Researchers from Chiral Photonics are hoping that a new tapered coupler design may clear the way for photonics-based high-speed computing and signal processing. They were recently issued a patent for a tapered coupler that they have named the Helica TC. It consists of two concentric cores and a cladding material. The cores have low index contrast but the outer core and cladding have high contrast. The low-index-contrast cores facilitate low-loss connectivity to standard fibers. The fiber then tapers down over its length, eliminating the inner core by the output end. At the output end, the high-index-contrast behavior supports low-loss connectivity to high-index-contrast structures such as planar waveguides. The design allows light from a conventional low-numerical-aperture fiber to be efficiently endface-coupled into another waveguide with smaller mode field dimensions and higher numerical aperture, eliminating the need for microlens-based coupling and air gaps. The technology supports both polarizing and polarization maintaining coupler variations.
According to Victor Kopp, director of R&D at Chiral Photonics, "We believe this is a significant enabling technology for planar nanophotonics and in the field of high index contrast photonics more generally. In addition to the endface and evanescent coupling devices we are currently supplying, we plan to use this technology to introduce a passive alignment solution for board-to-board and chip-to-chip interconnects."
Chiral Photonics released the Helica TC late in 2007 and optoelectronics developers are already using it to couple standard optical fiber to planar waveguide devices and photonic nanostructures.