369 results about "Second-harmonic generation" patented technology

An apparatus for and method of performing multi-photon light sheet microscopy (MP-LISH), combining multi-photon excited fluorescence with the orthogonal. illumination of light sheet microscopy are provided. With live imaging of whole Drosophila and zebrafish embryos, the high performance of MP-LISH compared to current state-of-the-art imaging techniques in maintaining good signal and high spatial resolution deep inside biological tissues (two times deeper than one-photon light sheet microscopy), in acquisition speed (more than one order of magnitude faster than conventional two-photon laser scanning microscopy), and in low phototoxicity are demonstrated. The inherent multi-modality of this new imaging technique is also demonstrated second harmonic generation light sheet microscopy to detect collagen in mouse tail tissue. Together, these properties create the potential for a wide range of applications for MP-LISH in 4D imaging of live biological systems.

An adaptive laser system for ophthalmic use is provided. In another aspect, a relatively inexpensive laser is employed. In another aspect of the present system, non-linear optical imaging uses multiphoton fluorescences and / or second harmonic generation, to create three-dimensional mapping of a portion of the eye in combination with automated feedback to assist with a surgical operation. In a further aspect of the present system, the patient interface uses laser induced markings or indicia to aid in focusing and / or calibration. Still another aspect employs temporal focusing of the laser beam pulse.

A capacitive microfabricated ultrasonic transducer (cMUT) is operated to improve its performance during harmonic imaging in non-linear media, such as in contrast agents or in human tissue. The cMUT is operated by inverting the transmit waveform to adjacently spaced azimuth elements, and combining at least two additional firings without adjacent inversion, for each transmit vector, thereby canceling the second harmonic generation of the cMUT; and thus, the performance of harmonic imaging using the cMUTs can achieve improvement.

A method of intracavity frequency conversion in a CW laser includes causing fundamental radiation to circulate in a laser resonator. The fundamental radiation makes a first pass through an optically nonlinear crystal where a fraction of the fundamental radiation generates second-harmonic radiation in a forward pass through the crystal. The residual fundamental radiation and the second-harmonic radiation are then sum-frequency mixed in forward and reverse passes through an optically nonlinear crystal such that a fraction of each is converted to third-harmonic radiation. The residual second-harmonic radiation and fundamental radiation from the sum-frequency mixing then make a reverse pass through the second-harmonic generating crystal where the second-harmonic radiation is converted back to fundamental radiation. The third harmonic radiation can be delivered from the resonator as output radiation, or can be used to pump another optically nonlinear crystal in an optical parametric oscillator. Second-harmonic radiation can also be used to pump an optical parametric oscillator.

A novel SH generator based on a photonic band gap (PBG), mixed half-quarter-wave, periodic structure is described. Both energy output and conversion efficiencies are nearly three orders of magnitude greater than for bulk, phase-matched devices of comparable lengths. Similar results for a GaAs / AlAs semiconductor periodic structure are also found. These results have immediate applications in frequency up- and down-conversion lasers, higher and lower harmonic generation, and Raman-type lasers, where either Stokes or anti-Stokes resonances can be enhanced or suppressed near the band edge. In general, the underlying mechanism requires the fields to be strongly confined, allowing for longer interaction times, increased effective gain lengths, and enhanced conversion efficiencies, although strong pump confinement alone can also result in significantly enhanced SH generation.

Entanglement-based QKD systems and methods with active phase tracking and stabilization are disclosed. The method includes generating in an initial state-preparation stage (Charlie) pairs of coherent photons (P1) at a first wavelength. Second harmonic generation and spontaneous parametric downconversion are used to generate entangled pairs of photons (P5) having the first wavelength—State detection stages (Alice and Bob) optically coupled to Charlie receive respective entangled photons from Charlie. The relative phase delays of the entangled photons are tracked using reference optical signals (P3) generated by Charlie and having the same wavelength as the entangled photons. Classical detectors (132A, 132B) detect the reference signals while single-photon detectors (130A, 130B) and a control unit (control unit C) generates an phase-correction signal that maintains the relative phases of the three phase delay loops (40, 100A,100B ) via adjustable phase-delay elements (MA, MB).

The present invention relates to an apparatus and methods for achieving phase-matching between various waves and / or modes by operation of a waveguide. Phase-matching between interacting waves is achieved by total internal reflection and transverse Bragg reflection waveguides. Using second harmonic generation in GaAs / AlGaAs as an example, properties are investigated and quantified such as nonlinear coupling efficiency, bandwidth, tunability, and limitations due to dispersion. The technique is advantageous when compared to alternate technologies, where it is particularly attractive as a material independent means to obtain ultra-low-loss nonlinear optical elements for monolithic integration with coherent light source and other active devices.

The present invention relates to methods for modulating a semiconductor laser and wavelength matching to a wavelength converter using monolithic micro-heaters integrated in the semiconductor laser. The present invention also relates to wavelength matching and stabilization in laser sources in general, without regard to whether the laser is modulated or whether second harmonic generation is utilized in the laser source. According to one embodiment of the present invention, a method of compensating for thermally induced patterning effects in a semiconductor laser is provided where the laser's heating element driving current IH is set to a relatively high magnitude when the laser's driving current ID is at a relatively low magnitude. Additional embodiments are disclosed and claimed.

Solid-state lasers pumped by incoherent or partially coherent, monochromatic light sources such as high power VCSEL arrays. Efficient and uniform injection of pumping energy into gain medium is achieved through spectral match of the pump source with the gain medium absorption and multi-bounce reflections of unabsorbed pump light in a diffusing pump chamber. One preferred embodiment of the diffusing pump chamber is a hollow cylinder coaxially surrounding the gain medium. One or more transparent windows, slit-shaped or otherwise, for transmission of pump light are evenly distributed around the perimeter of the chamber and are parallel to the axis. Another preferred embodiment of the diffusing pump chamber is a highly reflecting compound parabolic concentrator. A 2-D VCSEL array is employed as the pump source and the gain medium is located at the focusing point of the chamber. This invention demonstrates solid-state lasers that are compact, robust, low-cost, and able to produce high power output in CW or pulse modes for practical applications. An important application of the present invention is high-power solid-state lasers featuring wavelength conversion such as optical parametric oscillation and second-harmonic generation. Another important application of the present invention is injection seeding, especially for pulse mode with high repetition rates.

A composition is disclosed which is capable of being used for detection, comprising an encapsulated noble metal nanocluster. Methods for preparing the encapsulated noble metal nanoclusters, and methods of using the encapsulated noble metal nanoclusters are also disclosed. In certain embodiments, the noble metal nanoclusters are encapsulated by a dendrimer, a peptide, a small organic or inorganic molecule, or an oligonucleotide. The encapsulated noble metal nanoclusters have a characteristic spectral emission, wherein said spectral emission is varied by controlling the nature of the encapsulating material, such as by controlling the size of the nanocluster, the generation of a dendrimer, the incorporation of a functional group, and wherein said emission is used to provide information about a biological state. The emission is selected from the group consisting of nanocluster fluorescence, multiphoton excited nanocluster fluorescence, Stokes or Anti-Stokes Raman emission from the encapsulating material, and second harmonic generation.

A laser system provides harmonic generation in a laser beam pulse. In another aspect of the present invention, a laser operably remits a laser pulse, a gaseous optical medium operably creates third or greater harmonic generation in the pulse, and a controller characterizes and compensates for distortions in the pulse. A further aspect of the present invention employs multiple optical media arranged to cause cascading harmonic generations in a laser pulse.

Solid-state lasers pumped by incoherent or partially coherent, monochromatic light sources such as high power VCSEL arrays. Efficient and uniform injection of pumping energy into gain medium is achieved through spectral match of the pump source with the gain medium absorption and multi-bounce reflections of unabsorbed pump light in a diffusing pump chamber. One preferred embodiment of the diffusing pump chamber is a hollow cylinder coaxially surrounding the gain medium. One or more transparent windows, slit-shaped or otherwise, for transmission of pump light are evenly distributed around the perimeter of the chamber and are parallel to the axis. Another preferred embodiment of the diffusing pump chamber is a highly reflecting compound parabolic concentrator. A 2-D VCSEL array is employed as the pump source and the gain medium is located at the focusing point of the chamber. This invention demonstrates solid-state lasers that are compact, robust, low-cost, and able to produce high power output in CW or pulse modes for practical applications. An important application of the present invention is high-power solid-state lasers featuring wavelength conversion such as optical parametric oscillation and second-harmonic generation. Another important application of the present invention is injection seeding, especially for pulse mode with high repetition rates.

A one-dimensional transverse multiple mode laser is used for a one-dimensional illumination apparatus. A pumping light source, and a laser medium and a wavelength conversion device (nonlinear optical crystal or a nonlinear optical device) which are disposed in a resonator, are provided, and the nonlinear optical crystal or a nonlinear optical device is irradiated with a line beam obtained by exciting the laser medium in an elliptic transverse mode pattern. Then, a one-dimensional light modulation device is irradiated with the wavelength-converted line beam, and scanning with the beam modulated by the modulation device is conducted to produce a two-dimensional image. For example, in a green illumination optical system, in the case where the nonlinear optical device for obtaining visible rays through second harmonic generation from IR rays oscillated by a solid state laser medium has a periodical poling structure, stoichiometric composition periodical poling lithium tantalate having been subjected to vapor transport equilibration is used, whereby reliability is enhanced and a reduction in cost can be achieved through mass production.

A system for diagnostically evaluating the health of tissue within the fundus of an eye includes a f s laser source, an adaptive optical assembly, an imaging unit, and a computer. The adaptive optical assembly focuses a laser beam to a focal point in the fundus of the eye, and scans the fundus tissue according to a predetermined scanning pattern. Illumination of anisotropic tissue within the fundus, such as the photoreceptors and the Henle-fiber layer, induces a Second Harmonic Generation (SHG) response. Red photons, with a wavelength (λ) of about 880 nm, are converted to blue photons, with a wavelength of λ / 2, through the process of photon conversion. An imaging unit senses the blue photon return light, and uses the return light to generate an image of the fundus. The computer processes the image, and compares it to a template of healthy tissue to evaluate the health of the imaged tissue.

A harmonic generation / beam shaping system to generate a shaped beam having a harmonic relationship with a beam generated by a laser, including a first harmonic generation element and a second harmonic generation element arranged sequentially along an axial beam path extending between an input from the laser and an output of the harmonic generation / beam shaping system and at least two beam shaping elements located along the axial beam path. At least one of the least two beam shaping elements is located between the second harmonic generation element and the laser to transform the beam energy profile into a preferred profile to distribute the beam energy across a larger cross sectional area of at least one harmonic generation element or to reduce peaks in the energy distribution profile of the beam, or both, wherein the preferred profile may be a flat-top profile or a Bessel function profile.

A method and apparatus for determining the progressive potential of a disease is disclosed. The forward to backward propagating second harmonic generation signal derived from a second harmonic generation instrument is used to assess the collagen microstructure of imaged body tissue by way of numerical values that are in turn used to determine the progressive or metastatic potential of the disease. The disease may, for example, be a cancer such as breast cancer, lung fibrosis, colorectal adenocarcinoma, or the like. The apparatus may include in vivo instruments or laboratory diagnostic instruments with methods disclosed herein.

The invention relates to a multi-mode non-linear optical microscopy imaging method and device. The multi-mode non-linear optical microscopy imaging device mainly comprises a laser system, an optical scanning microscope and a non-linear optical signal detecting and acquiring system. The multi-mode non-linear optical microscopy imaging device can work in a single-laser-beam mode and a dual-laser-beam mode and can realize multi-mode non-linear optical microscopy imaging such as two-photon excited Fluorescence (TPEF) imaging, multiphoton high-order harmonic (such as second harmonic generation SHG, and third harmonic generation THG) scattering imaging, coherent Raman scattering (such as anti-Stokes CARS) microscopy imaging) on isolated biological tissues and living cells, so that various non-linear specific optical signals of biological tissue samples can be obtained in situ, so that the important basis is provided for the optical diagnosis and deep analysis of the samples. Besides, a reflection measurement manner disclosed by the invention can be further directly applied to the acquiring of various non-linear specific optical signals of live animals and the microscopy imaging.

The invention discloses a preparation method of a composite ZnO-mesoporous silica nanomaterial, namely a solvothermal in situ substitution method. The preparation method comprises the following steps of: uniformly mixing silicon-based molecular sieve powder, a ZnO precursor, a doping element and an organic solvent, adding the mixture into a high-pressure reaction kettle, and introducing a shielding gas to the reaction kettle for reaction; filtering the reaction mixture, washing, and drying to obtain dry powder; and heating and calcining the dry powder to obtain the composite ZnO-mesoporous silica nanomaterial. The composite ZnO-mesoporous silica nanomaterial prepared by the preparation method disclosed by the invention has the advantages of uniform ZnO loading, stable properties, excellent optical properties and catalytic properties and strong SHG (second harmonic generation) and TPL (two-photon luminescence) optical properties when used as an excellent catalyst for organic ester synthesis or as a laser nonlinear optical material, and is suitable for being prepared into a purple light-emitting material or a functional polymer additive. The preparation method disclosed by the invention has the advantages of wide and available raw materials, simplicity of operation and advantageous production cost.

Excitation light is split into two components with mutually orthogonal polarization. One component is fed clockwise and the other component is fed counterclockwise into a polarization maintaining loop. A second-order nonlinear optical medium disposed in the loop generates up-converted light from each excitation component by second harmonic generation, and generates down-converted light from the up-converted light by spontaneous parametric down conversion. A polarization manipulation unit manipulates the polarization direction of at least one of the excitation or down-converted components. The clockwise and counterclockwise components of the down-converted light are recombined and output as quantum entangled photon pairs having substantially the same wavelength as the excitation light. The optical components can be optimized for operation at this wavelength without the need to consider the shorter wavelength of the up-converted light.

A vertical external cavity surface emitting laser (VECSEL) in which the full-width at half maximum (FWHM) of laser light is reduced by two etalon filter layers to improve the efficiency of second harmonic (SHG) crystal is provided. The VECSEL includes: a laser chip for generating laser light; a first etalon filter layer formed on the laser chip; a second etalon filter layer that is formed on the first etalon filter layer and has a different refractive index than the first etalon filter layer; a first mirror separated from and disposed obliquely to the laser chip; a second mirror for reflecting the laser light reflected from the first mirror back to the first mirror to form a cavity with the laser chip; and an SHG crystal disposed along an optical path between the first and second mirrors and doubles the frequency of the laser light generated in the laser chip.

A pre-ionized medium created by a capillary discharge results in more efficient use of laser energy in high-order harmonic generation (HHG) from ions. It extends the cutoff photon energy, and reduces the distortion of the laser pulse as it propagates down the waveguide. The observed enhancements result from a combination of reduced ionization energy loss and reduced ionization-induced defocusing of the driving laser as well as waveguiding of the driving laser pulse. The discharge plasma also provides a means to spectrally tune the harmonics by tailoring the initial level of ionization of the medium.

A second harmonic generation laser system comprising: a non-linear frequency converting medium; and an external cavity pump laser that produces optical energy at a single mode and at a single frequency and that is disposed to provide the optical energy to the non-linear frequency converting medium.

The invention, which belongs to the integrated circuit technology field of a radio frequency wireless receiver, relates to a low-phase noise quadrature voltage-controlled oscillator based on an injection locked frequency multiplier; and the quadrature voltage-controlled oscillator can be applied to a wireless receiver integrated circuit. The quadrature voltage-controlled oscillator comprises: twovoltage-controlled oscillators, which work at a fundamental frequency f0; two pairs of coupling tubes; and a voltage-controlled oscillator, which works at second harmonic generation 2f0. Besides, thecoupling tubes and the voltage-controlled oscillator with a working frequency of 2f0 form an injection locked frequency multiplier. According to the invention, a phase noise is determined by a difference voltage-controlled oscillator with a working frequency of f0 and a phase error is determined by an injection locked frequency multiplier. Moreover, the low-phase noise quadrature voltage-controlled oscillator provided in the invention is not different from the traditional quadrature voltage-controlled oscillator; more particularly, there is no compromising relation between a phase noise and aphase error in the low-phase noise quadrature voltage-controlled oscillator, so that low phase noises can be realized on the premise that a high phase precision is ensured.

A periodically poled second harmonic generating crystal having a long axis, said crystal comprising Magnesium Oxide doped Congruent Lithium Niobate, Magnesium Oxide doped Stoichiometric Lithium Niobate, Stoichiometric Lithium Tantalate or Potassium Titanyl Phosphate wherein the poling planes of said periodically poled crystal are canted relative to said axis and a doubled, external cavity laser utilizing said crystal, comprising an external cavity pump laser section and an extra-cavity frequency doubling section.

A method for non-invasively probing at least one interface property in a layered structure having at least one interface. In one embodiment, the method includes the steps of exposing the layered structure to an incident photon beam at an incident angle to produce a reflection beam, measuring intensities of the second harmonic generation signals from the reflection beam, and identifying an initial second harmonic generation intensity and a time evolution of second harmonic generation intensity from the measured second harmonic generation intensities so as to determine the at least one interface property of the layered structure.

The invention discloses a general loop current control method for a modular multi-level converter considering low frequency oscillation. The general loop current control method is mainly used for restraining a low frequency oscillation loop current and a second harmonic generation loop current in a bridge arm loop current of the modular multi-level converter. The relation between a bridge arm voltage and the bridge arm loop current is analyzed to obtain the oscillation frequency of the low frequency oscillation loop current of the converter so as to provide beneficial evidence for the design of a control system; the cut-off frequency of a low pass filter is set according to the calculated value of the oscillation frequency; the bridge arm loop current passes through the low pass filter to obtain a direct current component, and then the direct current component is subtracted by the bridge arm loop current to obtain an alternating component of the bridge arm loop current; the alternating component contains a harmonic component of the low frequency oscillation loop current and a harmonic component of the second harmonic generation loop current; the alternating component passes through a regulator to obtain a control reference voltage of the bridge arm loop current, and the control reference voltage is added to a modulating signal. By means of the general loop current control method, a low frequency oscillation component and a second harmonic generation component in the bridge arm loop current are simultaneously restrained, the loop current control system is simplified, split-phase control over the loop currents is realized, loss of the converter is lowered, and the dynamic stability of the system is enhanced.

A laser system provides harmonic generation in a laser beam pulse. In another aspect of the present invention, a laser operably remits a laser pulse, a gaseous optical medium operably creates third or greater harmonic generation in the pulse, and a controller characterizes and compensates for distortions in the pulse. A further aspect of the present invention employs multiple optical media arranged to cause cascading harmonic generations in a laser pulse.