Showing papers on "Beam splitter published in 2007"

Self-collimating photonic crystal polarization beam splitter

Abstract: We present theoretical and experimental results of a polarization splitter device that consists of a photonic crystal (PhC) slab, which exhibits a large reflection coefficient for TE and a high transmission coefficient for TM polarization The slab is embedded in a PhC tile operating in the self-collimation mode Embedding the polarization-discriminating slab in a PhC with identical lattice symmetry suppresses the in-plane diffraction losses at the PhC-non-PhC interface The optimization of the PhC-non-PhC interface is thereby decoupled from the optimization of the polarizing function Transmissions as high as 35% for TM- and 30% for TE-polarized light are reported

Self-collimation in photonic crystal structures: a new paradigm for applications and device development

Abstract: In this paper, we report on the development of the self-collimation phenomenon in photonic crystal structures for integrated optics applications. In addition, detailed numerical analysis, design procedures, fabrication and characterization techniques are included. Applications presented in this paper include: channelless waveguiding, orthogonal bending of light, tunable beam splitter, all-optical analog-to-digital converter, reconfigurable optical switch, chemical/gas sensor and a three-dimensional optical interconnect bus.

Polarization beam splitter using a binary blazed grating coupler.

Abstract: A novel polarization beam splitter using a two-layer grating coupler is proposed and demonstrated. It can directly couple the normally incident light from fiber into two separate waveguides according to their polarization states while splitting them. It realizes high coupling efficiency and a good extinction ratio by using binary blazed grating couplers. The coupling length is less than 14 microm. The extinction ratio is better than 20 dB for both polarizations over a 40 nm wavelength range, and the coupling efficiencies for the two layers are 58% and 50%.

Polarizing beam splitter of a deep-etched fused-silica grating

Abstract: We described a highly efficient polarizing beam splitter (PBS) of a deep-etched binary-phase fused-silica grating, where TE- and TM-polarized waves are mainly diffracted in the −1st and 0th orders, respectively. To achieve a high extinction ratio and diffraction efficiency, the grating depth and period are optimized by using rigorous coupled-wave analysis, which can be well explained based on the modal method with effective indices of the modes for TE/TM polarization. Holographic recording technology and inductively coupled plasma etching are employed to fabricate the fused-silica PBS grating. Experimental results of diffraction efficiencies approaching 80% for a TE-polarized wave in the −1st order and more than 85% for a TM-polarized wave in the 0th order were obtained at a wavelength of 1550nm. Because of its compact structure and simple fabrication process, which is suitable for mass reproduction, a deep-etched fused-silica grating as a PBS should be a useful device for practical applications.

Exploring light propagating in photonic crystals with Fourier optics

Abstract: Photonic crystals (PhCs) act on light in two different ways: confinement and modification of propagation. Both phenomena rely on the complex interplay between multiply scattered waves that can form what is known as a Bloch mode. Here, we present a technique that allows direct imaging of Bloch modes, both in real space and in k-space. The technique gives access to the location of the field maxima inside the PhC, the dispersion relation, equifrequency surfaces, as well as reflection and transmission coefficients. Our key advance is that we retrieve the desired information comprehensively, without postprocessing or cumbersome near-field scanning techniques, even for modes that are nominally lossless, i.e., below the light line. To highlight the potential of the technique, we extract the dispersion curve of a coupled cavity waveguide consisting of as many as 100 cavities, as well as the equifrequency surfaces and polarization properties of a PhC beam splitter.

High-photon-number path entanglement in the interference of spontaneously down-converted photon pairs with coherent laser light

Abstract: We show that the quantum interference between down-converted photon pairs and photons from coherent laser light can produce a maximally path entangled $N$-photon output component with a fidelity greater than 90% for arbitrarily high photon numbers. A simple beam splitter operation can thus transform the two-photon coherence of down-converted light into an almost optimal $N$-photon coherence.

Mid-infrared optical coherence tomography.

Abstract: A time domain optical coherence tomography (OCT) system is described that uses mid-infrared light (6–8μm). To the best of our knowledge, this is the first OCT system that operates in the mid-infrared spectral region. It has been designed to characterize bioengineered tissues in terms of their structure and biochemical composition. The system is based upon a free-space Michelson interferometer with a germanium beam splitter and a liquid nitrogen cooled HgCdTe detector. A key component of this work has been the development of a broadband quantum cascade laser source (InGaAs∕AlInAs containing 11 different active regions of the three well vertical transition type) that emits continuously over the 6–8μm wavelength range. This wavelength range corresponds to the so called “mid-infrared fingerprint region” which exhibits well-defined absorption bands that are specifically attributable to the absorbing molecules. Therefore, this technology provides an opportunity for optical coherence molecular imaging without the need for molecular contrast agents. Preliminary measurements are presented.

Fingerprint detection using full-field swept-source optical coherence tomography

Abstract: We report the application of full-field swept-source optical coherence tomography for fingerprint detection. This system consists of a superluminescent diode as broadband light source and an acousto-optic tunable filter as wavelength-tuning device. The conventional optical coherence tomographic system was modified by coating aluminum oxide on one side of the beam splitter which is used as reference mirror and fingerprints on the glass slide as object. Low-coherence interferometry, nonmechanical scanning, and compactness are the main advantages of the proposed system over conventional fingerprint detection techniques. The present technique is noninvasive in nature and does not require any physical or chemical processing.

Optical pick-up head, optical information apparatus, and optical information reproducing method

Abstract: An optical information apparatus of the present invention includes: an optical pick-up head including: a light source; a diffraction unit; a condensing unit; a beam splitter; a photodetector; and a tracking error signal generator. An optical recording medium has tracks arranged substantially at a constant pitch. An average of a pitch is tp. When a main beam is placed on the track, a first sub-beam and a second sub-beam are placed between the tracks. The tracking error signal generator performs a differential arithmetic operation with respect to signals output from a light-receiving portion receiving the main beam to generate a first push-pull signal, performs a differential arithmetic operation with respect to signals output from the light-receiving portions receiving the first sub-beam and the second sub-beam to generate a second push-pull signal, and performs a differential arithmetic operation with respect to the first push-pull signal and the second push-pull signal to generate a tracking error signal, in a case where an amplitude of the first push-pull signal obtained at the pitch tp is fluctuated when the light beam is scanned in a direction orthogonal to the tracks of the optical recording medium.

Apparatus for dental oct imaging

Abstract: An apparatus (10) for obtaining an image of a tooth (20) includes an image sensor and a white light source (12) providing broadband polychromatic light and an ultraviolet light source providing narrow-band light. A combiner (15) directs broadband polychromatic light and narrow band light along a common illumination path to illuminate the tooth. A polarization beamsplitter (18) directs polarized light from the illumination path along an optical axis (216). An optical coherence tomography (OCT) imaging apparatus (70) splits the low coherence light into a sample path and a reference path and a dichroic element (78) directs the polarized illumination and the sample path low coherence light along the optical axis. An image processor (100) identifies a region of interest according to either a white light image (124), a fluorescent light image (120), or both and the OCT imaging apparatus obtains an OCT image over the region of interest.

Polarization conversion systems for stereoscopic projection

Abstract: A polarization conversion system (PCS) is located in the output light path of a projector. The PCS may include a polarizing beam splitter, a polarization rotating element, a reflecting element, and a polarization switch. Typically, a projector outputs randomly-polarized light. This light is input to the PCS, in which the PCS separates p-polarized light and s-polarized light at the polarizing beam splitter. P-polarized light is directed toward the polarization switch on a first path. The s-polarized light is passed on a second path through the polarization rotating element (e.g., a half-wave plate), thereby transforming it to p-polarized light. A reflecting element directs the transformed polarized light (now p-polarized) along the second path toward the polarization switch. The first and second light paths are ultimately directed toward a projection screen to collectively form a brighter screen image in cinematic applications utilizing polarized light for three-dimensional viewing.

Generation of continuous-wave broadband entangled beams using periodically poled lithium niobate waveguides

Abstract: Continuous-wave light beams with broadband quantum entanglement are created with two independent squeezed light beams generated by two periodically poled lithium niobate waveguides and a symmentric beam splitter. The quantum entanglement is confirmed with a sufficient criterion ΔA,B2=⟨[Δ(xA−xB)]2⟩+⟨[Δ(pA+pB)]2⟩<1 and the observed ΔA,B2 is 0.75 over the bandwidth of 30MHz. Although the bandwidth is limited by that of the detector so far, it would be broadened up to 10THz which would be only limited by the bandwidth of phase matching for the second-order nonlinear process.

Stereo projection apparatus using polarized solid state light sources

Abstract: A digital image projector includes a first polarized light source; a second polarized light source that is orthogonal in polarization state to the first polarized light source; a polarization beamsplitter disposed to direct light of either the first or second polarization along a common illumination axis; a MEMS spatial light modulator; and projection optics for delivering imaging light from the MEMS spatial light modulator.

Silicon beam splitter for far-infrared and terahertz spectroscopy

Abstract: Silicon beam splitters several millimeters thick offer numerous advantages over thin freestanding dielectric beam splitters. For routine spectroscopy for which resolutions of better than 1 cm−1 are not required, a silicon beam splitter can replace several Mylar beam splitters to span the entire far-infrared region. In addition to superior long-wavelength performance that extends well into the terahertz region, the silicon beam splitter has the additional advantage that its efficiency displays little polarization dependence.

Modulated light trigger for license plate recognition cameras

Abstract: A camera system comprises a CCD imaging device, an infrared illumination source, and a power modulator for amplitude modulating the infrared illumination, e.g., with a 7-kHz tone. A beam splitter is set in front of the CCD imaging device, and a photo-diode array is attached to the beam splitter to detect modulated infrared light returning from the same field of vision as the CCD imaging device Various tone filters, and triggers connected to the tone filters, will cause the CCD imaging device to take a digital picture when the returning modulated infrared light exceeds some threshold and comes from right areas of a picture frame. Such digital pictures will most probably include an image of a vehicle license plate that can be processed, and the results used to extract the registration data from a database.

Beam splitting and Hong-Ou-Mandel interference for stored light

Abstract: Storing and release of a quantum light pulse in a medium of atoms in the tripod configuration are studied. Each of these operations is realized by switching on and off two sets of properly chosen control fields. The system constitutes a kind of a flexible beam splitter in which the input and output ports concern photons of the same direction but well separated in time. A version of Hong-Ou-Mandel interference is discussed. It is also shown that a stored nonclassical light is split into two nonclassical beams, with their statistical properties being steered by a choice of the control fields.

Diffractive optical elements designed for highly precise far-field generation in the presence of artifacts typical for pixelated spatial light modulators

Abstract: Diffractive optical elements (DOEs) realized by spatial light modulators (SLMs) often have features that distinguish them from most conventional, static DOEs: strong coupling between phase and amplitude modulation, a modulation versus steering parameter characteristic that may not be precisely known (and may vary with, e.g., temperature), and deadspace effects and interpixel cross talk. For an optimal function of the DOE, e.g. as a multiple-beam splitter, the DOE design must account for these artifacts. We present an iterative design method in which the optimal setting of each SLM pixel is carefully chosen by considering the SLM artifacts and the design targets. For instance, the deadspace-interpixel effects are modeled by dividing the pixel to be optimized, and its nearest neighbors, into a number of subareas, each with its unique response and far-field contribution. Besides the customary intensity control, the design targets can also include phase control of the optical field in one or more of the beams in the beam splitter. We show how this can be used to cancel a strong unwanted zeroth-order beam, which results from using a slightly incorrect modulation characteristic for the SLM, by purposely sending a beam in the same direction but with the opposite phase. All the designs have been implemented on the 256 × 256 central pixels of a reflective liquid crystal on silicon SLM with a selected input polarization state and a direction of transmission axis of the output polarizer such that for the available different pixel settings a phase modulation of ∼2π rad could be obtained, accompanied by an intensity modulation depth as high as >95%.

Autofocus device for microscopy

Abstract: A microscope including an objective which images a sample along a microscope beam path, and an autofocus device, which is coupled into the microscope beam path via a beam splitter at a location behind the objective direction, a A light modulator for generating a two-dimensional, intensity-modulated modulation object, is located in the autofocus beam path in a plane conjugated to the focal plane of the objective or intersects the latter and is imaged into the focal plane of the objective A camera records a two-dimensional image onto which the modulation object's image is imaged The image plane of the camera intersects a plane that is conjugated to the modulation object or is located in the plane and the camera detecting the contrast of the modulation object's image located in the sample

Light Scattering Detector

Abstract: The light scattering detector according to the present invention aims at simultaneously measuring the molecular weight and size of particles having varieties of diameters. This detector facilitates the measurement operation and knowing how particles associate or dissociate as time progresses. In this detector, the emitted light (static light scattering measurement light) having a first wavelength by the first light source and the emitted light (dynamic light scattering measurement light) having a second wavelength which is different from the first wavelength by the second light source are combined by a beam splitter 5 and coaxially directed onto the sample sell 10 to which a liquid sample S is supplied. While the irradiated area by the static light scattering measurement light is large, the irradiated area by the dynamic light scattering measurement light, which is coherent light, is narrow. Detectors 12 which selectively detect the first wavelength and detectors 13 which selectively detect the second wavelength are placed so as to encircle the sample cell 10. The detection signals by the detectors 11, 12 and the detection signals by the detectors 13 are separately mathematically-operated by a data processor 15 to calculate the molecule weight and size of the particles in the sample S.

Interference of multimode photon echoes generated in spatially separated solid-state atomic ensembles.

Abstract: High-visibility interference of photon echoes generated in spatially separated solid-state atomic ensembles is demonstrated. The solid-state ensembles were LiNbO(3) waveguides doped with erbium ions absorbing at 1.53 microm. Bright coherent states of light in several temporal modes (up to 3) are stored and retrieved from the optical memories using two-pulse photon echoes. The stored and retrieved optical pulses, when combined at a beam splitter, show almost perfect interference, which demonstrates both phase preserving storage and indistinguishability of photon echoes from separate optical memories. By measuring interference fringes for different storage times, we also show explicitly that the visibility is not limited by atomic decoherence. These results are relevant for novel quantum-repeater architectures with photon-echo based multimode quantum memories.

Optical pickup device, recording and reproducing apparatus and gap detection method

Abstract: An optical pickup device and an optical recording and reproducing apparatus are suitable for use with a near-field optical recording and reproducing system. An optical pickup device comprises an objective lens composed of a solid immersion lens (SIL) the objective lens having a numerical aperture greater than 1, a beam splitter configured to reflect both of a p-polarized light component and an s-polarized light component of reflected lights from an optical recording medium when the optical pickup device irradiates the optical recording medium with a bundle of rays in a predetermined polarized state from a light source through the objective lens, a divider configured to divide incident light into a p-polarized light component and an s-polarized light component reflected by the beam splitter, and a photo-detector configured to separately detect the p-polarized light component and the s-polarized light component divided by the divider.

System and method for optical coherence tomography

Abstract: The system has an interferometer (10) for outputting light that irradiates a sample (1). A detector (30) has detector elements detecting light reflected by the sample when the system is operated in a real-time mode, where the light is converted into corresponding detector signals. The detector elements detect the reflected light for five times during change of optical distance of reflectors (11, 12, 25) to beam splitters (13, 24) when the system is operated in another real-time mode. A two-dimensional section is obtained by a spatial element of the sample in a preset depth of the sample. An independent claim is also included for a method for optical coherence tomography.

Self-contained multivariate optical computing and analysis system

Abstract: An optical analysis system includes a light source configured to radiate a first light along a first ray path; a modulator disposed in the first ray path, the modulator configured to modulate the first light to a desired frequency; a spectral element disposed proximate the modulator, the spectral element configured to filter the first light for a spectral range of interest of a sample; a cavity in communication with the spectral element, the cavity configured to direct the first light in a direction of the sample; a conical mirror configured to convert the first light reflecting from the sample into a second light, the cavity being further configured to direct the second light; a beamsplitter configured to split the second light into a first beam and a second beam; an optical filter mechanism disposed to receive the first beam, the optical filter mechanism configured to optically filter data carried by the first beam into at least one orthogonal component of the first beam; a first detector mechanism in communication with the optical filter mechanism to measure a property of the orthogonal component to measure the data; a second detector mechanism configured to receive the second beam for comparison of the property of the orthogonal component to the second beam; an accelerometer configured to control the data acquisition such that only detector signals during the period of time when the system is in the proper orientation such that the material sample (e.g., aspirin) is in proximity to the interrogation window are used for calculation; a computer having a data acquisition and conversion card, the computer disposed in the system in communication with the first and second detector mechanisms for signal processing; and a battery and charging system disposed in the system in electrical communication with the system to provide stand-alone operation capability.

Directional emitter and beam splitter based on self-collimation effect

Abstract: We present a self-collimation-based directional emitter and compact beam splitters in a two-dimensional photonic crystal by using the surface modification method. The simulation results show that highly directional emission with a small angular divergence is achieved over a relative bandwidth of about 10.2%. Furthermore, by only modifying the monolayer structure of the output surface, the compact beam splitters, including the Y-shaped, one-to-three, and one-to-five structures are realized. Such beam splitters have remarkable properties such as symmetrical energy distribution and high transmission.

Engineering maximally entangled N-photon NOON field states using an atom interferometer based on Bragg regime cavity QED

Abstract: We propose a scheme for generation of highly non-classical entangled field states of the type in the cavity QED scenario. The scheme utilizes an atomic analogue of the Mach–Zehnder interferometer having a quantized field in the high-Q cavity containing a superposition of zero and one photon that acts as the first beam splitter. The probability for production of the desired states may approach a value close to unity with high fidelity under prevailing experimental conditions.

50∕50 beam splitter using a one-dimensional metal photonic crystal with parabolalike dispersion

Abstract: The spatial dispersion properties of a one-dimensional metal photonic crystal have been analyzed and five types of dispersion curves have been shown at a normalized frequency less than 1. It is demonstrated that by exploiting a parabolalike dispersion behavior, a metal photonic crystal slab can be used to realize an exactly 50∕50 beam splitter.

Stereo projection optical system

Abstract: A stereo projection optical system, includes a first polarizing beam splitter configured for separating a light input into a first polarized light component and a second polarized light component; a first transmission-type spatial light modulator configured for receiving the first polarized light component; a second transmission-type spatial light modulator configured for receiving the second polarized light component; a second polarizing beam splitter positioned to receive the light outputs of the first, second spatial light modulators. The first and second transmission-type spatial light modulators respectively generate two images formed by the first polarized light component and the second polarized light component with spatial information. When a viewer wears glasses that have two polarizing lenses whose polarization directions are perpendicular to each other, the viewer can perceive projected images as being three-dimensional.

Stereo projection optical system

Abstract: A stereo projection optical system includes a polarizing beam splitter, a 2-way wheel, a digital micro-mirror device, and a total internal reflection prism. The polarizing beam splitter is configured for emitting two light outputs. The 2-way wheel includes a reflective region and a transmissive region. The reflective region is configured for reflecting the light outputs and the transmissive region is configured for transmitting the light outputs. The digital micro-mirror device is configured for superimposing spatial information on the light outputs. The total internal reflection prism configured for coupling the light outputs of the 2-way wheel into the digital micro-mirror device and transmitting a light output of the digital micro-mirror device. The stereo projection optical systems provide viewers three-dimensional images formed by two alternative polarized light beams whose polarizations are perpendicular to each other utilizing the 2-way wheel.

Implementation of diffractive optical element in four-wave mixing scheme for ex situ characterization of hydride vapor phase epitaxy-grown GaN layers.

Abstract: A holographic beam splitter has been integrated into a picosecond four-wave mixing (FWM) scheme. This modification significantly simplified the procedure of dynamic grating recording, thus making the FWM technique an easy-to-use tool for the holographic characterization of wide band gap materials. The novel FWM scheme was applied for characterization of hydride vapor phase epitaxy-grown undoped GaN layers of different thickness. It allowed the determination of carrier lifetime, diffusion coefficient, and carrier diffusion length by optical means, as well as the study of carrier recombination peculiarities with respect to dislocation and excess carrier density.

Laser distance measuring system with a shutter mechanism

Abstract: A laser distance measuring system includes an object lens, a beam splitter, a transmitter, a receiver, and a shutter mechanism. The beam splitter is disposed at one side of the object lens. The transmitter emits a laser beam that is split by the beam splitter into a measurement beam and a reference beam. The measurement beam passes through the object lens, and is reflected by an object to result in a reflected measurement beam passing through the object lens. The receiver is disposed to receive the reflected measurement beam and the reference beam. The shutter mechanism includes a beam masker operable to move to either block path of the reflected measurement beam to the receiver or path of the reference beam to the receiver.