A5100756586- Orbital Angular Momentum in Optics
- Advanced Fiber Laser Technologies
- Advanced Fiber Optic Sensors
- Near-Field Optical Microscopy
- Photonic Crystal and Fiber Optics
- Optical Coherence Tomography Applications
- Optical Network Technologies
- Gyrotron and Vacuum Electronics Research
- Particle Accelerators and Free-Electron Lasers
- Photonic and Optical Devices
- Particle accelerators and beam dynamics
- Advanced Fluorescence Microscopy Techniques
- Plasmonic and Surface Plasmon Research
- Laser-Plasma Interactions and Diagnostics
- Photocathodes and Microchannel Plates
- Quantum Information and Cryptography
- Advanced X-ray Imaging Techniques
- Optical Polarization and Ellipsometry
- Solid State Laser Technologies
- Laser Design and Applications
- Magnetic confinement fusion research
- Crystallography and Radiation Phenomena
- Adaptive optics and wavefront sensing
- Electron and X-Ray Spectroscopy Techniques
- Photoacoustic and Ultrasonic Imaging
Apple (United States)
2021
Boston University
2012-2018
Tsinghua University
2012-2017
Ministry of Education of the People's Republic of China
2013
Spin to orbital angular momentum (OAM) conversion using a device known as q-plate has gained recent attention convenient means of creating OAM beams. We show that the dispersive properties q=1/2 plate, specifically its group index difference Δng for ordinary and extraordinary polarization light, can be tuned achieving single-aperture, alignment-tolerant stimulated emission depletion (STED) nanoscopy with versatile control over color combinations well laser bandwidths. Point spread function...
The evolution of beam phase space in ionization injection into plasma wakefields is studied using theory and particle-in-cell simulations. process involves both longitudinal transverse mixing, leading initially to a rapid emittance growth followed by oscillation, decay, slow saturation. An analytic for this presented verified through This includes the effects distance (time), acceleration distance, wakefield structure, nonlinear charge forces, it also shows how ultralow beams can be produced methods.
Optical fiber links and networks are integral components within between cities' communication infrastructures. Implementing quantum cryptographic protocols on either existing or new will provide information-theoretical security to data transmissions. However, there is a need for ways increase the channel bandwidth. Using transverse spatial degree of freedom one way transmit more information tolerable error thresholds by extending common qubit high-dimensional key distribution (QKD) schemes....
Super-resolution imaging using the principles of stimulated emission depletion (STED) microscopy requires collinear excitation a sample with Gaussian-shaped beam and donut-shaped whose spin (polarization) orbital angular momentum (OAM) signs are aligned. We leverage recent advances in stable OAM mode propagation optical fibers for telecom applications to design, fabricate, validate utility vortex fiber as shaping device at visible near-IR wavelengths STED microscopy. Specifically, compact...
With progress of photoinjector technology, thermal emittance has become the primary limitation electron beam brightness. Extensive efforts have been devoted to study emittance, but experiment results differ between research groups and few can be well interpreted. Besides ambiguity photoemission mechanism, variations cathode surface conditions during preparation, such as work function, field enhancement factor, roughness, will cause differences. In this paper, we report an experimental...
Fiber-optic parametric wavelength conversion (PWC) below the zero-dispersion of silica is typically constrained by requirement a small, tightly confined mode with anomalous dispersion to achieve phase matching. This limits ability power scale PWC at arbitrary wavelengths. However, constraint lifted for higher-order modes. We demonstrate in 1 μm band via degenerate four-wave mixing pumped large effective area (>600 μm²) LP(0,7) double-clad fiber. obtain up 25% Stokes line 0.5 ns pump pulses,...
We report on investigations into the fundamental surface emission parameters, geometric field enhancement factor (β) and work function (φ), by making both Schottky-enabled photoemission measurements. The measurements were performed a copper in Tsinghua University S-band RF gun two separate experiments. Fitting our data to models for each experiment indicate that traditionally assumed high value of β(≈50-500) does not provide plausible explanation data, but incorporating low φ at some sites...
Optical fibers have long been used to impose spatial coherence shape free-space optical beams. Recent work has shown that one can use higher order fiber modes create more exotic beam profiles. We experimentally generate bottles from Talbot imaging in the coherent superposition of two excited with period gratings, and obtain a 28 μm × 6 bottle controlled contrast up 10.13 dB. Our geometry allows for phase tuning mode respect other, which enables us dynamically move free space.
We demonstrate a radiation mode coupler based on tilted fiber Bragg grating that spatially demultiplexes different modes in few-mode fiber. The observed patterns match well with those theoretically predicted using the volume current method. correlations measured relative modal weights obtained from this device and an accurate interferometric measurement used as reference, suggest technique has potential applications providing real-time, nondestructive power for division-multiplexed...
We demonstrate a sidetap modal channel monitor based on tilted Bragg grating, where different modes radiate at angles. qualitatively correlate the observed power partitioning with more accurate interferometer-based measurements.
We propose and analyze a scheme to generate enhanced ultrabroadband terahertz (THz) radiation through coherent transition emitted by ultrashort electron beams based on 10.5 m beamline at Tsinghua University. The proposed involves the initial compression of beam with few hundred pC charges using velocity bunching (i.e., RF compression) in an under-compression mode instead usual critical-compression order maintain positive energy chirp exit traveling wave accelerator. After long drift segment,...
We demonstrate, for the first time, four-wave mixing, in 1-μm spectral regime, an LMA silica fiber. Pumping a 618-μm2 LP07 mode (λZDW=1038.4 nm) with 1064.6-nm Nd:YAG laser results generation of modulation instability, and multiple Stokes/anti-Stokes lines, opening up prospect high-energy parametric processes fibers.
We demonstrate all-fiber STED illumination using vortex fiber modes excited via gratings. The grating's high purity mode conversion (98.7%) yields a depletion beam with 20.5dB extinction ratio, and the schematic is resistant to bends down 6mm radius.
We demonstrate the first proof of concept a fiber-based STED nanoscopy illumination system. The fiber yields naturally co-aligned vortex (dark-spot size ~198nm) and Gaussian beams (size ~340nm), potentially enabling sub-30nm resolution imaging.
We demonstrate higher-order-mode (Aeff up to ∼2000 μm2) propagation in a 100 μm outer diameter pure-silica fiber with low-index polymer jacket commonly used for laser pump guidance. This simple structure obviates the need complex designs deemed necessary realizing large-mode-area fibers. Modes ranging from HE1,12 HE1,22 were found propagate stably over 15 m this fiber. The index step is approximately 4 times larger than that obtained fluorine down doping; thus supports even higher-order...
We report the Tilt-Locking (TL) technique applied to lock a laser in pulsed regime 28 000 high finesse Fabry–Perot cavity. Preliminary experimental results show that TL is comparable with well-known Pound–Drever–Hall technique. This study first implement high-finesse optical Very and stable coupling obtained. The rate ∼80%, locking can last for more than 1 h. Furthermore, while previously published papers have focused on near field case, this we will give error signal shape simulation far...
Non-paraxial perturbation wave equations are solved for general astigmatic Gaussian beams the first time, to best of our knowledge, in angular spectrum representation by taking into account generic boundary conditions. Expressions second-order corrections derived and exemplified with an optical cavity made two cylindrical mirrors. can lead, depending on choice conditions, a transverse S-shaped beam mode, which has been qualitatively observed highly divergent non-planar four-mirror cavity.
We demonstrate tunable generation of orbital angular momentum (OAM) modes with low loss (0.7 dB) and high efficiency ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>></mml:mo> </mml:mrow> <mml:mn>90</mml:mn> <mml:mi mathvariant="normal">%</mml:mi> </mml:math> ) over a 230 nm in the visible near-infrared spectral range using all-fiber acousto-optic-induced long period gratings. This represents tuning almost 33% carrier...
We demonstrate higher-order-mode (Aeff~1800µm2) propagation in a 100-μm-OD pure-silica fiber with low-index polymer jacket commonly used for fiber-laser pump-guidance. This simple structure obviates the need complex designs deemed necessary realizing large-mode-area fibers.
We demonstrate single-aperture STED nanoscopy illumination with vortex-fiber modes excited by a dispersive q=1/2 plate at visible wavelengths. The vortex-fiber-compatible bias-voltage-tunable mode conversion of q-plates enables easy switching between multiple STED-wavelength pairs.
We present a class of fibers that enable the generation and propagation optical vortices. review recent results obtained with such in fields as different super-resolution microscopy telecom information-capacity scaling.