Efficient Fiber‐to‐Chip Interface via an Intermediated CdS Nanowire

Abstract

An efficient fiber-to-chip interface via an intermediated CdS nanowire is demonstrated. The fiber mode is firstly squeezed through a fiber taper drawn at the end of a single-mode fiber, then evanescently coupled into an intermediated CdS nanowire with a longitudinally tapering profile, and finally coupled into an on-chip silicon waveguide (SiW) via a waveguide taper fabricated on it. Since the fiber-nanowire-SiW cascade structure is designed to match effective indices in each coupling area, such a fiber-to-chip interface ensures a bidirectional coupling efficiency up to 90% and a 3-dB bandwidth over 100 nm in experiments. The difference of coupling efficiencies between the TM or TE modes is less than 0.5 dB in the spectral range of 1545-1635 nm. The footprint of the on-chip coupling structure is about 10 µm in size. The results may provide a compact, efficient, and versatile fiber-to-chip interface in applications including optical interconnects, coherent communication, and quantum optical circuitry.

Optical microfiber or nanofiber: a miniature fiber-optic platform for nanophotonics

“…(g) Optical microscope image of an SU8 capped tapered fiber placed on the fork silicon-nitride-waveguide (SiN WG) coupler for low-loss, high-bandwidth fiber-to-chip coupling [337] . (h) Optical microscope image of a fiber-nanowire-silicon-waveguide cascade structure for efficient fiber-to-chip coupling [338] . The operation wavelength ranges from 1520 to 1640 nm.…”

“…16(c)] [110] , semiconductor nanowires (e.g., CdS, CdSe, ZnO, and CdTe) [see Fig. 16(d)] [326][327][328][329][330] , ice MNFs [126] , niobium nitride (NBN) superconducting nanowire [331][332][333] , and on-chip silicon waveguides [334][335][336][337][338] , have been evanescently coupled using waveguiding MNFs to obtain efficient optical coupling.…”

“…More recently, Jin et al designed a cascaded coupling structure of a "fiber-nanowire-silicon waveguide" for effectiveindex matching in each coupling area [see Fig. 16(h)], enabling bidirectional coupling efficiency as high as 90% and a 3-dB bandwidth in excess of 100 nm (1520 to 1640 nm in wavelength) for both TE and TM polarizations [338] . In addition, in some cases where sharp fiber tapers are required (e.g., for ultra-compact optical coupling), one can consider a scheme proposed by Wu et al recently [340] .…”