Generation Of Cylindrical Vector Beams Research Articles

Intracavity cylindrical vector beam generation from all-PM Er-doped mode-locked fiber laser.

We demonstrate a practical method that is used to generate on-demand first- and higher-order cylindrical vector beams, in the 1550 nm band, directly from an all polarization maintaining mode-locked Er-fiber laser. On demand typical 1st order CVBs, including the radially and azimuthally polarized beams, can be easily achieved by properly adjusting the angle of a half-wave plate with respect to the fast axis of the vortex wave plate. The spatial beam mode can be flexibly switched with no disturbance on the time domain mode-locking output. The laser outputs the desired vector beams at 1571 nm with a spectral bandwidth at full-width at half-maximum of 32 nm. The mode-locked laser pulses have a repetition rate of 74.9 MHz. Moreover, the proposed method can be easily extended to create higher-order CVBs. Our research provides a convenient way to generate ultrafast pulses in highly flexible-controlled structured modes, which is essential for optical fabrication and light trapping applications.

Dissipative soliton resonance Ytterbium-doped fiber laser with cylindrical vector beam generation

We experimentally demonstrate a dissipative soliton resonance (DSR) Ytterbium-doped fiber laser with high-purity cylindrical vector beam (CVB) generation, using a mode-selective coupler (MSC) as transverse mode converter and splitter. The all-normal-dispersion mode-locked Ytterbium-doped fiber laser operating at DSR regime without spectral filter can deliver CVB pulses with a pulse duration of ∼733 ps and a pulse energy as high as ∼0.439 nJ. The radially and azimuthally polarized beams can be switched by adjusting the polarization controller, with a high mode purity measured to be >94.5%. This compact DSR fiber laser could find potential applications in the field of material processing, nonlinear optics and so on.

使用亚波长光栅器件产生圆柱型矢量光束

使用亚波长光栅器件产生圆柱型矢量光束

Mode-locked pulse generation from an all-FMF ring laser cavity

Experimental generation of stable mode-locked pulses and cylindrical vector beams (CVBs), from an all few-mode fiber (FMF) ring laser is first reported, to the best of our knowledge. In this laser, a section of few-mode erbium-doped fiber (FM-EDF) is used as the gain medium. The FM-EDF is pumped by 976 nm laser with LP11 mode, which is simultaneously converted and multiplexed through a homemade hybrid device, i.e., wavelength division multiplexing-mode selection coupler (WDM-MSC). All the components in our experiment are connected using FMF. The resulted CVB pulses have a spectral width of 0.33 nm with a repetition rate of 30.58 MHz under the pump power of 340 mW. Moreover, both azimuthally and radially polarized CVBs were achieved with a high purity of >95%. This mode-locked CVB fiber laser with an all FMF configuration opens the way to manipulate the transverse mode in mode-locked fiber lasers.

Generation of cylindrical and elliptical symmetrical vector beam on the Mach–Zehnder interferometer

We propose a principal scheme to generate the cylindrical and the elliptical symmetrical vector beam based on a modified Mach-Zehnder interferometer. The modified Mach-Zehnder interferometer, the wave plates, the Polarizing Beam Splitter (PBS) and the Dove prism are used in this optical system. Two different order polarized beams can be generated and combined by this system and the arbitrary-order cylindrical and elliptical vector beams can be obtained. With the help of this simple optical system, the various profile vector beams can be generated flexibly.

Optical field manipulation by dual magnetic resonances of a silicon metasurface.

In this Letter, we study the influence of magnetic mode dispersion on the performance of a metasurface cylindrical vector beam (CVB) generator. An optical field after a metasurface CVB generator can be manipulated by polarization-dependent transmittance arising from dual magnetic resonance of silicon nanopillars. A perfect CVB is only generated when the transmittances are equal for two orthogonal polarization. Two magnetic resonant wavelengths can be spatially separated because of the coherent superposition between the residual incident light and the generating CVB, which is potentially useful for a compact multiplex color router.

All-fiber mode-locked cylindrical vector beam laser using broadband long period grating

We propose and demonstrate an all-fiber passively mode-locked laser based on the mechanism of nonlinear polarization rotation and two-mode fiber long period grating (TMF-LPG) to generate ultrafast cylindrical vector beam (CVB) output. The central wavelength of the laser is 1567.2 nm, and 3 dB bandwidth is measured to be 5.64 nm. The pulse duration of the mode-locked laser is 970 fs and the repetition rate is 20.47 MHz. An eight-period TMF-LPG written in a two-mode fiber by a CO2 laser serves as a broadband transverse mode converter to achieve ultrafast CVBs generation with broader spectrum. The 15.0 dB bandwidth (corresponding to conversion efficiency greater than 96%) of the LPG is 75 nm, which perfectly covers the wide mode-locked spectrum. High purity radially and azimuthally polarized beams are obtained through adjusting the polarization controllers, and the mode purity is calculated to be 94.35%. The slope efficiency of the CVBs’ output is about 5.84%.

Passively Mode-Locked Ytterbium-Doped Fiber Laser With Cylindrical Vector Beam Generation Based on Mode Selective Coupler

We propose and demonstrate, for the first time to the best of our knowledge, a passively mode-locked ytterbium-doped fiber laser generating cylindrical vector beams (CVBs) using a mode selective coupler (MSC) as the transverse mode converter and splitter, and a semiconductor saturable absorber mirror for mode-locking. According to the coupling mode theory and the phase matching principle, the MSC was fabricated by weakly fused technology, having a low loss of about 0.5 dB and achieving LP11 mode with a high purity of >96%. The CVB fiber laser operates at a center wavelength of 1042.3 nm, with a 3 dB spectral width of 1.5 nm. The repetition rate of the mode-locked laser pulses is 18.58 MHz. The radially and azimuthally polarized vector beams can be switched by adjusting the polarization controllers in the fiber ring cavity, with a high mode purity measured to be >95%. The mode-locked CVB ytterbium-doped fiber laser has potential applications in optical tweezers, optical imaging, etc.

An actively Q-switched fiber laser with cylindrical vector beam generation

We demonstrate an actively Q-switched fiber laser with cylindrical vector beam (CVB) emission using a few-mode fiber Bragg grating as the mode selection component and an acousto-optic modulator to achieve Q-switching. To the best of our knowledge, this is the first such demonstration. Using a linear cavity configuration, an actively Q-switched CVB with a pulse width of about 64 ns, a pulse energy of 4.25 µJ and a repetition rate of 20 kHz has been obtained. Moreover, by tuning the polarization controllers radially and azimuthally, polarized Q-switched beams can be excited separately with a polarization purity of >94.5%. This compact Q-switched fiber laser with ns CVB pulse output could find potential applications in the field of material processing, nonlinear optics and so on.

Generation of Perfect Cylindrical Vector Beams With Complete Control Over the Ring Width and Ring Diameter

We propose the generation of high-purity perfect cylindrical vector beams (PCVB) using the Fourier transformation of Bessel–Gauss vector beams. The demonstration of PCVBs is implemented via an interferometric method employing a spatial light modulator that allows a fully independent control of the ring diameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R_D$</tex-math></inline-formula> ) and ring width ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_W$</tex-math></inline-formula> ) of the PCVB. The proposed scheme enables to generate different types of cylindrical vector beams with precise user-defined transverse dimensions. The dynamic control of the ring width, ring diameter, and the specific type of PCVBs desired is theoretically as well as experimentally demonstrated. The proposed experimental setup can not only be employed in the generation of arbitrary PCVB, but also in perfect vortex beams. The ability to generate fully tailorable cylindrical vector beams and vortex beams has implications for the efficient launch of exotic optical modes in specialty fibers, in the field of optical tweezers as well as for superresolution microscopy.

Generation of cylindrical vector beams in a mode-locked fiber laser using a mode-selective coupler

We experimentally obtain cylindrical vector beams (CVBs) in a passively mode-locked fiber laser based on nonlinear polarization rotation. A mode-selective coupler composed of both a single-mode fiber (SMF) and a two-mode fiber (TMF) is incorporated into the cavity to act as a mode converter from LP01 mode to LP11 mode with broad spectral bandwidth. CVBs in different mode-locked states including single-pulse, multi-pulse, and bound pulse are obtained, for the first time to our best knowledge. The ultrafast CVBs with different operation states have potential applications in many fields such as laser beam machining, nanoparticle manipulation, and so on.

Multiwavelength mode-locked cylindrical vector beam fiber laser based on mode selective coupler

We propose and demonstrate a multiwavelength mode-locked fiber laser with cylindrical vector beam generation for the first time, to the best of our knowledge. The mode-locking mechanism is based on a nonlinear polarization rotation effect in fiber, and the multiwavelength operation is contributed to by an in-line birefringence fiber filter with periodic multiple passbands, formed by incorporating a section of polarization maintaining fiber into the laser cavity with a fiber polarizer. Furthermore, by using a home-made mode selective coupler, which acts as both a mode converter from fundamental mode to higher-order mode and an output coupler, multiwavelength mode-locked cylindrical vector beams have been obtained. This may have potential applications in mode-division multiplexing optical fiber communication and material processing.

Switchable phase and polarization singular beams generation using dielectric metasurfaces

Singular beams which possess helical phase wavefront or spatially inhomogeneous polarization provide new freedom for optical field manipulation. However, conventional schemes to produce the singular beams have difficulty in realizing the flexible switch between different singular beams. In this work, we have experimentally demonstrated the capability of dielectric metasurfaces to generate three types of singular beams and switch between them at working wavelength of 1550 nm. We have shown vortex beam and cylindrical vector beam generation with single metasurface and cylindrical vector vortex beam generation with two cascaded metasurfaces. Moreover, experimental demonstration on switching cylindrical vector beam into vortex beam has also been done by combining one quarter-wave plate and a Glan laser polarizer. The experimental results match well with the analysis from the Jones matrix calculations. The average conversion efficiency of cylindrical vector beam to vortex beam was estimated to be 47.7%, which was about 2.3% lower than the theoretical prediction.

Q-plate for the Generation of Terahertz Cylindrical Vector Beams Fabricated by 3D Printing

We present the design, fabrication, and characterization of a q-plate with continuous birefringence variation at terahertz frequencies. This q-plate was fabricated by three-dimensional printing and is a simple solution for the generation of cylindrical vector beams. This device can find a number of applications in future terahertz technologies such as telecommunications.

Polarization conversion under focusing of vortex laser beams along the axis of anisotropic crystals

We report the development of an optical system based on diffractive optical elements and uniaxial crystals to produce radially and azimuthally polarized beams, including beams of higher orders. The conditions for the generation of beams with different polarization states in an anisotropic crystal with an arbitrary axially symmetric amplitude distribution are analyzed theoretically. The results of the experimental study on the generation of cylindrical vector beams in a calcite crystal agree with the results of the simulation.

Method of Generating Femtosecond Cylindrical Vector Beams Using Broadband Mode Converter

We experimentally obtain femtosecond cylindrical vector beams based on a mode-locked fiber laser (MLFL) by using a fused few-mode coupler. Pulses of 300 fs duration with radially and azimuthally polarized modes are directly delivered at the central wavelength of 1566 nm. The fused few-mode fiber coupler inserted inside the cavity acts as a mode converter from LP01 mode to LP11 mode with a wide bandwidth over 100 nm. The proof-of-concept generation of femtosecond cylindrical vector beams is efficient and useful in MLFLs.

Theoretical analysis of hollow ring-core optical fibre for transmitting orbital angular momentum modes

Ring-core optical fibre has been successfully demonstrated to have good performance for lifting mode degeneracy, and maintaining orbital angular momentum (OAM) modes in the first radial order, making it promising for applications of OAM mode multiplexing and generation of cylindrical vector beams. The degeneracy lift can be intensified using a hollow ring-core fibre, i.e. when the innermost layer of waveguide is air. The cut-off ring thickness for supporting the lowest OAM modes in radial order are obtained under various refractive index differences between the transport layer and the cladding. To optimize the design, our analysis addresses the dependence of modal properties on the fibre structure parameters, such as the effective area (Aeff) of respective OAM mode, and the differential mode delay.

Generation of cylindrical vector beams and optical vortex by two acoustically induced fiber gratings with orthogonal vibration directions.

Mode coupling from the fundamental vector mode (HE11x) to the cylindrical vector beams (CVBs) and optical vortex beams (OVBs) of a few-mode fiber excited by two acoustic flexural waves with orthogonal perturbations is achieved by using a composite acoustic transducer. The HE11x mode is converted to TM01 and TE01 modes, which have radial and azimuthal polarizations, by using the lowest-order acoustic flexural modes of F11x and F11y, respectively. Furthermore, HE11x mode can also be converted to the ± 1-order OVBs of HE21even±iHE21odd through the combined acoustic modes of F11x±iF11y. This technique provides a useful way of generating CVBs and OVBs in optical fiber with conveniently electrically-controlled mode conversion characteristics.

An Injection-Locked Single-Longitudinal-Mode Fiber Ring Laser With Cylindrical Vector Beam Emission

We demonstrate a fiber ring laser with narrow bandwidth single-longitudinal-mode cylindrical vector beam (CVB) output at C-band wavelength range for the first time to the best of our knowledge. A step index two-mode fiber Bragg grating is used as a transverse mode selector for CVB generation, while both the injection-locking technique and narrow bandwidth of the fiber Bragg grating lead to single-longitudinal-mode operation. The 3-dB bandwidth of the laser output is measured to be 60 dB. Mode distribution and optical spectra of few-mode fibers with periodic modulated refractive index profile, namely the few-mode fiber Bragg gratings with bent radius, are investigated theoretically and experimentally, which provide a comprehensive exploration of CVB's generation.

Flexible generation of femtosecond cylindrical vector beams (Invited Paper)

Femtosecond (fs) cylindrical vector beams (CVBs) have found use in many applications in recent years. However, the existing rigid generation methods seriously limit its development. Here, we propose a flexible method for generating fs-CVBs with arbitrary polarization order by employing half wave plates and vortex retarders. The polarization state, autocorrelation width, pulse width, and spectrum features of the input and generated CVB pulses are measured and compared. The results verify that the generated CVBs remain in the fs regime with no appreciable temporal distortion, and the energy conversion efficiency can reach as high as 96.5%, even for a third-order beam. As a flexible way to generate fs-CVBs, this method will have great significance for many applications.