Patent Application
20240061170
The present disclosure relates generally to photonic integrated circuitry, and more particularly, low-coherence interferometry and methods and systems thereof.
Existing low-coherence interferometer (LCI) systems such as those that utilize optical coherence tomography (OCT) have been demonstrated using components based on photonic integrated circuit (PIC) technology. Specifically, the interferometer is typically built, for example, with silicon photonics, but the input/output couplers and optical scanning systems are based on free space optics, and the light source and detectors are coupled with off-chip components. This approach is impractical for applications where these systems need to be integrated in larger modules that require compactness and portability. One such application is in virtual reality or augmented reality headsets, which both require components to be small to provide user comfort without compromising functionality.
In yet another application relating to eye tracking systems such as those based on camera imaging and specular reflection of illuminators, typical LCI systems cannot readily be integrated. Since eye tracking systems rely chiefly on surface reflection and geometric modelling to locate the pupil and extract gaze directions, due to this simplified modelling, they typically provide limited accuracy. Furthermore, eye tracking systems are also limited in terms of power efficiency and form-factor, since the system has to support both the camera and the lens stack. Thus, integrating an LCI system in these eye tracking system would provide significant benefits in terms of accuracy and power savings by obviating the need for power-hungry imaging systems. Unfortunately, current LCI systems cannot be integrated in the afore-mentioned eye tracking systems as result of their high degree of modularity and bulkiness.
The embodiments featured herein help solve or mitigate the above noted issues as well as other issues known in the art. For example, and not by limitation, the present disclosure provides an apparatus based on LCI principles that can be realized with photonic integrated circuits for out-of-plane in-field sensing applications. The exemplary apparatus can include one or more interferometers, light sources, photodetectors and optical input/output couplers and beam shaping optics for out-of-plane detection and in-field sensing. The exemplary apparatus can be a fully integrated system that has a compact form factor and high see-through quality, which makes it integrable and usable in an AR or a VR headset or in an eye tracking system.
The embodiments and teachings presented herein feature a novel optical I/O coupler (also referred to herein as opto-coupler) for out-of-plane in-field sensing. These embodiments have reduced or negligible dispersion relative to the dispersion typically encountered in a broadband source (or a tunable wavelength source) used in conventional out-of-plane couplers such as grating couplers. The embodiments are further advantageous because of their high degree of integration. They can include refractive and diffractive components for beam shaping.
The embodiments further include fully integrated photonic integrated circuits that can include one or more of the above-noted I/O couplers. The embodiments can achieve depth detection. They can be used as standalone devices or in an array of LCI devices used in a matrix configuration. Furthermore, the present disclosure also describes novel fabrication methods with which the embodiments may be fabricated to achieve a high degree of integration.
Additional features, modes of operations, advantages, and other aspects of various embodiments are described below with reference to the accompanying drawings. It is noted that the present disclosure is not limited to the specific embodiments described herein. These embodiments are presented for illustrative purposes only. Additional embodiments, or modifications of the embodiments disclosed, will be readily apparent to persons skilled in the relevant art(s) based on the teachings provided.
Illustrative embodiments may take form in various components and arrangements of components. Illustrative embodiments are shown in the accompanying drawings, throughout which like reference numerals may indicate corresponding or similar parts in the various drawings. The drawings are only for purposes of illustrating the embodiments and are not to be construed as limiting the disclosure. Given the following enabling description of the drawings, the novel aspects of the present disclosure should become evident to a person of ordinary skill in the relevant art(s).
While the illustrative embodiments are described herein for particular applications, it should be understood that the present disclosure is not limited thereto. Those skilled in the art and with access to the teachings provided herein will recognize additional applications, modifications, and embodiments within the scope thereof and additional fields in which the present disclosure would be of significant utility.
Generally, an LCI system typically includes a broadband light source or a tunable light source. For example, and not by limitation, an LCI system that is included in an optical coherence tomography (OCT) system can require the use of such a broadband or tunable light source. The requirement for the source's spectral range depends on the detection resolution, and typically, it is from 10 nm to tens or hundreds of nanometers. Existing systems out-couple light from the sample arm and/or reference arm of an interferometer to free-space optics from the edges of the photonic integrated circuit chip where optical scanning is implemented. However, this approach requires complex packaging for micro-optical devices or the resulting form factor is too large to be used in a wearable device such as AR or VR glasses.
Furthermore, due to the required spectral bandwidth, an optical I/O coupler with negligible optical dispersion is required for applications such as AR and VR glasses. The embodiments described herein feature photonic out-of-plane coupling which overcomes the dispersion issues in typical out-of-plane couplers, such as gratings, and the embodiments include transparent substrates which are suitable for AR or VR glasses. Several exemplary embodiments are described in detail below as well as methods for fabricating and integrating their various components together to yield highly compact photonic integrated circuits.
The waveguide may be made of a rigid material. For example, the waveguide may be made with deposited or grown thin film inorganic materials. In yet another implementation, the waveguide may be made on a flexible substrate, or it may be an optical fiber. In yet another implementation, the waveguide may include an optical fiber coupled to a light guiding element where the light guiding element is fabricated on a rigid or flexible substrate. The two portions, i.e., the optical fiber and the light guiding element may be interfaced using a coupler.
A waveguide that may be used in an exemplary embodiment can have a cross-sectional structure that is rectangular, circular, or elliptical, or it may have multiple cross-sections such as in the case of a tapered waveguide. In other implementations, the waveguide may be a single-ridged waveguide or a double-ridged waveguide. In yet other implementations, the waveguide may be a tapered waveguide. One of ordinary skill in the art will readily recognize that a waveguide that may be used in an exemplary embodiment can be structured in such a way to impart a desired waveguiding performance. For example, the waveguides may be structurally configured to have a specific propagation mode, such as, for example and not by limitation, a TE propagation mode or a TM propagation mode. Here, the act of structurally configuring the waveguide can include imparting a particular geometry to the waveguide and/or imparting a differential refractive index profile from cladding to core or from cladding to core to substrate.
As such, keeping in mind that the embodiments may make use of a wide variety of waveguide structures,
They system 200 can include a substrate 203 of thickness 202 in which there is a fabricated-PIC. The substrate 203 can be selected to impart specific waveguiding properties and for light transmissivity. The PIC may include one or more waveguides 205. For example, and not by limitation, the one or more waveguide 205 may be configured as described above with respect to
For example, and not by limitation, the mirror 215 may be deposited via DC magnetron sputtering, thermal evaporation, or e-beam evaporation. The material deposited may be a material that has a high reflection coefficient. For example, the deposited material may be a metal such as gold, aluminum, or nickel. One of ordinary skill in the art will readily understand that gold deposition, or any metal deposition, as construed herein, does not preclude intermediate deposition steps of adhesion layers nor the usage of surface finishing techniques that may be used to enhance reflectivity or reduce surface roughness. Furthermore, additional patterning techniques such as lift-off or wet etching may be used to further define the mirror 215.
In the system 200, when a light beam is inputted into the one or more waveguides 205, the output beams of the one or more waveguides 205 hit the mirror 215 and reflect at an angle to produce the rays 209 which are then collected at the lens 210. It is noted that while a lens is shown as a light collection and focusing apparatus, generally, a beam-shaping optical component may be used. Depending on the application, the beam may be focused or it may not be focused onto an object/subject. Furthermore, while a human eye is shown as the object that is illuminated by the system 200, the object can generally be any target. However, when the object is a human eye, the system 200 is configured to illuminate the eye, but without the user 201 being able to visualize the beam itself.
In some embodiments, the mirror 215 may have non-negligible transmissivity by design, such that a fraction of the light can pass through the mirror 215 while the majority is reflected. This scenario is illustrated by the beam 217 being transmitted through the mirror 215. In such implementations, a detector may be placed behind the mirror 215 to collected the transmitted beam 217 in order to infer the intensity and/or temporal resolution of the light beam carried by the one or more waveguides 205.
In the implementation 703 shown in
At a step 804, using a line of sight deposition process, a material may be deposited to fabricate the mirror on the sidewall of the trench. The material may be a metal for example, to provide a shiny surface for reflecting the light from the output waveguide at an angle towards a focus lens, as described previously in the context of
Those skilled in the relevant art(s) will appreciate that various adaptations and modifications of the embodiments described above can be configured without departing from the scope and spirit of the disclosure. Therefore, it is to be understood that, within the scope of the appended claims, the disclosure may be practiced other than as specifically described herein.
This application claims benefit to U.S. Provisional Patent Application No. 63/172,272 filed on Apr. 8, 2021, the disclosure of which is incorporated herein in its entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63172272 | Apr 2021 | US |
