We present a high-dispersive multilayer mirror for pulse stretching in a femtosecond fiber laser amplification system.The designed mirror contains 54 layers with a total physical thickness of 7.3 μm, which can provid...We present a high-dispersive multilayer mirror for pulse stretching in a femtosecond fiber laser amplification system.The designed mirror contains 54 layers with a total physical thickness of 7.3 μm, which can provide a positive group delay dispersion(GDD) of 600 fs2and a high reflectance over 99.9% from 1010 to 1070 nm. The samples were prepared by dual ion beam sputtering. The measured transmittance matches well with the theoretical result. The GDD characteristics of samples were tested by home-made white light interferometer. The measured GDD is higher than the design results,an average GDD of +722 fs2from 1010 nm to 1070 nm. The mirrors were employed in a Yb-doped large-mode-area photonic crystal fiber amplification system. An input pulse compressed by the gratings with autocorrelation function of83 fs is obtained with a stretched FWHM of 1.29 ps after 28 bounces between the dispersive mirrors. The results show that the multilayer dispersive mirror could be an effective and promising technique for pulse stretching in femtosecond amplification systems.展开更多
Spatiotemporal shaping of ultrashort pulses is pivotal for various technologies,such as burst laser ablation and ultrafast imaging.However,the difficulty of pulse stretching to subnanosecond intervals and independent ...Spatiotemporal shaping of ultrashort pulses is pivotal for various technologies,such as burst laser ablation and ultrafast imaging.However,the difficulty of pulse stretching to subnanosecond intervals and independent control of the spatial profile for each pulse limit their advancement.We present a pulse manipulation technique for producing spectrally separated GHz burst pulses from a single ultrashort pulse,where each pulse is spatially shapable.We demonstrated the production of pulse trains at intervals of 0.1 to 3 ns in the 800-and 400-nm wavelength bands and applied them to ultrafast single-shot transmission spectroscopic imaging(4 Gfps)of laser ablation dynamics with two-color sequentially timed all-optical mapping photography.Furthermore,we demonstrated the production of pulse trains containing a shifted or dual-peak pulse as examples of individual spatial shaping of GHz burst pulses.Our proposed technique brings unprecedented spatiotemporal manipulation of GHz burst pulses,which can be useful for a wide range of laser applications.展开更多
Optical time-stretch imaging enables the continuous capture of non-repetitive events in real time at a line-scan rate of tens of MHz—a distinct advantage for the ultrafast dynamics monitoring and high-throughput scre...Optical time-stretch imaging enables the continuous capture of non-repetitive events in real time at a line-scan rate of tens of MHz—a distinct advantage for the ultrafast dynamics monitoring and high-throughput screening that are widely needed in biological microscopy.However,its potential is limited by the technical challenge of achieving significant pulse stretching(that is,high temporal dispersion)and low optical loss,which are the critical factors influencing imaging quality,in the visible spectrum demanded in many of these applications.We present a new pulse-stretching technique,termed free-space angular-chirpenhanced delay(FACED),with three distinguishing features absent in the prevailing dispersive-fiber-based implementations:(1)it generates substantial,reconfigurable temporal dispersion in free space(41 ns nm^(−1))with low intrinsic loss(o6 dB)at visible wavelengths;(2)its wavelength-invariant pulse-stretching operation introduces a new paradigm in time-stretch imaging,which can now be implemented both with and without spectral encoding;and(3)pulse stretching in FACED inherently provides an ultrafast all-optical laser-beam scanning mechanism at a line-scan rate of tens of MHz.Using FACED,we demonstrate not only ultrafast laser-scanning time-stretch imaging with superior bright-field image quality compared with previous work but also,for the first time,MHz fluorescence and colorized time-stretch microscopy.Our results show that this technique could enable a wider scope of applications in high-speed and high-throughput biological microscopy that were once out of reach.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61705194)。
文摘We present a high-dispersive multilayer mirror for pulse stretching in a femtosecond fiber laser amplification system.The designed mirror contains 54 layers with a total physical thickness of 7.3 μm, which can provide a positive group delay dispersion(GDD) of 600 fs2and a high reflectance over 99.9% from 1010 to 1070 nm. The samples were prepared by dual ion beam sputtering. The measured transmittance matches well with the theoretical result. The GDD characteristics of samples were tested by home-made white light interferometer. The measured GDD is higher than the design results,an average GDD of +722 fs2from 1010 nm to 1070 nm. The mirrors were employed in a Yb-doped large-mode-area photonic crystal fiber amplification system. An input pulse compressed by the gratings with autocorrelation function of83 fs is obtained with a stretched FWHM of 1.29 ps after 28 bounces between the dispersive mirrors. The results show that the multilayer dispersive mirror could be an effective and promising technique for pulse stretching in femtosecond amplification systems.
基金supported by MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) (Grant No.JPMXS0118067246)K.S.was supported by JST ACT-X (JPMJAX22K8).Y.I.and A.I.were partly supported by JST PRESTO (JPMJPR2003 and JPMJPR1902,respectively)K.N.was partly supported by JST FOREST (JPMJFR215C).
文摘Spatiotemporal shaping of ultrashort pulses is pivotal for various technologies,such as burst laser ablation and ultrafast imaging.However,the difficulty of pulse stretching to subnanosecond intervals and independent control of the spatial profile for each pulse limit their advancement.We present a pulse manipulation technique for producing spectrally separated GHz burst pulses from a single ultrashort pulse,where each pulse is spatially shapable.We demonstrated the production of pulse trains at intervals of 0.1 to 3 ns in the 800-and 400-nm wavelength bands and applied them to ultrafast single-shot transmission spectroscopic imaging(4 Gfps)of laser ablation dynamics with two-color sequentially timed all-optical mapping photography.Furthermore,we demonstrated the production of pulse trains containing a shifted or dual-peak pulse as examples of individual spatial shaping of GHz burst pulses.Our proposed technique brings unprecedented spatiotemporal manipulation of GHz burst pulses,which can be useful for a wide range of laser applications.
基金supported by grants from the Research Grants Council of the Hong Kong Special Administrative Region of China(HKU 7172/12E,HKU 720112E,HKU 719813E,HKU 707712 P,HKU 17207715,HKU 17205215,HKU 17208414 and HKU 17304514)the University Development Funds of HKU.
文摘Optical time-stretch imaging enables the continuous capture of non-repetitive events in real time at a line-scan rate of tens of MHz—a distinct advantage for the ultrafast dynamics monitoring and high-throughput screening that are widely needed in biological microscopy.However,its potential is limited by the technical challenge of achieving significant pulse stretching(that is,high temporal dispersion)and low optical loss,which are the critical factors influencing imaging quality,in the visible spectrum demanded in many of these applications.We present a new pulse-stretching technique,termed free-space angular-chirpenhanced delay(FACED),with three distinguishing features absent in the prevailing dispersive-fiber-based implementations:(1)it generates substantial,reconfigurable temporal dispersion in free space(41 ns nm^(−1))with low intrinsic loss(o6 dB)at visible wavelengths;(2)its wavelength-invariant pulse-stretching operation introduces a new paradigm in time-stretch imaging,which can now be implemented both with and without spectral encoding;and(3)pulse stretching in FACED inherently provides an ultrafast all-optical laser-beam scanning mechanism at a line-scan rate of tens of MHz.Using FACED,we demonstrate not only ultrafast laser-scanning time-stretch imaging with superior bright-field image quality compared with previous work but also,for the first time,MHz fluorescence and colorized time-stretch microscopy.Our results show that this technique could enable a wider scope of applications in high-speed and high-throughput biological microscopy that were once out of reach.
