Optical vortices bearing orbital angular momentum (OAM) with fractional topological charge have many applications in particle guiding and transport, anisotropic edge enhancement, high-dimensional quantum entanglement, free-space optical communication. A vortex (FOV) breaks OAM orthogonality, though, making precise measurement complex difficult. This article shows how to measure the of a FOV by using two-dimensional multifocal array different integer charges. With an error detection below...

An all-fiber orbital angular momentum (OAM) generator enabling direct turning of the fundamental mode (${{\rm HE}_{11}}$HE11) to second OAM modes (${ l} = {\pm 2}$l=±2) with an efficiency $\sim90\% $∼90% has been proposed and experimentally demonstrated, which is realized based on utilization a second-order helical fiber grating written in few-mode fiber. This first time, best our knowledge, that achieved using only one component, i.e., long-period grating. The method opens new way...

An all-fiber orbital angular momentum (OAM) mode generator enabling simultaneous generation of the second- and third-order OAM modes with conversion efficiencies larger than 95% has been proposed experimentally demonstrated, which is realized by using a high-order helical long-period fiber grating (HLPG) written in thinned four-mode fiber. This first time, to best our knowledge, that two such have simultaneously obtained at wavelengths ranging from 1450 1620 nm only one component, i.e.,...

A novel fiber sensor, which enables us to simultaneously measure the torsion, strain, and temperature, is proposed experimentally demonstrated, based on utilization of two successively cascaded helical long-period gratings (TSC-HLPGs). By using approach, crosstalk effects among torsion can totally be discriminated for first time best our knowledge. Moreover, not only angle, but also direction determined simultaneously. Accuracies resolved angle are estimated ~0.8 °C within range 20 °C-100...

In this study, a nano-displacement measurement system is proposed and demonstrated both theoretically experimentally, which was based on modified Mach-Zehnder (M-Z) interferometer using two conjugated orbital angular momentum (OAM) beams. contrast to the previous M-Z-based OAM interferometer, reflection module inserted into reference arm instead of simple mirror. As result, effect transverse position-dependence phase-shift caused by dove prism can be clearly eliminated stable robust...

A polarization-independent dual-peak narrow-band filter is proposed and demonstrated theoretically experimentally, which realized by using a helical long-period fiber grating (HLPG) but with period small down to tens of micrometers. Unlike those excessively tilted gratings (Ex-TFGs) or the conventional (LPGs) micrometers where generated pairs (DPPs) are all strong polarization-dependence, DPPs obtained in this study polarization-independent, first time, best our knowledge, that underlying...

Abstract Orbital‐angular‐momentum (OAM) beams‐based interferometer has been found various applications in high‐precision metrology. However, most of its reported to date are limited 1D ones, and the simultaneous measurements for multidimensional displacement have rarely explored. Here an angular momentum superposition is first proposed demonstrated, which phases‐changes induced by rotational linear displacements, independently carried (SOAMS) beam containing different spin orbital momenta,...

An all-fiber scheme for stable orbital angular momentum (OAM) beam generation and propagation is proposed demonstrated. This based on a self-designed manufactured graded-index few mode fiber (GI-FMF) compatible selection coupler (MSC). The MSC, which consists of conventional single (SMF) the GI-FMF, can effectively couple fundamental in SMF to desired OAM GI-FMF phase matching condition. Meanwhile, breaks degeneracy between eigenmodes neighboring vector modes, thereby allowing preservation...

Based on the inverse Faraday effect, light-induced magnetization field distributions are investigated for a 4π tight focusing configuration with azimuthally polarized beams. It is found that superlong (16λ) chain, composed of 19 subwavelength (0.44λ) spherical spots longitudinal field, can be achieved in focal volume objective. Moreover, magnetic force particle or trains produced by tightly focused beams calculated and exploited stable trapping particles. These unique may find potential...

Orbital-angular-momentum (OAM) beams-based interferometers have recently been attracted significant interest and found various applications in the field of optical precision measurement. Whereas all-fiber OAM featured with superior characteristics compact size, low cost, extremely-low insertion-loss, inherent compatibility other fiber devices, less studied especially demonstrated experiment. In this study, we proposed experimentally an interferometer, where two conjugated beams generated by...

A full C- and L-band covered second-order orbital-angular-momentum (OAM) mode generator has been proposed experimentally demonstrated, which is realized by using a helical long-period fiber grating (HLPG) but inscribed in thinned four-mode fiber. By optimizing the design of period diameter HLPG, an ultra-broadband rejection filter with depth ∼23 dB, bandwidth ∼156 nm @-10 dB (ranging from 1522 to 1678 nm) ∼58 @-20 1574 1632 nm), successfully obtained as typical sample. To best our knowledge,...

Light propagation obeys Fermat's principle, and an important inference of principle is the optical Lagrange equation, from which light trace can be determined with a given refractive index. Here, we consider inverse problem how to derive index distribution planar geometric system once predetermined. Based on propose dynamic equation model associates trace. With consideration certain trace, illustrate process solving partial differential through first integral method. By setting function...

Abstract Recently, orbital angular momentum (OAM) has been adopted to measure the shape of static objects and translation motion moving in optical remote sensing. Most these studies rely on measuring intensity variation OAM beams. However, does not change with rotation spinning object, but its phase changes. The is proved be proportional object’s velocity. Since a rotating object will cause dependent time, needs measured instantaneously, support OAM-based velocity measurement. In this work,...

In this study, a broadband flat-top second-order orbital angular momentum mode (OAM) converter is proposed and demonstrated using phase-modulated helical long-period fiber grating (HLPG). The HLPG designed to be inscribed in thinned four-mode operated at wavelengths near the dispersion turning point (DTP). contrast most of HLPG-based OAM generators reported date, where high-order have rarely been achieved simultaneously, OAM(OAM-2) with bandwidth 113 nm @ -20 dB (ranging from 1530—1643 nm)...

Instead of inscribing the discrete phases into each local period seed HLPG, an equivalent approach to realize phase-only sampled multichannel helical long-period fiber grating (HLPG) has been demonstrated both theoretically and experimentally which is realized by superposing so-called sampling HLPGs with HLPG in a same region fiber. The proposed can greatly facilitate fabrication processes using direct CO₂ laser writing technique, meanwhile it enables provide much more design...

A novel DC-sampling method allowing generation of a multichannel helical long-period fiber grating (HLPG) has been proposed. Unlike the previous phase-only sampling where phases continuous function must be discretely adopted and inserted into local pitches (thus high precision setups for controlling all individual are essential), proposed can greatly facilitate fabrication HLPG by using CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>...

We present a simple method of spatial-division multiplexing/demultiplexing with orbital angular momentum (OAM) based on multi-ring optical fiber. Multi-ring fibers are ideal spatial division multiplexing carriers, providing more communication channels including orthogonal OAM and channels. propose an encoding scheme using perfect vortex array (MPVA) to make full use these achieve high-capacity data links. For improving the coupling efficiency, vortices whose radii independent topological...

A new method enabling the simultaneous generation of first- and second-order orbital angular momentum (OAM) modes has been proposed experimentally demonstrated, which is realized by using two consecutively- cascaded helical long-period fiber gratings (HLPGs). As a typical example, first-order (l = 1) OAM mode with conversion efficiency 94% -2 ) 83% have successfully obtained. This first report for HLPGs only. The may provide way to realize multiple in fiber.

A helical long-period fiber grating (HLPG)-based temperature-insensitive torsion and strain sensor is proposed experimentally demonstrated, which was realized by using a second-order HLPG written in thinned four-mode fiber. Simultaneous measurement of the accomplished power-interrogated scheme, i.e., torsion- strain-induced changes transmission spectrum two linear regions were especially used as testing objectives. The maximum sensitivity 665 pm/(rad/m) under ranging from −22.4 to 22.4 rad/m...

In this study, a novel and efficient method enabling fabrication of multichannel helical long-period fiber grating (HLPG) with almost the same channel spacing rejection depth has been proposed demonstrated for first time both theoretically experimentally, which is realized based on utilization so-called phase-only sampling technique. Unlike previous amplitude-type where either strong rectangular-type or Sinc-like index-modulation distribution generally demanded, requires minimum as well...

A broadband edge filter with linear dynamic ranges of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>40</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mi mathvariant="normal">n</mml:mi> mathvariant="normal">m</mml:mi> </mml:math> in wavelength and <mml:mn>93</mml:mn> mathvariant="normal">%</mml:mi> transmission loss has been demonstrated both theoretically experimentally, which is achieved by using a...

Building extraction from high spatial resolution imagery (HSRI) plays an important role in the remotely sensed application fields. However, automatically extracting buildings HSRI is still a challenging task due to such factors as large size variations of buildings, background complexity, appearance, etc. Especially, it difficult extract both crowded small and with accurate boundaries. To address these challenges, this paper presents end-to-end encoder–decoder model HSRI. The designed...

A stably acquiring and accurately demodulating interferogram is crucial for the interferometer to achieve ultra-high precision sensitivity measurements. In this study, a robust orbital angular momentum (OAM) beams-based Fizeau proposed experimentally demonstrated, which more compact stable than OAM interferometers with other structures due common optical path characteristic. accordance such an interferometric scheme, phase-demodulation method operated in domain of complex spectrum also...