Phase matching or quasi-phase matching(QPM)is of significant importance to the conversion efficiency of second harmonic generation(SHG)in artificial nonlinear crystals like lithium niobate(LN)crystal or microstructure...Phase matching or quasi-phase matching(QPM)is of significant importance to the conversion efficiency of second harmonic generation(SHG)in artificial nonlinear crystals like lithium niobate(LN)crystal or microstructured nonlinear crystals like periodic-poled lithium niobate(PPLN)crystals.In this paper,we propose and show that the incident angle of pump laser light can be harnessed as an alternative versatile tool to engineer QPM for high-efficiency SHG in a PPLN crystal,in addition to conventional means of period adjusting or temperature tuning.A rigorous model is established and analytical solution of the nonlinear conversion efficiency under the small and large signal approximation theory is obtained at different incident angles.The variation of phase mismatching and walk-off length with incident angle or incident wavelength are also explored.Numerical simulations for a PPLN crystal with first order QPM structure are used to confirm our theoretical predictions based on the exact analytical solution of the general large-signal theory.The results show that the narrow-band tunable SHG output covers a range of 532 nm–552.8 nm at the ideal incident angle from 0°to 90°.This theoretical scheme,fully considering the reflection and transmission at the air-crystal interface,would offer an efficient theoretical system to evaluate the nonlinear frequency conversion and help to obtain the maximum SHG conversion efficiency by selecting an optimum incident wavelength and incident angle in a specially designed PPLN crystal,which would be very helpful for the design of tunable narrow-band pulse nanosecond,picosecond,and femtosecond laser devices via PPLN and other microstructured LN crystals.展开更多
We propose the construction of a compact linac as the injector of a cancer therapy facility at the Institute of Modern Physics(IMP) of the Chinese Academy of Sciences(CAS). Based on a traditional setup, a new compact ...We propose the construction of a compact linac as the injector of a cancer therapy facility at the Institute of Modern Physics(IMP) of the Chinese Academy of Sciences(CAS). Based on a traditional setup, a new compact fast-bunching design is first introduced to optimize the 600 keV/u RFQ with a 0.05 pm A ^(12)C^(4+) beam. This shortens the RFQ structure length from the standard design value of272–230 cm while effectively regulating the particle loss and emittance growth. In addition, a detailed error analysis was performed after the optimization process. The error sources cover input beam parameters errors, machining errors and alignment errors. The simulation results show that the beam loss and emittance growth of the RFQ are acceptable and within typical ranges of error.展开更多
A 53.667 MHz CW(continuous-wave) heavy ion IH-DTL has been designed for the SSC-LINAC injector of HIRFL-CSR(Heavy Ions Research Facility at Lanzhou-Cooling Storage Ring). It accelerates ions with maximum mass-to-charg...A 53.667 MHz CW(continuous-wave) heavy ion IH-DTL has been designed for the SSC-LINAC injector of HIRFL-CSR(Heavy Ions Research Facility at Lanzhou-Cooling Storage Ring). It accelerates ions with maximum mass-to-charge ratio of 7.0 from 143 to 295 ke V/u. Low-power RF measurement of the IH-DTL1 has been taken to investigate the RF performance and the quality of the electric field distribution on the beam axis.The measured Q_0 value and the shunt impedance are 10,400 and 198 MX/m, respectively. The electric field distributions on and around the beam axis were evaluated and compared with the design value. By a new approach,the dipole field component is also estimated. The beam dynamics simulation using measured field distribution was presented in this paper. Based on the dynamics analysis in both transverse and longitudinal phase space, the field distribution can meet the design requirement. Finally, the RF conditioning and very first beam commissioning on the IH-DTL1 were finished. The beam test results agree well with the simulation results; what's more, the property of the variable output beam energy about the separated functions DTL was verified.展开更多
A new linac injector CSR-LINAC for the Cooler Storage Ring of the Heavy Ion Research Facility in Lanzhou(HIRFL-CSR) is proposed to improve the performance of the HIRFL. As a key component of the CSRLINAC, the 108.48-M...A new linac injector CSR-LINAC for the Cooler Storage Ring of the Heavy Ion Research Facility in Lanzhou(HIRFL-CSR) is proposed to improve the performance of the HIRFL. As a key component of the CSRLINAC, the 108.48-MHz radio frequency quadrupole(RFQ) is under design at the Institute of Modern Physics.Heavy ions with mass-to-charge ratios of 3–7 will be accelerated from 4 to 300 keV/u by the RFQ. In the beam dynamics design, the New Four-Section Procedure is adopted to improve the transmission efficiency and obtain a compact structure. In this paper, a transmission efficiency of 98.0% in the 3.07-m-long cavity was obtained. The Interdigital H-type structure is employed because of its mechanical stability and high shunt impedance. The RF performance of the cavity is investigated by the electromagnetic simulation. The optimized results of the electric field to meet the beam dynamics requirements are presented in this paper.展开更多
Nonlinear Raman-Nath diffraction(NRND)is a unique diffraction pattern formed when a high-intensity laser interacts with a nonlinear microstructure bulky medium relying only on the transverse phase matching condition.H...Nonlinear Raman-Nath diffraction(NRND)is a unique diffraction pattern formed when a high-intensity laser interacts with a nonlinear microstructure bulky medium relying only on the transverse phase matching condition.Here,we report on the first experimental observation of NRND in a submicron-thick periodically poled lithium niobate thin film(PPLNTF)by geometric reflection pumped via a near-infrared femtosecond pulse laser.We further observe the evolution of the diffracted signals after broadening of the pump laser via a fused silica plate.We systematically analyze the spectral properties of multi-order second harmonic generation(SHG)diffracted signals exhibiting asymmetric distributions and explicitly clarify their phase matching conditions,simultaneously considering the impacts of the incident pump wavelength,the sample poling period,and the incident angle on the properties of the angular distribution diffracted beams.The realization of NRND phenomena with appreciable on-chip efficiency at a submicron interaction length is mainly attributed to the significant contribution of domain walls to enhance the nonlinear effects along with the modulation of second-order nonlinear susceptibilitiesχ^((2)).This NRND scheme provides a high-resolution,non-destructive on-chip microstructure diagnostic method,and even has the potential to develop novel on-chip integrated optoelectronic devices for applications such as precision metrology,biosensing,and spectral analysis.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11974119)the Science and Technology Project of Guangdong Province,China(Grant No.2020B010190001)+2 种基金the Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2016ZT06C594)the National Key Research and Development Program of China(Grant Nos.2018YFA,0306200,and 2019YFB2203500)the Science and Technology Program of Guangzhou City(Grant No.2023A04J1309).
文摘Phase matching or quasi-phase matching(QPM)is of significant importance to the conversion efficiency of second harmonic generation(SHG)in artificial nonlinear crystals like lithium niobate(LN)crystal or microstructured nonlinear crystals like periodic-poled lithium niobate(PPLN)crystals.In this paper,we propose and show that the incident angle of pump laser light can be harnessed as an alternative versatile tool to engineer QPM for high-efficiency SHG in a PPLN crystal,in addition to conventional means of period adjusting or temperature tuning.A rigorous model is established and analytical solution of the nonlinear conversion efficiency under the small and large signal approximation theory is obtained at different incident angles.The variation of phase mismatching and walk-off length with incident angle or incident wavelength are also explored.Numerical simulations for a PPLN crystal with first order QPM structure are used to confirm our theoretical predictions based on the exact analytical solution of the general large-signal theory.The results show that the narrow-band tunable SHG output covers a range of 532 nm–552.8 nm at the ideal incident angle from 0°to 90°.This theoretical scheme,fully considering the reflection and transmission at the air-crystal interface,would offer an efficient theoretical system to evaluate the nonlinear frequency conversion and help to obtain the maximum SHG conversion efficiency by selecting an optimum incident wavelength and incident angle in a specially designed PPLN crystal,which would be very helpful for the design of tunable narrow-band pulse nanosecond,picosecond,and femtosecond laser devices via PPLN and other microstructured LN crystals.
基金supported by the National Natural Science Foundation of China(No.11375243)the Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06G373)
文摘We propose the construction of a compact linac as the injector of a cancer therapy facility at the Institute of Modern Physics(IMP) of the Chinese Academy of Sciences(CAS). Based on a traditional setup, a new compact fast-bunching design is first introduced to optimize the 600 keV/u RFQ with a 0.05 pm A ^(12)C^(4+) beam. This shortens the RFQ structure length from the standard design value of272–230 cm while effectively regulating the particle loss and emittance growth. In addition, a detailed error analysis was performed after the optimization process. The error sources cover input beam parameters errors, machining errors and alignment errors. The simulation results show that the beam loss and emittance growth of the RFQ are acceptable and within typical ranges of error.
基金supported by the National Natural Science Foundation of China(Nos.11375243 and 11405237)the Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06G373)
文摘A 53.667 MHz CW(continuous-wave) heavy ion IH-DTL has been designed for the SSC-LINAC injector of HIRFL-CSR(Heavy Ions Research Facility at Lanzhou-Cooling Storage Ring). It accelerates ions with maximum mass-to-charge ratio of 7.0 from 143 to 295 ke V/u. Low-power RF measurement of the IH-DTL1 has been taken to investigate the RF performance and the quality of the electric field distribution on the beam axis.The measured Q_0 value and the shunt impedance are 10,400 and 198 MX/m, respectively. The electric field distributions on and around the beam axis were evaluated and compared with the design value. By a new approach,the dipole field component is also estimated. The beam dynamics simulation using measured field distribution was presented in this paper. Based on the dynamics analysis in both transverse and longitudinal phase space, the field distribution can meet the design requirement. Finally, the RF conditioning and very first beam commissioning on the IH-DTL1 were finished. The beam test results agree well with the simulation results; what's more, the property of the variable output beam energy about the separated functions DTL was verified.
基金supported by the National Natural Science Foundation of China(Nos.11375243,11405237,and 11475235)the Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06G373)
文摘A new linac injector CSR-LINAC for the Cooler Storage Ring of the Heavy Ion Research Facility in Lanzhou(HIRFL-CSR) is proposed to improve the performance of the HIRFL. As a key component of the CSRLINAC, the 108.48-MHz radio frequency quadrupole(RFQ) is under design at the Institute of Modern Physics.Heavy ions with mass-to-charge ratios of 3–7 will be accelerated from 4 to 300 keV/u by the RFQ. In the beam dynamics design, the New Four-Section Procedure is adopted to improve the transmission efficiency and obtain a compact structure. In this paper, a transmission efficiency of 98.0% in the 3.07-m-long cavity was obtained. The Interdigital H-type structure is employed because of its mechanical stability and high shunt impedance. The RF performance of the cavity is investigated by the electromagnetic simulation. The optimized results of the electric field to meet the beam dynamics requirements are presented in this paper.
基金support from Science and Technology Project of Guangdong(2020B010190001)National Natural Science Foundation of China(11974119)Guangzhou Science and Technology Plan Project(2023A04J1309).
文摘Nonlinear Raman-Nath diffraction(NRND)is a unique diffraction pattern formed when a high-intensity laser interacts with a nonlinear microstructure bulky medium relying only on the transverse phase matching condition.Here,we report on the first experimental observation of NRND in a submicron-thick periodically poled lithium niobate thin film(PPLNTF)by geometric reflection pumped via a near-infrared femtosecond pulse laser.We further observe the evolution of the diffracted signals after broadening of the pump laser via a fused silica plate.We systematically analyze the spectral properties of multi-order second harmonic generation(SHG)diffracted signals exhibiting asymmetric distributions and explicitly clarify their phase matching conditions,simultaneously considering the impacts of the incident pump wavelength,the sample poling period,and the incident angle on the properties of the angular distribution diffracted beams.The realization of NRND phenomena with appreciable on-chip efficiency at a submicron interaction length is mainly attributed to the significant contribution of domain walls to enhance the nonlinear effects along with the modulation of second-order nonlinear susceptibilitiesχ^((2)).This NRND scheme provides a high-resolution,non-destructive on-chip microstructure diagnostic method,and even has the potential to develop novel on-chip integrated optoelectronic devices for applications such as precision metrology,biosensing,and spectral analysis.
