Showing papers on "Waveplate published in 2014"

Highly flexible broadband terahertz metamaterial quarter-wave plate

Abstract: Metamaterials offer exciting opportunities that enable precise control of light propagation, its intensity and phase by designing an artificial medium of choice. Inducing birefringence via engineered metamolecules presents a fascinating mechanism to manipulate the phase of electromagnetic waves and facilitates the design of polarimetric devices. In this paper, a high-efficiency, broadband, tunable and flexible quarter-wave plate based on a multilayer metamaterial is presented. Excellent achromatic π/2 phase retardance with high transmission is observed upon terahertz propagation through the quarter-wave plate. The calculated Stokes parameter represents the output polarization state numerically, indicating an excellent broadband conversion of linearly polarized light into circularly polarized light. The metamaterial-based quarter-wave plate demonstrated in this work could be an important step forward in the development of functional terahertz polarization conversion devices for practical applications.

Compact Projection Light Engine For A Diffractive Waveguide Display

Abstract: The technology provides a waveguide display having a compact projection light engine and a diffractive waveguide. The diffractive waveguide includes input diffraction gratings with rolled k-vectors. The projection light engine provides collimating light to a projected exit pupil external to the diffractive waveguide. The projection light engine components may include a light (or illuminating) source, microdisplay, lenticular screen, doublet, polarizing beam splitter (PBS), clean-up polarizer, fold mirror, curved reflector and quarter waveplate. A method of manufacturing a diffractive waveguide includes providing input gratings with rolled k-vectors. Rays of light are diffracted by, and passed through, a master hologram to form input diffraction gratings of a copy substrate. A second copy substrate may likewise be formed with a different master hologram. Multiple copy substrates may be assembled to form a multi-layer diffractive waveguide (or multiple diffractive waveguides) having input diffraction gratings with increased diffraction efficiency and angular bandwidth.

Eyepiece for near eye display system

Abstract: An optical display system configured to transmit light along a light path to a user's eye, the display system comprising a circular polarizing reflector configured to reflect light with a first polarization from an image source, a quarter wave plate downstream of the circular polarizing reflector in the light path and configured to rotate the polarization of the light to a second polarization, and a curved linear polarizing reflector downstream of the quarter wave plate and configured to reflect the light back through the quarter wave plate along the light path in the direction of the circular polarizing reflector. The quarter wave plate further configured to rotate the polarization of the light received from the curved linear polarizing reflector to a third polarization and the circular polarizing reflector further configured to receive said light from the quarter wave plate and transmit the light toward the user's eye.

Cladding-pumped ytterbium-doped fiber laser with radially polarized output.

Abstract: A simple technique for directly generating a radially polarized output beam from a cladding-pumped ytterbium-doped fiber laser is reported. Our approach is based on the use of a nanograting spatially variant waveplate as an intracavity polarization-controlling element. The laser yielded ∼32 W of output power (limited by available pump power) with a radially polarized TM01-mode output beam at 1040 nm with a corresponding slope efficiency of 66% and a polarization purity of 95%. The beam-propagation factor (M2) was measured to be ∼1.9–2.1.

Achromatic THz wave plate composed of stacked parallel metal plates

Abstract: We propose a simple achromatic terahertz wave plate composed of stacked parallel metal plates with a hole array. It consists of an ensemble of designed parallel plate waveguides; the high and low propagation speeds of waves in TE and TM waveguide modes with the same group velocity cause a constant phase difference over a wide frequency region. Using that wave plate, we obtained intense single- and multi-cycle THz pulses with circular polarization.

Polarization-multiplexed multifocal arrays by a π-phase-step-modulated azimuthally polarized beam.

Abstract: We demonstrate a polarization-multiplexed multifocal array capable of individually manipulating the focal polarization state in each focal spot. Breaking the rotational phase symmetry through adding a π-phase-step to an azimuthally polarized beam leads to a linear focal polarization state with high polarization purity. Through the superposition of such modulated azimuthal polarization fields at the back aperture of the objective, multifocal arrays with individually controllable and non-identical polarization states can be achieved. In addition, this approach exhibits a sub-diffraction-limited feature with an improved lateral resolution of 10% reduced full width at half-maximums in each linearly polarized focal spot. Consequently, applying this technique to parallel polarization-multiplexed optical recording is demonstrated.

Encoding high-order cylindrically polarized light beams.

Abstract: In this work we present a setup for the experimental production of cylindrically polarized beams, as well as other variations of polarized light beams. The optical system uses a single transmissive phase-only spatial light modulator, which is used to apply different spatial phase modulation to two output collinear R and L circularly polarized components. Different cylindrically polarized light beams can be obtained by applying different phase shifts to these two circularly polarized components. The system is very efficient since modulation is directly applied to the light beam (as opposed to other common methods operating in the first order of encoded diffraction gratings). Different variations to the cylindrically polarized light beams are also reported, obtained by adding linear or quadratic relative phase shifts between the two circular polarization components of the light beam. Experimental results are provided in all cases.

Achromatic prism-type wave plate for broadband terahertz pulses

Abstract: We demonstrated achromatic half- and quarter-wave plates for broadband terahertz pulses using phase retardation by internal total reflection. Prism-type wave plates realized ultra-broadband retardation stability up to 2.5 THz, which was the limitation of our experimental setup. Novel aspects of our work were use of a 3λ/4 plate as a quarter-wave plate and a multistacked prism-type (MSP) wave plate for a large-aperture THz beam. Real-time polarization imaging of two crossed bunches of hairs was performed to show the efficiency of the MSP wave plate. We clearly observed polarization dependence of the hair direction.

Compressive wavefront sensing with weak values

Abstract: We demonstrate a wavefront sensor that unites weak measurement and the compressive-sensing, single-pixel camera. Using a high-resolution spatial light modulator (SLM) as a variable waveplate, we weakly couple an optical field's transverse-position and polarization degrees of freedom. By placing random, binary patterns on the SLM, polarization serves as a meter for directly measuring random projections of the wavefront's real and imaginary components. Compressive-sensing optimization techniques can then recover the wavefront. We acquire high quality, 256 × 256 pixel images of the wavefront from only 10,000 projections. Photon-counting detectors give sub-picowatt sensitivity.

Atom magnetic sensor for optical pump magnetometer

Abstract: The invention belongs to the technical field of optical pump magnetometers and discloses an atom magnetic sensor for an optical pump magnetometer The atom magnetic sensor comprises a first half wave plate (1), a third half wave plate (5), a fourth half wave plate (8), a fifth half wave plate (9), a first polarization beam splitter prism (2), a third polarization beam splitter prism (6), a fourth polarization beam splitter prism (10), a fifth polarization beam splitter prism (7), a sixth polarization beam splitter prism (11), a first one-quarter wave plate (12), a second one-quarter wave plate (13), a first atom air chamber (14), a second atom air chamber (15), a first Helmholtz coil (16), a second Helmholtz coil (17), a first photoelectric detector (18) and a second photoelectric detector (19) By the adoption of the atom magnetic sensor, magnetic field measurement result errors caused by optical frequency shift in the laser optical pump atom magnetometer can be eliminated, and the performance index of the laser optical pump atom magnetometer can be improved

Polarization-Preserving Light Guide Plate for a Linearly Polarized Backlight

Abstract: We analyze the polarization-preserving property of two conventional edge-lit light guide plates (LGPs) based on scattering dots and refractive microgrooves and find that these two structures almost completely depolarize the incident linearly polarized light. We then propose a new edge-lit LGP based on total internal reflection (TIR). Simulation results show that such a TIR-based LGP can largely preserve the polarization state of the incident linearly polarized light. The polarization efficiency is 77.2%. By incorporating a linearly polarized LED to our proposed LGP, the overall optical gain is 1.54 compared with the backlight system with an unpolarized LED. At on-axis, the luminance is 2.4× higher. Because the output light is concentrated near the surface normal direction, no additional brightness enhancement film is needed. This polarization-preserving LGP enables a polarized or partially polarized LED backlight to be used, which in turn greatly enhances the optical efficiency of a LCD.

Tunable achromatic liquid crystal waveplates

Abstract: The wavelength dependence of phase retarders is considered as a challenge in different applications such as polarimetric systems. A novel achromatic waveplate based on two nematic liquid crystal retarders is designed and demonstrated tunable over a wide spectral range using different voltages applied to the two retarders. The achromatic behavior is achieved based on the fact that the dispersion of the retardation of liquid crystals is voltage dependent. Achromatic quarter and half-waveplates are demonstrated using the same device as well as the tunability of the achromatic operation range.

Performance of polarization modulation and calibration optics for the Daniel K. Inouye Solar Telescope

Abstract: The Daniel K. Inouye Solar Telescope (formerly Advanced Technology Solar Telescope) will be the world's largest solar telescope and polarimeter when completed in 2019. Efficient use of the telescope to address key science priorities calls for polarization measurements simultaneously over broad wavelength ranges and calibration of the telescope and polarimeters to high accuracy. Broadband polarization modulation and calibration optics utilizing crystal optics have been designed for this application. The performance of polarization modulators and calibration retarders is presented along with a discussion of the unique challenges of this application. Polarimeters operate over the ranges of 0.38-1.1 microns, 0.5-2.5 microns, and 1.0-5.0 microns. Efficient polarization modulation over these broad ranges led to modulators utilizing multiple wave plates and that are elliptical, rather than linear, retarders. Calibration retarders are linear retarders and are constructed from the same sub-component wave plate pairs as the polarization modulators. Polarization optics must address efficiency over broad wavelength ranges while meeting beam deflection, transmitted wave front error, and thermal constraints and doing so with designs that, though large in diameter, can be affordably manufactured.

Device and method for measuring synchronous phase shifting interference of Fizeau quasi-common optical path structure

Abstract: The invention relates to a device and a method for measuring synchronous phase shifting interference of a Fizeau quasi-common optical path structure. The device comprises a laser, a half wave plate, a focusing lens, a spatial filter, a circularly polarized light beam splitter (an optically active crystal), a spectroscope, a collimating lens, a reference mirror, a pin-hole diaphragm, an imaging lens, a light splitting and phase shifting system, a computer control system and a CCD camera. According to the device and the method disclosed by the invention, a synchronous phase shifting technology is combined with a Fizeau interference method, so that technical difficulties of a conventional interferometer in poor stability and disability of realizing dynamic measurement are solved; the device and the method are characterized by utilizing an optical rotation effect of the crystal and adding the circularly polarized light beam splitter with a very small splitting angle in the Fizeau interfering structure, so as to realize orthogonally polarized separation of reference lights and test lights in a common optical path. The device and the method disclosed by the invention avoid utilization of a high-quality quarter wave plate in a synchronous phase-shifting interference system, and also greatly decrease a phase measurement error caused by a stress birefrigent effect which exists in an optical element of the system.

A Raman waveplate for spinor Bose–Einstein condensates

Abstract: We demonstrate a waveplate for a pseudo-spin-1/2 Bose–Einstein condensate (BEC) using a two-photon Raman interaction. The angle of the waveplate is set by the relative phase of the optical fields, and the retardance is controlled by the pulse area. The waveplate allows us to image maps of the Stokes parameters of a BEC and thereby measure its relative ground-state phase. We demonstrate the waveplate by measuring the Stokes parameters of a coreless vortex.

Metallic stereostructured layer: An approach for broadband polarization state manipulation

Abstract: In this letter, we report a full-metallic broadband wave plate assembled by standing metallic L-shaped stereostructures (LSSs). We show that with an array of LSSs, high polarization conversion ratio is achieved within a broad frequency band. Moreover, by rotating the orientation of the array of LSSs, the electric components of the reflection beam in two orthogonal directions and their phase difference can be independently tuned. In this way, all the polarization states on the Poincare sphere can be realized. As examples, the functionalities of a quarter wave plate and a half wave plate are experimentally demonstrated with both reflection spectra and focal-plane-array imaging. Our designing provides a unique approach in realizing the broadband wave plate to manipulate the polarization state of light.

Cycloidal diffractive waveplate and method of manufacture

Abstract: A liquid crystal diffractive waveplate (50) comprising first and second substrate layers (52, 54), a liquid crystal layer (60C, 60H) provided between the first and second substrate layers, and transparent positive electrodes (56) and transparent negative electrodes (58) provided on the first substrate layer. The liquid crystal layer has a diffractive state (60C) in which the orientation of the optical axes of the liquid crystal molecules varies across a plane of the waveplate and a non-diffractivenon-diffractive state (60H) in which the optical axes of the liquid crystal molecules are all orientated in the same direction in the plane of the waveplate. The electrodes (56, 58) are arranged in an alternating series, such that when an electric voltage is applied to the electrodes an electric field is produced in the plane of the waveplate and the liquid crystal layer is switched from the diffractive state to the non- diffractivenon-diffractive state. A method of manufacturing the liquid crystal diffractive waveplate is also provided.

Vector vortex waveplates

Abstract: Method for fabrication of vector vortex waveplates of improved quality due to reduced singularity size and widened spectral band, the method comprising creating a boundary condition for vortex orientation pattern of a liquid crystal polymer on a substrate using materials with reversible photoalignment, equalizing exposure energy over the area of the waveplate by redistributing the energy of radiation used for photoalignment from the center of the beam to its peripheries, and using vector vortex waveplate as a linear-to-axial polarization converter. Fabrication of spectrally broadband vector vortex waveplates further comprises two or more liquid crystal polymer layers with opposite sign of twist.

Polarization conversions of linearly and circularly polarized lights through a plasmon-induced transparent metasurface

Abstract: Polarization control of the light can be realized by ultrathin plasmonic structures, which is generally based on the effect of extraordinary optical transmission. In this paper, we designed a U-shaped plasmon-induced transparent metasurface to investigate the polarization state conversions of resonantly transmitted light through reducing the structural symmetry by rotation. A significant optical polarization conversion capability is found for impinging light with linear as well as circular polarization. In particular, the different polarization conversions between the left-handed and right-handed circular lights manifest the characteristic of circular dichroism. The results are useful for the potential applications such as a broadband quarter-wave plate.

Submillimeter Polarimetry with PolKa, a Reflection-Type Modulator for the APEX Telescope

Abstract: Imaging polarimetry is an important tool for the study of cosmic magnetic fields. In our Galaxy, polarization levels of a few up to ~10% are measured in the submillimeter dust emission from molecular clouds and in the synchrotron emission from supernova remnants. Only few techniques exist to image the distribution of polarization angles as a means of tracing the plane-of-sky projection of the magnetic field orientation. At submillimeter wavelengths, polarization is either measured as the differential total power of polarization-sensitive bolometer elements, or by modulating the polarization of the signal. Bolometer arrays such as LABOCA at the APEX telescope are used to observe the continuum emission from fields as large as in diameter. Here we present PolKa, a polarimeter for LABOCA with a reflection-type waveplate of at least 90% efficiency. The modulation efficiency depends mainly on the sampling and on the angular velocity of the waveplate. For the data analysis, the concept of generalized synchronous demodulation is introduced. The instrumental polarization toward a point source is at the level of ~0.1%, increasing to a few percent at the -10 db contour of the main beam. A method to correct for its effect in observations of extended sources is presented. Our map of the polarized synchrotron emission from the Crab nebula is in agreement with structures observed at radio and optical wavelengths. The linear polarization measured in OMC1 agrees with results from previous studies, while the high sensitivity of LABOCA enables us to also map the polarized emission of the Orion Bar, a prototypical photon-dominated region.

Optical system for near-eye display

Abstract: Embodiments are disclosed herein that relate to compact optical systems for incorporation into near-eye display devices. One disclosed embodiment provides a near-eye display system comprising a light source, a first polarizing beam splitting surface configured to receive light from the light source, a mirror configured to reflect light passed by the first polarizing beam splitting surface, and a quarter wave plate positioned between the first polarizing beam splitting surface and the mirror. The near-eye display system further includes a second polarizing beam splitting surface positioned at an angle relative to the first polarizing beam splitting surface and a microdisplay configured to produce an image via light received from the second polarizing beam splitting surface.

Optical retarder system with programmable spectral retardance

Abstract: An optical system that works as a retarder waveplate with programmable spectral retardance is proposed. The system is based on a pixelated liquid crystal on silicon (LCoS) spatial light modulator (SLM). The input light beam is spectrally dispersed and different spectral components are projected onto different pixels of the LCoS-SLM. A different retardance is then addressed for each pixel, adapted to the incoming wavelength. Light reflected from the SLM is then recombined by the same setup. In this way a programmable polarization spectrum can be encoded. We illustrate the broadband characterization that is required for proper use of the system. Then several examples are shown, including spectral compensation to yield retarders with constant retardance, retarders with abrupt changes in the spectral retardance function, or bandpass variable retarder filters. The system is also demonstrated to provide programmable light spectrum generation.

Structural illumination-based random scattering optical beyond-diffraction-limit imaging system and method

Abstract: The invention discloses a structural illumination-based random scattering optical beyond-diffraction-limit imaging system and method. The objective of the invention is mainly to solve the problems of complicated techniques, long imaging time, difficult realization of system structure and low imaging resolution of existing similar technologies. The imaging system includes a light source, a beam expander, a spatial light modulator, a lambda/4 wave plate, a beam expanding lens group, a light blocking plate, lenses, a random scattering medium, a convergence lens, and a CCD camera; light beams emitted by the light source are subjected to beam expansion of the beam expander and thereafter enter the spatial light modulator, so that 0-level light and +/-1-level light are obtained; the 0-level light and +/-1-level light pass through the lambda/4 wave plate, so that circularly polarized light can be obtained; after being subjected to beam expansion of the beam expanding lens group, the circularly polarized light reaches the light blocking plate, and the +/-1-level light is reserved; the +/-1-level light is interfered when passing through the lenses, and structural light can be generated, and an observation target can be illuminated; and the illuminated observation target enters the random scattering medium, and strong scattering occurs, and light beams enter the CCD camera through the convergence lens. The structural illumination-based random scattering optical beyond-diffraction-limit imaging system of the invention has the advantages of simple structure and high imaging resolution, and can be used for optical super resolution imaging.

Terahertz waveguide test system

Abstract: The invention discloses a terahertz waveguide test system which comprises a femtosecond laser device, a half wave plate and a polarization beam splitter. The half wave plate and the polarization beam splitter are arranged at the output end of the femtosecond laser device, the polarization beam splitter divides a light beam into pump light and detection light, the pump light is gathered on a terahertz emitter through a pump light path, the generated terahertz radiation waves pass through a waveguide test module and then are gathered on a terahertz detector, and the terahertz radiation waves and the detection light beam are coupled to the terahertz detector for testing in a collinear mode. The system is further provided with three delay table systems which can be used for compensating and changing the optical path difference in the process of wave guide measuring. The system has the advantages of being strong in generality, simple in erecting, capable of being repeatedly used many times and wide in spectral measuring range in the terahertz waveguide test and application.

Submillimeter Polarimetry with PolKa, a reflection-type modulator for the APEX telescope

Abstract: Imaging polarimetry is an important tool for the study of cosmic magnetic fields. In our Galaxy, polarization levels of a few up to $\sim$10\% are measured in the submillimeter dust emission from molecular clouds and in the synchrotron emission from supernova remnants. Only few techniques exist to image the distribution of polarization angles, as a means of tracing the plane-of-sky projection of the magnetic field orientation. At submillimeter wavelengths, polarization is either measured as the differential total power of polarization-sensitive bolometer elements, or by modulating the polarization of the signal. Bolometer arrays such as LABOCA at the APEX telescope are used to observe the continuum emission from fields as large as $\sim0\fdg2$ in diameter. %Here we present the results from the commissioning of PolKa, a polarimeter for Here we present PolKa, a polarimeter for LABOCA with a reflection-type waveplate of at least 90\% efficiency. The modulation efficiency depends mainly on the sampling and on the angular velocity of the waveplate. For the data analysis the concept of generalized synchronous demodulation is introduced. The instrumental polarization towards a point source is at the level of $\sim0.1$\%, increasing to a few percent at the $-10$db contour of the main beam. A method to correct for its effect in observations of extended sources is presented. Our map of the polarized synchrotron emission from the Crab nebula is in agreement with structures observed at radio and optical wavelengths. The linear polarization measured in OMC1 agrees with results from previous studies, while the high sensitivity of LABOCA enables us to also map the polarized emission of the Orion Bar, a prototypical photon-dominated region.

Bandwidth adjustable liquid crystal terahertz wave plate based on porous graphene transparent electrode

Abstract: The invention discloses a bandwidth adjustable liquid crystal terahertz wave plate based on a porous graphene transparent electrode Sub-wavelength metal wire gratings are arranged on the inner side of a substrate of an incidence surface, porous graphene is arranged on the inner side of a substrate on an exit surface, and the two substrates made of fused quartz are sealed and combined to form a liquid crystal box Two light-control orientation layers are sandwiched between the metal wire gratings and the porous graphene in the liquid crystal box, liquid crystal materials are sandwiched between the two light-control orientation layers, and the liquid crystal materials are terahertz electronic control large birefringence liquid crystal materials Parallel orientation of liquid crystals is achieved in the liquid crystal box through the mode of light-control orientation, and a 45-degree included angle is formed between the orientation direction and the direction of the metal wire gratings According to the bandwidth adjustable liquid crystal terahertz wave plate based on the porous graphene transparent electrode, the electronic control birefringence characteristic of the liquid crystals is used, phase delay of ordinary light and extraordinary light is regulated through voltage to correspond to specific wave plates with different frequencies, and the bandwidth adjustable liquid crystal terahertz wave plate has the advantages of being superwide in frequency band, capable of achieving automatic polarization, high in transmittance, large in modulation amount, rapid in response and the like and can be widely applied in the booming terahertz field