Showing papers on "Waveplate published in 2001"

Method and apparatus using laser pulses to make an array of microcavity holes

Abstract: A method and apparatus for forming an array of microcavities in the surface of a metal film uses an excimer laser or an ultrashort laser which to produce a beam of laser light pulses. An optical mask divides the beam into multiple beams and a lens system focuses the multiple beams onto the metal film. The device operates by generating multiple beams of laser pulses of a first diameter and then magnifying the pulses by a magnification factor less than 1 to produce multiple beams of pulses having a second diameter, less than the first diameter, which are applied to the metal film. The magnification factor and the intensity of the laser is such that the fluence of the laser on the optical mask is not sufficient to cause ablation while the fluence on the metal film is sufficient to cause ablation. A diffractive optical element may be used in the device in place of the optical mask. The apparatus includes a quarter wave plate that converts the beam of laser light pulses into a beam of circularly polarized pulses. The apparatus also includes a device that homogenizes the intensity of the laser light pulses before they are applied to the optical mask.

Propagation of polarized light in birefringent turbid media: time-resolved simulations

Abstract: A Monte Carlo model was used to analyze the propagation of polarized light in linearly birefringent turbid media, such as fibrous tissues. Linearly and circularly polarized light sources were used to demonstrate the change of polarizations in turbid media with different birefringent parameters. Videos of spatially distributed polarization states of light backscattered from or propagating in birefringent media are presented.

Polarization beam splitters using polarization diffraction gratings.

Abstract: We report a polarization beam splitter that uses polarization gratings written onto a zero-twist nematic liquid-crystal display. We show three configurations. The first two separate the diffracted light into two orthogonally polarized orders that are either linearly or circularly polarized. In the third configuration, we demonstrate a novel case for which the output is separated into two nonorthonormal polarization states. One component is linearly polarized and the second is circularly polarized.

Reflection and refraction optical system and projection exposure apparatus using the same

Abstract: A reflection and refraction optical system includes a polarization beam splitter, a concave mirror, a lens group and a quarter waveplate, wherein an additional waveplate is provided to transform S-polarized light from the polarization beam splitter into circularly polarized light.

Optimized spinning design for low PMD fibers: an analytical approach

Abstract: It is known that the differential group delay (DGD) due to polarization mode dispersion (PMD) can be effectively reduced by spinning the fiber during drawing. In this paper, we propose an analytical approach that allows optimization of the spinning design. The fundamental idea is that, in the absence of polarization coupling, an optimized spinning profile can balance the effects of the intrinsic linear birefringence so that the differential group delay can be forced to be periodic and, consequently, have a limited amplitude as a function of distance. Our approach Is independent of the spin profile. In other words, with a fixed set of parameters that characterize a particular spin function, we are able to find analytically the values corresponding to a periodic DGD in a deterministic regime. Numerical results based on waveplate model confirm the analytical prediction and show that PMD can be reduced by about two orders of magnitude with respect to the same fiber without spinning, even after the introduction of random polarization coupling.

Optical component for producing linearly polarized light

Abstract: A polarization mask for producing light of locally different polarization from unpolarized or uniformly polarized light. On the light output side, discrete areas with different polarization directions are present, which are either static or switchable. The mask is useful for, among other things, the transfer of polarization pattern onto a PPN layer.

Polarization errors associated with zero-order achromatic quarter-wave plates in the whole visible spectral range

Abstract: By a combination of quarter-wave plates made of different birefringent materials it is possible to produce achromatic quarter-wave plates whose degree of achromatism is dependant on the dispersions of birefringence and on the thicknesses of the individual quarter-wave plates. These waveplates are widely used in optical instrumentation and the residual errors associated with these devices can be very important in high resolution spectro-polarimetry measurements. The misalignment of optic axis in a double crystal waveplate is one of the main source of error and leads to elliptical eigenpolarization modes in the retarder and the oscillation of its orientation according to the wavelength. This paper will discuss, first, how the characteristics of a quartz-MgF2 quarter-wave plate is affected by such a misalignment. A correlation with the experiment is then achieved in order to highlight the interest of taking a possible tilt error into consideration when doing polarimetric measurements.

Spectroscopic ellipsometer without rotating components

Abstract: A spectroscopic ellipsometer having a multiwavelength light source, spectrometer (or wavelength-scanning monochromator and photodetector), a polarizer and polarization analyzer, and one or more objectives in the illumination and collection light paths, further comprises a stationary polarization modulator that modulates the light polarization versus wavelength. Modulator can be an optically active crystal rotating the linear polarization plane by a different angle for each wavelength or a non-achromatic waveplate retarder that varies the relative phase delay of the polarization components periodically over wavelength. The measured spectrum can be used to characterize selected features or parameters of a sample, e.g. by comparison with one or more theoretical spectra.

Wavelength discretely tunable semiconductor laser

Abstract: A wavelength discretely tunable semiconductor laser that addresses wide wavelength tuning range, is mode hopping free, has high output power, has fast wavelength switching time, is wavelength locking free and is relatively simple. Four exemplary embodiments disclosed herein utilize a wavelength discretely tunable semiconductor laser that comprises a discretely tunable filter and laser amplifier. In the first embodiment, the tuning element comprises a pair of cascade Fabry-Perot filters, each having a plurality of characteristic narrow transmission passbands that pass only the cavity mode under the passband. The spacing between the narrow transmission passbands are slightly different in one filter from the other filter so that only one passband from each filter can be overlapped in any given condition over the entire active element gain spectral range, thereby permitting lasing only at a single cavity mode passed by the cascade double filters. One of the two etalon filters can be made with a plurality of transmission passbands predetermined by industry, application and international standards, making this element an intra-cavity wavelength reference and eliminating further wavelength locking needs for the tunable laser. In a second embodiment, one of the two etalons is replaced by a wedge filter. The filter optical path change and thus the transmission passband shift are achieved by translating the wedge filter in a direction perpendicular to the optical axis. In a third embodiment, one of the two etalon filters is replaced by a polarization interference filter. The polarization interference filter consists of an electro-optically-tunable birefringent waveplate, a fixed birefringent waveplate, the laser cavity and T.E. polarization light emitted from the laser diode. In a fourth embodiment, the laser and wavelength tuning structure are integrated on a semiconductor substrate by epitaxy processes.

Retardation plate and fabrication method thereof, and plate for circularly polarizing light, 1/2 wave plate and reflection-type liquid crystal display device utilizing the retardation plate

Abstract: The present invention provides a broad band retardation plate that can be fabricated by a simple process and uniformly retards light incident of the entire visible light region. The retardation plate contains materials including positive or negative intrinsic double refraction values. When retardation values in wavelengths of 450 nm, 550 nm, and 650 nm are defined as Re(450), Re(550) and Re(650), respectively, the retardation plate satisfies the relational expression of Re(450)

Chiral laser utilizing a quarter wave plate

Abstract: The inventive chiral laser achieves lasing by placing an electro-luminescent emitting layer with quarter wave plate properties and a layer of cholesteric liquid crystal (CLC) between two electrodes. The electrode connected to the emitting layer is highly reflective and serves as a source of electrons, while the second electrode, connected to the hole-transporting CLC, serves as a source of holes. The recombination of electrons and holes in the emitting layer produces luminescence. If a right handed CLC structure is used, then right circularly polarized emission is reflected from the CLC as right circularly polarized light, and then converted to linear polarized light by passing through quarter wave plate emitting layer. It is then reflected by the electrode and converted again into the right circularly polarized light in a second pass through the quarter wave plate emitting layer. The emitted and reflected light emissions are incrementally amplified on each pass through the emitting layer and thus a laser cavity is formed. Once a predefined lasing threshold is reached, lasing occurs perpendicular to the CLC layer. Because the laser cavity is formed only for right circularly polarized light, polarized laser emission will occur.

Spectral Modulation, or Ripple, in Retardation Plates for Linear and Circular Polarization

Abstract: High‐resolution spectropolarimetry sometimes suffers from a spectral modulation in polarization and position angle. It is shown that this artifact can be attributed to multiple reflections within the plates of the wave plate assembly and that the effect is inherent to the use of wave plates except at the design wavelength. The treatment given applies to strictly plane‐parallel wave plate elements and complete coherence, and consequently the predicted ripple amplitudes are upper limits. It is possible that plates of poorer optical quality will not show this effect so prominently, but otherwise a simple modification to normal observing practice can be used to eliminate the ripple.

Optical phased array for depolarized optical beam control

Abstract: A optical phased array device for optical beams with general polarization. A reflective embodiment of the inventive optical phased array interposes a quarter-wave plate between a linearly polarized liquid crystal layer and a mirror. A controllable voltage applied across the liquid crystal layer causes a first linearly polarized component of an incident optical beam to be phase shifted when it passes through the liquid crystal layer. The polarization of the optical beam is rotated by 90° when it travels through the quarter-wave plate, is reflected from the mirror, and travels back through the quarter-wave plate. The second linearly polarized component of the optical beam, orthogonal to the first, is phase shifted when it passes back through the liquid crystal layer. A transmissive embodiment of the inventive optical array interposes a half-wave plate between two linearly polarized liquid crystal layers. The first linearly polarized component is phase shifted by the first liquid crystal layer and the second component, orthogonal to the first, is phase shifted by the second layer.

Dynamic eigenstates of polarization

Abstract: We propose the concept of a dynamic eigenstate of polarization (DES) to describe the sensitivity of the output polarization of an optical component relative to the change of a key parameter characterizing its birefringent characteristics The concept is a generalization of the concept of principal states developed for polarization mode dispersion to generalized parameters such as temperature, pressure, voltage, angular adjustment, etc We discuss the application of the DES concept in some detail for polarization control and polarization sensitivity relative to temperature

Polarization dispersion compensating apparatus

Abstract: A polarization dispersion compensation apparatus includes a polarization controller, a polarization beam splitter, an optical delay circuit, and a polarization beam combiner. The polarization controller controls polarization of an optical signal so that the polarization axis of the input optical signal substantially coincides with the optical axis of an optical transmission line, and the polarization beam splitter section splits the optical signal into two polarized components perpendicular to each other. The optical delay circuit section causes a difference in delay between the two polarized components, and the polarization beam combiner section combines the two polarized components output from the optical delay circuit section. Each of the polarization beam splitter section and the polarization beam combiner section includes a symmetric Mach-Zehnder interferometer having optical transmission lines in two arms, each arm including a temperature control and a birefringence portion for compensating polarization dispersion between the two polarized components.

High-isolation dense wavelength division multiplexer utilizing birefringent plates and a non-linear interferometer

Abstract: The present invention provides a dense wavelength division multiplexer for separating an optical signal into optical channels. The dense wavelength division multiplexer (500) includes at least one birefringent plate (509) for separating an optical signal into a plurality of optical channels, at least one half wave plate (510), a lens (513) and a non-linear interferometer (514) for introducing a phase difference between the plurality of optical channels. The present invention provides for an ease in alignment and a higher tolerance to drifts.

Polarization diversity for birefringent filters

Abstract: A birefringent filter includes an input optical apparatus for receiving an input optical beam and producing therefrom parallel first and second optical beams offset in a first direction and having the same polarization. A birefringent filter unit receives the first and second polarized optical beams and produces a first and second elliptically polarized optical beams. An output optical apparatus combines predetermined components of the first and second elliptically polarized optical beams to form a first and second elliptical polarized output beams. The two output beams have intensities that vary inversely, in a periodic manner, as a function of frequency of the input optical beam.

Virtual waveplate and optical channel interleaver formed therewith

Abstract: A conventional interleaver, based on a stack of waveplates, relies on the orientation and the birefringence of the waveplates to differentiate the polarizations of one set of channels from another, so that the one set of channels can be separated from the other. The present invention relates to a virtual waveplate that is used to replace a birefringent waveplate. A virtual waveplate imposes a phase delay between the extraordinary ray and the ordinary ray by separating one from the other and differentiating the actual path lengths taken thereby, before recombining them. An interleaver constructed with the virtual waveplates of the present invention can be substantially a-thermal and potentially chromatic dispersion free.

LP-6: Design of a Quarter Wave Plate with Wide Viewing Angle and Wide Wavelength Range for High Quality Reflective LCDs

Abstract: One polarizer type reflective LCDs require a quarter wave plate. However, conventional quarter wave plate using uniaxial retardation films have poor viewing angle and high wavelength dependences. In this paper, we designed a quarter wave plate with wide viewing angle and wide wavelength range by using three biaxial retardation films. In addition, we realized a high quality reflective LCD with wide viewing angle range and high contrast ratio by applying this quarter wave plate and wide-view polarizer to the R-OCB cell.

Optical element, light source apparatus, optical head apparatus, and optical information processing apparatus

Abstract: A first semiconductor laser emits a light beam L 1 with a first wavelength polarized in an x-axis direction. A second semiconductor laser emits a light beam L 2 with a second wavelength polarized in the x-axis direction. A wavelength plate functions as a (2m+1)λ/2 plate (m is an integer) with respect to the light beam L 1 , and functions as a nλ plate (n is an integer) with respect to the light beam L 2 . A polarization anisotropic hologram element diffracts the light polarized in the x-axis direction, and transmits the light polarized in the y-axis direction. Consequently, an apparent emission point of diffracted light L 2 ′ may be allowed to coincide with an emission point of the light beam L 1 . A light source apparatus thus constructed can emit two light beams with different wavelengths at a low cost and a high efficiency with optical axes aligned in a simple configuration.

Quarter-wave plate, circularly polarizing plate and display device

Abstract: PROBLEM TO BE SOLVED: To develop a wave plate functioning as a quarter-wave plate over a wide wavelength region such as a visible ray region and which can be mass- produced and very thin, and to develop a circularly polarizing plate excellent in antireflection for a wide band. SOLUTION: The quarter-wave plate (1) comprises a birefringent layer (12) giving a phase difference of one-half wavelength to a monochromatic ray arranged on a monolayer stretched film (11) giving a phase difference of one- quarter wavelength to a monochromatic ray where the birefringent layer consists of a fixed orientation layer of a liquid crystalline compound. The circularly polarizing plate comprises a polarizing film (3) laminated on the birefringent layer side of the quarter-wave plate. A display device comprises a liquid crystal cell or an organic EL(electroluminescence) element with the quarter-wave plate or the circularly polarizing plate arranged on at least one side thereof. COPYRIGHT: (C)2002,JPO

Polarization state conversion in optically active spectroscopy

Abstract: The invention describes a method to eliminate instrumental offset in measurement of optically active scattering and circular dichroism. The method uses the time-average measurement of the light that is systematically transformed by series of optical devices. The optical devises perform the function of rotating linearly polarized light, interconventing left and right circular polarized light, converting circular polarized light to rotating linear polarized light and converting linear polarized light to alternating left and right circular polarized light.

Method for the measurement of retardation of wave plates based on laser frequency-splitting technology

Abstract: A method with high precision for measurement of optical re- tardation angles of wave plates is presented, based on laser birefringent longitudinal-mode-splitting technology. When a wave plate is placed in the laser cavity, a laser longitudinal mode will be split into two modes because of the birefringence of the wave plate. The optical retardation angle of the wave plate is proportional to the ratio of the frequency dif- ference between the two modes to the laser longitudinal-mode interval. The retardation angle can be determined by measuring these two fre- quencies. The method uses a compact setup and attains high resolution and accuracy. The error is less than 8 arcmin. The paper discusses a crystal quarter-wave plate at 632.8-nm wavelength as an example, but the method is suited for other laser wavelengths and wave plates. © 2001 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1371287) Subject terms: optical retardation angle; wave plate; laser birefringent longitudinal-mode splitting.

Circularly polarized light extraction optical element and method of manufacturing the optical element

Abstract: A circularly polarized light extraction optical element (10) capable of effectively suppressing the lowering of the display quality of a display caused by light-dark patterns appearing on the display surface of the display even when a circularly polarized light plate and an elliptically polarized light plate are brought into a cross nicol state and the circularly polarized light extraction optical element is disposed therebetween, and providing a circularly polarized light having a continuous selectively reflected wave zone without optical singular point even when the circular polarized light extraction optical element is manufactured by stacking a plurality of liquid crystal layers each other, comprising a liquid crystal layer (12) planar-disposed and having a cholesteric ordinality, wherein two major surfaces (12A) and (12B) of the liquid crystal layer (12) opposed to each other are substantially identical to each other in the directions of directors (Da, Db) of liquid crystal molecules through the entire area of the surfaces (12A, 12B) and, when the liquid crystal layer (12) is formed of the plurality of liquid crystal layers, the directions of the directors of the liquid crystal molecules should desirably be substantially parallel with each other near the boundary of the liquid crystal layers adjacent to each other.

Laminated quarter-wave plate, circularly polarizing plate and liquid crystal display device using the same, and method for manufacturing the same

Abstract: PROBLEM TO BE SOLVED: To provide a quarter-wave plate suited to compensate birefringence, a circularly polarizing plate and a liquid crystal display device using the same, and a method for manufacturing the same. SOLUTION: Representing in-plane principal refractive indexes by nx, ny and the refractive index in the thickness direction by nz, the quarter-wave plate is constructed by laminating a quarter-wave plate satisfying a relation Nz=(nx-nz)/(nx-ny)>1.05 and a half-wave plate in such a way that respective directions of in-plane lag axes are made to intersect each other. Also the circularly polarizing plate is constructed by laminating a polarizing plate on the quarter-wave plate.

Wide range tunable filter

Abstract: A wide range tunable filter is provided. A randomly polarized incoming beam is converted into two orthogonally polarized beams. A ½ wave plate and filter block turns these two beams into four beams. Two of the four beams have a single range of wavelengths and two beams have the remaining wavelengths. Each pair of beams is orthogonally polarized. A ½ wave plate and birefringent crystal positioned after the filter block combine the two beams having the single range of wavelengths and combines the two beams having the remaining wavelengths. The invention includes a thermal compensator to correct the angle of the filter with respect to the incident light.

Optical frequency conversion by a rotating molecular wave plate.

Abstract: We demonstrate efficient four-wave mixing in low-pressure molecular deuterium without the need for phase matching. We use two laser fields with opposite circular polarizations to produce a strong excitation of a rovibrational transition at a frequency of 3167 cm 21 . The coherent molecular motion, in turn, modulates a third laser field (also circularly polarized) and results in highly efficient single-sideband conversion. © 2001 Optical Society of America OCIS codes: 190.2620, 190.5650, 270.1670, 300.6270. Four-wave mixing in atomic and molecular gases has served, for more than 30 years, as an eff icient tool for producing coherent radiation at desired wavelengths. 1 An important development in this area was the invention of nonlinear optics at maximal coherence, 2,3 which allowed 100% frequency conversion without the need for phase matching, under conditions in which the nonlinear susceptibility is of the order of the linear susceptibility. This technique relied on all-resonant laser-pulse propagation in an atomic medium (L scheme) and utilized electromagnetically induced transparency. 4

Beam splitter and wave plate made of crystal material, and optical device, exposure device and inspection device equipped with the crystal optical parts

Abstract: PROBLEM TO BE SOLVED: To obtain a beam splitter which can maintain preferable optical performance without having substantial influences of birefringence even when a birefringent crystal material such as fluorite is used. SOLUTION: The beam splitter is made of a crystal belonging to the cubic system. The incident direction of a beam to the beam splitter and the exiting direction of the beam from the beam splitter are preliminarily controlled to be almost coincident with the crystalline axis [100] of the crystal or with a crystalline axis optically equivalent to the above crystalline axis.