686 results about "Acousto-optic modulator" patented technology

An optical coherence tomography (OCT) system including an interferometer provides illuminating light along a first optical path to a sample and an optical delay line and collects light from the sample along a second optical path remitted at several scattering angles to a detector. In one embodiment, illuminating light is directed along a number of incident light paths through a focusing lens to a sample. The light paths and focusing lens are related to the sample and to both the incident light source and the detector. In another embodiment, a focusing system directs light to a location in the sample. A transmission grating or acousto-optic modulator directs light from the sample at an angle representative of the wavelength of the incident light on the transmission grating or acousto-optic modulator.

The invention discloses a COTDR (coherent detection based optical time-domain reflectometry) fused long-distance coherent detection brilouin optical time-domain analyzer which comprises a narrow-linewidth laser, two couplings, a microwave signal source, an electro-optic modulator, an isolator, a long-distance sensing optical fiber, an optical circulator, a 3 db coupling, a pulse modulator, an Er-doped fiber amplifier, a scrambler, a pulse signal generator, a balancing photoelectric detector, an electrical frequency spectrum analyzer, a data processing module and an acousto-optic modulator. According to the invention, the signal-to-noise ratio of BOTDA (brilouin optical time domain analysis) is improved by using a coherent detection method, a non-local effect of a BOTDA system is reduced in a double-sideband detection mode, and the sensing distance is more than 70 km under the condition of no light amplification such as raman; and according to the invention, the COTDR is fused to a coherent detection based BOTDA system, and the system can run in a breakpoint testing mode, so that the defect that the traditional BOTDA can not run when a sensing fiber has breakpoints and can not carry out positioning on breakpoints is effectively overcome, thereby enhancing the adaptability and practicability of the sensing system.

An optical pulse source comprising a DPSS pump laser, a photonic crystal fiber (PCF), and acousto-optic modulator (AOM) gating device is disclosed. The pump pulses are coupled through lenses to the AOM gating device, which is synchronized to the pump laser and is operable to gate the pump pulses to a reduced repetition rate Rr=Rf/N, where Rf is the pump laser fundamental frequency. The pulses from the AOM are injected via optics into the PCF. Propagation through the PCF causes the pulses to broaden spectrally to produce optical supercontinuum pulses. An optical pulse source that further includes an acousto-optical tunable filter (AOTF) operable to convert the optical supercontinuum pulses into wavelength variable output pulses is also provided. A method of scaling the energy of the optical supercontinuum pulses is also disclosed.

An apparatus for adjusting the wavelength of a laser capable of lasing at multiple wavelengths by using a single acousto-optical modulator and a pair of optical reflectors inside a laser cavity. By adjusting the frequency and amplitude of the radio-frequency source to the acousto-optical modulator, undesired wavelengths are suppressed in the laser cavity, leaving appreciable gain only at the desired wavelength.

The present invention addresses the problem of stabilizing signals in magnetic field measurement using optical pumping. In order to solve the problem, disclosed is a light source apparatus (10) that is characterized in having: a light intensity fluctuation detection circuit (130) that detects intensity fluctuation of light outputted from a laser output unit (11); and an acousto-optic modulator (121) that corrects light intensity on the basis of light intensity fluctuation detected by means of the light intensity fluctuation detection circuit (130) such that the light intensity is constant Furthermore, a magnetic field measuring apparatus of the present invention is characterized in having: one sensor unit that passes therethrough light outputted from a light source unit: and a signal control processor that eliminates the light intensity fluctuation on the basis of two lights passed through the sensor unit.

Methods and apparatus for reducing the coherence of an optical signal that is used to interrogate optical interferometric sensors are disclosed. The optical field phasor of the interrogation source is modulated in a controlled manner to produce a broadened optical source power spectrum at the output of the source unit. The output from the source unit is launched into an optical sensor network, comprising a multiple of optical pathways from its input to the detection unit, where pairs of optical pathways form sensor interferometers. A compensating interferometer with delay difference similar to the sensor delay difference may be arranged in a serially coupled manner with the optical sensor network, either before or after the network. The optical output power from the source unit may either be continuous or pulsed with a pulse duration similar to the sensor delay. The coherence modulation may be performed through direct modulation of the source or through external modulation of the light with piezoelectric ring modulator, a Lithium niobate phase or intensity modulator, or an acoustooptic modulator.

Femtosecond pump/probe experiments using short X-Ray and optical pulses require precise synchronization between 100 meter-10 km separated lasers in a various experiments. For stabilization in the hundred femtosecond range a CW laser is amplitude modulated at 1-10 GHz, the signal retroreflected from the far end, and the relative phase used to correct the transit time with various implementations. For the sub-10 fsec range the laser frequency itself is upshifted 55 MHz with an acousto-optical modulator, retroreflected, upshifted again and phase compared at the sending end to a 110 MHz reference. Initial experiments indicate less than 1 fsec timing jitter. To lock lasers in the sub-10 fs range two single-frequency lasers separated by several teraHertz will be lock to a master modelocked fiber laser, transmit the two frequencies over fiber, and lock two comb lines of a slave laser to these frequencies, thus synchronizing the two modelocked laser envelopes.

The invention discloses an optical fiber distributed disturbance sensor which comprises an optical fiber laser, a bidirectional distributed Raman amplification unit and a photoelectric detection and signal processing unit, wherein an output end of the optical fiber laser is connected with a first coupler; two output ends of the first coupler are respectively connected with an acoustic optical modulator and a third coupler; the bidirectional distributed Raman amplification unit is connected with the acoustic optical modulator by a first circulator and is connected with the third coupler by the first circulator; the photoelectric detection and signal processing unit is connected with the third coupler and used for receiving an interference-enhanced optical signal in the third coupler, converting the optical signal into an electric signal and carrying out subsequent data processing. In the optical fiber distributed disturbance sensor, the back scattering light intensity and the signal-to-noise ratio of the tail end of the optical fiber can be improved by the bidirectional distributed Raman amplification structure so as to improve the sensing distance of the optical fiber distributed disturbance sensor; and the light power received by a detector can be improved through the interference of a part of continuous light output by a light source and the back scattering light, so as to improve the signal-to-noise ratio of the system. The sensor is a combination of conventional photoelectric devices, has a simple structure and is easy to realize.

The invention discloses a device of measuring the line-width of a laser with narrow line-width and a method of measuring the line-width based on a optical fiber delay self-heterodyne method; in the hardware device, an optical fiber delay line is connected between a first and a second couplers; an acousto-optic modulator is connected between the first and the second couplers; the measured laser is connected to the input of the first coupler, and a photoelectric detector is connected to the output of the second coupler; the photoelectric detector is connected with a spectrum analyzer. In the line-width measurement, simulation models of the line-width triangle v of the laser and the spectrum-width triangle f of the photoelectric current heterodyne signal are built in the frequency shift delay self-heterodyne methodology, and the function relation between the line-width triangle v of the laser and the spectrum-width triangle f of the photoelectric current heterodyne signal is obtained fitting of the three-level proportion function model. The invention presents that with the short optical fiber delay self-heterodyne method, the device can eliminate the deficiency of greatly reduced measuring precision because of not enough delayed time in the delay self-heterodyne method when the length of the delay optical fiber is less than 6 times coherence length of the laser, so as to provide an effective method of precisely measuring the line-width of the laser with narrow line-width in projects.

An RF power controller arrangement prevents excessive RF power-based thermal loading of an RF signal processing device, such an as acousto-optic modulator, by controllably constraining the product of the average on-duration of a baseband modulation signal and RF input power to realize no more than a prescribed value of RF energy supplied to the modulator.

The invention discloses a laser cavity outer power stabilizing device and a laser cavity outer power stabilizing method. Reference signals are taken out from a laser system through an unpolarized beam splitter, and an acoustic optical modulator is used as an executor to form a negative feedback loop so as to realize stabilization of optical power. A 1/2 wave plate and a polarizing beam splitter are inserted into a light path to perform polarization and purification, and polarization drift of a laser system can be converted into power fluctuation, so that the splitting ratio of the unpolarized beam splitter is constant and the long-term stability of the optical power is improved; and the acoustic optical modulator is used as an execution element, and the amplitude modulation end of a driver of the acoustic optical modulator can be modulated by using low voltage, so that the noise of a control circuit can be remarkably reduced, the short-term stability of high optical power can be realized, and meanwhile, the stability of the optical power in a large dynamic range can be realized.

The invention discloses a rubidium atomic magnetometer and a magnetic field measuring method. Based on the principle of nonlinear magneto-optic rotation, and through combination of timing control and tracking type frequency locking control, the atomic magnetometer achieves a large dynamic measurement range, high magnetic field sampling rate and high sensitivity. A DSP timing control module controls on-off of an acousto-optic modulator and a radio-frequency signal source in the physical part of the rubidium atomic magnetometer according to timing combination to adjust the magnetic field sampling rate N. The DSP timing control module further controls acquisition triggering of a data acquisition card. A calculation unit gets the Larmor precession frequency (f) through fast Fourier transform with use of a received rubidium atom Larmor precession free relaxation signal, and further calculates the value of an external magnetic field. The calculation unit selects a high magnetic field sampling rate module or a low magnetic field sampling rate module before measurement according to the pre-judged dynamic range of a to-be-measured magnetic field, and sets whether a tracking type frequency locking work mode is used when the low magnetic field sampling rate module is selected. In the working process, data is acquired and processed, and the value of the magnetic field is output.

A method and apparatus for reducing speckle during inspection of articles used in the manufacture of semiconductor devices, including wafers, masks, photomasks, and reticles. The coherence of a light beam output by a coherent light source, such as a pulsed laser, is reduced by disposing elements in a light path. Examples of such elements include optical fiber bundles; optical light guides; optical gratings; an integrating sphere; and an acousto-optic modulator. These various elements may be combined as desired, such that light beams output by the element combinations have optical path length differences that are greater than a coherence length of the light beam output by the coherent light source.

The invention discloses a double-beam multi-functional z scanning optical non-linear measuring device and a double-beam multi-functional z scanning optical non-linear measuring device method. The device uses two light sources and can conveniently switch the light sources; an adjustable attenuation slice is adopted, so laser power is continuously adjustable from 0 and 100 percent; an acoustic optical modulator and a signal generator are adopted, so the pulse width and pulse period of emergent laser are adjustable; and transmission open hole and transmission closed hole data of a sample can be measured and reflecting open hole and transmission open hole data of the sample can also be measured. The device and the method not only can measure nonlinear absorption coefficient and nonlinear refractive index of a transparent sample, but also can measure nonlinear refractive index of a nontransparent sample; and a cold light source serving as an illumination light source is added into the device, a CCD camera is used for observing surface appearance of the sample and an optical filter is used for filtering the effect of the laser, so the measuring accuracy and correctness of the nonlinear absorption coefficient and nonlinear refractive index of the transparent sample and a partially transparent sample are enhanced.

Laser pulses are selected from a group of closely spaced laser pulses with an optical modulator by adjusting pulse timing relative to an impingement interval. An adjusted pulse is moved from an impingement interval to a non-impingement interval and is blocked. The blocked laser source is stabilized by running nearly continuously. Pulse selection with multiple laser sources is achieved with a single acousto-optic modulator.

A distribution type sensing optical fiber is characterized in that thousands of fiber gratings with ultra-low reflectance are carved on a common single-mode fiber, so that the common single-mode fiber and the fiber gratings are integrated; the reflectance R of the fiber gratings is set to be 0.1-1%, and accordingly multi-path reflection is effectively lowered. An intensity distribution type demodulation system comprises a distribution type feedback semiconductor laser device, an acousto-optic modulator, a circulator, a coupler, the distribution type sensing optical fiber, a photoelectric detector and an intensity modulation device. The distribution type feedback semiconductor laser device sends out continuous laser into the acousto-optic modulator, the laser is modulated into pulse laser with the pulse width of W, the pulse laser enters the circulator and sequentially travels through a first grating, a second grating, a third grating to the Nth grating on the distribution type sensing optical fiber, reflected light enters an unbalance interferometer from the C3 end of the circulator for interference, interference light output by the unbalance interferometer enters the photoelectric detector, and the photoelectric detector outputs electric signals to an intensity demodulation device.

A laser-based workpiece processing system includes sensors connected to a sensor controller that converts sensor signals into focused spot motion commands for actuating a beam steering device, such as a two-axis steering mirror. The sensors may include a beam position sensor for correcting errors detected in the optical path, such as thermally-induced beam wandering in response to laser or acousto-optic modulator pointing stability, or optical mount dynamics.

The invention relates to a femtosecond laser carrier envelope offset frequency lock system based on a heterodyne interferometric method. The system is characterized by comprising a femtosecond laser light source system, an acousto-optic modulator, a controllable optical path retardation device, a light splitting prism, a first photoelectric detector, a phase lock amplifier, a phase difference voltage conversion device and a PID controller. Heterodyne interferometry can be conducted on first-level phase-shift diffraction light modulated by the acousto-optic modulator and zero-level diffraction light which is not modulated, and after mixing of interference signals with different wavelengths, direct-current level lock pulse envelope alignment is achieved; optical frequency comb envelope offset frequency is locked by means of interference signal phase, the linear process does not exist, high non-linear optical fibers, frequency doubling crystals and the like are not needed, and the system is simple in structure and low in requirement for laser energy.

The invention provides an acoustic optical modulator-based high-stability laser frequency scanning device. Laser passes through two coaxial diaphragms and is divided into two paths by a polarization beam splitter prism; one path of output passes through a quarter-wave plate, a No. 3 diaphragm and a No. 1 lens which are coaxial with one another, and enters a No. 1 acoustic optical modulator; diffraction-order laser light passes through a No. 4 diaphragm and a No. 2 lens which are coaxial with each other, and is reflected by a zero-degree high reflective mirror along an original path; the other path of output passes through two 45-degree planar reflecting mirrors and is regulated into parallel light through an optical fiber of which the two ends are matched with optical fiber matching heads, and the parallel light enters a No. 2 acoustic optical modulator through a No. 1 glass flat plate and a No. 3 lens in sequence; diffracted light enters a No. 2 glass flat plate through a No. 5 diaphragm and a No. 4 lens. By adopting the device, the spatial stability and power stability of laser light can be ensured at the same time.

The invention discloses a dual-wavelength superheterodyne-interference wide-range high-precision real-time displacement measuring system and method. The system is composed of two lasers between which the wavelength difference is deltalambda, three polarization splitting prisms, four splitting prisms, two acousto-optic modulators, four 1/4 waveplates, five planar mirrors, three Polaroids, a super-narrowband filter plate, two large-bandwidth transimpedance photoelectric detectors, two low-bandwidth high-sensitivity photoelectric detectors, a reference reflector, a measured reflector, a signal processing circuit and a host computer. According to the invention, a synthesized wavelength interference signal generated by dual wavelengths is used to improve the measuring range of the system, so that the measuring range of the system is greater than the range of single-wavelength interference; a superheterodyne interference method is used to demodulate and filter output signals, the phase of the synthesis wavelength can be measured directly, and real-time measurement is realized; and the super-narrowband filter plate is used to collect single-wavelength interference signals, and the precision of single-wavelength interference measurement is ensured while the measuring range is widened.

The invention relates to a collinear femto-second laser polarized pump detecting system, comprising that a pulse laser is output by a polarized output pulse laser; the laser is rotated in the polarization direction by a wave plate; a light-splitting device divides the laser beam into two beams vertical to each other in the polarization direction; a reflector receives and reflects the laser beams; an acoustooptic modulator modulates the laser beams; an aperture transmits the modulated laser beams; an acoustooptic modulator driver transmits modulation signals for the acoustooptic modulator; an electrically controlled travelling carriage moves forward and backward; an analyzer transmits the laser beams which are vertical to each other in the polarization direction; a photodetector receives the laser transmitted by the analyzer; a magnet fixes an adjusting rack so as to fix a sample; a focusing lens irradiates the laser on the surface of the sample; and an electrically controlled revolving stage fixes the wave plate. The invention combines the two beams of light vertical to each other in the polarization direction by polarized coupling; therefore, the system can ensure spatial coherence of the two beams of light on the sample, thereby avoiding the problem of adjusting direction of light beam; thus, the operation is simpler.