31 results about "Third order dispersion" patented technology

By compensating polarization mode-dispersion as well chromatic dispersion in photonic crystal fiber pulse compressors, high pulse energies can be obtained from all-fiber chirped pulse amplification systems. By inducing third-order dispersion in fiber amplifiers via self-phase modulation, the third-order chromatic dispersion from bulk grating pulse compressors can be compensated and the pulse quality of hybrid fiber / bulk chirped pulse amplification systems can be improved. Finally, by amplifying positively chirped pulses in negative dispersion fiber amplifiers, low noise wavelength tunable seed source via anti-Stokes frequency shifting can be obtained.

By compensating polarization mode-dispersion as well chromatic dispersion in photonic crystal fiber pulse compressors, high pulse energies can be obtained from all-fiber chirped pulse amplification systems. By inducing third-order dispersion in fiber amplifiers via self-phase modulation, the third-order chromatic dispersion from bulk grating pulse compressors can be compensated and the pulse quality of hybrid fiber / bulk chirped pulse amplification systems can be improved. Finally, by amplifying positively chirped pulses in negative dispersion fiber amplifiers, low noise wavelength tunable seed source via anti-Stokes frequency shifting can be obtained.

Compact high brightness light sources for the mid and far IR spectral region, and exemplary applications are disclosed based on passively mode locked Tm fiber comb lasers. In at least one embodiment the coherence of the comb sources is increased in a system utilizing an amplified single-frequency laser to pump the Tm fiber comb laser. The optical bandwidth generated by the passively mode locked Tm fiber comb laser is further decreased by using simultaneous 2nd and 3rd order dispersion compensation using either appropriate chirped fiber Bragg gratings for dispersion compensation, or fibers with appropriately selected values of 2nd and 3rd order dispersion. Fibers with large anomalous values of third order dispersion, or fibers with large numerical apertures, for example fibers having air-holes formed in the fiber cladding may be utilized.

The invention discloses a spectrum OCT (optical coherent tomography) image method and relative system based on optical scanning delay line, wherein it arranges an optical scanning delay line in a reference arm of a spectrum OCT system, to realize scatter-free phase shift of reference light and system scatter compensation. And when guides in optical scanning delay line based on double gratings, the invention can generate group speed scatter and third-order scatter formed by any marks in large change range, to accurately match the scatters of reference arm and sample arm in spectrum OCT system. The scatter-free phase shift and scatter compensation can assure the axial resolution ratio of spectrum OCT system, eliminate coherent noise, and expand the image depth for one time. The invention is significant for dual-spectrum OCT system with ultra-high resolution ratio.

A fiber Chirped Pulse Amplification (CPA) laser system includes a fiber mode-locking oscillator for generating a laser for projecting to a fiber stretcher for stretching a pulse width of the laser. The fiber CPA laser system further includes a multistage amplifier for amplifying the laser and a high-order dispersion compensating compressor for compensating high order dispersions and compressing the pulse width of the laser. The high-order dispersion compensating compressor further includes a pair of gratings coupled with a pair of prisms, a grating pair engraved on the surfaces of a pair of prisms, a chirped grating pair and a phase modulator consists of a grating and a deformable mirror, for generating a negative group velocity dispersion (GVD) and a negative third order dispersion (TOD) for the laser.

An optical component of the present invention is compensated its optical dispersion, including third order dispersion, at low loss using optical dispersion compensating element comprising multi-layer film. In the optical component, an optical dispersion compensating element and a functional element are connected in series along an optical path.

The present invention discloses dispersion compensating method and system for optically coherent tomographic imaging (OCT). The system has one increased blazed grating parallelly set with the original blazed grating in a single grating fast scanning optical delay line, and thus one independently regulated variable of interval between two blazed gratings and capacity of generating group velocity dispersion and third-order dispersion in great varying range and arbitrary sign combination, so that the OCT system may obtain precise matching between the dispersion of the reference arm and the dispersion of the sample arm and longitudinal resolution approaching the theoretical calculated value. The double grating system has wide dispersion regulating range, wide compensation spectrum range and small residual dispersion other than the capacity of independently controlling phase delay and group delay, and possesses three functions of depth scan, phase modulation and dispersion compensation.

The invention discloses a certainty soliton mode locking method for a Kerr optical frequency comb in an optical microcavity. A pump laser power is set to be less than optical microcavity parametric oscillation threshold valve power; the generated pump laser is modulated; the frequency of a modulating signal is accordant with free frequency spectrum width of the optical microcavity; the amplitude of the modulating signal is obtained by calculating three-order dispersion value of the optical microcavity; the pump laser, after being subjected to phase modulation, enters the optical microcavity through a microcavity coupler in a coupling manner; the coupling coefficient is controlled to enable the optical microcavity to work in a critical coupling state; the pump laser is scanned from a long wavelength direction to a short wavelength direction in the optical microcavity; the spectrum of the output pump laser is collected at the output end of the optical microcavity; and in case that the current pump laser spectrum comprises a smooth envelope, the soliton mode locking is finished, and the scanning is stopped. According to the certainty soliton mode locking method for the Kerr optical frequency comb in the optical microcavity, the problems of high randomness, low reliability, high probability of disturbance and the like of the existing Kerr optical frequency comb mode locking scheme are overcame, so that the rapid and accurate soliton mode locking is realized.

Embodiments of the present invention generally relate to high energy, ultrashort pulses from a net normal dispersion ytterbium fiber laser with an anomalous dispersion higher-order mode fiber. More specifically, embodiments of the present invention relate to a fiber oscillator with all-fiber dispersion compensation delivering pulse parameters comparable to solid-state oscillators having good compensation of higher order dispersion and intracavity nonlinearities. In one embodiment of the present invention, an oscillator comprises a length of single mode fiber and a length of higher-order mode fiber, where the group delay dispersion (GDD) of the higher-order mode fiber is chosen to match 50% or more of the GDD of the single mode fiber; wherein a third-order dispersion of the oscillator matches a nonlinear phase buildup in a cavity of the oscillator, and the nonlinear phase buildup is dependent upon the pulse energy of the oscillator.

An optical delay element including a photonic crystal line defect optical waveguide is disclosed that has a large group refractive index and has small or nearly constant wavelength dispersion of the group refractive index in a wide wavelength region for practical use. The optical delay element includes a line defect optical waveguide formed in a photonic crystal structure, and the volume of the line defect optical waveguide is less than the volume of a single line defect optical waveguide. Thereby, the waveguide band of the line defect optical waveguide has two zero points in the third order dispersion curve of the line defect optical waveguide, and the sign of the third order dispersion curve is inverted near the zero points. Therefore, the waveguide band of the line defect optical waveguide is modified, and this enables expansion of the wavelength region having a large group refractive index, small wavelength dispersion of the group refractive index, and small wavelength dispersion of the speed of optical pulses.

A short-pulse fiber amplifier system (10) is designed so that nonlinear phase shifts and third-order dispersion are purposely introduced that compensate each other. In particular, the nonlinear phase shift accumulated in the amplifier is compensated by the third-order dispersion of the combination of a fiber stretcher (12) and a grating compressor (16). In the presence of third-order dispersion, an optimal nonlinear phase shift reduces the pulse duration, and enhances the peak power and pulse contrast compared to the pulse produced in linear propagation.

The invention discloses a mid-infrared chirped pulse amplifying device. The mid-infrared chirped pulse amplifying device comprises a femtosecond laser, a synchronous narrowband picosecond laser, a beam splitter, a near-infrared pulse stretcher, a non-linear frequency converter, an optical parametric chirped pulse amplier and a mid-infrared pulse compressor. Due to the fact that grism pairs and grating pairs are matched with each other to serve as the pulse stretcher and the pulse compressor, usage of a mid-infrared pulse stretcher is avoided, residual third-order dispersion in compression pulses in the process that the grating pairs serve as the pulse stretcher and the pulse compressor is eliminated, and the mid-infrared chirped pulse amplifying device is particularly suitable for generation of mid-infrared ultra-short ultra-strong pulse lasers with the frequency lower than hundreds of femtoseconds.

Compact high brightness light sources for the mid and far IR spectral region, and exemplary applications are disclosed based on passively mode locked Tm fiber comb lasers. In at least one embodiment the coherence of the comb sources is increased in a system utilizing an amplified single-frequency laser to pump the Tm fiber comb laser. The optical bandwidth generated by the passively mode locked Tm fiber comb laser is further decreased by using simultaneous 2nd and 3rd order dispersion compensation using either appropriate chirped fiber Bragg gratings for dispersion compensation, or fibers with appropriately selected values of 2nd and 3rd order dispersion. Fibers with large anomalous values of third order dispersion, or fibers with large numerical apertures, for example fibers having air-holes formed in the fiber cladding may be utilized.

The invention discloses a dispersion compensation method based on a Fourier domain optical coherence tomography technology, which belongs to the technical field of optical coherence tomography. An interference signal is obtained according to a light intensity signal of output light of a Fourier domain optical coherence tomography system, then the interference signal is converted to obtain a complex interference signal, namely an analytic signal, a relation between a phase and a wave number is extracted, and third-order polynomial fitting is carried out; and finally, phase compensation is conducted on the analytic signal by utilizing the calculated second-order dispersion factor and third-order dispersion factor to realize the effect of eliminating the influence of high-order dispersion inthe Fourier domain optical coherence tomography imaging system and achieve the purpose of improving the axial resolution of the Fourier domain optical coherence tomography imaging system. The method is simple in operation mode, and dispersion compensation in continuous real-time imaging can be realized only by one-time measurement and calibration in an experiment.

The present invention relates to an OPCPA apparatus. The OPCPA of the present invention includes an optical pulse stretcher (100) for outputting chirped laser light using odd-order dispersion (third-order dispersion is mainly used). A pump laser (200) outputs pump laser light. An OPA unit (300) receives the pump laser light and the chirped laser light (signal), amplifies the signal using the pump laser light, and generates an idler. An optical signal separation unit (400) separates output light of the OPA unit into the signal, the idler, and remaining light (pump). An optical pulse compressor (600) compensates for pulse chirping caused by odd-order dispersion that is imparted by the optical pulse stretcher, thus temporally compressing the signal and the idler, which overlap each other.

A fiber Chirped Pulse Amplification (CPA) laser system includes a fiber mode-locking oscillator for generating a laser for projecting to a fiber stretcher for stretching a pulse width of the laser. The fiber CPA laser system further includes a multistage amplifier for amplifying the laser and a high-order dispersion compensating compressor for compensating high order dispersions and compressing the pulse width of the laser. The high-order dispersion compensating compressor further includes a pair of gratings coupled with a pair of prisms, a grating pair engraved on the surfaces of a pair of prisms, a chirped grating pair and a phase modulator consists of a grating and a deformable mirror, for generating a negative group velocity dispersion (GVD) and a negative third order dispersion (TOD) for the laser.

The invention provides a method for debugging a compressor of an ultra-short pulse laser system. The method comprises the following steps of: exporting a part of laser output by an oscillator as reference light by using a half mirror; guiding the reference light and main laser passing a whole system to the same spectrograph to generate an interference pattern, wherein bright fringes and dark fringes in the interference pattern are spectral domain and spatial domain comprehensive equiphase lines; determining rest second-order and third-order chromatic dispersion in a visualized manner by using the shapes of the equiphase lines; adjusting the grating distance and rotating angle of a parallel grating pair of the compressor in order to flatten and widen the equiphase lines and obtain ultra-short pulse laser output. The method may debug the compressor of the large ultra-short pulse laser system in a visualized and simple manner.

The invention discloses a novel femtosecond optical fiber amplifier which is characterized by comprising the components of a femtosecond oscillation output module which is used for outputting polarized light with positive dispersion ray, a pre-compression module which is used for pre-compression and obtaining certain negative dispersion light, a double-clad optical fiber amplifying module which is used for energy amplification and restraining third-order dispersion through phase adjustment, and a secondary compression module which is used for outputting after secondary compression; wherein the femtosecond oscillation output module, the pre-compression module, the double-clad optical fiber amplifying module and the secondary compression module are successively arranged. The novel femtosecond optical fiber amplifier has a compact structure. Two compression modules are used and can perform cooperated adjustment for obtaining an optimal output pulse shape. Firstly, little negative dispersion is introduced into the femtosecond oscillation output module beforehand. Pre-amplification is performed through the pre-compression module. The pulse energy can be effectively amplified, and simultaneously a sidelobe energy caused by the third-order dispersion of an optical pulse after amplification is reduced, thereby obtaining the pulse with an approximate Fourier transform limited shape. The novel femtosecond optical fiber amplifier is particularly suitable for a micro-machining industry which is very sensitive to thermal effect.

The present invention discloses dispersion compensating method and system for optically coherent tomographic imaging (OCT). The system has one increased blazed grating parallelly set with the original blazed grating in a single grating fast scanning optical delay line, and thus one independently regulated variable of interval between two blazed gratings and capacity of generating group velocity dispersion and third-order dispersion in great varying range and arbitrary sign combination, so that the OCT system may obtain precise matching between the dispersion of the reference arm and the dispersion of the sample arm and longitudinal resolution approaching the theoretical calculated value. The double grating system has wide dispersion regulating range, wide compensation spectrum range and small residual dispersion other than the capacity of independently controlling phase delay and group delay, and possesses three functions of depth scan, phase modulation and dispersion compensation.

A short-pulse fiber amplifier system (10) is designed so that nonlinear phase shifts and third-order dispersion are purposely introduced that compensate each other. In particular, the nonlinear phase shift accumulated in the amplifier is compensated by the third-order dispersion of the combination of a fiber stretcher (12) and a grating compressor (16). In the presence of third-order dispersion, an optimal nonlinear phase shift reduces the pulse duration, and enhances the peak power and pulse contrast compared to the pulse produced in linear propagation.

A short pulse fiber laser amplification system includes a special fiber stretcher, managed preamplifier, managed amplifier chain, and managed compressor to control an increase of a passive dispersion by managing a third order dispersion (TOD) to a group velocity dispersion (GVD) ratio for matching a nonlinearity chirp. In an exemplary embodiment, the TOD to GVD ratio is managed between approximately 1.5 to 15 fs to match a nonlinearity in range between 1π to 10π. In another exemplary embodiment, the TOD to GVD ratio is managed between approximately 15 to 705 fs to match a nonlinearity in range between 1π to 50π.

A short pulse fiber laser amplification system includes a special fiber stretcher, managed preamplifier, managed amplifier chain, and managed compressor to control an increase of a passive dispersion by managing a third order dispersion (TOD) to a group velocity dispersion (GVD) ratio for matching a nonlinearity chirp. In an exemplary embodiment, the TOD to GVD ratio is managed between approximately 1.5 to 15 fs to match a nonlinearity in range between 1π to 10π. In another exemplary embodiment, the TOD to GVD ratio is managed between approximately 15 to 705 fs to match a nonlinearity in range between 1π to 50π.

The invention discloses a mid-infrared chirped pulse amplifying device. The mid-infrared chirped pulse amplifying device comprises a femtosecond laser, a synchronous narrowband picosecond laser, a beam splitter, a near-infrared pulse stretcher, a non-linear frequency converter, an optical parametric chirped pulse amplier and a mid-infrared pulse compressor. Due to the fact that grism pairs and grating pairs are matched with each other to serve as the pulse stretcher and the pulse compressor, usage of a mid-infrared pulse stretcher is avoided, residual third-order dispersion in compression pulses in the process that the grating pairs serve as the pulse stretcher and the pulse compressor is eliminated, and the mid-infrared chirped pulse amplifying device is particularly suitable for generation of mid-infrared ultra-short ultra-strong pulse lasers with the frequency lower than hundreds of femtoseconds.

The invention discloses a dispersion compensation method based on Fourier domain optical coherence tomography technology, which belongs to the technical field of optical coherence tomography. The invention obtains the interference signal according to the light intensity signal of the output light of the Fourier domain optical coherence tomography system, and then transforms the interference signal to obtain a complex interference signal, that is, an analytical signal, and then extracts the relationship between the phase and the wave number and performs a third-order polynomial simulation. Finally, use the calculated second-order and third-order dispersion factors to perform phase compensation on the analytical signal to achieve the effect of eliminating the effect of high-order dispersion in the Fourier domain optical coherence tomography system, and to improve the Fourier domain optical coherence layer. The purpose of analyzing the axial resolution of the imaging system. The operation mode of the invention is simple, and the dispersion compensation in the continuous real-time imaging can be realized only by measuring and calibrating once in the experiment.

The invention discloses a system and method for accurately measuring three-order dispersion of an optical fiber. The system comprises a wide spectrum light source, a light splitting device, an electro-optic modulator, a programmable optical processor, a light merging device, a photoelectric detector, a vector network analyzer and a processor. A passband broadening factor B is calculated by the processor according to system response data of the vector network analyzer, whether the passband broadening factor B exceeds a preset threshold is judged, and if so, the processor iteratively calculatesa dispersion compensation coefficient and continuously controls the programmable optical processor to produce a new compensation baseband signal until the passband broadening factor B does not exceedthe preset threshold. When the calculated passband broadening factor B does not exceed the preset threshold, it indicates that the three-order dispersion value in the optical fiber is accurately compensated, and the three-order dispersion value in the to-be-measured optical fiber is accurately determined according to the final passband broadening factor B in accordance with the relationship between the compensation amount and the residual amount.

The invention discloses a novel femtosecond optical fiber amplifier, which is characterized by comprising a femtosecond oscillation output module arranged in sequence for outputting linearly polarized light with positive dispersion, and a precompression for precompressing and obtaining a certain negative dispersion light. module, a double-clad optical fiber amplification module for energy amplification and self-phase adjustment to suppress third-order dispersion, and a secondary compression module for output after secondary compression. The structure of this case is compact, and two compression modules are used, which can be adjusted in conjunction to obtain the best output pulse shape. First, a small amount of negative dispersion is pre-introduced in the femtosecond oscillation output module. At the same time, the side lobe energy caused by the third-order dispersion of the amplified optical pulse is weakened, and a pulse with an approximate shape of the Fourier transform limit is obtained, which is very suitable for the micromachining industry that is very sensitive to thermal effects.

The invention discloses a deterministic soliton mode-locking method for a Kerr optical comb in an optical microcavity. The power of the pumping laser is set to be lower than the parametric oscillation threshold power of the optical microcavity, and the generated pumping laser is modulated. The frequency of the modulated signal is the same as The free spectrum width of the optical microcavity is consistent, and the modulated signal amplitude is calculated according to the third-order dispersion value of the optical microcavity. The phase-modulated pump laser is coupled into the optical microcavity through the microcavity coupler, and the coupling coefficient is controlled so that the optical microcavity The cavity works in the critical coupling state. In the optical microcavity, the pump laser is scanned from the long wavelength direction to the short wavelength direction, and the output spectrum of the pump laser is collected at the output of the optical microcavity. Once the current spectrum of the pump laser has a smooth package network, indicating that the soliton mode locking has been completed at this time, stop scanning. The present invention overcomes the problems of strong randomness, poor reliability and susceptibility to disturbance of the existing Kerr optical comb mode-locking scheme, thereby realizing soliton mode-locking rapidly and deterministically.

An optical delay element including a photonic crystal line defect optical waveguide is disclosed that has a large group refractive index and has small or nearly constant wavelength dispersion of the group refractive index in a wide wavelength region for practical use. The optical delay element includes a line defect optical waveguide formed in a photonic crystal structure, and the volume of the line defect optical waveguide is less than the volume of a single line defect optical waveguide. Thereby, the waveguide band of the line defect optical waveguide has two zero points in the third order dispersion curve of the line defect optical waveguide, and the sign of the third order dispersion curve is inverted near the zero points. Therefore, the waveguide band of the line defect optical waveguide is modified, and this enables expansion of the wavelength region having a large group refractive index, small wavelength dispersion of the group refractive index, and small wavelength dispersion of the speed of optical pulses.