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Message: Patent Application
Another new patent application; a continuation of 2 patents that were granted April 13th this year. Work associated with POET's collaboration at University of Ottawa (Millview Photonics).
Office
United States of America
Application Number
17228076
Application Date
12.04.2021
Publication Number
Publication Date
29.07.2021
Applicants
POET Technologies, Inc.
Inventors
Suresh Venkatesan
Miroslaw Florjanczyk
Trevor Hall
Peng Liu
Jing Yang
Title
(EN) Dual Core Waveguide
Abstract
(EN)
The invention described herein pertains to the structure and formation of dual core waveguide structures and to the formation of optical devices including spot size converters from these dual core waveguide structure for the receiving and routing of optical signals on substrates, interposers, and sub-mount assemblies.
A few points I’ve pulled from the application:
In the prior art shown in FIG. 1, a lens is inserted in the optical path between the optical fiber mounted at the edge of the substrate and the planar waveguide to focus the optical signal from the relatively large core of the optical fiber to the much thinner planar waveguide. The diameter of a typical single mode optical fiber used in communication networks for the transmission of optical wavelengths in the range of 1100 to 1600 nm is typically 8-10 microns. Typical dielectric planar waveguides, on the other hand, are on the order of less than a micron to a few microns in thickness. In general, dielectric waveguides are susceptible to increasing stress with increasing film thickness, hence limiting the tolerable thicknesses of dielectric waveguides. Dimensional differences between the diameter of the core of the optical fiber and the planar waveguides in many applications that utilize dielectric waveguides, require tight alignment tolerances between the planar waveguides and the optical fibers to limit losses in the optical signal in transitioning from the optical fiber to the planar waveguide. The tight spatial and angular alignment tolerances and the need for lenses between the end of the optical fiber and the end facet of the planar waveguide, increase the complexity of the overall assembly relative to preferable alternatives in which the tolerances can be widened and for which the lenses can be eliminated. Tight alignment tolerances can also require costly polishing or finishing of the fiber termination. Alternatively, passive alignment techniques, if available, are preferable over the active alignment techniques that require a more complex procedure for providing suitable alignment and optimization of the signal transmission across the optical fiber/planar waveguide interface.
Referring to FIG. 2, an optical fiber with cladding is shown in proximity to the edge facet of a thick planar waveguide on substrate. The edge facet is substantially aligned to the planar waveguide edge facet without the requirement for the lens (as was shown in FIG. 1.) A three-dimensional perspective drawing of this structure is shown in FIG. 2. Thick planar waveguides enable direct transmission of the optical signal from an optical fiber, or a similarly positioned optoelectronic or optical device without the requirement for the focusing lens that is shown in FIG. 1. Thick planar waveguides on the order of the diameter of the core of the optical fiber are known in the art, and are typically polymers. Dielectric films are preferred over polymers due to their inherent dimensional and material stability, the capability to control the optical properties of these materials, and the available knowledge base for the formation and patterning of these films, among other benefits. Thick dielectric film structures, however, are susceptible to prohibitively increasing stress with increasing film thickness. High film stress can lead to deformation of the substrate, delamination of the films, and other undesirable effects. In addition to the potential problems that arise with the formation of thick dielectric planar waveguides, planar waveguides with thicknesses on the order of the core diameter of a typical single mode optical fiber can allow for optical signal propagation in undesirable or non-optical modes. Preferably, optical signals are limited to single mode propagation once the signals have been received into a photonic integrated circuit, for example, for signal processing operations such as multiplexing and demultiplexing, among others
In Provisional application 62/621,659, a thick dielectric structure suitable for use in forming thick planar waveguides, on the order of the diameter of single mode fibers, is included for reference herein in its entirety. In Provisional application 62/621,659, thick dielectric film structures are formed from stacks of silicon oxide and silicon oxynitride layers with low stress and with controllable optical properties that are suitable in some embodiments for receiving optical signals from proximally positioned optical fibers without stringent alignment requirements and without the requirement for the use of lenses as further described herein. The advantages of thick silicon oxynitride film structures for use in planar waveguides include dimensional stability, controllable optical properties, the availability of known patterning methods, and the capability to achieve passive alignment of optical fibers and planar waveguides, among others
The above, essentially stating how the invention allows them to create fibre-thick waveguide structures (for simplified coupling of fibre) using dielectric films without compromised (stressed) structural integrity. So, they’ve come up with an invention that takes the advantages of dielectrics and added the thickness capability typically seen in polymers, without the inherent weaknesses usually associated with either polymers or thick dielectrics.
Referring to FIG. 6, the planar optical circuit of FIG. 5 consisting of an arrayed waveguide device, is shown with anticipated propagation profiles of the optical signal at various locations in the optical circuit. In the exemplary optical circuit shown in FIG. 6, an incoming optical signal is provided to the sub-mount in the attached optical fiber at the left-bottom of FIG. 6, and propagates from the left edge of the device, through the arrayed waveguide, and out the right-bottom part of the circuit to the output fibers. The input to an arrayed waveguide, in some embodiments, is a multiplexed optical signal consisting of a number of distinct wavelengths of light. In an embodiment, the incoming optical signal is a multiplexed signal, and consists, for example, of a set of 16 different wavelengths, centered around 1550 nm in increments of 20 nm. In another embodiment, the incoming optical signal is a multiplexed signal consisting of eight wavelengths of light, centered around 1300 nm, in increments of 20 nm. In yet another embodiment, the incoming optical signal is a multiplexed signal consisting of four wavelengths centered around 850 nm in increments of 15 nm. An arrayed waveguide provides a means for separating the various wavelengths in the incoming optical signal, and then providing distinct physical channels within which to direct the individual signals. In this example, the circuit contains sixteen output fibers, for example, to provide a unique channel for each of the demultiplexed wavelengths from the incoming signal.
As we’ve already seen, the invention permits integration with arrayed waveguides (4, 8 or 16 channel, and perhaps more)
In embodiments, the upper core of the dual core waveguide has a higher refractive index than the lower core. In embodiments of the dual core waveguide, the dual core structure is fabricated from a polymer material or a dielectric material, or a combination of these materials; or is fabricated from a stack of silicon nitride, silicon oxide, or silicon oxynitride layers, or a combination of these materials; or is fabricated from a composite structure of multiple layers of silicon nitride, silicon oxide, and silicon oxynitride layers.
It appears the invention can be fabricated from a variety of substances, including polymers, to create products of varying properties and performing specific functions.
I believe this just scratches the surface, IMO.
https://patentscope.wipo.int/search/en/detail.jsf?docId=US331912305&_cid=P11-KRZP6H-91720-1
The related patents granted earlier this year:
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