Optical true delay lines(OTDLs)of low propagation losses,small footprints and high tuning speeds and efficiencies are of critical importance for various photonic applications.Here,we report fabrication of electro-opti...Optical true delay lines(OTDLs)of low propagation losses,small footprints and high tuning speeds and efficiencies are of critical importance for various photonic applications.Here,we report fabrication of electro-optically switchable OTDLs on lithium niobate on insulator using photolithography assisted chemo-mechanical etching.Our device consists of several low-loss optical waveguides of different lengths which are consecutively connected by electro-optical switches to generate different amounts of time delay.The fabricated OTLDs show an ultra-low propagation loss of^0.03dB/cm for waveguide lengths well above 100 cm.展开更多
We investigate nonlinear interaction of nitrogen molecules with a two-color laser field composed by an intense 800 nm laser pulse and a weak 400 nm laser pulse.It is demonstrated that the spectrum of 400 nm pulses is ...We investigate nonlinear interaction of nitrogen molecules with a two-color laser field composed by an intense 800 nm laser pulse and a weak 400 nm laser pulse.It is demonstrated that the spectrum of 400 nm pulses is dramatically broadened when the two beams temporally overlap.In comparison,the spectral broadening in argon is less pronounced,although argon atoms and nitrogen molecules have comparable ionization potentials.We reveal that the dramatic spectral broadening originates from the greatly enhanced nonlinear optical effects in the near-resonant condition of interaction between the 400 nm pulses and the nitrogen molecular ions.展开更多
The heterogeneous integration of photonic integrated circuits(PICs)with a diverse range of optoelectronic materials has emerged as a transformative approach,propelling photonic chips toward larger scales,superior perf...The heterogeneous integration of photonic integrated circuits(PICs)with a diverse range of optoelectronic materials has emerged as a transformative approach,propelling photonic chips toward larger scales,superior performance,and advanced integration levels.Notably,two-dimensional(2D)materials,such as graphene,transition metal dichalcogenides(TMDCs),black phosphorus(BP),and hexagonal boron nitride(hBN),exhibit remarkable device performance and integration capabilities,offering promising potential for large-scale implementation in PICs.In this paper,we first present a comprehensive review of recent progress,systematically categorizing the integration of photonic circuits with 2D materials based on their types while also emphasizing their unique advantages.Then,we discuss the integration approaches of 2D materials with PICs.We also summarize the technical challenges in the heterogeneous integration of 2D materials in photonics and envision their immense potential for future applications in PICs.展开更多
We demonstrate high-quality(intrinsic Q factor∼2.8×106)racetrack microresonators fabricated on lithium niobate thin film with a free spectral range(FSR)of∼86 pm.By integrating microelectrodes alongside the two ...We demonstrate high-quality(intrinsic Q factor∼2.8×106)racetrack microresonators fabricated on lithium niobate thin film with a free spectral range(FSR)of∼86 pm.By integrating microelectrodes alongside the two straight arms of the racetrack resonator,the resonance wavelength around 1550 nm can be red shifted by 92 pm when the electric voltage is raised from−100 V to 100 V.The microresonators with the tuning range spanning over a full FSR are fabricated using photolithography assisted chemo-mechanical etching.展开更多
We experimentally demonstrate N2^＋ lasing actions at the wavelengths of 353.3, 353.8, and 354.9 nm using a circularly polarized femtosecond laser. The three laser lines correspond to the B2∑u^＋（v＇ = 5, 4, 3） →...We experimentally demonstrate N2^＋ lasing actions at the wavelengths of 353.3, 353.8, and 354.9 nm using a circularly polarized femtosecond laser. The three laser lines correspond to the B2∑u^＋（v＇ = 5, 4, 3） → X2∑g^＋（v = 4, 3, 2） transitions, respectively. Particularly, we reveal the pressure-dependent gain dynamics of these lasing actions from highly excited vibrational states with a pump-probe scheme. Our experimental results confirm that electron eollisional excitation plays an important role in the establishment of a population inversion of N2^＋ lasing at these wavelengths.展开更多
We report on an experimental investigation on the dynamic decoherence process of molecular rotational wavepackets during femtosecond laser filamentation based on time-dependent mean wavelength shifts of a weak probe p...We report on an experimental investigation on the dynamic decoherence process of molecular rotational wavepackets during femtosecond laser filamentation based on time-dependent mean wavelength shifts of a weak probe pulse. Details of periodic revival structures of transient alignment can be readily obtained from the measured shifted spectra due to the periodic modulation of the molecular refractive index. Using the method, we measured decoherence lifetimes of molecular rotational wavepackets in N2and O2under different experimental conditions. Our results indicate that decoherence lifetimes of molecular rotational wavepackets are primarily determined by the relative population of rotational states in the wave packet and intermolecular collisions,rather than the focusing intensity.展开更多
Spatio-temporal coupling characteristics of ultrafast laser pulses are quantitatively tailored. An asymmetric microstructure is induced in the focal volume when the laser scans perpendicularly to the direction of the ...Spatio-temporal coupling characteristics of ultrafast laser pulses are quantitatively tailored. An asymmetric microstructure is induced in the focal volume when the laser scans perpendicularly to the direction of the spatial chirp in fused silica. The tilted direction reverses when adding a Dove prism into the light path. The sign of the pulse front tilt can be turned from positive to negative by changing the group delay dispersion by steps. We reveal that the tilted direction of a microstructure depends on spatial chirp, and the interplay between spatiotemporal chirp leads to the change of tilted angles.展开更多
基金Supported by the National Key R&D Program of China(Grant No.2019YFA0705000)the National Natural Science Foundation of China(Grant Nos.11734009,61590934,and 11874375)+1 种基金the Strategic Priority Research Program of CAS(Grant No.XDB16030300)the Key Project of the Shanghai Science and Technology Committee(Grant No.17JC1400400).
文摘Optical true delay lines(OTDLs)of low propagation losses,small footprints and high tuning speeds and efficiencies are of critical importance for various photonic applications.Here,we report fabrication of electro-optically switchable OTDLs on lithium niobate on insulator using photolithography assisted chemo-mechanical etching.Our device consists of several low-loss optical waveguides of different lengths which are consecutively connected by electro-optical switches to generate different amounts of time delay.The fabricated OTLDs show an ultra-low propagation loss of^0.03dB/cm for waveguide lengths well above 100 cm.
基金Supported by the National Key Research and Development Program of China under Grant No 2018YFB0504400the National Natural Science Foundation of China under Grant Nos 11822410,11734009 and 61575211+4 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDB16030300the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences under Grant No QYZDJ-SSW-SLH010the Key Project of the Shanghai Science and Technology Committee under Grant No 18DZ1112700the Shanghai Rising-Star Program under Grant No 17QA1404600the Youth Innovation Promotion Association of the Chinese Academy of Sciences under Grant No 2018284
文摘We investigate nonlinear interaction of nitrogen molecules with a two-color laser field composed by an intense 800 nm laser pulse and a weak 400 nm laser pulse.It is demonstrated that the spectrum of 400 nm pulses is dramatically broadened when the two beams temporally overlap.In comparison,the spectral broadening in argon is less pronounced,although argon atoms and nitrogen molecules have comparable ionization potentials.We reveal that the dramatic spectral broadening originates from the greatly enhanced nonlinear optical effects in the near-resonant condition of interaction between the 400 nm pulses and the nitrogen molecular ions.
文摘The heterogeneous integration of photonic integrated circuits(PICs)with a diverse range of optoelectronic materials has emerged as a transformative approach,propelling photonic chips toward larger scales,superior performance,and advanced integration levels.Notably,two-dimensional(2D)materials,such as graphene,transition metal dichalcogenides(TMDCs),black phosphorus(BP),and hexagonal boron nitride(hBN),exhibit remarkable device performance and integration capabilities,offering promising potential for large-scale implementation in PICs.In this paper,we first present a comprehensive review of recent progress,systematically categorizing the integration of photonic circuits with 2D materials based on their types while also emphasizing their unique advantages.Then,we discuss the integration approaches of 2D materials with PICs.We also summarize the technical challenges in the heterogeneous integration of 2D materials in photonics and envision their immense potential for future applications in PICs.
基金funded by the National Key R&D Program of China(No.2019YFA0705000)the National Natural Science Foundation of China(Nos.12004116,11874154,and 11734009)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB16030300)the Shanghai Municipal Science and Technology Major Project(No.2019SHZDZX01)the Natural Science and Engineering Research Council of Canada(NSERC)Discovery(No.RGPIN-2020-05938)。
文摘We demonstrate high-quality(intrinsic Q factor∼2.8×106)racetrack microresonators fabricated on lithium niobate thin film with a free spectral range(FSR)of∼86 pm.By integrating microelectrodes alongside the two straight arms of the racetrack resonator,the resonance wavelength around 1550 nm can be red shifted by 92 pm when the electric voltage is raised from−100 V to 100 V.The microresonators with the tuning range spanning over a full FSR are fabricated using photolithography assisted chemo-mechanical etching.
基金supported by the National Basic Research Program of China(Grant Nos.2011CB808102 and 2014CB921300)the National Natural Science Foundation of China(Grant Nos.11134010,11204332,and11304330)the Program of Shanghai Subject Chief Scientist(Grant No.11XD1405500)
文摘We experimentally demonstrate N2^＋ lasing actions at the wavelengths of 353.3, 353.8, and 354.9 nm using a circularly polarized femtosecond laser. The three laser lines correspond to the B2∑u^＋（v＇ = 5, 4, 3） → X2∑g^＋（v = 4, 3, 2） transitions, respectively. Particularly, we reveal the pressure-dependent gain dynamics of these lasing actions from highly excited vibrational states with a pump-probe scheme. Our experimental results confirm that electron eollisional excitation plays an important role in the establishment of a population inversion of N2^＋ lasing at these wavelengths.
基金supported by the National Basic Research Program of China(No.2014CB921303)the National Natural Science Foundation of China(Nos.61575211,11674340,61405220,11404357,61605227,61705034,and 11704066)+5 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB16000000)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(No.QYZDJ-SSW-SLH010)the Shanghai Yangfan Program(No.16YF1412700)the Natural Science Foundation of Jiangxi Province(No.20171BAB211007)the Science and Technology Project of Jiangxi Provincial Education Department(Nos.GJJ160587 and GJJ160576)the Shanghai Rising-Star Program(No.17QA1404600)
文摘We report on an experimental investigation on the dynamic decoherence process of molecular rotational wavepackets during femtosecond laser filamentation based on time-dependent mean wavelength shifts of a weak probe pulse. Details of periodic revival structures of transient alignment can be readily obtained from the measured shifted spectra due to the periodic modulation of the molecular refractive index. Using the method, we measured decoherence lifetimes of molecular rotational wavepackets in N2and O2under different experimental conditions. Our results indicate that decoherence lifetimes of molecular rotational wavepackets are primarily determined by the relative population of rotational states in the wave packet and intermolecular collisions,rather than the focusing intensity.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.11774220,11604202,and 61735010)
文摘Spatio-temporal coupling characteristics of ultrafast laser pulses are quantitatively tailored. An asymmetric microstructure is induced in the focal volume when the laser scans perpendicularly to the direction of the spatial chirp in fused silica. The tilted direction reverses when adding a Dove prism into the light path. The sign of the pulse front tilt can be turned from positive to negative by changing the group delay dispersion by steps. We reveal that the tilted direction of a microstructure depends on spatial chirp, and the interplay between spatiotemporal chirp leads to the change of tilted angles.
