WO2024010876A1 - Planar lightguide circuit chip device adapted for use with laser cleaved fibers - Google Patents

Abstract

The present disclosure relates to planar lightguide circuit chip device including a planar lightguide circuit chip. The planar lightguide circuit chip includes a silicon substrate and a core layer supported by the silicon substrate. The core layer includes at least one lightguide. The silicon substrate defines at least one alignment groove for aligning an optical fiber with the lightguide. The silicon substrate also defines a recess at an end of the alignment groove for accommodating a flare at an end of the optical fiber.

Description

PLANAR LIGHTGUIDE CIRCUIT CHIP DEVICE ADAPTED FOR USE WITH LASER CLEAVED FIBERS

Cross-Reference to Related Application(s)

This application is being filed on July 6, 2023, as a PCT International application and claims the benefit of and priority to U.S. Provisional Application No. 63/358,618, filed July 6, 2022, the disclosure of which is hereby incorporated by reference in its entirety.

Technical Field

The present disclosure relates generally to light conveying devices such as planar lightguide circuit chip devices.

Background

Planar lightguide circuit chips can be manufactured using wafer manufacturing technology in which lightguides are provided on a wafer substrate using techniques including deposition (e.g., chemical vapor deposition, flame hydrolysis deposition, etc.), patterning (e.g., lithographic patterning) and etching (e.g., reactive ion etch, inductively coupled plasma dry etching, etc.). After the lightguides have been defined on the wafer substrate the wafer substrate can be diced to manufacture a plurality of planar lightguide circuit chips. Optical fibers can be optically coupled to planar lightguide circuit chips via v-groove blocks bonded to the planar lightguide chips and/or grating couplers.

Summary

One aspect of the present disclosure relates to planar lightguide circuit chip device including a planar lightguide circuit chip. The planar lightguide circuit chip includes a silicon substrate and a core layer supported by the silicon substrate. The core layer includes at least one lightguide. The silicon substrate defines at least one alignment groove for aligning an optical fiber with the lightguide. The silicon substrate also defines a recess at an end of the alignment groove for accommodating a flare at an end of the optical fiber. A variety of additional aspects will be set forth in the description that follows. The aspects can relate to individual features and to combinations of features. It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the examples disclosed herein are based.

Brief Description of the Drawings

Figure 1 depicts a side cross-sectional view of a planar lightguide circuit chip device in accordance with the principles of the present disclosure;

Figure 2 depicts a top view of a planar lightguide circuit chip device in accordance with the principles of the present disclosure;

Figure 3 depicts a cross-sectional view taken along section line 3-3 of the planar lightguide circuit chip device of Figure 2;

Figure 4 depicts an optical fiber in accordance with the principles of the present disclosure;

Figure 5 depicts a cross-sectional view taken along the line 5-5 of Figure 4;

Figure 6 depicts a side cross-sectional view of a planar lightguide circuit chip device in accordance with the principles of the present disclosure;

Figure 7 depicts a top view of a planar lightguide circuit chip device in accordance with the principles of the present disclosure;

Figure 8 a cross-sectional view taken along section line 8-8 of the planar lightguide circuit chip device of Figure 2;

Figure 9 depicts a plurality of optical fibers in accordance with the principles of the present disclosure;

Figure 10 depicts a side cross-sectional view of a planar lightguide circuit chip device in accordance with the principles of the present disclosure;

Figure 11 depicts a side cross-sectional view of a planar lightguide circuit chip device in accordance with the principles of the present disclosure; and

Figure 12 depicts a top view of a planar lightguide circuit chip device in accordance with the principles of the present disclosure. Detailed Description

Aspects of the present disclosure relate to fiber alignment systems for aligning optical fibers with lightguides (i.e., waveguides, cores, optical pathways, etc.) of a planar lightguide circuit chip. In one example, the alignment system is integrated with the planar lightguide circuit chip and includes at least one fiber alignment v- groove for aligning an optical fiber with a lightguide of the planar lightguide circuit chip, and a recessed region for accommodating a flared end of an optical fiber positioned within the v-groove. In certain example, the optical fiber is a laser cleaved optical fiber. An example laser for performing laser cleaving can include a CO2 laser.

Common materials used in the manufacture of planar lightguide circuit chips include silicon, silicon nitride and silica. A typical configuration for a planar lightguide chip includes a base layer, a first cladding layer deposited on the first cladding layer, a core layer deposited on the first cladding layer and a second cladding layer deposited over the core layer. The core layer is typically patterned and etched to form a desired lightguide arrangement. In the case of silica-on-silicon planar lightguide circuit chip, the base layer can include silicon, the core layer can include doped silica (e.g., germanium-doped silica) and the first and second cladding layers can include silicon dioxide. In the case of a silicon-on-insulator planar lightguide circuit chip, the base layer can include silicon, the core layer can include silicon and the first and second cladding layers can include silicon dioxide. In the case of a silicon-nitride-on-insulator planar lightguide circuit chip, the base layer can include silicon, the core layer can include silicon nitride and the first and second cladding layers can include silica.

Figures 1-3 depict an optical device 20 in accordance with the principles of the present disclosure. The optical device 20 includes a planar lightguide circuit chip 22. The planar lightguide circuit chip 22 includes a length L that extends between first and second opposite ends 32, 34. The planar lightguide circuit chip 22 also includes a width W perpendicular to the length L, and a thickness T that is perpendicular to both the length L and the width W. The width W extends between opposite first and second sides 36, 38 of the planar lightguide circuit chip 22 and the thickness T extends between main top and bottom sides 40, 42 of the planar lightguide circuit chip 22. Referring to Figure 1, the planar lightguide circuit chip 22 includes a base substrate 44 that in a preferred example is made of a material having a composition including a silicon. Still referring to Figure 1, the planar lightguide circuit chip 22 also includes a first cladding layer 46 deposited on the base substrate 44, a core layer 48 deposited on the first cladding layer 46, and a second cladding layer 50 deposited over the core layer 48. In one example, the first and second cladding layers 46 and 50 are made of a material having a composition including silicon dioxide, and the core layer 48 is made of a material having a composition including doped silica. In a preferred example, the core layer 48 includes a plurality of lightguides 52 adapted for conveying light via total internal reflection.

In alternative examples, the base substrate 44, the cladding layers 46, 50 and the core layer 48 can be made of materials having other compositions (e.g., compositions such as those described above or other compositions). In a preferred example, the materials are selected such that through the cooperation of the core layer and the cladding layers light can be conveyed through light guides of the core layer by total internal reflection. In certain examples, the base substrate 44 is constructed of material in which fiber alignment structures such as alignment grooves (e.g., v-grooves) can be formed (e.g., by etching or other techniques). The lightguide 52 can be arranged in a row with the lightguides 52 spaced apart from one another in accordance with a center-to-center spacing S. It will be appreciated that lightguides 52 are spaced apart from one another across the width W of the planar lightguide circuit chip 22.

Referring to Figures 2 and 3, the planar lightguide circuit chip 22 includes a plurality of fiber alignment grooves 60 for aligning optical fibers 62 (e.g., bare optical fibers including a core and a cladding layer) of the bare-fiber optical connector 26 with the lightguides 52 of the planar light guide circuit chip 22. In the depicted example, the fiber alignment grooves 60 are arranged in a row and are relatively positioned with the same center-to-center spacing S as the lightguides 52. In a preferred example, the fiber alignment grooves 60 are v-grooves each having first and second fiber alignment surfaces 64, 66 that are angled relative to one another. In other examples, the alignment grooves may have other configurations such as curved (e.g., arc-shaped, semicircular-shaped) or U-shaped configurations. In the depicted example, each fiber alignment groove 60 is positioned to co-axially align one of the optical fibers 62 with a corresponding one of the lightguides 52. The fiber alignment grooves 60 can be defined in the base substrate 44 of the planar lightguide circuit chip 22.

In the depicted example, the optical fibers 62 can include ends 100 (see FIG. 4) that oppose and are co-axially aligned with ends of the lightguides 52 when the optical fibers 62 are positioned within the alignment grooves 60. In the depicted example, the optical fibers 62 are flared at the ends 100 (e.g., see flared portion 102). In certain examples, optical fibers 62 have been laser cleaved (e.g., with a CO2 laser), and the flaring can be the result of the laser cleaving process. In certain examples, the flaring can have a longitudinal dimension A in the range of 100-400 micrometers, or in the range of 150-300 micrometers; and the flaring can have a radial dimension B in the range of 0.5-4.0 micrometers or in the range of 0.5-2.0 micrometers. The planar lightguide circuit chip 22 includes structure for preventing the flaring of the ends of the optical fibers 62 from interfering with effective co-axial alignment of the optical fibers 62 with the lightguides 52 via contact with the alignment surfaces of the alignment grooves 60. In one example, such structure can include a recess 110 for receiving the flared portions 102 of the optical fibers 62 when the optical fibers 62 are positioned in the fiber alignment grooves 60. In one example, the recess 110 is located between ends of the fiber alignment grooves 60 and ends of the lightguides 52. In one example, the recess 110 has a depth that is deeper that corresponding depths of the alignment grooves 60. In some examples, the recess 110 has a depth D of at least 130 micrometers or at least 135 micrometers, and a dimension C measured along the lengths of the alignment grooves 60 of at least 300 micrometers or at least 400 micrometers. In certain examples, the recess 110 can be a slot (e.g., a trough) that extends across the fiber alignment grooves 60 and across the width W of the planar lightguide chip 22. In one example, a length of the slot is perpendicularly oriented relative to the fiber alignment grooves 60.

As shown at Figure 1, the planar lightguide circuit chip 22 includes a main body 68 and an extension 70 that projects outwardly from the main body 68 at the second end 34 of the planar lightguide circuit chip 22. The fiber alignment grooves 60 are defined at a top side 72 of the extension 70 that is stepped down from the main top side 40 of the planar lightguide circuit chip 22. The fiber alignment grooves 60 are arranged in a row that extends across the width W of the planar lightguide circuit chip 22. In the depicted example, the alignment grooves 60 have lengths that extend in an orientation along the length L of the planar light guide circuit chip 22 from an outer edge 74 of the extension 70 to the recess 110. In one example, end faces of the lightguides 52 align with the alignment grooves 60. In one example, the extension 70 is a unitary portion of the base substrate 44. The optical device 20 can include springs for biasing the optical fibers 62 into the alignment grooves 60. An example spring arrangement is disclosed in United States Provisional Application Number 63/291,002. In other examples, a retention member 300 (see FIG. 10) can be bonded to the base layer 44 to secure the optical fibers 62 within the alignment grooves 60. In the depicted example, the fibers 62 are sandwiched between the retention member 300 and the extension 70.

Figures 6-9 depict an alternative example including an optical device 220 having the same construction as the optical device 20 except a recess 210 is defined in part by an end surface 211 (e.g., facet) of a main body of the optical device 220. The end surface 211 is obliquely angled relative to longitudinal axes 213 of the alignment grooves 260. Ends of lightguides 252 are located at the end surface 211 and are angled to be co-planar with the end surface 211. As depicted, the recess 210 is a slot. As depicted in Figure 7, the end surface 211 can be angled relative to the fiber alignment grooves 260 in an orientation extending across the width of the device 220 and across the plurality of grooves 260. In one example, the wall 211 can be angled relative to the fiber alignment grooves 260 at an angle in the range of 6-10 degrees relative to a reference plane 215 perpendicular to the longitudinal axes 213 of the grooves 260. In another example, as shown at FIGS. 11 and 12, the end surface 211 as well as the ends of the lightguides 252 can be angled along the height H of the end surface 211 as compared to along the length of the end surface 211 as depicted at Figure 7.

Figure 9 depicts optical fibers 262 cleaved at an cleave angle. In one embodiment, the optical fibers 262 can be cleaved at an angle in the range of 6-10 degrees (i.e., in the range of 6-10 degrees relative to a reference plane perpendicular to central axes of the fibers 262). In one example, the end surface 211 and the ends of the lightguides 252 at the end surface 211 can be obliquely angled relative to the alignment grooves 260 to match the cleave angle of the optical fibers 262 so that the opposing ends of the lightguides 252 are parallel to the ends of the fibers 262 when the fibers are aligned with the lightguides 252 via the grooves 260.

A bare fiber portion of an optical fiber includes a core 120 surrounded by a cladding layer 122 (see FIG. 5) with no coating provided over the cladding layer.

Claims

What is claimed is:

1. An optical device comprising: a planar lightguide circuit chip including a silicon substrate and a core layer supported by the silicon substrate, the core layer including at least one lightguide, the silicon substrate defining at least one alignment groove for aligning an optical fiber with the lightguide, the silicon substrate also defining a recess at an end of the alignment groove for accommodating a flare at an end of the optical fiber.

2. The optical device of claim 1, wherein the alignment groove is a v-groove including fiber alignment surfaces that are angled relative to one another.

3. The optical device of claim 1, wherein the lightguide is one of a plurality of lightguides defined by the core layer, wherein the optical fiber is one of a plurality of optical fibers, wherein the alignment groove is one of a plurality of alignment grooves defined by the silicon substrate for aligning the optical fibers with the lightguides, and wherein recess is a slot.

4. The optical device of claim 3, wherein the alignment grooves are parallel, and the slot extends across the alignment grooves.

5. The optical device of claim 4, wherein the planar lightguide circuit chip includes a main body and an extension that projects outwardly from the main body, wherein the alignment grooves are defined on the extension, wherein the slot is located at a region between ends of the alignment grooves and ends of the lightguide, and wherein the ends of the lightguides are located at an end surface of the main body which defines a side of the slot.

6. The optical device of claim 5, wherein the extension is a unitary portion of the silicon substrate.

7. The optical device of claim 3, wherein the end surface and the ends of the lightguides are oriented at an oblique angle relative to longitudinal axes of the alignment grooves, and wherein the optical fibers are angle cleaved at an cleave angle that matches the oblique angle.

8. The optical device of claim 7, wherein the oblique angle is in the range of 6-10 degrees relative to a reference plane perpendicular to the longitudinal axes of the alignment grooves.