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

Abstract

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.

Generation and Nonlinear Frequency Conversion of Nanosecond Cylindrical Vector Beams in Two-Mode Fiber

“…An average power of 42 mW is measured for the nanosecond pulse before injecting into TMF via a micro-objective (MO1 40x, 0.65). The mode stripper (MS) is used to purify the laser beam to be the linearly-polarized fundamental vector mode, by filtering out the high-order vector modes through critical bending loss [22]. When the linearly-polarized fundamental mode (HE and HE y 11 modes can be respectively coupled to TM01 and TE01 modes with phase-matching condition to be satisfied [23], simultaneously.…”

“…A supercontinuum (Yslphotonics SC-5) is adopted as the broadband light source (BLS) with polarization state to be adjusted via an optical fiber in-line polarization controller (PC). To further eliminate the effects of the unwanted high-order vector modes (TE01, HE e/o 21 , TM01) before the AIFG, a mode tripper (MS1) [22,23], which is made of 4 turns of TMF wound on a 10 mm diameter rod, is used to ensure a pure fundamental mode launching. The diameter of TMF for forming the AIFG is etched down to 28 μm by hydrofluoric (HF) acid to adjust the resonance wavelength based on the phase matching condition and to enhance the overlap between the acoustic and optical waves [24], thus increasing the acousto-optic coupling efficiency of the AIFG within the 10 cm long etched segment.…”

Temperature Insensitivity Polarization-Controlled Orbital Angular Momentum Mode Converter Based on an LPFG Induced in Four-Mode Fiber

“…This study represents the first time (to our knowledge) that ±1-order OAM modes have been experimentally generated by tuning a polarization controller (PC), placed at the front of 4MF-LPFG an LPFG on a 4FM. The fundamental principle of this OAM conversion can be explained as follows [ 13 , 22 , 23 ]. The linearly-polarized input light (LP 01 ) can be considered the superposition of two vector modes: and .…”

All-Fiber Laser With Agile Mode-Switching Capability Through Intra-Cavity Conversion

“…Applications of such kind of device include mode-locked fiber lasers [21] and Q-switched fiber lasers [22]. In terms of mode conversion, it has also been adopted for generating cylinder beams and optical vortex beams [23]- [27]. It should be noted that fast mode-switching capability of the above-mentioned fiber laser based on AIFG has not been fully studied and the output powers of these fiber lasers are relatively low (less than several tens of milliwatts).…”