Fiber angular displacement sensor utilizing orbital angular momentum beam interference.

In this Letter, a highly sensitive and wide-range sensing system for fiber angular displacement measurement based on orbital angular momentum (OAM) beam interference is proposed and experimentally demonstrated. The system utilizes a micro polarization-maintaining fiber (PMF) as the angular displacement sensing element, effectively converting the angular displacement of fiber bending into an interference phase difference through the interaction of OAM modes and spherical wave interference. A dedicated algorithm is developed to demodulate the rotational characteristics of the interference image, enabling precise angular displacement measurement.

3D-printed fiber-based perfect vortex beam generator.

An all-fiber focused perfect vortex beam (PVB) generator is reported and fabricated by using 3D printing technology. The generator is constructed by integrating a designed spiral axicon zone plate (SAZP) on the fiber-end facet. The ring diameters of the generated beams are independent of the topological charges and positively correlated with the wave vectors in the transverse direction.

All-fiber focused optical vortex array generator based on a Dammann-Kinoform spiral zone plate.

An optical vortex array (OVA) provides more degrees of freedom for modulation by controlling the number and spatial distribution of optical vortices (OVs). However, traditional approaches such as spatial light modulation need to utilize numerous complex optical components to generate an OVA and bulky objective lenses to focus it. We reported a highly integrated all-fiber generator of the focused optical vortex array (FOVA) in this work.

Tunable Bessel beam generator based on a 3D-printed helical axicon on a fiber tip.

We demonstrate a tunable and fully enclosed fiber-based Bessel beam generator that has the potential for applications in a tough environment. This generator consists of a few-mode fiber (FMF), a short section of graded index fiber (GIF), and a 3D-printed helical axicon. The FMF provides tunable modes that carry an orbital angular momentum (OAM).

Tunable mode convertor based on fiber Bragg grating inscribed in graded-index nine-mode fiber.

A tunable mode convertor is experimentally demonstrated based on a fiber Bragg grating (FBG), which is fabricated in a graded-index nine-mode fiber by using a femtosecond laser. Nine linearly polarized (LP) modes were excited and the coupling efficiency of them can reach 90%. By adjusting the polarization controller, the ±1st-, ±2nd-, ±3rd-, and ±4th-order orbital angular momentum (OAM) modes were excited, which means the OAM tuning of 0-±1ℏ, 0-±2ℏ, 0-±3ℏ, and 0-±4ℏ were achieved.

Focused vortex beam generator suitable for optical fiber spanners in a complex liquid environment.

We experimentally demonstrated an all-fiber focused vortex beam (FVB) generator which was prepared by milling a spiral zone plate (SZP) on the Au-coated end face of a hybrid fiber by focused ion beam (FIB). In this generator, the fundamental modes propagating in the hybrid fiber are focused while being modulated into high-order orbital angular momentum (OAM) mode by the SZP at the end face. The focus length and topological charge were designed and then were both theoretically and experimentally verified.

Direct generation of orbital angular momentum in orthogonal fiber Bragg grating.

We experimentally demonstrated an all-fiber reflective orbital angular momentum (OAM) generator based on orthogonal fiber Bragg grating (OFBG). The OFBG is formed by using a femtosecond laser to prepare two fiber Bragg gratings with a certain spacing in orthogonal planes. The ±1st- and ±2nd-order OAM modes were directly excited in this OFBG, and the chirality of the OAM modes depends on the relative positions of the two FBGs.

High-order orbital angular momentum mode conversion based on a chiral long period fiber grating inscribed in a ring core fiber.

A chiral long period fiber grating (CLPFG) was designed according to the phase-matching condition and conservation law of angular momentum, and was inscribed in a ring core fiber (RCF). This CLPFG was used to directly excite the ±2- and ±3-order orbital angular momentum (OAM) modes. The coupling efficiency of the OAM mode is up to 98.