We study the nonlinear process of second harmonic generation in photonic time-crystals,materials with refractive index that varies abruptly and periodically in time,and obtain the phase matching condition for this pro...We study the nonlinear process of second harmonic generation in photonic time-crystals,materials with refractive index that varies abruptly and periodically in time,and obtain the phase matching condition for this process.We find conditions for which the second harmonic generation is highly enhanced even in the absence of phase matching,governed by the exponential growth of the modes residing in the momentum gap of the photonic time crystal.Additionally,under these conditions,a cascade of higher-order harmonics is generated at growing exponential rates.The process is robust,with no requirement for phase-matching,the presence of a resonance or a threshold,drawing energy from the modulation.展开更多
Typically, photonic waveguides designed for nonlinear frequency conversion rely on intuitive and established principles, including index guiding and bandgap engineering, and are based on simple shapes with high degree...Typically, photonic waveguides designed for nonlinear frequency conversion rely on intuitive and established principles, including index guiding and bandgap engineering, and are based on simple shapes with high degrees of symmetry. We show that recently developed inverse-design techniques can be applied to discover new kinds of microstructured fibers and metasurfaces designed to achieve large nonlinear frequency-conversion efficiencies. As a proof of principle, we demonstrate complex, wavelength-scale chalcogenide glass fibers and gallium phosphide three-dimensional metasurfaces exhibiting some of the largest nonlinear conversion efficiencies predicted thus far,e.g., lowering the power requirement for third-harmonic generation by 104 and enhancing second-harmonic generation conversion efficiency by 107. Such enhancements arise because, in addition to enabling a great degree of tunability in the choice of design wavelengths, these optimization tools ensure both frequency-and phase-matching in addition to large nonlinear overlap factors.展开更多
Deep ultraviolet coherent light,particularly at the wavelength of 193 nm,has become indispensable for semiconductor lithography.We present a compact solid-state nanosecond pulsed laser system capable of generating 193...Deep ultraviolet coherent light,particularly at the wavelength of 193 nm,has become indispensable for semiconductor lithography.We present a compact solid-state nanosecond pulsed laser system capable of generating 193-nm coherent light at the repetition rate of 6 kHz.One part of the 1030-nm laser from the homemade Yb:YAG crystal amplifier is divided to generate 258 nm laser(1.2 W)by fourth-harmonic generation,and the rest is used to pump an optical parametric amplifier producing 1553 nm laser(700 mW).Frequency mixing of these beams in cascaded LiB_(3)O_(5) crystals yields a 193-nm laser with 70-mW average power and a linewidth of less than 880 MHz.By introducing a spiral phase plate to the 1553-nm beam before frequency mixing,we generate a vortex beam carrying orbital angular momentum.This is,to our knowledge,the first demonstration of a 193-nm vortex beam generated from a solid-state laser.Such a beam could be valuable for seeding hybrid ArF excimer lasers and has potential applications in wafer processing and defect inspection.展开更多
This paper demonstrates an approach that negative uniaxial crystal has a relative anomalous dispersion effect which can compensate group velocity delay, and applies this approach to nonlinear frequency conversion of a...This paper demonstrates an approach that negative uniaxial crystal has a relative anomalous dispersion effect which can compensate group velocity delay, and applies this approach to nonlinear frequency conversion of an ultrafast laser field. High efficiency of the third harmonic generation is experimentally fulfilled by adopting a collinear configuration of doubing-compensation-tripling system. Through finely adjusting the incident angle and optical axis direction of the compensation plate, it obtains ultraviolet （UV） output energy of 0.32 mJ centered at 270 nm with spectral bandwidth of 2 nm when input beam at 800 nm was 70 fs pulse duration and 6 mJ pulse energy which was extracted from Ti：sapphire laser system by a diaphragm, corresponding to an 800-to-270 nm conversion efficiency of 5.3% and a factor-of-l.6 improvement in the third harmonic generation of UV band in comparison with a general conventional configuration. Furthermore, when the full energy of 18 mJ from a Ti：sapphire laser system was used and optimized, the UV emission could reach 0.83 mJ.展开更多
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
It is commonly assumed that nonlinear frequency conversion requires lasers with high coherence;however,this assumption has constrained our broader understanding of coherence and overlooked the potential role of incohe...It is commonly assumed that nonlinear frequency conversion requires lasers with high coherence;however,this assumption has constrained our broader understanding of coherence and overlooked the potential role of incoherence in nonlinear interactions.In this work,we study the synthesis of optical spatial coherence in second harmonic generation using quadratic nonlinear photonic crystals.We demonstrate a method where the second harmonic coherence is customized by employing quantitative phase retrieval and a complex square-root filter sequentially on fundamental frequency speckles.As a proof-of-concept,we experimentally show incoherent imaging of a smiley face transitioning from infrared to visible light.Moreover,we apply this method to produce two representative types of structured light beams in second harmonic generation:incoherent vortex and Airy beams.During the nonlinear synthesis of incoherent vortex beams,we have,for the first time,experimentally verified the conservation of orbital angular momentum in the nonlinear frequency conversion process of a low-coherence source.Furthermore,the generated second-harmonic incoherent Airy beam preserves the self-acceleration characteristics of its fundamental frequency counterpart,remaining unaffected by reductions in coherence.Our results not only deepen the fundamental understanding of optical coherence but also unlock exciting possibilities for applications in infrared imaging and fluorescence microscopy where optical nonlinear interactions play an important role.展开更多
Considering the transmission and reflection of TE-polarized pump light at the air–crystal interface,the second harmonic generation(SHG)in a lithium niobate(LN)crystal is investigated theoretically and systematically ...Considering the transmission and reflection of TE-polarized pump light at the air–crystal interface,the second harmonic generation(SHG)in a lithium niobate(LN)crystal is investigated theoretically and systematically in this work.In previous studies,the theoretical analyses of reflection and transmission of incident wave in the process of nonlinear frequency conversion were not considered in LN crystal on account of the complicated calculations.First,we establish a physical picture describing that a beam of light in TE mode transports in the LN crystal considering transmission and reflection at the crystal surface and generates nonlinear second-order optical polarization in crystal.Then we analytically derive the reflection coefficient and transmission coefficient of pump light by using the dispersion relationships and electromagnetic boundary conditions.We construct the nonlinear coupled wave equations,derive and present the small signal approximation solution and the general large signal solution exactly.Under the transmission model and reflection model,we find that the conversion efficiency of the second-harmonic wave is obviously dependent on transmission coefficient and other general physical quantities such as the length of LN crystal and the amplitude of pump light.Our analytical theory and formulation can act as an accurate tool for the quantitative evaluation of the SHG energy conversion efficiency in an LN crystal under practical situations,and it can practically be used to treat other more complicated and general nonlinear optics problems.展开更多
We report on an idler-resonant femtosecond optical parametrical oscillator(OPO)based on BiB_(3)O_(6)(BiBO)crystal,synchronously pumped by a frequency-doubled,mode-locked Yb:KGW laser at 515 nm.The idler wavelengths of...We report on an idler-resonant femtosecond optical parametrical oscillator(OPO)based on BiB_(3)O_(6)(BiBO)crystal,synchronously pumped by a frequency-doubled,mode-locked Yb:KGW laser at 515 nm.The idler wavelengths of OPO can be tuned from 1100 nm to 1540 nm.At a repetition rate of 75.5 MHz,the OPO generates as much as 400 mW of idler power with 3.1 W of pump power,the corresponding pulse duration is 80 fs,which is 1.04 times of Fourier transform-limited(FTL)pulse duration at 1305 nm.In addition,the OPO exhibits excellent beam quality with M^(2)<1.8 at 1150 nm.To the best of our knowledge,this is the first idler-resonant femtosecond OPO pumped by 515 nm.展开更多
Broadband frequency-tripling pulses with high energy are attractive for scientific research,such as inertial confinement fusion,but are difficult to scale up.Third-harmonic generation via nonlinear frequency conversio...Broadband frequency-tripling pulses with high energy are attractive for scientific research,such as inertial confinement fusion,but are difficult to scale up.Third-harmonic generation via nonlinear frequency conversion,however,remains a trade-off between bandwidth and conversion efficiency.Based on gradient deuterium deuterated potassium dihydrogen phosphate(KD_(x)H_(2-x)PO_(4),DKDP)crystal,here we report the generation of frequency-tripling pulses by rapid adiabatic passage with a low-coherence laser driver facility.The efficiency dependence on the phase-matching angle in a Type-II configuration is studied.We attained an output at 352 nm with a bandwidth of 4.4 THz and an efficiency of 36%.These results,to the best of our knowledge,represent the first experimental demonstration of gradient deuterium DKDP crystal in obtaining frequency-tripling pulses.Our research paves a new way for developing high-efficiency,large-bandwidth frequency-tripling technology.展开更多
A 125 MHz fiber-based frequency comb source in the mid-infrared wavelength region is presented. The source is based on difference frequency generation from a polarization-maintaining Er-doped fiber pump laser and cove...A 125 MHz fiber-based frequency comb source in the mid-infrared wavelength region is presented. The source is based on difference frequency generation from a polarization-maintaining Er-doped fiber pump laser and covers a spectrum between2900 cm^(-1) and 3400 cm^(-1) with a simultaneous bandwidth of 170 cm^(-1) and an average output power up to 70 m W. The source is equipped with actuators and active feedback loops, ensuring long-term stability of the repetition rate, output power, and spectral envelope. An absorption spectrum of ethane and methane was measured using a Fourier transform spectrometer to verify the applicability of the mid-infrared comb to multispecies detection. The robustness and good long-and short-term stability of the source make it suitable for optical frequency comb spectroscopy of hydrocarbons.展开更多
基金supported by the Israel Science Foundation through the MAPATS programby the US Air Force Office for Scientific Research,AFOSR.
文摘We study the nonlinear process of second harmonic generation in photonic time-crystals,materials with refractive index that varies abruptly and periodically in time,and obtain the phase matching condition for this process.We find conditions for which the second harmonic generation is highly enhanced even in the absence of phase matching,governed by the exponential growth of the modes residing in the momentum gap of the photonic time crystal.Additionally,under these conditions,a cascade of higher-order harmonics is generated at growing exponential rates.The process is robust,with no requirement for phase-matching,the presence of a resonance or a threshold,drawing energy from the modulation.
文摘Typically, photonic waveguides designed for nonlinear frequency conversion rely on intuitive and established principles, including index guiding and bandgap engineering, and are based on simple shapes with high degrees of symmetry. We show that recently developed inverse-design techniques can be applied to discover new kinds of microstructured fibers and metasurfaces designed to achieve large nonlinear frequency-conversion efficiencies. As a proof of principle, we demonstrate complex, wavelength-scale chalcogenide glass fibers and gallium phosphide three-dimensional metasurfaces exhibiting some of the largest nonlinear conversion efficiencies predicted thus far,e.g., lowering the power requirement for third-harmonic generation by 104 and enhancing second-harmonic generation conversion efficiency by 107. Such enhancements arise because, in addition to enabling a great degree of tunability in the choice of design wavelengths, these optimization tools ensure both frequency-and phase-matching in addition to large nonlinear overlap factors.
基金supported by the Research Project of the Aerospace Information Research Institute,the Chinese Academy of Sciences(Grant Nos.E1Z1D101 and E2Z2D101)the Chinese Academy of Sciences(Grant No.E33310030D)the Guangzhou Basic and Applied Basic Research Foundation(Grant Nos.2023A04J0336 and 2023A04J0024).
文摘Deep ultraviolet coherent light,particularly at the wavelength of 193 nm,has become indispensable for semiconductor lithography.We present a compact solid-state nanosecond pulsed laser system capable of generating 193-nm coherent light at the repetition rate of 6 kHz.One part of the 1030-nm laser from the homemade Yb:YAG crystal amplifier is divided to generate 258 nm laser(1.2 W)by fourth-harmonic generation,and the rest is used to pump an optical parametric amplifier producing 1553 nm laser(700 mW).Frequency mixing of these beams in cascaded LiB_(3)O_(5) crystals yields a 193-nm laser with 70-mW average power and a linewidth of less than 880 MHz.By introducing a spiral phase plate to the 1553-nm beam before frequency mixing,we generate a vortex beam carrying orbital angular momentum.This is,to our knowledge,the first demonstration of a 193-nm vortex beam generated from a solid-state laser.Such a beam could be valuable for seeding hybrid ArF excimer lasers and has potential applications in wafer processing and defect inspection.
基金Project supported by the National Basic Research Program of China (Grant No 2006CB0806001)the Program for Changjiang and Innovative Research Team in UniversityShanghai Leading Academic Discipline Project (Grant No B408)
文摘This paper demonstrates an approach that negative uniaxial crystal has a relative anomalous dispersion effect which can compensate group velocity delay, and applies this approach to nonlinear frequency conversion of an ultrafast laser field. High efficiency of the third harmonic generation is experimentally fulfilled by adopting a collinear configuration of doubing-compensation-tripling system. Through finely adjusting the incident angle and optical axis direction of the compensation plate, it obtains ultraviolet （UV） output energy of 0.32 mJ centered at 270 nm with spectral bandwidth of 2 nm when input beam at 800 nm was 70 fs pulse duration and 6 mJ pulse energy which was extracted from Ti：sapphire laser system by a diaphragm, corresponding to an 800-to-270 nm conversion efficiency of 5.3% and a factor-of-l.6 improvement in the third harmonic generation of UV band in comparison with a general conventional configuration. Furthermore, when the full energy of 18 mJ from a Ti：sapphire laser system was used and optimized, the UV emission could reach 0.83 mJ.
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support provided by Israel Science Foundation,grants 969/22 and 3117/23.
文摘It is commonly assumed that nonlinear frequency conversion requires lasers with high coherence;however,this assumption has constrained our broader understanding of coherence and overlooked the potential role of incoherence in nonlinear interactions.In this work,we study the synthesis of optical spatial coherence in second harmonic generation using quadratic nonlinear photonic crystals.We demonstrate a method where the second harmonic coherence is customized by employing quantitative phase retrieval and a complex square-root filter sequentially on fundamental frequency speckles.As a proof-of-concept,we experimentally show incoherent imaging of a smiley face transitioning from infrared to visible light.Moreover,we apply this method to produce two representative types of structured light beams in second harmonic generation:incoherent vortex and Airy beams.During the nonlinear synthesis of incoherent vortex beams,we have,for the first time,experimentally verified the conservation of orbital angular momentum in the nonlinear frequency conversion process of a low-coherence source.Furthermore,the generated second-harmonic incoherent Airy beam preserves the self-acceleration characteristics of its fundamental frequency counterpart,remaining unaffected by reductions in coherence.Our results not only deepen the fundamental understanding of optical coherence but also unlock exciting possibilities for applications in infrared imaging and fluorescence microscopy where optical nonlinear interactions play an important role.
基金the National Natural Science Foundation of China(Grant No.11974119)the Science and Technology Project of Guangdong Province,China(Grant No.2020B010190001)+1 种基金the Guangdong Innovative and Entrepreneurial Research Team Program,China(Grant No.2016ZT06C594)the National Key Research and Development Program of China(Grant No.2018YFA 0306200)。
文摘Considering the transmission and reflection of TE-polarized pump light at the air–crystal interface,the second harmonic generation(SHG)in a lithium niobate(LN)crystal is investigated theoretically and systematically in this work.In previous studies,the theoretical analyses of reflection and transmission of incident wave in the process of nonlinear frequency conversion were not considered in LN crystal on account of the complicated calculations.First,we establish a physical picture describing that a beam of light in TE mode transports in the LN crystal considering transmission and reflection at the crystal surface and generates nonlinear second-order optical polarization in crystal.Then we analytically derive the reflection coefficient and transmission coefficient of pump light by using the dispersion relationships and electromagnetic boundary conditions.We construct the nonlinear coupled wave equations,derive and present the small signal approximation solution and the general large signal solution exactly.Under the transmission model and reflection model,we find that the conversion efficiency of the second-harmonic wave is obviously dependent on transmission coefficient and other general physical quantities such as the length of LN crystal and the amplitude of pump light.Our analytical theory and formulation can act as an accurate tool for the quantitative evaluation of the SHG energy conversion efficiency in an LN crystal under practical situations,and it can practically be used to treat other more complicated and general nonlinear optics problems.
基金Key-Area Research and Development Program of Guangdong Province,China(Grant No.2018B090904003)the National Natural Science Foundation of China(Grant Nos.11774410 and 91850209)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB16030200).
文摘We report on an idler-resonant femtosecond optical parametrical oscillator(OPO)based on BiB_(3)O_(6)(BiBO)crystal,synchronously pumped by a frequency-doubled,mode-locked Yb:KGW laser at 515 nm.The idler wavelengths of OPO can be tuned from 1100 nm to 1540 nm.At a repetition rate of 75.5 MHz,the OPO generates as much as 400 mW of idler power with 3.1 W of pump power,the corresponding pulse duration is 80 fs,which is 1.04 times of Fourier transform-limited(FTL)pulse duration at 1305 nm.In addition,the OPO exhibits excellent beam quality with M^(2)<1.8 at 1150 nm.To the best of our knowledge,this is the first idler-resonant femtosecond OPO pumped by 515 nm.
基金supported by the President Funding Independent Project of the China Academy of Engineering Physics(No.YZJJZL2024200)the National Natural Science Foundation of China(No.62405298)the National Key Research and Development Program of China(No.2023YFA1608503).
文摘Broadband frequency-tripling pulses with high energy are attractive for scientific research,such as inertial confinement fusion,but are difficult to scale up.Third-harmonic generation via nonlinear frequency conversion,however,remains a trade-off between bandwidth and conversion efficiency.Based on gradient deuterium deuterated potassium dihydrogen phosphate(KD_(x)H_(2-x)PO_(4),DKDP)crystal,here we report the generation of frequency-tripling pulses by rapid adiabatic passage with a low-coherence laser driver facility.The efficiency dependence on the phase-matching angle in a Type-II configuration is studied.We attained an output at 352 nm with a bandwidth of 4.4 THz and an efficiency of 36%.These results,to the best of our knowledge,represent the first experimental demonstration of gradient deuterium DKDP crystal in obtaining frequency-tripling pulses.Our research paves a new way for developing high-efficiency,large-bandwidth frequency-tripling technology.
基金supported by the Foundation for Polish Science within the First TEAM program co-financed by the European Union under the European Regional Development Fund (No.First TEAM/2017-4/39)the Knut and Alice Wallenberg Foundation (No.KAW 2015.0159)。
文摘A 125 MHz fiber-based frequency comb source in the mid-infrared wavelength region is presented. The source is based on difference frequency generation from a polarization-maintaining Er-doped fiber pump laser and covers a spectrum between2900 cm^(-1) and 3400 cm^(-1) with a simultaneous bandwidth of 170 cm^(-1) and an average output power up to 70 m W. The source is equipped with actuators and active feedback loops, ensuring long-term stability of the repetition rate, output power, and spectral envelope. An absorption spectrum of ethane and methane was measured using a Fourier transform spectrometer to verify the applicability of the mid-infrared comb to multispecies detection. The robustness and good long-and short-term stability of the source make it suitable for optical frequency comb spectroscopy of hydrocarbons.
