Abstract
Abstract Using an all-fiber mode selective coupler (MSC) at the visible band, here we experimentally demonstrate a generating and wavelength multiplexing scheme for the cylindrical vector (CV) and vortex beams (VBs). The proposed MSCs act as efficient mode converters to produce spectrally insensitive high-order modes (HOMs) at the wavelength ranging from 450 to 980 nm, which have broad operation bandwidth (more than 7 nm), high mode conversion efficiency (94%), and purity (98%), and low insert loss (below 0.5 dB). By adjusting the polarization state and the phase shift of linear polarization (LP)11 mode respectively, the donut-shaped CVs and circular-polarization VBs are achieved. The focused intensity distribution of the donut beam on the cross- and axial-sections is monitored by using a confocal system. The all-fiber solution of producing and multiplexing HOMs opens a new route for stimulated emission depletion microscopy applications.
Highlights
Orthogonal multiplexing technology of high-order modes (HOMs) transmitted in few-mode fiber (FMF) has surpassed the capacity barrier in the traditional single mode fiber (SMF) communication system and provided the possibility for further exploring the freedom degrees of light beams, such as amplitude, phase, wavelength, and polarization [1,2,3,4]
Using an all-fiber mode selective coupler (MSC) at the visible band, here we experimentally demonstrate a generating and wavelength multiplexing scheme for the cylindrical vector (CV) and vortex beams (VBs)
The visible HOMs can be researched for stimulated emission depletion (STED) microscopy, and have provided nanoscale resolution to visualize the complex details of subcellular structure [14,15,16]
Summary
Orthogonal multiplexing technology of high-order modes (HOMs) transmitted in few-mode fiber (FMF) has surpassed the capacity barrier in the traditional single mode fiber (SMF) communication system and provided the possibility for further exploring the freedom degrees of light beams, such as amplitude, phase, wavelength, and polarization [1,2,3,4]. The optical vortex beam (OVB) characterized by the helical wavefront can be generated by combining two orthogonal vector modes [18] These beams with special polarization state and phase characteristic have significant applications, such as high-resolution measurement [19], particle trapping and manipulation [20], remote sensing technology [21, 22], etc. We experimentally demonstrate an allfiber scheme for generating HOMs and wavelength multiplexing at visible band based on a mode selective coupler (MSC). This is the first report that the MSC acts as an allfiber mode generator and multiplexer at visible wavelength and can be potentially applied in STED microscopy
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