Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Generation of 300 nm bandwidth 0.5 mJ pulses near 1 mu m in a single stage gas filled hollow core fiber
No full textJapan Society for the Promotion of Science (JSPS) KAKENHI [JP26287145, JP15K04696]; Photon Frontier Network of the Ministry of Education, Culture, Sports, Science and Technology (MEXT)A simple and compact spectral-broadening system is presented that is based on a single-stage statically pressurized Ar filled core fiber. By optimizing the inner diameter of the core fiber, a bandwidth of 300 nm is obtained. This is the broadest bandwidth known to date with millijoule level energy near the 1- mu m wavelength by a single stage filled core fiber. (C)2017 Optical Society of Americ
Internal Laser Writing of High-Aspect-Ratio Microfluidic Structures in Silicate Glasses for Lab-on-a-Chip Applications
No full textNational Basic Research Program of China [2014CB921300]; National Natural Science Foundation of China [61590934, 11134010, 61327902]Femtosecond laser direct writing is unique in allowing for fabrication of 3D micro- and nanofluidic structures, thereby enabling rapid and efficient manipulation of fluidic dynamics in 3D space to realize innovative functionalities. Here, I discuss the challenges in producing fully functional and highly integrated 3D micro- and nanofluidic systems with potential applications ranging from chemical and biological analyses to investigations of nanofluidic behaviors. In particular, I review the achievements we have made in the past decade, which have led to 3D microchannels with controllable cross-sectional profiles and large aspect ratios, 3D nanofluidic channels with widths of several tens of nanometers, and smooth inner walls with roughness on the order of similar to 1 nm. Integration of the microfluidics with other functional microcomponents including microoptics and microelectrodes will also be discussed, followed by conclusions and the future perspective
Self-Referenced Spectral Interferometry for Femtosecond Pulse Characterization
No full textNational Natural Science Foundation of China (NSFC) [11274327, 61521093, 61527821]; Chinese Academy of Sciences [YZ201538, XDB160106]Since its introduction in 2010, self-referenced spectral interferometry (SRSI) has turned out to be an analytical, sensitive, accurate, and fast method for characterizing the temporal profile of femtosecond pulses. We review the underlying principle and the recent progress in the field of SRSI. We present our experimental work on this method, including the development of self-diffraction (SD) effect-based SRSI (SD-SRSI) and transient-grating (TG) effect-based SRSI (TG-SRSI). Three experiments based on TG-SRSI were performed: (1) We built a simple TG-SRSI device and used it to characterize a sub-10 fs pulse with a center wavelength of 1.8 mu m. (2) On the basis of the TG effect, we successfully combined SRSI and frequency-resolved optical gating (FROG) into a single device. The device has a broad range of application, because it has the advantages of both SRSI and FROG methods. (3) Weak sub-nanojoule pulses from an oscillator were successfully characterized using the TG-SRSI device, the optical setup of which is smaller than the palm of a hand, making it convenient for use in many applications, including sensor monitoring the pulse profile of laser systems. In addition, the SRSI method was extended for single-shot characterization of the temporal contrast of ultraintense and ultrashort laser pulses
Spatiotemporal propagation dynamics of intense optical pulses in loosely confined gas-filled hollow-core fibers
No full textWe numerically study the propagation dynamics of intense optical pulses in gas-filled hollow-core fibers (HCFs). The spatiotemporal dynamics of the pulses show a transition from tightly confined to loosely confined characteristics as the fiber core is increased, which manifests as a deterioration in the spatiotemporal uniformity of the beam. It is found that using the gas pressure gradient does not enhance the beam quality in large-core HCFs, while inducing a positive chirp in the pulse to lower the peak power can improve the beam quality. This indicates that the self-focusing effect in the HCFs is the main driving force for the propagation dynamics. It also suggests that pulses at longer wavelengths are more suitable for HCFs with large cores because of the lower critical power of self-focusing, which is justified by the numerical simulations. These results will benefit the generation of energetic few-cycle pulses in large-core HCFs
High-power continuous-wave narrow-linewidth 253.7 nm deep-ultraviolet laser
No full textNational Natural Science Foundation of China (NSFC) [91436105]; Strategic Priority Research Program of the Chinese Academy of Sciences (CAS) [XDB21030800]A 760 mW stable continuous-wave narrow-linewidth 253.7 nm deep-ultraviolet laser is developed for laser cooling of mercury atoms. It is based on a high-power 1014.8 nm room-temperature fiber laser amplifier and two cascaded efficient frequency-doubling stages. The saturated absorption spectrum of Hg-202 on the 6(1)S(0)-6(3)P(1) transition is demonstrated with a high signal-to-noise ratio. This deep-ultraviolet laser has significant applications in quantum optics and laser cooling of mercury atoms in 2D and 3D magneto-optical traps
Non-invasive three-dimension control of light between turbid layers using a surface quasi-point light source for precorrection
No full textManipulating light non-invasively through inhomogeneous media is an attractive goal in many disciplines. Wavefront shaping and optical phase conjugation can focus light to a point. Transmission matrix method can control light on multiple output modes simultaneously. Here we report a non-invasive approach which enables three-dimension (3D) light control between two turbid layers. A digital optical phase conjugation mirror measured and conjugated the diffused wavefront, which originated from a quasi-point source on the front turbid layer and passed through the back turbid layer. And then, because of memory effect, the phase-conjugated wavefront could be used as a carrier wave to transport a pre-calculated wavefront through the back turbid layer. The pre-calculated wavefront could project a desired 3D light field inside the sample, which, in our experiments, consisted of two 220-grid ground glass plates spaced by a 20 mm distance. The controllable range of light, according to the memory effect, was calculated to be 80 mrad in solid angle and 16 mm on z-axis. Due to the 3D light control ability, our approach may find applications in photodynamic therapy and optogenetics. Besides, our approach can also be combined with ghost imaging or compressed sensing to achieve 3D imaging between turbid layers
Complete measurement of spatiotemporally complex multi-spatial-mode ultrashort pulses from multimode optical fibers using delay-scanned wavelength-multiplexed holography
No full textU. S. National Science Foundation (NSF) [ECCS-1307817, ECCS-1609808]; Georgia Research Alliance (GRA); China Scholarship Council (CSC)We introduce a simple delay-scanned complete spatiotemporal intensity-and-phase measurement technique based on wavelength-multiplexed holography to characterize long, complex pulses in space and time. We demonstrate it using pulses emerging from multi-mode fiber. This technique extends the temporal range and spectral resolution of the single-frame STRIPED FISH technique without using an otherwise-required expensive ultranarrow-bandpass filter. With this technique, we measured the complete intensity and phase of up to ten fiber modes from a multi-mode fiber (normalized frequency V approximate to 10) over a similar to 3ps time range. Spatiotemporal complexities such as intermodal delay, modal dispersion, and material dispersion were also intuitively displayed by the retrieved results. Agreement between the reconstructed color movies and the monitored time-averaged spatial profiles confirms the validity to this delay-scanned STRIPED FISH method
Deuteron-deuteron fusion in laser-driven counter-streaming collisionless plasmas
No full textNational Basic Research Program of China [2013CBA01501, 2013CB834401]; National Science Foundation of China [11135012, 11135005, 11375114]; Science Challenge Project [TZ2016005]; Global R&D Networking Program - Republic of Korea's Ministry of Science, ICT and Future Planning [NRF-2012-0004839]; Science and Technology Commission of Shanghai Municipality [11DZ2260700]Nuclear fusion reactions are the most important processes in nature to power stars and produce new elements, and lie at the center of the understanding of nucleosynthesis in the universe. It is critically important to study the reactions in full plasma environments that are close to true astrophysical conditions. By using laser-driven counter-streaming collisionless plasmas, the fusion d + d -> He-3 + n is studied in a Gamow-like window around 27 keV. The results give hints that astrophysical nuclear reaction yields can be modulated significantly by the self-generated electromagnetic fields and the collective motion of the plasma. This plasma-version minicollider may provide a novel tool for studies of astrophysics-interested nuclear reactions, as well as a useful tool to constrain the models of plasma colliding dynamic
Phase Matching Using the Linear Electro-Optic Effect
No full textNational Natural Science Foundation of China [11204327, 11304332]Phase matching is a necessary condition for achieving high-efficiency optical-frequency conversion. To date, practical means of accomplishing phase matching in homogeneous crystals remain limited, despite considerable efforts. Herein, we report a new class of methods aimed at achieving quasiperfect phase matching, based on controllable birefringence produced via the linear electro-optic effect, termed "voltage-tuning phase matching." The wave vectors of the induced polarization and the generated fields can be matched and maintained along the direction of propagation by introducing an external electric field. We analyze the validity and feasibility of this method theoretically and demonstrate it experimentally by applying the linear electro-optic effect and fourth-harmonic generation simultaneously in a partially deuterated KH2PO4 crystal. Quasiperfect phase matching is achieved systematically over a temperature range of the initial phase-matching temperature +/- 2 degrees C. Moreover, this method can overcome the limitation of the birefringence in traditional technologies and provides new functionalities for conventional nonlinear materials as well as low-birefringence and isotropic materials. This technology may significantly impact the study of optical-frequency conversion and has promise for a broad range of applications in nonlinear optics
Compensation for the spatial periodic modulation of the near-field beam with an improved iterative weight-based method
No full textAn improved iterative weight-based method is studied to compensate for the spatial periodic modulation (SPM) of the near-field beam, Based on the beam angular spectrum transmit formula (ASTF). the required phase that compensates for the intensity distribution of the incident SPM beam is iterated by this algorithm, which can contribute to improve the uniformity and quality of the output near-field beam. The experimental results show that the similarity values is improved from 0.9878 to 0.9947 and is getting closer to 1. The modulation degree M of the output near-field beam is decreased from 1.3631 to 1.3401 and the contrast degree C is decreased from 0.3018 to 0.2635 by using the liquid-crystal spatial light modulator (SLM). This indicates that the experiment verifies the feasibility of this iterative method to compensate for the SPM of the near-field beam