456 results about "Birefringent crystal" patented technology

A method for producing low-noise laser output at wavelengths ranging from IR through visible to UV in various operation modes from a monolithic microchip laser comprises schemes of (1) generating one or two fundamental beam(s) from light source(s) selected upon the desired wavelength(s), polarization(s), and other features related to the desired laser output; (2) intracavity beam combination/separation due to the walk-off effect in one or more birefringent crystal(s) transparent to the propagating lights and highly anisotropic; (3) wavelength conversion in one or more nonlinear optical crystal(s); (4) compact and efficient pump source(s); and (5) minimization of intracavity loss/noise. One resonator cavity supports only one fundamental beam, which eliminates the green problem. The gain media can be selected from an extensive group of materials including isotropic and naturally birefringent crystals, with polarization dependent or independent laser emissions. Laser devices constructed in accordance with the inventive method are demonstrated with various configurations.

A transmitter subsystem generates an optical signal which contains multiple subbands of information. The subbands have different polarizations. For example, in one approach, two or more optical transmitters generate optical signals which have different polarizations. An optical combiner optically combines the optical signals into a composite optical signal for transmission across an optical fiber. In another approach, a single optical transmitter generates an optical signal with multiple subbands. The polarization of the subbands is varied, for example by using a birefringent crystal. In another aspect of the invention, each optical transmitter generates an optical signal containing both a lower optical sideband and an upper optical sideband (i.e., a double sideband optical signal). An optical filter selects the upper optical sideband of one optical signal and the lower optical sideband of another optical signal to produce a composite optical signal.

The invention concerns a microlithography projection objective and a microlithographic projection exposure apparatus with a microlithography projection objective, having at least one lens of birefringent material. In accordance with an aspect of the invention, a microlithography projection objective has an optical axis and at least one lens of uniaxial birefringent crystal whose principal axis is oriented parallel to the optical axis, wherein all lenses of uniaxial birefringent crystal comprise the same crystal material, wherein light is tangentially polarised in the lens of uniaxial birefringent crystal and wherein the lens of uniaxial birefringent crystal has a diffractive power different from zero and has a plane exit face or a non-plane but refractive power-less exit face.

A method for producing low-noise laser output at various wavelengths and/or in various operation modes in a monolithic microchip laser comprises schemes of generating two fundamental beams in separate cavities, precise intracavity beam combination based on the walk-off effect in birefringent crystal, and wavelength conversion in nonlinear optical crystals. The fundamental beams are produced from light sources selected upon the desired wavelengths, polarizations, and other features related to the laser output. Low-noise laser devices operated in SLM or with spectra of flat-top or desired bandwidths are constructed according to the method. High-volume fabrication is feasible. Apparatus of compact size and efficient frequency conversion is demonstrated with various configurations including those for generating low-noise 491 nm laser, as a replacement of Argon ion laser.

An integrated isolator array is provided having a plurality of waveguides fabricated in a planar optical substrate, each waveguide having input and output sections. An isolator subassembly is received within a transverse trench formed in the substrate between the input and output sections such that it intersects the optical paths of the waveguides. The isolator subassembly, which may consist of layers of Faraday rotator material sandwiched between layers of birefringent crystal material, permits the forward passage of light from the input sections to the output sections of the waveguides while preventing the backward passage of light from the output to the input sections. Each waveguide input section is preferably adapted with a mode-expanding input taper to collimate light propagating through the waveguide. Similarly, each output section is preferably adapted with a mode-reducing output taper to reduce the mode size of forward-traveling light to match that of an output fiber, as well as to collimate light traveling backward within the output section.

The invention discloses a spectrum scaling apparatus used for a spectrum imager. The apparatus is characterized in that: a light beam which is emitted by a broadband light source (1) goes through a diaphragm (2) and a collimating lens (3) and irradiates a wavelength tuning optical filter (4), a plurality of narrowband optical signals which are distributed in a comb-shaped mode and have different wavelengths are outputted, after light intensity adjusting by a broadband bandpass optical filter (5), the signals enter into an integrating sphere (9) from an integrating sphere incident light hole (6) for depolarization and space uniformity processing, and an integrating sphere light extraction hole (8) outputs a surface light source. A spectrum imager to be measured is placed on the light extraction hole (8) for spectrum scaling. According to the apparatus, a birefringence crystal is utilized to carry out light transmission rate modulation, a passband peak value position and a bandwidth size can be adjusted, a plurality of narrowband light intensity signals changing with a wavelength are provided in a broadband range, wavelength scanning is not needed when carrying out spectrum scaling on the spectrum imager, wavelength scaling with one-time imaging is realized, and the apparatus is suitable for scaling a large field of view and large caliber spectrum imager.

Contrast compensation for a liquid crystal display projection system is provided with a trim retarder that includes a single-layer retarder element that has an in-plane retardance that is shifted from a zero-order half-wave at a predetermined wavelength by a predetermined amount. This near half-wave plate provides similar contrast compensation and azimuthal angle sensitivity to conventional relatively low-magnitude trim retarders, yet is readily fabricated with inorganic birefringent crystals with a manageable thickness tolerance.

The invention comprises an assembly (a) by which two polarized beam sources (1) and (2) of different wavelength by means of polarizing beam splitters (5) can be superimposed. By means of a dispersively birefringent crystal (6) both beams are rectified to reconstitute the linear polarization.

If, as assumed in (b), the beam sources can react spectrally to feedback, an additional polarization filter (8) and a partially reflecting coating (9) can ensure that suitable wavelengths are established automatically.

This assembly can be scaled as depicted in (b). By help of further dispersively birefringent crystals (6) and birefringent displacers more beams can be combined into a single beam, eight sources in the given setup.

A transmitter subsystem generates an optical signal which contains multiple subbands of information. The subbands have different polarizations. For example, in one approach, two or more optical transmitters generate optical signals which have different polarizations. An optical combiner optically combines the optical signals into a composite optical signal for transmission across an optical fiber. In another approach, a single optical transmitter generates an optical signal with multiple subbands. The polarization of the subbands is varied, for example by using a birefringent crystal. In another aspect of the invention, each optical transmitter generates an optical signal containing both a lower optical sideband and an upper optical sideband (i.e., a double sideband optical signal). An optical filter selects the upper optical sideband of one optical signal and the lower optical sideband of another optical signal to produce a composite optical signal.

The invention relates to a method capable of adjusting the polarization and the intensity of a terahertz wave rapidly and continuously. According to the method, a focusing lens is arranged at the outlet of a femto-second laser; incident laser passes through the focusing lens and a doubling frequency crystal in sequence to generate frequency doubled light; the frequency doubled light and remaining fundamental frequency laser pass through a uniaxial birefringent crystal wafer together; according to the principle that the refractive indexes of the fundamental frequency laser and the frequency doubled light in a uniaxial birefringent crystal are different, the optical path difference, namely the time delay, between the fundamental frequency laser and the frequency doubled light can be changed by adjusting the thickness of the uniaxial birefringent crystal wafer and the spatial included angle between a glass piece and an incident light beam, so that the relative phase between the fundamental frequency laser and the frequency doubled light is changed; and therefore, the polarization and the intensity of the finally generated terahertz wave are adjusted. Finally, the generated terahertz wave enters a terahertz wave detection system after being filtered by a high-resistance silicon wafer. By the method, the polarization and the intensity of the terahertz wave can be adjusted rapidly and continuously; and the operation is simple, rapid and effective.

The method of the invention comprises the following steps: (1) moving a BBO crystal to change the distance from the BBO crystal to a plasma to obtain the relationship between the angle theta of the polarization direction of T-Hz wave relative to horizontal direction and the distance d from the BBO crystal to the plasma; (2) substituting the refractive indexes of T-Hz wave under different frequencies to a formula for calculating phase delay, thus obtaining the relationship of phase delay between the two axes of the birefringent crystal along with frequency change; (3) respectively selecting a corresponding T-Hz wave frequency f1 when the phase delay is odd times of pi and a corresponding T-Hz wave frequency f2 when the phase delay is even times of pi, moving the BBO crystal, and measuring the motion distance delta d of the BBO crystal corresponding to the T-Hz waves of frequency f1 and f2 at the nearest neighbor part with the minimum amplitude; and (4) calculating the included angle alpha between the birefringent crystal optical axis and the horizontal direction. Therefore, the invention can measure the optical axis direction of the birefringent crystal without rotating the birefringent crystal, thereby ensuring the measurement along the optical axis direction of the birefringent crystal to be more convenient and accurate.

The invention relates to a single fibre bi-directional assembly comprising a TO tube seat, a laser, an isolating part, a 45-degree optical filter, a 0-degree optical filter, a fiber connector and a probe, wherein the laser is encapsulated in the TO tube seat. An isolator system and a wavelength division multiplexing system in the single fibre bi-directional component share one 45-degree multifunctional optical filter, which saves a popolaroid or a birefringent crystal in the isolator so that the assembly is more reasonable in structure, besides, the cost for producing the BOSA is reduced either.

Provided is a method for preparing a two-dimensional metallic photonic crystal structure in large area through femtosecond laser direct writing. The invention provides a method and experiment device for preparing the periodically-distributed two-dimensional photonic crystal structure with the feature size being the sub-micron dimension in one step in the large area by focusing identical-wavelength double-pulse femtosecond laser on the surface of metal through a plano-convex cylindrical lens, and the identical-wavelength double-pulse femtosecond laser is obtained based on the spectrophotometry of birefringent crystals and has the features of collinear transmission, cross polarization and picosecond time delay. Two-dimensional periodic structure patterns can be effectively regulated and controlled by changing the energy and the number of pulses of input laser, the thicknesses and the azimuth angles of the birefringent crystals and the like. Through the combined design of different linear polarization directions and the variable time delay feature of two femtosecond laser pulses and focusing of the cylindrical lens, preparation of the two-dimensional metallic photonic crystal structure within the large area is achieved conveniently and quickly. The novel preparation method adopting the double-pulse femtosecond laser with cross polarization and variable time delay has potential important applications in the field of material micro-nano processing and preparation.

To optimise the transformation rate (efficiency) in the optical frequency conversion of laser beams of ultra-short light pulses in optically non-linear media such as a crystal (56), a double refracting crystal (54) is arranged in the beam path before the optically non-linear medium (56). The length of the double refracting crystal (54) is selected and the orientation of its optical crystal axis in relation to the propagation direction of the laser beams involved in the frequency conversion is set such that the change caused by the double refracting crystal (54) in the location, time and direction of incidence of the laser pulses (14) and (16) on the optically non-linear medium (56) and the resulting change in the spatial and temporal overlap of the laser pulses in the optically non-linear medium (56) for optical frequency conversion in the crystal (56) give a conversion efficiency which is higher than the conversion efficiency which would be achieved without the double refracting crystal (54).

The invention relates to a method for continuously regulating central frequency and spectrum width of THz (terahertz) wave. A bundle of ultrafast laser pulse passes through a movable birefringence crystal oblique split pair and a zero-order quarter wave plate to generate a novel specially-polarized light field by a polarizing gate method. The novel light field passes through a polarizer to obtain laser pulse with width of narrow pulse with linear polarization. Laser pulses different in width are obtained by controlling inserting quantity of the birefringence crystal oblique split pair, and accordingly the function of regulating central frequency and spectrum width of the THz wave is achieved. A device is simple and easy to operate, the width of the novel laser pulse can be changed only two crystals of the birefringence crystal oblique split pair simultaneously move oppositely at equal distance, and accordingly the central frequency and the spectrum width are adjusted. The method is suitable for light sources of various pulse widths and wavelengths.

The invention discloses a miniaturized full Stokes vector polarization imaging device based on a binary digital coded birefringent crystal, including a spectral filter (1), an imaging lens (2), a binary digital coded birefringent crystal sheet (3), a micro polarizer array (4), and a light intensity detector (5). Binary digital coding is carried out on the birefringent crystal sheet by making use of the birefringence effect of a birefringent crystal and using a micro sodium optical processing method, and the birefringent crystal sheet is integrated with the micro polarizer array and the light intensity detector to form a compact and fully-functional full Stokes vector polarization imaging device. A full Stokes vector can be acquired through only one exposure, and the real-time performance is good. The device has a compact structure and a stable system. The micro optical structure is large, the requirement on precision is low, the cost is low, and the device can be mass produced. The device has low requirement on environment, and has stable performance. The device can be widely used in important areas such as astronomical polarization imaging, biological tissue detection and medicinediagnosis, remote sensing imaging, and target detection.

A polarization-interferometry based tunable periodic filter includes polarization defining components such as polarizing beam splitters or polarizing beam displacers located on the input and output sides of a phase retarder such as a birefringent crystal. A polarization independent input consisting of multiple optical channels having a periodic frequency spacing is converted to a branched output of optical channels in which each branch has a periodic frequency spacing that is different from that of the input, and which are interleaved with each other. The output period is tunable by adjusting the phase delay of orthogonal polarization components. A contrast ratio of >=20 dB can be realized. The device allows the mux/demux of up to 200 WDM channels with a 50 GHz frequency spacing. Applications of the device include a band splitter, a wavelength selective cross-connect, and a wavelength monitor.

The present invention discloses an integrated reflective phase bias device, a fiber laser and a light wave and microwave phase detector. The phase bias device comprises a fiber holder, a collimation lens, a polarizing prism, a Faraday rotator, a birefringent crystal and a mirror. According to the device, the fiber laser and the light wave and microwave phase detector, two polarization-maintaining fibers with mutually vertical directions are fixed in the fiber holder, the light with mutually vertical polarization directions are separated by the polarizing prism, only one collimator, one Faraday rotator, one birefringent crystal and one mirror are needed, the size is small, the stability is high, the price is low, and no any adjustment is needed. The phase bias device is used in the fiber laser, a self started mode-locked pulse train can be obtained, the characteristic of the pulse train is not interfered by an external environment, and the phase bias device can be applied to various complex environments with high noise, heavy pollution or emission. The phase bias device is used in the light wave and microwave phase detector, thus the light wave and microwave phase detector is compact and is not interfered by the outside, and the working is more reliable.