interferometer, realized without a beam splitter, the fringe contrast depends on the size of the source. The use of a slit source increases the optical throughput of source-size-limited spectrometers.

High resolution reduction catadioptric relay lens

Abstract: An optical system of a NX reduction catadioptric relay lens having sub-half micron resolution over the utlraviolet band width is described. A spherical mirror with a stop at the mirror is used to work at substantially the desired reduction ratio and the desired high numerical aperture sufficient to provide the desired high resolution. A beam splitting cube with appropriate coatings is used to form an accessible image of an object on an image plane. Refracting correctors in the path of the slow beam incident on the mirror and in the path of the fast beam reflected on the mirror are designed to fix the aberrations of the image formed by the mirror. The beam splitter coatings are chosen in such a way that beams reflected from and transmitted therethrough suffer no net aberration as a result of multiple reflections within the thin film beam splitter coatings and therefore are substantially free of aberration, distortion and apodization which would result from the beam splitting surface in the absence of these coatings.

Visual image display apparatus having a video display for one eye and a controllable shutter for the other eye

Abstract: An optical apparatus using a display device is comprised of a lens system having an optical axis, a display device for displaying a video image on the optical axis, a beam splitter for splitting information of visual image, the beam splitter being formed so as to incline an angle of about 45 degrees relative to the optical axis and located under the lens system, and a shutter device disposed in front of the beam splitter for controlling transmission of image from the surrounding, wherein the video image is shown as a virtual image with the image from the surroundings when viewer peeps the video image from the back of the beam splitter.

Complex amplitude reflectance of the liquid crystal light valve.

Abstract: The complex amplitude reflectance of the liquid crystal light valve (LCLV) is determined as a function of the writing intensity and applied voltage using an approximate model. The input and output polarizers are assumed to have arbitrary directions. The theoretical results based on this model match our experimental measurements. This theory allows us to optimize the operation of the LCLV as an intensity or phase-only spatial light modulator. When the polarizers are orthogonal and the input polarizer is at -34 degrees with the front liquid crystal director, the intensity reflectance reaches 100% (compared to 81% for the conventional configuration). Phase-only modulation is realizable by use of appropriate applied voltage bias and configuration of polarizers.

Polarization independent coherent lightwave detection arrangement

Abstract: A polarization independent coherent lightwave detection arrangement is disclosed which utilizes an optical hybrid (11) including a single polarization beam splitter (12) and a set of three polarization maintaining optical couplers (one input (22), two output (16,20)). By controlling the polarization state of the local oscillator to remain at a fixed value, polarization independent recovery of a transmitted data signal may be accomplished. Phase independence may be incorporated by replacing the pair of output polarization maintaining optical couplers with a pair of phase diversity optical hybrids.

Simultaneous dual field of view sensor

Abstract: An optical system (10) for producing dual fields of view simultaneously. The system (10) includes a first optical system (12) for producing a first field of view image and a second optical system (36) for producing a second field of view image where the angular displacement of the second field of view is different from that of the first field of view. A dichroic beamsplitter (22) is disposed in the present invention so as to reflect light from the first optical system (12). The dichroic beamsplitter (22) is also disposed so as to simultaneously transmit light from the second optical system (36). As a result, the reflected light (20) is primarily composed of light of a first wavelength band and the transmitted light is primarily composed of a second wavelength band. The light from the two different fields of view are then directed to a dual filter (32) which passes the first wavelength band in one portion and passes the second wavelength band in another portion. Light passing through the dual filter (32) may then be focused onto a sensor (34) which will then detect the first field of view image on one area and simultaneously detect the second field of view image on another area.

Light amplifying device

Abstract: A light amplifying device comprising an optical oscillator constituted by first and second reflective mirrors and a common reflective mirror disposed in an optically opposite relation to each other, a polarized beam splitter for making a laser beam incoming from the side of the common reflective mirror incident on the first or second reflective mirror, and for making laser beams incoming from the sides of the first and second reflective mirrors incident on the common mirror, first and second amplifying media disposed in optical paths of the respective laser beams for amplifying the laser beams, and an optical element for rotating the polarizing plane of the laser beam reflected by the common reflective mirror by a predetermined angle. The laser beams emitted from the first and second amplyfying media are repeatedly between the first and second reflective mirrors and the common reflective mirror while being amplified through the respective amplifying media, for being emitted from the common reflective mirror as a high-energy synthesized laser beam in a single polarized state.

High-isolation polarization-independent optical circulator coupled with single-mode fibers

Abstract: A high-isolation polarization-independent optical circulator is reported. The goal is to provide a simple structure that sharply diminishes the degradation on the isolation caused by imperfection of polarization separation in the polarizing beam splitters. The circulator structure is almost the same as that of a conventional circulator except that a birefringent plate is added to each port to achieve high isolation. The effectiveness of the added birefringent plate has been confirmed by calculation and experiment. Insertion loss and isolation of the fabricated circulator coupled with single-mode fibers have been measured to be 29.9 dB, respectively, for 1.299 mu m wavelength light. A loss ratio over 28.9 dB has been realized. >

Durable optical elements fabricated from free standing polycrystalline diamond and non-hydrogenated amorphous diamond like carbon (dlc) thin films

Abstract: Optical elements, and methods for fabricating them, are described wherein each element includes a free standing (self supporting) polycrystalline continuous thin film of diamond combined with a non-hydrogenated amorphous diamond like carbon (DLC) film having a high percentage of sp 3 bonding. These elements may be designed to have optically smooth surfaces, have wide optical transmission ranges (for example, be transparent across the infrared portion of the spectrum), and exhibit exceptional durability characteristics. Optical instruments that include such elements are also described, along with the derivative benefits, such as improved operating performance and lower maintenance requirements, realized using the novel optical elements. In particular, a polarization Michaelson interferometer (PMI) is taught which is operative over the entire range from far infrared into the visible portion of the spectrum without requiring the exchange of beam splitters or beam polarizers. These performance benefits are achieved as a result of the transmission characteristics of the novel optical elements associated with the PMI.

Diffuse on-axis light source

Abstract: A light source suitable for illuminating work pieces imaged by machine vision cameras. A beam splitter mirror is located within the camera optical axis, a uniform intensity light source provides light to a diffuser and the diffused light is reflected from the beam splitter to uniformly illuminate the object being observed by the camera with a minimum of stray reflections or glare. Stray and incidental light is absorbed by a light trap located in opposed relation to the diffuser.

Optical scanning device with confocal beam path using a light source array and a detector array

Abstract: A description is given of a device for three-dimensional investigation having a confocal beam path, in which an illumination array (12; 22; 31; 83) is imaged in a focal plane (13f; 87), which is located on or in the vicinity of the surface (14o) of the object (14). The radiation reflected in the focal plane is imaged via a beam splitter directly onto the receiver surface of a CCD receiver (17; 91). The imaging of the illumination array (12; 22; 31; 83) on the receiver surface is performed in this case in such a way that either the light-sensitive regions of the receiver act as confocal diaphragms, or that signals of the detector elements which receive only light scattered outside the focal plane (13f; 87) are not taken, or are taken separately, into account in the evaluation. The pitch of illumination generated in the focal plane (13f; 87) can be both fixed and variable. A variable pitch of illumination can, for example, be realised by a luminescence diode array. Investigations in transmitted light are also possible using the device.

Interferometer spectrometer having means for varying the optical path length while maintaining alignment

Abstract: An interferometer which may be used in a Fourier transform infra red spectrometer comprises a beam splitter (10), first and second fixed mirrors (18,26), path length variation means (20), and a folding mirror (16). The optical components are mounted on a casting (8) such that the beam splitter (10) and folding mirror (16) are arranged parallel to each other and the fixed mirrors (18,26) are attached to a single face of the casting in the same plane. The path length variation means (20) comprises two parallel opposed mirrors (22,24) which are rotatable to vary the length of the optical path between the beam splitter (10) and the fixed mirror (26).

Fiber optic communication method and apparatus providing mode multiplexing and holographic demultiplexing

Abstract: In a fiber optic communication system, an acoustooptic modulator operates to provide a coherent light beam that is data encoded in the beam's time domain, for example by intensity modulation of the beam. A spatial light modulator then operates to address encode the beam by modulating the beam in the space domain. The resulting data and address modulated beam possesses the property of orthogonality. This beam is now transmitted to the input of a multimode optical fiber. The speckle pattern that exits the output of the optical fiber also exhibits orthogonality. This output beam is presented to a beam splitter in order to produce two spatially modulated speckle light patterns therefrom. These two beams are then focused onto photorefractive means whereat a hologram is produced. This hologram operates to address decode the beam output of the optical fiber. Detector means now operates to detect the data by receiving the beam as it is diffracted by the hologram. Ring and star interconnect networks are described.

Interferometer for in situ measurement of thin film thickness changes

Abstract: An interferometer 10 for measuring the position of the process surface 21 of a substrate 20 includes a coherent light source 12 for providing a light beam 14 which is partially transmitted and partially reflected by a beam splitter 16. The reflected light beam 18 is reflected off of the process surface 21 and the transmitted light beam 30 is reflected off of a translator 32 which vibrates a predetermined distance at a predetermined frequency. The phase shift between the light beams 22, 31 reflected off of translator 32 and the process surface 21 is measured using a photodetector 24, which provides an output signal 26 to a feedback servo unit 28. The servo unit 28 provides an output signal 38 which controls the vibration of translator 32. The output signal 38 of servo unit 28 is also indicative of the position of the process surface 21.

Temperature controlled detectors for infrared-type gas analyzers

Abstract: A detector unit which is capable of outputting electrical signals proportional in magnitude to the intensity of that energy in a beam thereof which lies in two different wavelength bands. A beam splitter directs energy in those bands from the entire compass of the beam to a data detector and a reference detector, and bandpass filters and optical traps in front of those detectors ensure that only energy in the selected bands and from the beam reach them. The detectors are mounted in precisely aligned relationship with each other and the beam splitter on, and are electrically isolated from, a monolithic, conductive, isothermal support which allows them to be maintained at the same, selected temperature by a system including data and reference detector heaters and a temperature responsive controller.

Diffraction-limited blazed reflection diffractive microlenses for oblique incidence fabricated by electron-beam lithography.

Abstract: Blazed reflection diffractive microlenses potentially have many uses. The fabrication accuracy and the optical characteristics of these microlenses can be greatly improved compared with transmission diffractive microlenses. The reflection microlenses for oblique incidence can be flexibly used without a beam splitter. The functions of the electron-beam writing system that we developed have been expanded so that the diffraction-limited microlenses for oblique incidence can be fabricated. It is demonstrated that the fabricated microlens exhibits diffraction-limited focusing characteristics with 78% high efficiency at a large oblique angle of 30°. These microlenses could be used as key devices in planar optics and optical interconnections.

Focus sensing apparatus using electrical AGC to enhance differential focus error signal

Abstract: A focus sensing apparatus for determining the focus of an illuminating beam relative to an optical disk is disclosed herein. In one preferred embodiment, a light source generates a linearly polarized beam which is collimated by a collimating lens. The collimated beam is then converged by an objective lens onto the surface of the optical disk. The disk reflects the illuminating beam focused thereon back through the objective lens to a polarization beam splitter. A portion of the optical energy incident on the beam splitter is then redirected to form a servo beam, wherein the degree of collimation of the servo beam is indicative of the focus position of the illuminating beam. A beam separation module having a reflectivity which varies in response to the angle of incidence of optical energy thereon is positioned to intercept the servo beam. The beam separation module is operative to separate the servo beam into two beams which could be transmitted and reflected beams of substantially similar shape and intensity. Electrical signals produced by photodetective elements in response to incidence of the transmitted and reflected beams thereon may then be used to differentially generate a focus error signal. Gain control circuitry is provided to compensate for asymmetrical changes in beam intensity and maintain balanced detector channels during the generation of the differential focus error signal.

Polarization switching light source, optical receiver, and coherent optical transmission system

Abstract: A polarization switching light source includes a semiconductor laser for outputting laser output light, a phase modulation circuit for subjecting phase modulation of a predetermined cyclic pattern to the semiconductor laser by supplying a pulse current thereto, a beam splitter for dividing output light from the semiconductor laser into first and second branch output light components having substantially the same power, an optical delay member for delaying the first branch output light with respect to the second branch output light by a predetermined amount, and a mixing member for mixing the first branch output light component, delayed by the optical delay member, with the second branch output light component while their polarization states are caused to be orthogonal. A delay time of the first branch output light component with respect to the second branch output light component is set to be a fraction of an integer of the period of the phase modulation.

Optical disk apparatus and optical head

Abstract: An overwritable optical disk apparatus in which a finite conjugate optical system is employed. The apparatus comprises an optical head for converging diffused light from a light source onto an optical disk for performing data write/read operation, a driving unit for rotating the disk and a beam splitter for guiding the light reflected from the optical disk to a photodetector for detecting light reflected from the optical disk. Influence of disk displacement occurring in accompanying the rotation of the disk and disk eccentricity are suppressed to a minimum by encasing rotatably the optical disk within a credit card size casing which is adapted to be loaded and held stationarily in the optical disk apparatus. Thin structure of the optical head and miniaturization of the optical disk apparatus are realized with light utilization efficiency for data write/read operation being increased.

90 degree optical hybrid for coherent receivers

Abstract: The power losses and noise of the present 90-deg hybrid optical coherent receiver are minimized through the use of a six-port configuration in which channel balancing is furnished by half-wave plates. The 90-deg shift is introduced between orthogonally polarized beam components by a quarter-wave plate, and the output ports are phase-shifted by 180 deg through the sole use of the half-wave plates and polarizing beam splitters.

Non-mechanical optical path switching and its application to dual beam spectroscopy including gas filter correlation radiometry

Abstract: A non-mechanical optical switch is provided for alternately switching a monochromatic or quasi-monochromatic light beam along two optical paths. A polarizer polarizes light into a single, e.g., vertical component which is then rapidly modulated into vertical and horizontal components by a polarization modulator. A polarization beam splitter then reflects one of these components along one path and transmits the other along the second path. In the specific application of gas filter correlation radiometry, one path is directed through a vacuum cell and one path is directed through a gas correlation cell containing a desired gas. Reflecting mirrors cause these two paths to intersect at a second polarization beam splitter which reflects one component and transmits the other to recombine them into a polarization modulated beam which can be detected by an appropriate single sensor.

Theory of an atomic beam splitter based on velocity-tuned resonances.

Abstract: We develop the theory of an atomic beam splitter in which a monoenergetic beam of two-level atoms is incident normally to a classical standing-wave light field. The incident atomic wave function can be split into two coherent components with transverse momenta \ifmmode\pm\else\textpm\fi{}(2n+1)\ensuremath{\Elzxh}k using velocity-tuned resonances, where n is the order of the resonance. We discuss the cases of zero- and first-order resonances in detail, and show that the velocity-tuned resonances are renormalized due to a high-frequency Stark shift. Numerical results that display the effects of a finite momentum spread in the incident atomic beam are presented.