An efficient high-energy eye-safe optical parametric oscillator (OPO) based on a type-Ⅱ non-critically phasematched KTP crystal is demonstrated. The KTP OPO is pumped by a quasi-cw diode side-pumped electrooptic Q-...An efficient high-energy eye-safe optical parametric oscillator (OPO) based on a type-Ⅱ non-critically phasematched KTP crystal is demonstrated. The KTP OPO is pumped by a quasi-cw diode side-pumped electrooptic Q-switched Nd:YAG laser in a compound-cavity configuration. The maximum output energy of the signal wavelength at 1.57 μm b 66.5 m J, corresponding to an electrical-to-optical conversion efficiency of 4.47% and an optical-to-optical conversion efficiency of 12.1%. The pulse width (FWHM) is about 3.6 ns with a peak power of 18.5 MW. The output energy is insensitive to repetition rate and demonstrates good stability.展开更多
Recent progresses about optical pumped tunable terahertz (THz) sources are interviewed, including THz parametric oscillation (TPO) and difference frequency generation (DFG). We develop high efficiency and high p...Recent progresses about optical pumped tunable terahertz (THz) sources are interviewed, including THz parametric oscillation (TPO) and difference frequency generation (DFG). We develop high efficiency and high power surface-emitted TPO, as well as DFG with nonlinear crystals. A novel scheme for the high efficiency DFG source based on the Cherenkov phase-matching technology is comprehensively investigated in both bulk crystals. The widely tunable optical THz radiation is also researched based on the organic nonlinear 4-N,N-dimethylamino-4'-N'- methylstilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS) crystal.展开更多
The three-dimensional thermal properties of 18-core photonic crystal fiber lasers operated under natural convection are investigated.The temperature sensing technique based on a fiber Bragg grating sensor array is pro...The three-dimensional thermal properties of 18-core photonic crystal fiber lasers operated under natural convection are investigated.The temperature sensing technique based on a fiber Bragg grating sensor array is proposed to measure the longitudinal temperature distribution of a 1.6-m-long ytterbium-doped 18-core photonic crystal fiber.The results show that the temperature decreases from the pump end to the launch end exponentially.Moreover,the radial temperature distribution of the fiber end is investigated by using the full-vector finite-element method.The numerical results match well with the experimental data and the coating temperature reaches 422.7K,approaching the critical value of polymer cladding,when the pumping power is 40 W.Therefore the fiber end cooling is necessary to achieve power scaling.Compared with natural convection methods,the copper cooling scheme is found to be an effective method to reduce the fiber temperature.展开更多
We investigate the single-mode condition and power fraction of an air cladding total internal reflection(TIR)guided porous polymer THz fiber.It is shown that the single mode condition and a high fraction of power in a...We investigate the single-mode condition and power fraction of an air cladding total internal reflection(TIR)guided porous polymer THz fiber.It is shown that the single mode condition and a high fraction of power in air holes cannot be simultaneously met in porous fibers.Employing the V parameter and the Lorentz–Lorenz formula,we analyze this problem theoretically.展开更多
1 IntroductionTime-division synchronous code-division multiple access (TD-SCI)MA) is a 3G wireless communica- tion standard developed in China and adopted by ITU. It has high spectrum efficiency; it providesgood sy...1 IntroductionTime-division synchronous code-division multiple access (TD-SCI)MA) is a 3G wireless communica- tion standard developed in China and adopted by ITU. It has high spectrum efficiency; it providesgood system slability; and it lowers network construction costs. After many years of development, it is now at the stage of large-scale application.展开更多
Recent progresses made by authors on monochromatic and tunable terahertz (THz) generation based on nonlinear optics are reviewed, including THz parametric oscillation (TPO) and difference frequency generation (DF...Recent progresses made by authors on monochromatic and tunable terahertz (THz) generation based on nonlinear optics are reviewed, including THz parametric oscillation (TPO) and difference frequency generation (DFG). From the technical point of view, we develop extra- and intra-cavity surface-emitted TPO, as well as DFG with QPM-GaAs crystal. From the point of view of mechanism, Cherenkov phase-matching is comprehensively investigated in both bulk crystal and planar waveguide. A novel scheme for cascading enhanced Cherenkov DFG in waveguide is proposed. From the point of view of material, organic crystal 4-N,N-dimethylamino-4'-N'-methyl-stibazolium tosylate (DAST) is utilized as the nonlinear medium.展开更多
A newly grown Ba Ga4Se7 crystal has been synthesized via the Bridgman-Stockbarger technique.This new crystal has advantages of high nonlinear optics(NLO) coefficients,high laser damage thresholds,and wide transparen...A newly grown Ba Ga4Se7 crystal has been synthesized via the Bridgman-Stockbarger technique.This new crystal has advantages of high nonlinear optics(NLO) coefficients,high laser damage thresholds,and wide transparent regions.The Ba Ga4Se7 crystal has bright application prospects as a nonlinear gain medium in mid-infrared and terahertz regions.In this paper,the crystalline structure and synthetic method of the Ba Ga4Se7 crystal are introduced.The refractive indices and absorption coefficients along three dielectric axes between 0.1 THz and 1.0 THz are also obtained.The terahertz difference frequency generation(THz-DFG) characteristics based on the BaG a4Se7 crystal in the frequency range of 0.1 THz to 1.0 THz are analyzed theoretically and the phase-matching conditions are calculated.The application of Ba Ga4Se7 crystals in terahertz wave generation is also discussed.展开更多
The improved range Doppler algorithm is proposed to abate the trade-off between resolutions and depth of focus in spectral domain optical coherence tomography. By considering the finite beam width and the shape of the...The improved range Doppler algorithm is proposed to abate the trade-off between resolutions and depth of focus in spectral domain optical coherence tomography. By considering the finite beam width and the shape of the wavefronts produced by the Gaussian beam, a physical diffraction model is presented to simulate the light propagation process in the sample. The two-dimensional processing of the spectrum data is decomposed into two one-dimensional processings of Stolt transform and matched filter. Experimental results show that image reconstruction can be achieved. The transverse and axial resolutions are both improved significantly, especially in the out-of-focus range, and the resolutions are almost equivalent throughout the entire region of interest.展开更多
The modal of 18-core photonic crystal fiber laser is discussed and calculated.And corresponding far-field distribution of the supermodes is given by Fresnel diffraction integral.For improving beam quality,the mode sel...The modal of 18-core photonic crystal fiber laser is discussed and calculated.And corresponding far-field distribution of the supermodes is given by Fresnel diffraction integral.For improving beam quality,the mode selection method based on the Talbot effect is introduced.The reflection coefficients are calculated,and the result shows that an in-phase supermode can be locked better at a large propagation distance.展开更多
By using a spherical wave as the reference wave, we recorded the in-line phase-shifting digital hologram of the 25th element of Chinese standard No. 3 resolution test pattern, and gave the corresponding numerical reco...By using a spherical wave as the reference wave, we recorded the in-line phase-shifting digital hologram of the 25th element of Chinese standard No. 3 resolution test pattern, and gave the corresponding numerical reconstructed results. Some problems concerning with the digital hologram recording and reconstruction of the diffractive object at a short distance are discussed. The experimental result shows that the resolution of the reconstructed image is better than 10μm, which is the limit by using this experimental arrangement.展开更多
A surface plasmon resonance(SPR) sensor based on a multi-core photonic crystal fiber(PCF) is presented in this paper.There is only one analyte channel positioned in the center of the PCF cross section,rather than seve...A surface plasmon resonance(SPR) sensor based on a multi-core photonic crystal fiber(PCF) is presented in this paper.There is only one analyte channel positioned in the center of the PCF cross section,rather than several closely arranged analyte channels around the central core.So the design of this sensor not only reduces the consumption of gold and samples,but also effectively avoids the interference between neighboring analyte channels.Optical field distributions of this fiber at different wavelengths and the sensing properties of this sensor are theoretically analyzed and discussed using finite element method(FEM).Simulation results confirm that both the thickness of metallic layer and the fiber structural parameters have significant effect on sensing performance.The amplitude sensitivity of the sensor is found to be 1.74×10-5RIU,and the spectral sensitivity is 3300 nm/RIU,corresponding to a resolution of 3.03×10-5 RIU.Finally,in order to achieve PCF-SPR sensing characteristics,an experiment design scheme based on spectroscopic detection method is proposed.展开更多
An effective mode selection is important for the multi-core photonic crystal fiber(PCF)to obtain good output.Talbot cavity is popular to lock the in-phase mode,but few satisfactory experimental results have been repor...An effective mode selection is important for the multi-core photonic crystal fiber(PCF)to obtain good output.Talbot cavity is popular to lock the in-phase mode,but few satisfactory experimental results have been reported.In this paper,a dual-Talbot cavity with reflected mirrors on each side of PCF is designed to lock the in-phase mode.The design gains the advantage of in-phase mode against out-of-phase mode.What’s more,it can weaken the influence brought by the imperfect end facet of the fiber.The corresponding theoretical analyses and the experiment are taken.The experimental results suggest that the dual-Talbot cavity improves the capacity of mode selection.展开更多
Negative refraction and subwavelength imaging properties of a two-dimensional (2D) photonic crystal (PC) slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air...Negative refraction and subwavelength imaging properties of a two-dimensional (2D) photonic crystal (PC) slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air holes immersed in a dielectric. For a certain frequency range in the third photonic band, the directions of the group velocities and the phase velocities can be opposite, so the PC can work as a kind of negative refractive-index material. The light radiated from a point source can form a subwavelength image spot through the PC slab. Negative refraction and an effective refractive index of the PC slab n = -1 can be achieved for the incident wave with its incident angle within a certain range.展开更多
Space-division multiplexing (SDM) using multi-core fibers (MCFs) and few-mode fibers (FMFs) was proposed as a solution to increase capacity and/or reduce the cost per bit of fiber-optic transmission. Advances in...Space-division multiplexing (SDM) using multi-core fibers (MCFs) and few-mode fibers (FMFs) was proposed as a solution to increase capacity and/or reduce the cost per bit of fiber-optic transmission. Advances in passive and active SDM devices as well as digital signal processing have led to impressive SDM transmission demonstrations in the laboratory. Although the perceived advantages in terms of capacity and cost per bit that SDM offers over parallel SMF bundles are not universally accepted, SDM is beginning to emerge as an indispensable solution in major network segments. The introduction of the spatial degree of freedom allows optical networks to overcome fundamental limitations such as fiber nonlinearity as well practical limitations such as power delivery. We describe these application scenarios that the optical communications industry has already began to explore. From a fundamental science point of view, concepts such as the principal modes, generalized Stokes space, and multi-component solitons discovered in SDM research will likely have a broad impact in other areas of science and engineering.展开更多
基金Supported by the Research Fund for the Doctoral Program of Higher Education under Grant No 20070420118, the Tianjin Municipal Primary Application and Frontier Technology Research Plan under Grant No 07JCYBJC06200, the National Basic Research Programme of China under Grant No 2007CB310403, and the National Natural Science Foundation of China under Grant No 60801017.
文摘An efficient high-energy eye-safe optical parametric oscillator (OPO) based on a type-Ⅱ non-critically phasematched KTP crystal is demonstrated. The KTP OPO is pumped by a quasi-cw diode side-pumped electrooptic Q-switched Nd:YAG laser in a compound-cavity configuration. The maximum output energy of the signal wavelength at 1.57 μm b 66.5 m J, corresponding to an electrical-to-optical conversion efficiency of 4.47% and an optical-to-optical conversion efficiency of 12.1%. The pulse width (FWHM) is about 3.6 ns with a peak power of 18.5 MW. The output energy is insensitive to repetition rate and demonstrates good stability.
基金supported by the National High Technology Research and Development Program of China(863)under Grant No.2011AA010205National Natural Science Foundation of China under Grant No.6117201061101058,61107086,and 61275120+2 种基金the CAEP THz Science and Technology Foundation under Grant No.CAEPTHZ201201 and CAEPTHZ201304the Natural Science Foundation of Tianjin under Grant No.11JCYBJC01100 and 13ZCZDSF02300the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No.20120032110053
文摘Recent progresses about optical pumped tunable terahertz (THz) sources are interviewed, including THz parametric oscillation (TPO) and difference frequency generation (DFG). We develop high efficiency and high power surface-emitted TPO, as well as DFG with nonlinear crystals. A novel scheme for the high efficiency DFG source based on the Cherenkov phase-matching technology is comprehensively investigated in both bulk crystals. The widely tunable optical THz radiation is also researched based on the organic nonlinear 4-N,N-dimethylamino-4'-N'- methylstilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS) crystal.
基金Supported by the National Basic Research Program of China under Grant No 2010CB327801the Key Program of National Natural Science Foundation of China under Grant No 60637010THE Natural Science Research Project in University of Hebei Province under Grant No Z2010163.
文摘The three-dimensional thermal properties of 18-core photonic crystal fiber lasers operated under natural convection are investigated.The temperature sensing technique based on a fiber Bragg grating sensor array is proposed to measure the longitudinal temperature distribution of a 1.6-m-long ytterbium-doped 18-core photonic crystal fiber.The results show that the temperature decreases from the pump end to the launch end exponentially.Moreover,the radial temperature distribution of the fiber end is investigated by using the full-vector finite-element method.The numerical results match well with the experimental data and the coating temperature reaches 422.7K,approaching the critical value of polymer cladding,when the pumping power is 40 W.Therefore the fiber end cooling is necessary to achieve power scaling.Compared with natural convection methods,the copper cooling scheme is found to be an effective method to reduce the fiber temperature.
基金by the National Basic Research Program of China under Grant Nos 2010CB397801 and 2007CB310403.
文摘We investigate the single-mode condition and power fraction of an air cladding total internal reflection(TIR)guided porous polymer THz fiber.It is shown that the single mode condition and a high fraction of power in air holes cannot be simultaneously met in porous fibers.Employing the V parameter and the Lorentz–Lorenz formula,we analyze this problem theoretically.
文摘1 IntroductionTime-division synchronous code-division multiple access (TD-SCI)MA) is a 3G wireless communica- tion standard developed in China and adopted by ITU. It has high spectrum efficiency; it providesgood system slability; and it lowers network construction costs. After many years of development, it is now at the stage of large-scale application.
基金supported by the National High Technology Research and Development Program of China(863)under Grant No.2011AA010205National Natural Science Foundation of China under Grant No.61172010 61101058,61107086,and 61275120+2 种基金the CAEP THz Science and Technology Foundation under Grant No.CAEPTHZ201201 and CAEPTHZ201304the Natural Science Foundation of Tianjin under Grant No.11JCYBJC01100 and 13ZCZDSF02300the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No.20120032110053
文摘Recent progresses made by authors on monochromatic and tunable terahertz (THz) generation based on nonlinear optics are reviewed, including THz parametric oscillation (TPO) and difference frequency generation (DFG). From the technical point of view, we develop extra- and intra-cavity surface-emitted TPO, as well as DFG with QPM-GaAs crystal. From the point of view of mechanism, Cherenkov phase-matching is comprehensively investigated in both bulk crystal and planar waveguide. A novel scheme for cascading enhanced Cherenkov DFG in waveguide is proposed. From the point of view of material, organic crystal 4-N,N-dimethylamino-4'-N'-methyl-stibazolium tosylate (DAST) is utilized as the nonlinear medium.
基金supported by the National Basic Research Program of China(973)under Grant No.2015CB755403 and No.2014CB339802National High Technology Research and Development Program(863)under Grant No.2011AA010205+6 种基金National Natural Science Foundation of China under Grant No.61107086No.61172010and No.61471257Natural Science Foundation of Tianjin under Grant No.14JCQNJC02200Science and Technology Support Program of Tianjin under Grant No.14ZCZDGX00030Specialized Research Fund for the Doctoral Program of Higher Education under Grant No.20120032110053CAEP THz Science and Technology Foundation under Grant No.CAEPTHZ201304
文摘A newly grown Ba Ga4Se7 crystal has been synthesized via the Bridgman-Stockbarger technique.This new crystal has advantages of high nonlinear optics(NLO) coefficients,high laser damage thresholds,and wide transparent regions.The Ba Ga4Se7 crystal has bright application prospects as a nonlinear gain medium in mid-infrared and terahertz regions.In this paper,the crystalline structure and synthetic method of the Ba Ga4Se7 crystal are introduced.The refractive indices and absorption coefficients along three dielectric axes between 0.1 THz and 1.0 THz are also obtained.The terahertz difference frequency generation(THz-DFG) characteristics based on the BaG a4Se7 crystal in the frequency range of 0.1 THz to 1.0 THz are analyzed theoretically and the phase-matching conditions are calculated.The application of Ba Ga4Se7 crystals in terahertz wave generation is also discussed.
基金supported by the National Natural Science Foundation of China under Grant No. 30800245
文摘The improved range Doppler algorithm is proposed to abate the trade-off between resolutions and depth of focus in spectral domain optical coherence tomography. By considering the finite beam width and the shape of the wavefronts produced by the Gaussian beam, a physical diffraction model is presented to simulate the light propagation process in the sample. The two-dimensional processing of the spectrum data is decomposed into two one-dimensional processings of Stolt transform and matched filter. Experimental results show that image reconstruction can be achieved. The transverse and axial resolutions are both improved significantly, especially in the out-of-focus range, and the resolutions are almost equivalent throughout the entire region of interest.
基金supported by the National Basic Research Program of China(No.2010CB327801)the Key Program of National Natural Science Foundation of China(No.60637010)
文摘The modal of 18-core photonic crystal fiber laser is discussed and calculated.And corresponding far-field distribution of the supermodes is given by Fresnel diffraction integral.For improving beam quality,the mode selection method based on the Talbot effect is introduced.The reflection coefficients are calculated,and the result shows that an in-phase supermode can be locked better at a large propagation distance.
文摘By using a spherical wave as the reference wave, we recorded the in-line phase-shifting digital hologram of the 25th element of Chinese standard No. 3 resolution test pattern, and gave the corresponding numerical reconstructed results. Some problems concerning with the digital hologram recording and reconstruction of the diffractive object at a short distance are discussed. The experimental result shows that the resolution of the reconstructed image is better than 10μm, which is the limit by using this experimental arrangement.
基金supported by the Major State Basic Research Development Program of China(No.2010CB327801)
文摘A surface plasmon resonance(SPR) sensor based on a multi-core photonic crystal fiber(PCF) is presented in this paper.There is only one analyte channel positioned in the center of the PCF cross section,rather than several closely arranged analyte channels around the central core.So the design of this sensor not only reduces the consumption of gold and samples,but also effectively avoids the interference between neighboring analyte channels.Optical field distributions of this fiber at different wavelengths and the sensing properties of this sensor are theoretically analyzed and discussed using finite element method(FEM).Simulation results confirm that both the thickness of metallic layer and the fiber structural parameters have significant effect on sensing performance.The amplitude sensitivity of the sensor is found to be 1.74×10-5RIU,and the spectral sensitivity is 3300 nm/RIU,corresponding to a resolution of 3.03×10-5 RIU.Finally,in order to achieve PCF-SPR sensing characteristics,an experiment design scheme based on spectroscopic detection method is proposed.
基金the National Basic Research Program of China(No.2010CB327801)the Program for New Century Excellent Talents in University of Ministry of Education of China(No.NCET-10-0610)
文摘An effective mode selection is important for the multi-core photonic crystal fiber(PCF)to obtain good output.Talbot cavity is popular to lock the in-phase mode,but few satisfactory experimental results have been reported.In this paper,a dual-Talbot cavity with reflected mirrors on each side of PCF is designed to lock the in-phase mode.The design gains the advantage of in-phase mode against out-of-phase mode.What’s more,it can weaken the influence brought by the imperfect end facet of the fiber.The corresponding theoretical analyses and the experiment are taken.The experimental results suggest that the dual-Talbot cavity improves the capacity of mode selection.
基金supported by the National Key Basic Research Special Foundation of China(Nos.2006CB921702 and 2007CB310403)the National Natural Science Foundation of China(Nos.10674185 and 10801017) the Youth Foundation of Minzu University of China.
文摘Negative refraction and subwavelength imaging properties of a two-dimensional (2D) photonic crystal (PC) slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air holes immersed in a dielectric. For a certain frequency range in the third photonic band, the directions of the group velocities and the phase velocities can be opposite, so the PC can work as a kind of negative refractive-index material. The light radiated from a point source can form a subwavelength image spot through the PC slab. Negative refraction and an effective refractive index of the PC slab n = -1 can be achieved for the incident wave with its incident angle within a certain range.
基金This work has been supported in part by the National Basic Research Program of China (973) (No. 2014CB340104/1), the National Natural Science Foundation of China (NSFC) (Grant Nos. 61377076, 61307085 and 61431009).
文摘Space-division multiplexing (SDM) using multi-core fibers (MCFs) and few-mode fibers (FMFs) was proposed as a solution to increase capacity and/or reduce the cost per bit of fiber-optic transmission. Advances in passive and active SDM devices as well as digital signal processing have led to impressive SDM transmission demonstrations in the laboratory. Although the perceived advantages in terms of capacity and cost per bit that SDM offers over parallel SMF bundles are not universally accepted, SDM is beginning to emerge as an indispensable solution in major network segments. The introduction of the spatial degree of freedom allows optical networks to overcome fundamental limitations such as fiber nonlinearity as well practical limitations such as power delivery. We describe these application scenarios that the optical communications industry has already began to explore. From a fundamental science point of view, concepts such as the principal modes, generalized Stokes space, and multi-component solitons discovered in SDM research will likely have a broad impact in other areas of science and engineering.