464 results about "Spontaneous emission" patented technology

A laser utilizes a cavity design which allows the stable generation of high peak power pulses from mode-locked multi-mode fiber lasers, greatly extending the peak power limits of conventional mode-locked single-mode fiber lasers. Mode-locking may be induced by insertion of a saturable absorber into the cavity and by inserting one or more mode-filters to ensure the oscillation of the fundamental mode in the multi-mode fiber. The probability of damage of the absorber may be minimized by the insertion of an additional semiconductor optical power limiter into the cavity. To amplify and compress optical pulses in a multi-mode (MM) optical fiber, a single-mode is launched into the MM fiber by matching the modal profile of the fundamental mode of the MM fiber with a diffraction-limited optical mode at the launch end, The fundamental mode is preserved in the MM fiber by minimizing mode-coupling by using relatively short lengths of step-index MM fibers with a few hundred modes and by minimizing fiber perturbations. Doping is confined to the center of the fiber core to preferentially amplify the fundamental mode, to reduce amplified spontaneous emission and to allow gain-guiding of the fundamental mode. Gain-guiding allows for the design of systems with length-dependent and power-dependent diameters of the fundamental mode. To allow pumping with high-power laser diodes, a double-clad amplifier structure is employed. For applications in nonlinear pulse-compression, self phase modulation and dispersion in the optical fibers can be exploited. High-power optical pulses may be linearly compressed using bulk optics dispersive delay lines or by chirped fiber Bragg gratings written directly into the SM or MM optical fiber. High-power cw lasers operating in a single near-diffraction-limited mode may be constructed from MM fibers by incorporating effective mode-filters into the laser cavity. Regenerative fiber amplifiers may be constructed from MM fibers by careful control of the recirculating mode. Higher-power Q-switched fiber lasers may be constructed by exploiting the large energy stored in MM fiber amplifiers.

A method for increasing the speed of a bipolar transistor, includes the following steps: providing a bipolar transistor having emitter, base, and collector regions; providing electrodes for coupling electrical signals with the emitter, base, and collector regions; and adapting the base region to enhance stimulated emission to the detriment of spontaneous emission, so as to reduce carrier recombination lifetime in the base region.

Apparatus and method for amplifying laser signals using segments of fibers of differing core diameters and / or differing cladding diameters to suppress amplified spontaneous emission and non-linear effects such as four-wave mixing (FWM), self-phase modulation, and stimulated Brillouin and / or Raman scattering (SBS / SRS). In some embodiments, different core sizes have different sideband spacings (spacing between the desired signal and wavelength-shifted lobes). Changing core sizes and providing phase mismatches prevent buildup of non-linear effects. Some embodiments further include a bandpass filter to remove signal other than the desired signal wavelength and / or a time gate to remove signal at times other than during the desired signal pulse. Some embodiments include photonic-crystal structures to define the core for the signal and / or the inner cladding for the pump. Some embodiments include an inner glass cladding to confine the signal in the core and an outer glass cladding to confine pump light in the inner cladding.

A laser amplifier includes a laser active slab with a source of pump power to amplify an input laser beam, the laser active slab including a block of laser active material having opposed lateral faces defining a wedge lateral dihedral angle, opposed longitudinal faces, and opposed parallel transverse faces, the wedge lateral dihedral angle specified to minimize parasitic amplified spontaneous emission. The source of pump power may be one or more laser diode bars and microlenses producing a gain sheet in the laser active slab. The lateral faces may include optical coatings highly transmitting at a wavelength of the pump power and highly reflecting at a lasing wavelength to provide a folded path for the input laser beam though the gain sheet. The laser amplifier may optionally include one or more external mirrors highly reflecting at the lasing wavelength positioned and oriented to provide one or more additional zig-zag passes through the gain sheet for the input laser beam and to provide a multi-pass-amplified laser beam.

An optical apparatus design and method for suppressing cladding-mode gain in fiber- and other waveguide-amplification devices. In some embodiments, a signal-wavelength-absorbing core or region is included within the pump cladding or the pump waveguide, in order to absorb signal-wavelength radiation that occurs in the regions where only pump-wavelength radiation is wanted. This absorbing region prevents cladding-mode gain, thus preserving more pump-wavelength excitation for amplifying the desired signal radiation. In other embodiments, the refractive-index profile of the fiber or other waveguide is adjusted to reduce the numeric aperture and thus reduce the angle of light that will remain in the cladding. Since amplified spontaneous emission (ASE) occurs at all angles, a lower-NA fiber will leak a higher proportion of ASE (since a relatively lower portion of the ASE radiation is within the smaller angle that is retained within a low-NA fiber), while pump light, which was introduced into the fiber within the lower-NA angle will remain in the cladding.

A semiconductor laser device is made of a group III nitride semiconductor having a major growth surface defined by a nonpolar plane or a semipolar plane. The semiconductor laser device includes a cavity having an active layer containing In and distributed Bragg reflectors coating both cavity end faces of the cavity respectively. In each of the distributed Bragg reflectors, a central wavelength λc of a reflectance spectrum satisfies the relation λSP−10 nm≦λc≦λSP+10 nm with respect to an emission peak wavelength λSP of spontaneous emission in the active layer.

The present invention relates to an optical transmission apparatus capable of suppressing a transitional gain variation when a number of signal wavelengths changes, and maintaining communication quality in optical signals. The optical transmission apparatus is provided with an optical power control device that varies light power of light for each wavelength component corresponding to a wavelength channel, the light including signal light and spontaneous emission light; a wavelength arrangement information obtaining unit that obtains arrangement information of the wavelength channel of the signal light; and a control unit that controls the power control device based on the arrangement information obtained at the wavelength arrangement information obtaining unit so that light power of a wavelength component of the signal light and light power of a wavelength component other than the wavelength component of the signal light become substantially equal.

Provided is an inverted population of hydrogen, formed from a novel catalytic reaction of hydrogen atoms to form lower-energy hydrogen. The inverted population of hydrogen is capable of lasing. The power may be utilized as laser light or the light due to stimulated or spontaneous emission may be converted to electricity with a pholon-to-electric converter such as a photovoltaic cell.

The invention discloses a method for locking Raman gains of a target and a Raman OFA (optical fiber amplifier). The OFA comprises a coupler and a control unit, wherein the control unit comprises a gain locking module; and a detection circuit formed by a filter and an optical power detector is connected between the output end of the coupler and the input end of the control unit. In the method, the control unit is utilized to adjust the power of a pump laser, thus the power of detected OOB (out of band) ASE (amplified spontaneous emission) optical signals is consistent with that of the targeted OOB ASE optical signals, and the amplification gains of the target is locked. The optical path structure of the OFA is simple, the Raman gains can be configured flexibly in accordance with the circuit conditions, and the gains of the Raman OFA can be automatically controlled and locked.

An optical network terminator for terminating and reducing the accumulated noise in optical networks, particularly ring based networks. The terminator eliminates problems of noise accumulation from amplifier spontaneous emission (ASE), thermal noise, etc., while providing bi-directional communications in the optical network. The optical network may have any topology including ring, star, mesh, point-to-point, etc. In the case of an optical ring, the ring is broken and an optical terminator is placed in line therewith. The optical network terminator includes a filer such as an optical demultiplexer / multiplexer or Fiber Bragg Grating (FBG) based filter. Each individual wavelength of light is filtered and a multi-wavelength optical output is generated whereby the noise accumulation is removed. Each channel is adapted to only pass a band-limited signal around the center frequency corresponding to the wavelengths supported by the particular optical ring network. Channel equalization uses variable optical attenuators and monitors in line with each channel. Channels currently not in use may be disconnected from the ring remotely by setting the corresponding optical attenuator to a low enough level.

A fluorescence light scanning microscope (2) comprises a light source providing excitation light (8) for exciting a fluorophore in a sample to be imaged for spontaneous emission of fluorescence light, and suppression light (7) for suppressing spontaneous emission of fluorescence light by the fluorophore on a common optical axis (4), the suppression wavelength differing from the excitation wavelength; an objective (19) focusing both the excitation (8) and the suppression (7) light to a focus point; a detector (21) detecting fluorescence light (11) spontaneously emitted by the fluorophore; and a chromatic beam shaping device (1) arranged on the common optical axis (4), and including a birefringent chromatic optical element (3) adapted to shape a polarization distribution of the suppression light (7) such as to produce an intensity zero at the focus point, and to leave the excitation light such as to produce a maximum at the focus point.

Provided is an inverted population of hydrogen, formed from a novel catalytic reaction of hydrogen atoms to form lower-energy hydrogen. The inverted population of hydrogen is capable of lasing. The power may be utilized as laser light or the light due to stimulated or spontaneous emission may be converted to electricity with a photon-to-electric converter such as a photovoltaic cell.

A method of determining the gain characteristic of a Raman amplifier includes the steps of launching a pump light signal into a fiber; preliminary adjusting the power of the pump light signal to a value that lies in a range where the amplified spontaneous emission noise originating from the pump light signal is substantially proportional to the on / off gain provided by the power of the pump light signal; monitoring the power of the amplified spontaneous emission noise signal; varying the power of the pump light signal; measuring a variation in the power of the amplified spontaneous emission noise signal corresponding to the pump power variation; and determining the gain characteristic of the amplifier from the relative variation in pump power and the measured variation in noise power.

Systems and methods for devices that include a structure having at least one resonant cavity and at least one emitter having an emission frequency that is substantially in the telecommunication wavelengths are provided. The emission frequency can be coupled to the resonant frequency of resonant cavity so that emitted wavelengths corresponding to the resonant wavelengths of the resonant cavity are enhanced. Moreover, the devices of the present invention may be capable of operating at room temperatures.

A method of high spatial resolution imaging a structure in a sample comprises: marking the structure with molecules of a fluorescent dye; selecting a first wavelength for excitation light which excites the molecules of the fluorescent dye via a multi photon process for spontaneous emission of fluorescent light; focussing pulses of the excitation light into the sample to excite those molecules of the fluorescent dye present in a focal area of the focussed excitation light; selecting a second wavelength shorter than the first wavelength for de-excitation light which de-excites excited molecules of the fluorescent dye prior to their spontaneous emission; during a plurality of the pulses of the excitation light, continuously directing the de-excitation light onto the sample to de-excite excited molecules of the fluorescent dye, which are located outside an measurement area which is a fraction of the focal area; and recording the fluorescent light spontaneously emitted by the molecules of the fluorescent dye in the sample.

A parallel optical fiber amplifier having a configuration in which a C-band silica-based erbium-doped fiber amplifier (EDFA) stage and an L-band EDFA stage are coupled together in parallel in such a fashion that a reverse amplified spontaneous emission (ASE) light emitted from the C-band and / or L-band EDFA stage is reused as a secondary pumping source for an amplification in the L-band EDFA stage. In the optical fiber amplifier of the present invention, the reverse ASE light emitted from the C-band EDFA stage and the reverse ASE light emitted from the L-band EDFA stages supplied to the L-band EDFA stage so that they can be reused for improving the power conversion efficiency of the entire system and for reducing the noise factor thereof.

A spontaneous firing explosive composition for use in a gas generator for an airbag containing a fuel, an oxidizer, a combustion modifier, and a binder.

A particle measurement system using a single component light collecting system with an aperture having a portion within direct view of the light detector. An aperture assembly extending into a sample may be self-concealing by having an extended portion to block light from directly illuminating the light detector. Alternatively, a smooth, reflective inside surface of the aperture assembly provides for self-concealment by causing spontaneous emitted light to have low angles of reflection. In either case, spontaneously emitted light is substantially prevented from reflecting directly into the light detector, thereby reducing light noise to the level of molecular noise.

A new broadband source having a discrete set of spectral emission lines having high peak power in each line is provided by placing a gain medium in a reflective cavity comprising reflective front and back surfaces. A cavity feedback factor less than unity is achieved by providing reflectivity of one surface substantially lower than the reflectivity of the other surface such that spontaneous emission in the gain medium is linearly amplified just below the lasing threshold. In an alternative arrangement, a movable external back surface placed at a prescribed distance from the gain medium provides a means to achieve a free spectral range and finesse of the emission lines to match a pitch of a detector array in a SD-OCT system. By simultaneously providing high power to each detector element of the array, sensitivity and imaging speed of SD-OCT system are significantly improved.

A fiber amplifier module for amplifying a signal pulse includes an optically pumped double-pass fiber amplifier in which a fiber Bragg grating reflects an amplified pulse in between the first and second amplification passes, and transmits most forward-propagating amplified spontaneous emission (ASE) generated by the optical pumping. The reflected amplified pulse from the double-pass amplifier, and reverse-propagating ASE generated by the optical pumping are reflected from another fiber Bragg grating that again reflects the amplified pulse and transmits most of the ASE. The twice-reflected amplified pulse can be delivered from the amplifier as an output pulse or passed to another amplifier module for further amplification. The amplifier fiber is operated in a saturated or near saturated mode. This reduces amplification of any portion of the forward-propagating ASE that is reflected into reverse propagation by the fiber Bragg grating of the double-pass amplifier.

Optical telecommunications system, comprising: a station (1) for transmitting optical signals, comprising a transmission signal generator (2), capable of generating at least two signals at wavelengths lying within a band of predetermined width, and a multiplexer (3) of the optical signals; a station (8) for receiving the optical signals; and an optical fibre line connecting the said multiplexer of the transmission station to the receiving station. The optical fibre line includes at least one optical amplifier (7) comprising at least one fibre (12) doped with a rare earth, at least one source of pumping radiation (14) for the said doped fibre, and a gain stabilization circuit. The gain stabilization circuit comprises: a separator of the transmission signals from the spontaneous emission of the amplifier, connected after the doped fibre and capable of sending the transmission signals to the output of the amplifier and the spontaneous emission to a further output, and a loop circuit for the re-circulation of the said spontaneous emission collected from the said further output and re-injected before the said doped fibre of the amplifier.

A spontaneous emission display includes a support, a first electrode section provided on the support and having a fine wire structure portion made of a conductive metal and a translucent conductive film, and a display section formed on the first electrode section and having a light-emitting layer. The volume resistance of the fine wire structure portion of the first electrode is 10−4 Ω·cm or less and / or the surface resistance thereof is 100 Ω / sq or less. The volume resistance of the conductive film is 0.05 Ω·cm or more and / or the surface resistance thereof is 100 Ω / sq or more. When the surface resistance of the first electrode section before a bending test is denoted by R1 and that after the bending test is denoted by R2, R2 / R1<18 is satisfied.

The present invention includes a method of fabricating an optically-pumped disk-array solid-state laser amplifier having one or more disks, wherein one or more of the one or more disks having two opposed surfaces, including the steps of patterning a photoresist mask on one or more of the two opposed surfaces of the one or more disks and processing the one or more disks through the patterned photoresist mask, whereby the temperature profile improved radially across the disk's surface, amplified spontaneous emission are reduced, or combinations thereof.

The present invention provides a semiconductor light emitting device realizing lower detection level of spontaneous emission light by a semiconductor photodetector and improvement in light detection precision by selectively reflecting spontaneous emission light. The semiconductor light emitting device includes a semiconductor light emitting element for generating light including stimulated emission light having a wavelength λo and spontaneous emission light having a wavelength band including the wavelength λo, a multilayer filter having a stack structure in which a low-refractive-index layer having a thickness of λ1 / (4×na) (λ1<λo and na denotes refractive index) and a high-refractive-index layer having a thickness of λ1 / (4×nb) (nb>na and nb denotes refractive index) are alternately stacked, and a semiconductor photodetector having a light absorption layer that absorbs a part of light passed through the multilayer filter.

The invention discloses a multi-wavelength light source-based Brillouin optical time domain reflectometer which comprises a multi-wavelength laser, a coupler, an electrooptical modulator, an erbium-doped optical fiber amplifier, an optical filter, a circulator, a double-balanced detector and a signal acquiring and processing system, wherein continuous light of the multi-wavelength laser is divided into two paths, wherein one path is modulated into pulse light through the electrooptical modulator and the other path is modulated to obtain continuous light of a local oscillator through an electrooptical modulator sideband. Multi-wavelength detection pulse light is amplified by the erbium-doped optical fiber amplifier, subjected to spontaneous emission noise filtration by the optical filter and is injected into a sensing optical fiber by the circulator. Stokes Brillouin back scattering light in the sensing optical fiber is coherent with local oscillator light through the circulator, is subjected to photovoltaic conversion through the double-balanced detector and then is fed into the signal acquiring and processing system to obtain a Brillouin scattering spectrum on the whole optical fiber and further obtain the temperature and strain distribution on the optical fiber.

The invention relates to optical fibers for use in optical amplification of light, such as in optical fiber amplifiers and lasers and for use in delivery of high power light, in particular to a scheme for reducing amplified spontaneous emission at undesired wavelengths. The invention further relates to articles, methods and use. An object of the invention is achieved by a micro-structured optical fiber, which is adapted to guide light by the photonic bandgap effect and to have one or more pass bands and at least one stop-band over a wavelength range from λstop1 to λstop2. In an aspect of the invention, the at least one stop-band provides filter functions that suppress nonlinear effects. In another aspect, the core region is actively doped, and the active material has an emission spectrum with a higher value of the emission cross section σE at a wavelength λASE between λstop1 and λstop2 than outside said wavelength range such that amplified spontaneous emission and lasing within the wavelength range from λstop1 to λstop2 is reduced. In still another aspect, the optical fiber exhibits photonic bandgaps at different wavelength ranges in different radial directions of a cross section of the optical fiber.

A vertical cavity surface emitting laser (VCSEL) integrated with a photodetector is provided. The photodetector is attached to a bottom surface of the VCSEL by a bonding layer, which includes a window of a predetermined diameter. The bonding layer is a eutectic bonding layer. An air gap exists within the window and mainly transmits a laser beam. Most of spontaneous emission light incident at an angle is blocked by an area of the bonding layer other than the window, and even some of the spontaneous emission light that heads toward the window cannot easily passes through the window due to a big difference between refractive indices of a semiconductor layer and the air. Thus, the eutectic bonding layer greatly reduces a voltage drop at an interface between the VCSEL and the photodetector, thereby contributing to mass production.