arXiv subjects

Changjun Min

Publications and source records attributed to Changjun Min.

10 recordsLinked to original sources

arXiv2026

Multi-mode fiber enabled multi-wavelength optical trapping and dynamic manipulation

Optical fiber tweezers offer distinct advantages for long-distance manipulation, compact integration, and minimally invasive operation in biological environments. However, most optical fiber tweezers rely on single-mode fibers (SMFs), which are constrained by limited optical mode diversity and reduced control flexibility. Although multi-mode fibers (MMFs) support a wider spectrum of propagation modes, their inherent mixed guided modes with low coherence become a long-standing limitation for the design of focused trapping configurations. To address these limitations, we propose and experimentally validate a fully MMF-based optical tweezer system integrated with a micro-lens structure fabricated on the fiber facet, enabling stable optical trapping across multiple wavelengths and dynamic manipulation of trapped cells. Employing 532 nm continuous-wave and 800 nm femtosecond lasers, we demonstrate that both light sources can generate tightly focused optical spots through the micro-lens with a high numerical aperture (NA>0.7), achieving robust trapping and axial dynamic manipulation of cells. Compared with conventional SMF-based tweezers, this approach leverages the broadband and multi-mode properties of MMFs, allows for wavelength-flexible and dynamically adjustable trapping of cells, and paves the way for lab-on-fiber biophotonic platforms with potential applications such as interventional manipulation, cell sorting, and cellular fluorescence analysis.

physics.optics↗

arXiv2026

Ultrafast wide-field 3D topography with extended depth of field

Ultrafast optical imaging has enabled direct observation of femtosecond-nanosecond dynamics, yet three-dimensional (3D) dynamic measurements at high numerical aperture (NA) remain hindered by the intrinsically shallow depth of field (DoF) of conventional microscopes. Here, we propose an ultrafast, wide-field pump-probe interferometric microscope on a telecentric platform that significantly extends the effective DoF to ~18 micrometer at a high NA of 0.9 while maintaining high spatial resolution (down to 235 nm) and temporal resolution (~170 fs). The system enables single-frame 3D topography reconstruction without axial scanning or multi-view acquisition. We demonstrate these capabilities by capturing axial material flow during laser-induced microsphere melting that remain unobservable with conventional narrow-DoF systems, and by tracking the azimuthal rotation of ablation lobes during axial propagation of temporal focused spatiotemporal optical vortex (TF-STOV) pulses, directly revealing the spatiotemporal evolution of STOV-matter interactions

physics.optics↗

arXiv2026

Temporal Focusing Enables Distortion-Resistant high-intensity Spatiotemporal Optical Vortices

Spatiotemporal optical vortices (STOVs) carry transverse orbital angular momentum and offer new degrees of freedom for light-matter interactions. Yet conventional focusing of STOVs introduces spatiotemporal astigmatism: the beam diffracts while the pulse duration stays constant, causing the vortex to deform away from focus. Here we overcome this limitation by introducing spectral phase modulation into a temporal focusing configuration, where angular dispersion forces the pulse to compress only at the geometric focus so that the spatial and temporal dimensions focus and defocus together. Our approach generates stable STOVs with self-similar, distortion-free evolution over an extended focal region. Besides, the orbital angular momentum vector can be continuously steered from purely longitudinal to strongly tilted orientations by adjusting the spatial dispersion, objective focal length, or input beam size. More importantly, our method offers full compatibility with high NA focusing geometry, allowing high-intensity and high-resolution applications. We validate these properties through femtosecond laser ablation under high-NA conditions and interferometric spatiotemporal field reconstruction under low-NA conditions.

physics.optics↗

arXiv2025

Synthetic Spatiotemporal Plasmonic Vortices On Chip

Spatiotemporal vortices are polychromatic modes that intertwine orbital angular momentum (OAM) in space and time. Here we introduce a new class of such vortices, spatiotemporal plasmonic vortices (STPVs), carrying nontrivial topological spin textures. They are generated by chronotopic interference of temporally delayed plasmonic eigen-vortices, where a $\pi$-phase dislocation in the space-frequency domain maps into a 2$\pi$ spiraling phase in space-time, with the resulting focus-defocus dynamics emulate U(1) gauge transitions. Using interferometric time-resolved photoemission electron microscopy (ITR-PEEM), we directly image their nanometer-attosecond (nano-atto) evolution and control vortex number and position. Quantum-path analysis of coherent two-photon photoemission (2PP) processes reveals the nonlinear plasmonic polarization fields and angular-momentum conservation, establishing STPVs as a platform for probing spatiotemporally structured quantum matter.

cond-mat.mes-hall↗

arXiv2025

Controllable perfect spatiotemporal optical vortices

Spatiotemporal optical vortices (STOVs), as a kind of structured light pulses carrying transverse orbital angular momentum (OAM), have recently attracted significant research interest due to their unique photonic properties. However, general STOV pulses typically exhibit an annular intensity profile in the spatiotemporal plane, with a radius that scales with the topological charge, limiting their potential in many applications. Here, to address this limitation, we introduce the concept of perfect spatiotemporal optical vortices (PSTOVs). Unlike STOV pulses, the intensity distribution of PSTOV wavepackets is nearly independent of the topological charge. We show that such wavepackets can be generated by applying the spatiotemporal Fourier transform to a Bessel-Gaussian mode in the spatiotemporal frequency domain. More importantly, the mode distribution of PSTOV wavepackets can be freely controlled by introducing azimuthal-dependent phase modulation, enabling conversion from a standard annular profile to arbitrary polygonal shapes. Finally, experimental results confirm the successful generation of these wavepackets. Our findings will expand the study of STOV pulses and explore their potential applications in optical communications, information processing, topological photonics, and ultrafast control of light-matter interactions.

physics.optics↗

arXiv2021

Graphene Based Opt-Thermoelectric Tweezers

Since the discovery of graphene, its excellent physical properties has greatly improved the performance of many optoelectronic devices and brought important technological revolution to optical research and application. Here, we introduce graphene into the field of optical tweezers technology and demonstrate a new thermoelectric optical tweezers technology based on graphene. This technology can not only reduce the incident light energy by 2 orders of magnitude (compared with traditional optical tweezers), but also bring new advantages such as much broader working bandwidth and larger working area than the thermoelectric optical tweezers based on gold film widely studied before. Compared with gold film, graphene has more novel characteristics like high thermal conductivity, high uniformity and easy process. Thus, we found even monolayer graphene can achieve stable trapping for particles in a broad band, and the performance is enhanced with more graphene layers. Furthermore, structured graphene patterns can be easily generated to holographically trap multiple particles as desired shapes. This work verifies the great application potential of two-dimensional materials in op-tical tweezers technology, and it will promote more promising applications in cell trapping, tapping or concentration of biomolecules, microfluidics and biosensors.

physics.optics↗

arXiv2020

Few-layer hyperbolic multilayer for spontaneous emission enhancement

Multilayer hyperbolic metamaterials consisting of alternating metal and dielectric layers have important applications in spontaneous emission enhancement. In contrast to the conventional choice of at least dozens of layers in multilayer structures to achieve tunable Purcell effect on quantum emitters, our numerical calculations reveal that multilayers with fewer layers and thinner layers would outperform in Purcell effect. These discoveries are attributed to the negative contributions by an increasing layer number to the imaginary part of the reflection coefficient, and the stronger coupling between surface plasmon polariton modes on a thinner metal layer. This work could provide fundamental insights and practical guide for optimizing the local density of optical states enhancement functionality of ultrathin and even two-dimensional photon sources.

physics.optics↗

arXiv2018

Orbital angular momentum conversion of optical field without spin state

As one fundamental property of light, the orbital angular momentum (OAM) of photon has elicited widespread interest. Here, we theoretically demonstrate that the OAM conversion of light without any spin state can occur in homogeneous and isotropic medium when a specially tailored locally linearly polarized (STLLP) beam is strongly focused by a high numerical aperture (NA) objective lens. Through a high NA objective lens, the STLLP beams can generate identical twin foci with tunable distance between them controlled by input state of polarization. Such process admits partial OAM conversion from linear state to conjugate OAM states, giving rise to helical phases with opposite directions for each focus of the longitudinal component in the focal field.

physics.optics↗

arXiv2017

Ultra-broadband On-chip Twisted Light Emitter

On-chip twisted light emitters are essential components for orbital angular momentum (OAM) communication devices, which could address the growing demand for high-capacity communication systems by providing an additional degree of freedom for wavelength/frequency division multiplexing (WDM/FDM). Although whispering gallery mode enabled OAM emitters have been shown to possess some advantages, such as being compact and phase accurate, their inherent narrow bandwidth prevents them from being compatible with WDM/FDM techniques. Here, we demonstrate an ultra-broadband multiplexed OAM emitter that utilizes a novel joint path-resonance phase control concept. The emitter has a micron sized radius and nanometer sized features. Coaxial OAM beams are emitted across the entire telecommunication band from 1450 to 1650 nm. We applied the emitter for OAM communication with a data rate of 1.2 Tbit/s assisted by 30-channel optical frequency combs (OFC). The emitter provides a new solution to further increase of the capacity in the OFC communication scenario.

physics.optics↗

arXiv2009

Optimization of quantum interferometric metrological sensors in the presence of photon loss

We optimize two-mode, entangled, number states of light in the presence of loss in order to maximize the extraction of the available phase information in an interferometer. Our approach optimizes over the entire available input Hilbert space with no constraints, other than fixed total initial photon number. We optimize to maximize the Fisher information, which is equivalent to minimizing the phase uncertainty. We find that in the limit of zero loss the optimal state is the so-called N00N state, for small loss, the optimal state gradually deviates from the N00N state, and in the limit of large loss the optimal state converges to a generalized two-mode coherent state, with a finite total number of photons. The results provide a general protocol for optimizing the performance of a quantum optical interferometer in the presence of photon loss, with applications to quantum imaging, metrology, sensing, and information processing.

quant-ph↗