Low-insertion-loss femtosecond laser-inscribed three-dimensional high-density mux/demux devices

Recently,transmitting diverse signals in different cores of a multicore fiber(MCF)has greatly improved the communication capacity of a single fiber.In such an MCF-based communication system,mux/demux devices with broad bandwidth are of great significance.In this work,we design and fabricate a 19-channel mux/demux device based on femtosecond laser direct writing.The fabricated mux/demux device possesses an average insertion loss of 0.88 dB and intercore crosstalk of no more than−29.1 dB.Moreover,the fabricated mux/demux device features a broad bandwidth across the C+L band.Such a mux/demux device enables low-loss 19-core fiber(de)multiplexing over the whole C+L band,showing a convincing potential value in wavelength-space division multiplexing applications.In addition,a 19-core fiber fan-in/fan-out system is also established based on a pair of mux/demux devices in this work.

Ultracompact phase plate fabricated by femtosecond laser two-photon polymerization for generation of Mathieu–Gauss beams

The Mathieu beam is a typical nondiffracting beam characterized by its propagation invariance and self-reconstruction.These extraordinary properties have given rise to potentialities for applications such as optical communications,optical trapping,and material processing.However,the experimental generation of Mathieu–Gauss beams possessing high quality and compactness is still challenging.In this work,even and helical Mathieu phase plates with different orders m and ellipticity parameters q are fabricated by femtosecond laser two-photon polymerization.The experimentally generated nondiffracting beams are propagationinvariant in several hundred millimeters,which agree with numerical simulations.This work may promote the miniaturization of the application of nondiffracting beams in micronanooptics.

Tailoring light on three-dimensional photonic chips: a platform for versatile OAM mode optical interconnects

Explosive growth in demand for data traffic has prompted exploration of the spatial dimension of lightwaves, which provides a degree of freedom to expand data transmission capacity. Various techniques basedon bulky optical devices have been proposed to tailor light waves in the spatial dimension. However, theirinherent large size, extra loss, and precise alignment requirements make these techniques relativelydifficult to implement in a compact and flexible way. In contrast, three-dimensional (3D) photonic chips withcompact size and low loss provide a promising miniaturized candidate for tailoring light in the spatialdimension. Significantly, they are attractive for chip-assisted short-distance spatial mode optical interconnectsthat are challenging to bulky optics. Here, we propose and fabricate femtosecond laser-inscribed 3D photonicchips to tailor orbital angular momentum (OAM) modes in the spatial dimension. Various functions on theplatform of 3D photonic chips are experimentally demonstrated, including the generation, (de)multiplexing,and exchange of OAM modes. Moreover, chip-chip and chip–fiber–chip short-distance optical interconnectsusing OAM modes are demonstrated in the experiment with favorable performance. This work paves the wayto flexibly tailor light waves on 3D photonic chips and offers a compact solution for versatile opticalinterconnects and other emerging applications with spatial modes.