Research on supercontinuum sources on silicon has made significant progress in the past few decades.However,conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engin...Research on supercontinuum sources on silicon has made significant progress in the past few decades.However,conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engineering by optimizing the core thickness or introducing the cladding with special materials and structures.We propose and demonstrate supercontinuum generation using long-periodgrating(LPG)waveguides on silicon with a C-band pump.The LPG waveguide is introduced for quasi-phase matching,and the generated supercontinuum spectrum is improved greatly with grating-induced dispersive waves.In addition,the demonstrated LPG waveguide shows a low propagation loss comparable with regular silicon photonic waveguides without gratings.In experiments,when using a 1550-nm 75-fs pulse pump with a pulse energy of 200 pJ,the supercontinuum spectrum generated with the present LPG waveguide shows an ultrabroad extent from 1150 to 2300 nm,which is much wider by 200 nm than that achieved by dispersionengineered uniform silicon photonic waveguides on the same chip.This provides a promising option for on-chip broadband light source for silicon photonic systems.展开更多
We demonstrate the generation of supercontinuum(SC) spectrum covering S+C+L band of optical communication by injecting 1.4 ps optical pulses with center wavelength of 1552 nm and repetition rate of 10 GHz into an all-...We demonstrate the generation of supercontinuum(SC) spectrum covering S+C+L band of optical communication by injecting 1.4 ps optical pulses with center wavelength of 1552 nm and repetition rate of 10 GHz into an all-normal dispersion photonic crystal fiber(PCF) with length of 80 m. The experimental results are in good agreement with the numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking(WB).展开更多
We report on the fabrication of the lO-mm-long lithium niobate ridge waveguide and its supercontinuum gen- eration at near-visible wavelengths （around 800hm）. The waveguides are fabricated by a combination of MeV co...We report on the fabrication of the lO-mm-long lithium niobate ridge waveguide and its supercontinuum gen- eration at near-visible wavelengths （around 800hm）. The waveguides are fabricated by a combination of MeV copper ion implantation followed by wet etching in a proton exchanged lithium niobate planar waveguide. Using a mode-locked Ti：sapphire laser with a central wavelength of 800nm, the generated broadest supereontinuum through the ridge waveguides spans 302 nm （at -30 dB points）, from 693 to 995 nm. Temporal coherence proper- ties of the supercontinuum are experimentally studied by a Michelson interferometer and the coherence length of the broadest supercontinuum is measured to be 5.2 μm. Our results offer potential for a compact and integrated supercontinuum source for applications including bio-imaging, spectroscopy and optical communication.展开更多
An intense supercontinuum（SC） in the near-ultraviolet range is generated from filamentation by focusing a 400-nm laser into fused silica with a microlens array（MLA）. The spectrum of the SC is shown to be sensitive...An intense supercontinuum（SC） in the near-ultraviolet range is generated from filamentation by focusing a 400-nm laser into fused silica with a microlens array（MLA）. The spectrum of the SC is shown to be sensitive to the distance between the MLA and fused silica. In our optimal conditions, the near-ultraviolet SC can cover a range of 350-600 nm,where a bandwidth of approximately 55 nm above the 1μJ/nm spectral energy density and 20 nm bandwidth with tens ofμJ/nm are achieved. In addition, the energy conversion efficiency of the 400 nm laser for SC generation is further analyzed.A maximum conversion efficiency of 66% is obtained when the entrance face of fused silica is set around the focus of the MLA.展开更多
Picosecond pulse pumped supercontinuum generation in photonic crystal fiber is investigated by performing a series of comparative experiments. The main purpose is to investigate the supercontinuum generation processes...Picosecond pulse pumped supercontinuum generation in photonic crystal fiber is investigated by performing a series of comparative experiments. The main purpose is to investigate the supercontinuum generation processes excited by a given pump source through the experimental study of some specific fibers. A 20-W all-fiber picosecond master oscillator-power amplifier （MOPA） laser is used to pump three different kinds of photonic crystal fibers for supercontinuum generation. Three diverse supercontinuum formation processes are observed to correspond to photonie crystal fibers with distinct dis- persion properties. The experimental results are consistent with the relevant theoretical results. Based on the above analyses, a watt-level broadband white light supercontinuum source spanning from 500 nm to beyond 1700 nm is demonstrated by using a picosecond fiber laser in combination with the matched photonic crystal fiber. The limitation of the group velocity matching curve of the photonic crystal fiber is also discussed in the paper.展开更多
We theoretically investigate the high-order harmonic generation from stretched molecules in a linearly polarized intense field. By adopting an infrared pulse combined with an ultraviolet （UV） attosecond pulse, the i...We theoretically investigate the high-order harmonic generation from stretched molecules in a linearly polarized intense field. By adopting an infrared pulse combined with an ultraviolet （UV） attosecond pulse, the ionization process can be controlled effectively. In this excitation scheme, the harmonic spectrum beyond Ip ＋ 3.17Up is significantly enhanced by two orders, where Ip and Up = e^2E0^2/（4mew^2） are the ionization and ponderomotive potential, then smooth broadband supercontinuum with the bandwidth of about 120 eV is obtained, which leads to an isolated sub-60- as attosecond pulse with a high signal-noise ratio. Moreover, the bandwidth of the supercontinuum is weakly dependent on the location and pulse duration of the UV pulse.展开更多
We report supercontinuum （SC） generation in a lead silicate SF57 photonic crystal fiber by using a 1550 nm pump source. The effective nonlinear coefficient of the SF57 fiber is simulated to be 111.5 W-1 .km- 1 at 15...We report supercontinuum （SC） generation in a lead silicate SF57 photonic crystal fiber by using a 1550 nm pump source. The effective nonlinear coefficient of the SF57 fiber is simulated to be 111.5 W-1 .km- 1 at 1550 nm. The fiber also shows ultraflat dispersion from 1700 nm to 2100 nm. Our results reveal that with an increase of the average power of the incident pulse from 10 mW to 90 mW, the SC of the SF57 photonic crystal fiber is generated from 1300 nm to 1900 nm with high stability and without significant change in spectral broadening.展开更多
High power supercontinuum(SC) is generated by focusing 800 nm and 400 nm femtosecond laser pulses in fused silica with a microlens array. It is found that the spectrum of the SC is getting broader compared with the ca...High power supercontinuum(SC) is generated by focusing 800 nm and 400 nm femtosecond laser pulses in fused silica with a microlens array. It is found that the spectrum of the SC is getting broader compared with the case of a single laser pulse, and the spectral energy density between the two fundamental laser wavelengths is getting significantly higher by optimizing the phase matching angle of the BBO. It exceeds μJ/nm over 490 nm range which is from 380 nm to 870 nm,overcoming the disadvantage of relative lower power in the ranges far from the fundamental wavelength.展开更多
Spectral modulation and supercontinuum generation of a probe pulse is investigated by using the plasma grating induced by the interference of two infrared femtosecond laser pulses. The dependences of the supercontinuu...Spectral modulation and supercontinuum generation of a probe pulse is investigated by using the plasma grating induced by the interference of two infrared femtosecond laser pulses. The dependences of the supercontinuum generation from the probe pulse on the time delay, the relative polarization angle between the probe pulse and the two-pump pulses, and the input probe pulse energy are investigated. The far-field spatial profiles of the three pulses are measured with different time delays and relative polarization angle, and the core energy of the probe pulse as functions of the time delay and relative polarization angle are also shown.展开更多
We utilized a set of fused silica thin plates to broaden the spectrum of 1kHz,30 fs Ti:sapphire amplified laser pulses to an octave.Following the compression by chirped mirror pairs,the generated few-cycle pulses were...We utilized a set of fused silica thin plates to broaden the spectrum of 1kHz,30 fs Ti:sapphire amplified laser pulses to an octave.Following the compression by chirped mirror pairs,the generated few-cycle pulses were focused onto an argon filled gas cell.We detected high order harmonics corresponding to a train of 209 as pulses,characterized by the reconstruction of attosecond beating by interference of two-photon transition(RABITT)technique.Compared with the conventional attosecond pulse trains,the broad harmonics in such pulse trains cover more energy range,so it is more efficient in studying some typical cases,such as resonances,with frequency resolved RABITT.As the solid thin plates can support high power supercontinuum generation,it is feasible to tailor the spectrum to have different central wavelength and spectral width,which will make the RABITT source work in different applications.展开更多
Simultaneously increasing the spectral bandwidth and average output power of mid-infrared supercontinuum sources remains a major challenge for their practical application.We particularly address this issue for the lon...Simultaneously increasing the spectral bandwidth and average output power of mid-infrared supercontinuum sources remains a major challenge for their practical application.We particularly address this issue for the long mid-infrared spectral region through experimental developments of short tapered rods made from selenide glass by means of supercontinuum generation in the femtosecond regime.Our simple post-processing of glass rods unlocks potentially higher-power and coherent fiber-based supercontinuum sources beyond the 10-μm wave-band.By using a 5-cm-long tapered Ge-Se-Te rod pumped at 6μm,a supercontinuum spanning from 2 to 15μm(3–14μm)with an average output power of 93 m W(170 m W)is obtained for 500-k Hz(1-MHz)repetition rate.Additional experiments on other glass families(silica and tellurite)covering distinct spectral regions are also reported to develop and support our analyses.We demonstrate that ultra-broadband spectral broadenings over entire glass transmission windows can be achieved in few-cm-long segments of tapered rods by a fine adjustment of input modal excitation.Numerical simulations are used to confirm the main contribution of the fundamental mode in the ultrafast nonlinear dynamics,as well as the possible preservation of coherence features.Our study opens a new route,to our knowledge,towards the power scaling of high-repetition-rate fiber supercontinuum sources over the full molecular fingerprint region.展开更多
Ultrafast supercontinuum generation in gas-filled waveguides is an enabling technology for many intriguing applications ranging from attosecond metrology towards biophotonics,with the amount of spectral broadening cru...Ultrafast supercontinuum generation in gas-filled waveguides is an enabling technology for many intriguing applications ranging from attosecond metrology towards biophotonics,with the amount of spectral broadening crucially depending on the pulse dispersion of the propagating mode.In this study,we show that structural resonances in a gas-filled antiresonant hollow core optical fiber provide an additional degree of freedom in dispersion engineering,which enables the generation of more than three octaves of broadband light that ranges from deep UV wavelengths to near infrared.Our observation relies on the introduction of a geometric-induced resonance in the spectral vicinity of the ultrafast pump laser,outperforming gas dispersion and yielding a unique dispersion profile independent of core size,which is highly relevant for scaling input powers.Using a krypton-filled fiber,we observe spectral broadening from 200 nm to 1.7μm at an output energy of B 23μJ within a single optical mode across the entire spectral bandwidth.Simulations show that the frequency generation results from an accelerated fission process of solitonlike waveforms in a non-adiabatic dispersion regime associated with the emission of multiple phase-matched Cherenkov radiations on both sides of the resonance.This effect,along with the dispersion tuning and scaling capabilities of the fiber geometry,enables coherent ultra-broadband and high-energy sources,which range from the UV to the mid‐infrared spectral range.展开更多
We report the demonstration of a mid-infrared(MIR)supercontinuum(SC)laser delivering a record-breaking average output power of more than 40 W with a long-wavelength edge up to 3.5μm.The all-fiberized configuration wa...We report the demonstration of a mid-infrared(MIR)supercontinuum(SC)laser delivering a record-breaking average output power of more than 40 W with a long-wavelength edge up to 3.5μm.The all-fiberized configuration was composed of a thulium-doped fiber amplifier system emitting a broadband spectrum covering 1.9–2.6μm with pulse repetition rate of 3 MHz,and a short piece of germania fiber.A 41.9 W MIR SC with a whole spectrum of 1.9–3.5μm was generated in a piece of 0.2-m-long germania fiber,with a power conversion efficiency of 71.4%.For an even shorter germania fiber(0.1 m),an SC with even higher output power of 44.9 W(corresponding to a conversion efficiency of 76.5%)was obtained,but the energy conversion toward the long-wavelength region was slightly limited.A continuous operation for 1 hour with output power of 32.6 W showed outstanding power stability(root mean square 0.17%)of the obtained SC laser.To the best of the authors’knowledge,for the first time,this work demonstrates the feasibility of germania fiber on generating a 40-W level MIR SC with high efficiency and excellent power stability,paving the way to real applications requiring high power and high reliability of MIR SC lasers.展开更多
High flatness, wide bandwidth, and high-coherence properties of supercontinuum(SC) generation in fibers are crucial in many applications. It is challenging to achieve SC spectra in a combination of the properties, sin...High flatness, wide bandwidth, and high-coherence properties of supercontinuum(SC) generation in fibers are crucial in many applications. It is challenging to achieve SC spectra in a combination of the properties, since special dispersion profiles are required, especially when pump pulses with duration over 100 fs are employed. We propose an all-solid microstructured fiber composed only of hexagonal glass elements. The optimized fiber possesses an ultraflat all-normal dispersion profile, covering a wide wavelength interval of approximately 1.55 μm. An SC spectrum spanning from approximately 1030 to 2030 nm(corresponding to nearly one octave) with flatness<3 dB is numerically generated in the fiber with 200 fs pump pulses at 1.55 μm. The results indicate that the broadband ultraflat SC sources can be all-fiber and miniaturized due to commercially achievable 200-fs fiber lasers. Moreover, the SC pulses feature high coherence and a single pulse in the time domain, which can be compressed to 13.9-fs pulses with high quality even for simple linear chirp compensation. The Fourier-limited pulse duration of the spectrum is 3.19 fs, corresponding to only 0.62 optical cycles.展开更多
We demonstrate the generation of supercontinuum (SC) of over 1350 nm by injecting 790-nm, 15-fs, 74-MHz optical pulses into a 183-mm-long microstructured fiber with combination core and random cladding. The maximum to...We demonstrate the generation of supercontinuum (SC) of over 1350 nm by injecting 790-nm, 15-fs, 74-MHz optical pulses into a 183-mm-long microstructured fiber with combination core and random cladding. The maximum total power of SC is 73 mW with 290-mW pump power from 40x microscope objective. The wavelength and power ranging in SC as well as the polarization states and waveguide modes of the visible light can be tuned by adjusting the input end of MF.In particular, white light has been observed. To our knowledge, this is the first report of tunable properties in SC generation process using microstructured fiber with combination core and random cladding.展开更多
In this paper,the optimum supercontinuum(SC)spectrum generation in a dispersion decreasing fiber is presented.Three normalized parameters for the pump pulse and SC fiber are introduced.It is found that the shape of an...In this paper,the optimum supercontinuum(SC)spectrum generation in a dispersion decreasing fiber is presented.Three normalized parameters for the pump pulse and SC fiber are introduced.It is found that the shape of an SC spectrum is uniquely specified by the input soliton order,the normalized dispersion slope and the normalized effective fiber length.For a pumping condition with a given input soliton order and a given normalized dispersion slope,by optimizing the normalized effective fiber length,the residual spectral peak in the SC spectrum can be suppressed effectively,and a broad SC spectrum with optimum spectral flatness can be obtained.展开更多
We report on compact and robust supercontinuum generation and post-compression using transmission of light through multiple thin solid plates at the Swiss FEL X-ray free-electron laser facility.A single stage consisti...We report on compact and robust supercontinuum generation and post-compression using transmission of light through multiple thin solid plates at the Swiss FEL X-ray free-electron laser facility.A single stage consisting of three thin plates followed by a chirped mirror compressor achieves compression of initially 30-fs pulses with 800-nm center wavelength to sub-10-fs duration.We also demonstrate a two-stage implementation to compress the pulses further to sub-5-fs duration.With the two-stage setup,the generated supercontinuum includes wavelengths ranging from 500 to 1100 nm.The multiplate setup is compact,robust,and stable,which makes it ideal for applications at free-electron laser facilities such as pump-probe experiments and laser-arrival timing tools.展开更多
An overview of the progress on pulse-preserving, coherent, nonlinear fiber-based supercontinuum generation is presented. The context encompasses various wavelength ranges and pump sources, starting with silica photoni...An overview of the progress on pulse-preserving, coherent, nonlinear fiber-based supercontinuum generation is presented. The context encompasses various wavelength ranges and pump sources, starting with silica photonic crystal fibers pumped with 1.0 μm femtosecond lasers up to chalcogenide step-index and microstructured fibers pumped from optical parametric amplifiers tuned to mid-infrared wavelengths. In particular, silica and silicatebased all-normal dispersion(ANDi) photonic crystal fibers have been demonstrated for pumping with femtosecond lasers operating at 1.56 μm with the recorded spectra covering 0.9–2.3 μm. This matches amplification bands of robust fiber amplifiers and femtosecond lasers. The review therefore focuses specifically on this wavelength range, discussing glass and nonlinear fiber designs, experimental results on supercontinuum generation up to the fundamental limit of oxide glass fiber transmission around 2.8 μm, and various limitations of supercontinuum bandwidth and coherence. Specifically, the role of nonlinear response against the role of dispersion profile shape is analyzed for two different soft glass ANDi fibers pumped at more than 2.0 μm. A spatio-temporal interaction of the fundamental fiber mode with modes propagating in the photonic lattice of the discussed ANDi fibers is shown to have positive effects on the coherence of the supercontinuum at pump pulse durations of 400 fs. Finally, the design and development of graded-index, nanostructured core optical fibers are discussed.In such structures the arbitrary shaping of the core refractive index profile could significantly improve the engineering flexibility of dispersion and effective mode area characteristics, and would be an interesting platform to further study the intermodal interaction mechanisms and their impact on supercontinuum coherence for subpicosecond laser pumped setups.展开更多
A spectrally flat mid-infrared supercontinuum(MIR-SC) spanning 2.8–3.9 μm with a maximum output power of 411 mW was generated in a holmium-doped ZBLAN fiber amplifier(HDZFA). A broadband fiber-based SC covering the ...A spectrally flat mid-infrared supercontinuum(MIR-SC) spanning 2.8–3.9 μm with a maximum output power of 411 mW was generated in a holmium-doped ZBLAN fiber amplifier(HDZFA). A broadband fiber-based SC covering the 2.4–3.2 μm region was designed to seed the amplifier. Benefiting from the broadband seed laser,the obtained SC had a high spectral flatness of 3 dB over the range of 2.93–3.70 μm(770 nm). A spectral integral showed that the SC power beyond 3 μm was 372 mW, i.e., a power ratio of 90.6% of the total power. This paper,to the best of our knowledge, not only demonstrates the first spectrally flat MIR-SC directly generated in fluoride fiber amplifiers, but also reports the highest power ratio beyond 3 μm obtained in rare-earth-doped fluoride fiber until now.展开更多
Chalcogenide(ChG)glasses have the characteristics of a wide transparency window(over 20μm)and high optical nonlinearity(up to 103 times greater than that of silica glasses),exhibiting great advantages over silica and...Chalcogenide(ChG)glasses have the characteristics of a wide transparency window(over 20μm)and high optical nonlinearity(up to 103 times greater than that of silica glasses),exhibiting great advantages over silica and other soft glasses in optical property at mid-infrared(MIR)wavelength range.These make them excellent candidates for MIR supercontinuum(SC)generation.Over the past decades,great progress has been made in MIR SC generation based on ChG fibers in terms of spectral extension and output power improvement.In this paper,we introduce briefly the properties of ChG glasses and fibers including transmission,nonlinearity,and dispersion,etc.Recent progress in MIR SC generation based on ChG fibers is reviewed from the perspective of pump schemes.We also present novel ChG fibers such as As-free,Te-based,and chalcohalide fibers,which have been explored and employed as nonlinear fibers to achieve broadband SC generation.Moreover,the potential applications of MIR SC sources based on ChG fibers are discussed.展开更多
基金supported by the UK’s Engineering and Physical Sciences Research Council(Grant Nos.EP/V000624/1,EP/X03495X/1,EP/X041166/1,and EP/T02643X/1)the Royal Society(Grant No.RG\R2\232531).
文摘Research on supercontinuum sources on silicon has made significant progress in the past few decades.However,conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engineering by optimizing the core thickness or introducing the cladding with special materials and structures.We propose and demonstrate supercontinuum generation using long-periodgrating(LPG)waveguides on silicon with a C-band pump.The LPG waveguide is introduced for quasi-phase matching,and the generated supercontinuum spectrum is improved greatly with grating-induced dispersive waves.In addition,the demonstrated LPG waveguide shows a low propagation loss comparable with regular silicon photonic waveguides without gratings.In experiments,when using a 1550-nm 75-fs pulse pump with a pulse energy of 200 pJ,the supercontinuum spectrum generated with the present LPG waveguide shows an ultrabroad extent from 1150 to 2300 nm,which is much wider by 200 nm than that achieved by dispersionengineered uniform silicon photonic waveguides on the same chip.This provides a promising option for on-chip broadband light source for silicon photonic systems.
基金supported by the Guangdong Science and Technology Program(No.2012B090600009)the Guangdong Natural Science Fund(No.10451170003004948)
文摘We demonstrate the generation of supercontinuum(SC) spectrum covering S+C+L band of optical communication by injecting 1.4 ps optical pulses with center wavelength of 1552 nm and repetition rate of 10 GHz into an all-normal dispersion photonic crystal fiber(PCF) with length of 80 m. The experimental results are in good agreement with the numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking(WB).
基金Supported by the National Natural Science Foundation of China under Grant Nos 61575129 and 11375105the Postdoctoral Science Foundation of China under Grant No 2016M602511+1 种基金the Shenzhen Science and Technology Planning under Grant No JCYJ20160422142912923the State Key Laboratory of Nuclear Physics and Technology,Peking University
文摘We report on the fabrication of the lO-mm-long lithium niobate ridge waveguide and its supercontinuum gen- eration at near-visible wavelengths （around 800hm）. The waveguides are fabricated by a combination of MeV copper ion implantation followed by wet etching in a proton exchanged lithium niobate planar waveguide. Using a mode-locked Ti：sapphire laser with a central wavelength of 800nm, the generated broadest supereontinuum through the ridge waveguides spans 302 nm （at -30 dB points）, from 693 to 995 nm. Temporal coherence proper- ties of the supercontinuum are experimentally studied by a Michelson interferometer and the coherence length of the broadest supercontinuum is measured to be 5.2 μm. Our results offer potential for a compact and integrated supercontinuum source for applications including bio-imaging, spectroscopy and optical communication.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB922404)the National Natural Science Foundation of China(Grant Nos.11274053,11474039,11474040,and 11004240)+1 种基金the Science and Technology Department of Jilin Province,China(Grant No.20170519018JH)the Innovation Fund of Changchun University of Science and Technology,China(Grant No.XJJLG-2016-02)
文摘An intense supercontinuum（SC） in the near-ultraviolet range is generated from filamentation by focusing a 400-nm laser into fused silica with a microlens array（MLA）. The spectrum of the SC is shown to be sensitive to the distance between the MLA and fused silica. In our optimal conditions, the near-ultraviolet SC can cover a range of 350-600 nm,where a bandwidth of approximately 55 nm above the 1μJ/nm spectral energy density and 20 nm bandwidth with tens ofμJ/nm are achieved. In addition, the energy conversion efficiency of the 400 nm laser for SC generation is further analyzed.A maximum conversion efficiency of 66% is obtained when the entrance face of fused silica is set around the focus of the MLA.
基金supported by the State Key Program of the National Natural Science Foundation of China(Grant No.61235008)the Postgraduate Innovation Foundation of National University of Defense Technology,China(Grant No.B110704)
文摘Picosecond pulse pumped supercontinuum generation in photonic crystal fiber is investigated by performing a series of comparative experiments. The main purpose is to investigate the supercontinuum generation processes excited by a given pump source through the experimental study of some specific fibers. A 20-W all-fiber picosecond master oscillator-power amplifier （MOPA） laser is used to pump three different kinds of photonic crystal fibers for supercontinuum generation. Three diverse supercontinuum formation processes are observed to correspond to photonie crystal fibers with distinct dis- persion properties. The experimental results are consistent with the relevant theoretical results. Based on the above analyses, a watt-level broadband white light supercontinuum source spanning from 500 nm to beyond 1700 nm is demonstrated by using a picosecond fiber laser in combination with the matched photonic crystal fiber. The limitation of the group velocity matching curve of the photonic crystal fiber is also discussed in the paper.
基金Project supported by the National Natural Science Foundation of China(Grant No.10774054)the National Key Basic Research Special Foundation of China(NKBRSFC)(Grant No.2006CB806006)
文摘We theoretically investigate the high-order harmonic generation from stretched molecules in a linearly polarized intense field. By adopting an infrared pulse combined with an ultraviolet （UV） attosecond pulse, the ionization process can be controlled effectively. In this excitation scheme, the harmonic spectrum beyond Ip ＋ 3.17Up is significantly enhanced by two orders, where Ip and Up = e^2E0^2/（4mew^2） are the ionization and ponderomotive potential, then smooth broadband supercontinuum with the bandwidth of about 120 eV is obtained, which leads to an isolated sub-60- as attosecond pulse with a high signal-noise ratio. Moreover, the bandwidth of the supercontinuum is weakly dependent on the location and pulse duration of the UV pulse.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61178026 and 60978028)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20091333110010)+1 种基金the Natural Science Foundation of Hebei Province, China (Grant No. E2012203035)the NCRIS, Australia
文摘We report supercontinuum （SC） generation in a lead silicate SF57 photonic crystal fiber by using a 1550 nm pump source. The effective nonlinear coefficient of the SF57 fiber is simulated to be 111.5 W-1 .km- 1 at 1550 nm. The fiber also shows ultraflat dispersion from 1700 nm to 2100 nm. Our results reveal that with an increase of the average power of the incident pulse from 10 mW to 90 mW, the SC of the SF57 photonic crystal fiber is generated from 1300 nm to 1900 nm with high stability and without significant change in spectral broadening.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12074228,11774038,and 11474039)the Taishan Scholar Project of Shandong Province,China(Grant No.tsqn201812043)+1 种基金Natural Science Foundation of Shandong Province,China(Grant No.ZR2021MA023)the Innovation Group of Jinan(Grant No.2020GXRC039)。
文摘High power supercontinuum(SC) is generated by focusing 800 nm and 400 nm femtosecond laser pulses in fused silica with a microlens array. It is found that the spectrum of the SC is getting broader compared with the case of a single laser pulse, and the spectral energy density between the two fundamental laser wavelengths is getting significantly higher by optimizing the phase matching angle of the BBO. It exceeds μJ/nm over 490 nm range which is from 380 nm to 870 nm,overcoming the disadvantage of relative lower power in the ranges far from the fundamental wavelength.
基金the National Natural Science Foundation of China(Grant Nos.11135002,11075069,91026021,and 11075068)the Scholarship Award for Excellent Doctoral Student of Ministry of Education,China
文摘Spectral modulation and supercontinuum generation of a probe pulse is investigated by using the plasma grating induced by the interference of two infrared femtosecond laser pulses. The dependences of the supercontinuum generation from the probe pulse on the time delay, the relative polarization angle between the probe pulse and the two-pump pulses, and the input probe pulse energy are investigated. The far-field spatial profiles of the three pulses are measured with different time delays and relative polarization angle, and the core energy of the probe pulse as functions of the time delay and relative polarization angle are also shown.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFB0405202)the Major Program of the National Natural Science Foundation of China(Grant No.61690221)+1 种基金the Key Program of the National Natural Science Foundation of China(Grant No.11434016)the National Natural Science Foundation of China(Grant Nos.11574384,11674386,and 11774277)
文摘We utilized a set of fused silica thin plates to broaden the spectrum of 1kHz,30 fs Ti:sapphire amplified laser pulses to an octave.Following the compression by chirped mirror pairs,the generated few-cycle pulses were focused onto an argon filled gas cell.We detected high order harmonics corresponding to a train of 209 as pulses,characterized by the reconstruction of attosecond beating by interference of two-photon transition(RABITT)technique.Compared with the conventional attosecond pulse trains,the broad harmonics in such pulse trains cover more energy range,so it is more efficient in studying some typical cases,such as resonances,with frequency resolved RABITT.As the solid thin plates can support high power supercontinuum generation,it is feasible to tailor the spectrum to have different central wavelength and spectral width,which will make the RABITT source work in different applications.
基金Agence Nationale de la Recherche(Fiberspec Project ANR-24-CE29-1653-02,EQUIPEX+SMARTLIGHT contract ANR-21-ESRE-0040)Conseil Régional de Bourgogne-Franche-Comté。
文摘Simultaneously increasing the spectral bandwidth and average output power of mid-infrared supercontinuum sources remains a major challenge for their practical application.We particularly address this issue for the long mid-infrared spectral region through experimental developments of short tapered rods made from selenide glass by means of supercontinuum generation in the femtosecond regime.Our simple post-processing of glass rods unlocks potentially higher-power and coherent fiber-based supercontinuum sources beyond the 10-μm wave-band.By using a 5-cm-long tapered Ge-Se-Te rod pumped at 6μm,a supercontinuum spanning from 2 to 15μm(3–14μm)with an average output power of 93 m W(170 m W)is obtained for 500-k Hz(1-MHz)repetition rate.Additional experiments on other glass families(silica and tellurite)covering distinct spectral regions are also reported to develop and support our analyses.We demonstrate that ultra-broadband spectral broadenings over entire glass transmission windows can be achieved in few-cm-long segments of tapered rods by a fine adjustment of input modal excitation.Numerical simulations are used to confirm the main contribution of the fundamental mode in the ultrafast nonlinear dynamics,as well as the possible preservation of coherence features.Our study opens a new route,to our knowledge,towards the power scaling of high-repetition-rate fiber supercontinuum sources over the full molecular fingerprint region.
基金the federal state of Thuringia(FKZ:2012FGR0013 and FKZ:2016FGR0051)support from the Humboldt Foundation.R.S.acknowledges support from German Research Foundation(DFG)for funding through International Research Training Group(IRTG)2101support from German Research Foundation(DFG)via the project SCHM2655/3-1.
文摘Ultrafast supercontinuum generation in gas-filled waveguides is an enabling technology for many intriguing applications ranging from attosecond metrology towards biophotonics,with the amount of spectral broadening crucially depending on the pulse dispersion of the propagating mode.In this study,we show that structural resonances in a gas-filled antiresonant hollow core optical fiber provide an additional degree of freedom in dispersion engineering,which enables the generation of more than three octaves of broadband light that ranges from deep UV wavelengths to near infrared.Our observation relies on the introduction of a geometric-induced resonance in the spectral vicinity of the ultrafast pump laser,outperforming gas dispersion and yielding a unique dispersion profile independent of core size,which is highly relevant for scaling input powers.Using a krypton-filled fiber,we observe spectral broadening from 200 nm to 1.7μm at an output energy of B 23μJ within a single optical mode across the entire spectral bandwidth.Simulations show that the frequency generation results from an accelerated fission process of solitonlike waveforms in a non-adiabatic dispersion regime associated with the emission of multiple phase-matched Cherenkov radiations on both sides of the resonance.This effect,along with the dispersion tuning and scaling capabilities of the fiber geometry,enables coherent ultra-broadband and high-energy sources,which range from the UV to the mid‐infrared spectral range.
基金supported by the State Key Laboratory of Pulsed Power Laser Technology(No.SKL2020ZR06).
文摘We report the demonstration of a mid-infrared(MIR)supercontinuum(SC)laser delivering a record-breaking average output power of more than 40 W with a long-wavelength edge up to 3.5μm.The all-fiberized configuration was composed of a thulium-doped fiber amplifier system emitting a broadband spectrum covering 1.9–2.6μm with pulse repetition rate of 3 MHz,and a short piece of germania fiber.A 41.9 W MIR SC with a whole spectrum of 1.9–3.5μm was generated in a piece of 0.2-m-long germania fiber,with a power conversion efficiency of 71.4%.For an even shorter germania fiber(0.1 m),an SC with even higher output power of 44.9 W(corresponding to a conversion efficiency of 76.5%)was obtained,but the energy conversion toward the long-wavelength region was slightly limited.A continuous operation for 1 hour with output power of 32.6 W showed outstanding power stability(root mean square 0.17%)of the obtained SC laser.To the best of the authors’knowledge,for the first time,this work demonstrates the feasibility of germania fiber on generating a 40-W level MIR SC with high efficiency and excellent power stability,paving the way to real applications requiring high power and high reliability of MIR SC lasers.
基金National Natural Science Foundation of China(NSFC)(61475171,11374084,61705244,61307056)Natural Science Foundation of Shanghai(17ZR1433900,17ZR1434200)
文摘High flatness, wide bandwidth, and high-coherence properties of supercontinuum(SC) generation in fibers are crucial in many applications. It is challenging to achieve SC spectra in a combination of the properties, since special dispersion profiles are required, especially when pump pulses with duration over 100 fs are employed. We propose an all-solid microstructured fiber composed only of hexagonal glass elements. The optimized fiber possesses an ultraflat all-normal dispersion profile, covering a wide wavelength interval of approximately 1.55 μm. An SC spectrum spanning from approximately 1030 to 2030 nm(corresponding to nearly one octave) with flatness<3 dB is numerically generated in the fiber with 200 fs pump pulses at 1.55 μm. The results indicate that the broadband ultraflat SC sources can be all-fiber and miniaturized due to commercially achievable 200-fs fiber lasers. Moreover, the SC pulses feature high coherence and a single pulse in the time domain, which can be compressed to 13.9-fs pulses with high quality even for simple linear chirp compensation. The Fourier-limited pulse duration of the spectrum is 3.19 fs, corresponding to only 0.62 optical cycles.
基金This work was supPorted by the Henan Cultivatlon Project for University Innovatlon Thlents.
文摘We demonstrate the generation of supercontinuum (SC) of over 1350 nm by injecting 790-nm, 15-fs, 74-MHz optical pulses into a 183-mm-long microstructured fiber with combination core and random cladding. The maximum total power of SC is 73 mW with 290-mW pump power from 40x microscope objective. The wavelength and power ranging in SC as well as the polarization states and waveguide modes of the visible light can be tuned by adjusting the input end of MF.In particular, white light has been observed. To our knowledge, this is the first report of tunable properties in SC generation process using microstructured fiber with combination core and random cladding.
基金supported by the Guangdong Natural Science Fund(No.1414050001224)the National Instrumentation Program(No.2012YQ14000511)the Guangdong Science and Technology Program(No.2012B090600009)
文摘In this paper,the optimum supercontinuum(SC)spectrum generation in a dispersion decreasing fiber is presented.Three normalized parameters for the pump pulse and SC fiber are introduced.It is found that the shape of an SC spectrum is uniquely specified by the input soliton order,the normalized dispersion slope and the normalized effective fiber length.For a pumping condition with a given input soliton order and a given normalized dispersion slope,by optimizing the normalized effective fiber length,the residual spectral peak in the SC spectrum can be suppressed effectively,and a broad SC spectrum with optimum spectral flatness can be obtained.
文摘We report on compact and robust supercontinuum generation and post-compression using transmission of light through multiple thin solid plates at the Swiss FEL X-ray free-electron laser facility.A single stage consisting of three thin plates followed by a chirped mirror compressor achieves compression of initially 30-fs pulses with 800-nm center wavelength to sub-10-fs duration.We also demonstrate a two-stage implementation to compress the pulses further to sub-5-fs duration.With the two-stage setup,the generated supercontinuum includes wavelengths ranging from 500 to 1100 nm.The multiplate setup is compact,robust,and stable,which makes it ideal for applications at free-electron laser facilities such as pump-probe experiments and laser-arrival timing tools.
基金Funding.Fundacja na rzecz Nauki Polskiej(FNP)(First TEAM/2016-1/1)
文摘An overview of the progress on pulse-preserving, coherent, nonlinear fiber-based supercontinuum generation is presented. The context encompasses various wavelength ranges and pump sources, starting with silica photonic crystal fibers pumped with 1.0 μm femtosecond lasers up to chalcogenide step-index and microstructured fibers pumped from optical parametric amplifiers tuned to mid-infrared wavelengths. In particular, silica and silicatebased all-normal dispersion(ANDi) photonic crystal fibers have been demonstrated for pumping with femtosecond lasers operating at 1.56 μm with the recorded spectra covering 0.9–2.3 μm. This matches amplification bands of robust fiber amplifiers and femtosecond lasers. The review therefore focuses specifically on this wavelength range, discussing glass and nonlinear fiber designs, experimental results on supercontinuum generation up to the fundamental limit of oxide glass fiber transmission around 2.8 μm, and various limitations of supercontinuum bandwidth and coherence. Specifically, the role of nonlinear response against the role of dispersion profile shape is analyzed for two different soft glass ANDi fibers pumped at more than 2.0 μm. A spatio-temporal interaction of the fundamental fiber mode with modes propagating in the photonic lattice of the discussed ANDi fibers is shown to have positive effects on the coherence of the supercontinuum at pump pulse durations of 400 fs. Finally, the design and development of graded-index, nanostructured core optical fibers are discussed.In such structures the arbitrary shaping of the core refractive index profile could significantly improve the engineering flexibility of dispersion and effective mode area characteristics, and would be an interesting platform to further study the intermodal interaction mechanisms and their impact on supercontinuum coherence for subpicosecond laser pumped setups.
基金National Natural Science Foundation of China(NSFC)(61435009)
文摘A spectrally flat mid-infrared supercontinuum(MIR-SC) spanning 2.8–3.9 μm with a maximum output power of 411 mW was generated in a holmium-doped ZBLAN fiber amplifier(HDZFA). A broadband fiber-based SC covering the 2.4–3.2 μm region was designed to seed the amplifier. Benefiting from the broadband seed laser,the obtained SC had a high spectral flatness of 3 dB over the range of 2.93–3.70 μm(770 nm). A spectral integral showed that the SC power beyond 3 μm was 372 mW, i.e., a power ratio of 90.6% of the total power. This paper,to the best of our knowledge, not only demonstrates the first spectrally flat MIR-SC directly generated in fluoride fiber amplifiers, but also reports the highest power ratio beyond 3 μm obtained in rare-earth-doped fluoride fiber until now.
基金National Natural Science Foundations of China(NSFCs)(Nos.61875094,62090064)K.C.Wong Magna Fund in Ningbo University.
文摘Chalcogenide(ChG)glasses have the characteristics of a wide transparency window(over 20μm)and high optical nonlinearity(up to 103 times greater than that of silica glasses),exhibiting great advantages over silica and other soft glasses in optical property at mid-infrared(MIR)wavelength range.These make them excellent candidates for MIR supercontinuum(SC)generation.Over the past decades,great progress has been made in MIR SC generation based on ChG fibers in terms of spectral extension and output power improvement.In this paper,we introduce briefly the properties of ChG glasses and fibers including transmission,nonlinearity,and dispersion,etc.Recent progress in MIR SC generation based on ChG fibers is reviewed from the perspective of pump schemes.We also present novel ChG fibers such as As-free,Te-based,and chalcohalide fibers,which have been explored and employed as nonlinear fibers to achieve broadband SC generation.Moreover,the potential applications of MIR SC sources based on ChG fibers are discussed.
