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Optical systems provide a new and practical platform for studying Bloch oscillations. This study investigates the fundamental-mode propagation of polarization-dependent Bloch oscillations. By using the three-dimensional properties of femtosecond laser direct writing, we fabricate a polymer-based gradient waveguide array and determine the Bloch oscillations under different polarization inputs by using the birefringence gradient and the equivalent refractive index, thus exhibiting a polarization-dependent Bloch period. Our results provide a new, to the best of our knowledge, paradigm for two-dimensional optical Bloch modes and highlight the influence of optical polarization in the same system, which provides a possibility to observe richer physics related to Bloch oscillations in one structure.In this Letter, we present wave propagation models of spatially partially coherent (or spatially incoherent) light to compress the computational load of forward and back propagations in inverse problems. In our model, partially coherent light is approximated as a set of random or plane wavefronts passing through spatial bandpass filters, which corresponds to an illumination pupil, and each wave coherently propagates onto a sensor plane through object space. We show that our models reduce the number of coherent propagations in inverse problems, which are essential in optical control and sensing, such as computer-generated holography (CGH) and quantitative phase imaging. We verify the proposed models by numerical and experimental demonstrations of CGH incorporating spatially partially coherent light.Nanophotonics based on localized surface plasmon resonance (LSPR) has emerged as a vibrant arena for research into enhanced light-matter interactions with potential applications in imaging, sensing, and computing. However, the low quality (Q) factor of LSPR is a significant barrier to comprehensive device applications. Here, we demonstrate that coupling the LSPR of a gold nanowire array with the optical bound states in the continuum (BIC) of a dielectric double-layer grating can significantly increase the Q factor of LSPR. We realize two hybrid modes with Q factors of up to 111 at 558 nm and 83 at 582 nm, which are about 14 and 10 times larger than those of an uncoupled gold nanowire array. Based on temporal coupled-mode theory, we further show that the resonance frequencies and Q factors of the hybrid modes can be modulated and optimized by varying relevant structural parameters. This coupled system provides a new platform for improving the figures of merit (FoMs) of LSPR-based refractive index sensors, and the concept of LSPR-BIC coupling can be extended to other similar nanosystems.An H-shaped acoustic micro-resonator (AmR)-based quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor is demonstrated for the first time. The H-shaped AmR has the advantages of easy optical alignment, high utilization of laser energy, and reduction in optical noise. The parameter of the H-shaped AmR is designed based on the standing wave enhancement characteristic. The performance of the H-shaped AmR-based QEPAS sensor system and bare quartz tuning fork (QTF)-based sensor system are measured under the same conditions by choosing water vapor (H2O) as the target gas. Compared with the QEAPS sensor based on a bare QTF, the detection sensitivity of the optimal H-shaped AmR-based QEPAS sensor exhibits a 17.2 times enhancement.In this Letter, we report the fabrication of fiber Bragg gratings (FBGs) in home-made Ho3+/Pr3+ co-doped single-cladding fluoroaluminate (AlF3) glass fibers and its application in watt-level lasing at the mid-infrared (MIR) wavelength of 2.86 µm. The FBGs were inscribed using an 800 nm femtosecond (fs) laser direct-writing technique. find more The FBG properties were investigated for different pulse energies, inscription speeds, grating orders, and transversal lengths. A second-order FBG with a high reflectivity of 99% was obtained at one end of a 16.5-cm-long gain fiber. Under 1150 nm laser pumping, this fiber yielded a power exceeding 1 W at 2863.9 nm with an overall laser efficiency of 17.7%. The fiber laser showed a FWHM bandwidth of 0.46 nm and long-term spectral stability.All-inorganic cesium lead halide perovskite (CsPbX3; X = Cl, Br) nanocrystals (NCs) are synthesized via a modified hot injection method using 3-mercaptopropyltrimethoxysilane (MPTMS), together with oleic acid and oleylamine, for in situ passivation of the surface defects. The surface chemistry, revealed by Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) techniques, shows an absence of Si-O-Si network and C-O groups on these in situ passivated CsPbX3 NCs, denoted as InMP-CsPbX3, which is in strong contrast to the counterpart NCs obtained via a postsynthesis exchange strategy. The x-ray diffraction (XRD) pattern indicates a lattice structure significantly strained from the cubic structure. The synthesis of these InMP-CsPbX3 NCs is highly reproducible, and the colloids are stable in nonpolar solvents. The emission wavelength of CsPb(Cl/Br)3 mixed halide perovskite NCs is tuned from 405 nm to 508 nm by reducing the nominal Cl/Br ratio, while the photoluminescence quantum yield (PLQY) is greatly enhanced over the whole spectral range. More importantly, the InMP-treatment is among the few strategies that are promising for electroluminescence in light-emitting diodes.We report the fabrication and characterization of a five-tube nested hollow-core anti-resonant fiber (Nested HC-ARF), which exhibits outstanding optical performance in terms of a record attenuation value of 0.85 dB/km at 2 µm wavelength range with a 200 nm bandwidth below 2 dB/km and excellent modal purity. The power handling capability of the Nested HC-ARF is also demonstrated in this work. Pulses of 75 W, 160 ps from the thulium-doped fiber laser are delivered using a 6-m-long fabricated Nested HC-ARF. The tested fiber is coiled into a 20 cm bending radius and achieves a coupling efficiency of 86.7%. The maximum average power of 60.5 W is transmitted through our Nested HC-ARF in a robust single-mode fashion without introducing any damage to the input and output fiber end-faces, which demonstrates the superior ability of such a fiber for high-power laser delivery.A rather narrow field of view (FOV) has always been considered as an essential limitation of spectral imagers based on acousto-optical tunable filters (AOTFs). We demonstrate a computational technique to overcome this constraint. It is based on preliminary precise spectral-angular characterization of beam transformation caused by light diffraction on an acoustic wave and consequent correction of acquired stack of spectral images. This technique is applicable for any geometry of acousto-optic interaction and opens the way for the development of AOTFs with significantly expanded FOV.Super-resolution microscopy (SRM) unveils details of subcellular organelles and provides a technical foundation for cellular biology research. Long-term, non-invasive live-cell super-resolution imaging requires low-intensity illumination and high image quality. Here, we present a new, to the best of our knowledge, method based on time-resolved detection termed fluorescence spatiotemporal modulation, in which highly spatially resolved photons in the beam center are extracted by taking the difference of the photons in the beam periphery with a weighted coefficient. The experimental results show a sub-100 nm resolution at tens of microwatts of laser power. Our proposed method requires only one laser, laying a foundation for a lower-cost multi-color super-resolution imaging system.We present a method for acquiring a sequence of time-resolved images in a single shot, called single-shot non-synchronous array photography (SNAP). In SNAP, a pulsed laser beam is split by a diffractive optical element into an array of angled beamlets whose illumination fronts remain perpendicular to the optical axis. Different time delays are imparted to each beamlet by an echelon, enabling them to probe ultrafast dynamics in rapid succession. The beamlets are imaged onto different regions of a camera by a lenslet array. Because the illumination fronts remain flat (head-on) independently of beamlet angle, the exposure time in SNAP is fundamentally limited only by the laser pulse duration, akin to a "global shutter" in conventional imaging. We demonstrate SNAP by capturing the evolution of a laser induced plasma filament over 20 frames at an average rate of 4.2 trillion frames per second (Tfps) and a peak rate of 5.7 Tfps.Broadband metasurfaces have attracted significant attention for a variety of applications in imaging and communication systems. Here, a method to alleviate the chromatic aberrations issue is proposed in the microwave region using dynamic phase compensation enabled by a reconfigurable metasurface. The dispersion characteristic of the meta-atom implemented with varactor diodes can be flexibly manipulated electronically, such that the dispersion-induced phase distortions over a wide frequency band can be compensated dynamically to achieve broadband performances. Various aberration-free functionalities can be realized with the proposed active metasurface. Near-field measurements are performed on a fabricated prototype to demonstrate aberration-free beam bending and hologram imaging, showing good agreement with simulation results. Such an active metasurface platform paves the way to efficient devices for wireless power transfer, sensors, and communication and antenna systems at radio or much higher frequencies.A radial shearing dynamic wavefront sensor is theorized and experimentally verified. The proposed sensor is based on a geometric phase lens pair that generates two radially sheared wavefronts. A polarization pixelated camera instantaneously obtains polarization-multiplexed phase maps from a single acquired image using a spatial phase-shifting technique. Experimental tests applied several wavefront shapes with a deformable mirror. The results were compared with a Shack-Hartmann wavefront sensor to evaluate the performance.We demonstrate an optical parametric chirped-pulse amplifier (OPCPA) that uses birefringence phase matching in a step-index single-mode optical fiber. The OPCPA is pumped with chirped pulses that can be compressed to sub-30-fs duration. The signal (idler) pulses are generated at 905 nm (1270 nm), have 26 nJ (20 nJ) pulse energy, and are compressible to 70 fs duration. The short compressed signal and idler pulse durations are enabled by the broad bandwidth of the pump pulses. Numerical simulations guiding the design are consistent with the experimental results and predict that scaling to higher pulse energies will be possible. Forgoing a photonic crystal fiber for phase-matching offers practical advantages, including allowing energy scaling with mode area.We demonstrate a broadband and flat millimeter-wave (MMW) noise source based on the heterodyne of two Fabry-Perot lasers subject to optical feedback. Different mode intervals between two lasers are designed to generate beat terms at specific frequencies. As a proof-of-concept demonstration, a MMW noise signal with a 3-dB bandwidth of 50 GHz (limited by the measurement bandwidth) and flatness of less than 2.9 dB is experimentally achieved. The physical origination of the broadband flat MMW noise generation is analyzed, and the properties of the MMW signal are characterized. The proposed method has the potential to generate a broadband flat noise signal in the MMW or even the terahertz region.