OPTICAL SUBASSEMBLY FOR NON-RECIPROCAL COUPLING OF LIGHT AND ASSEMBLY PROCESS THEREOF

Abstract

An optical subassembly for non-reciprocal coupling of light from a planar optical waveguide output to an optical fiber includes a carrier configured to support the optical subassembly, an optical fiber fixed to the optical subassembly, a focusing optical system consisting two foci with one focus coincident with the input of optical fiber, an optical isolator to transmit light unidirectionally between two foci, an input boundary provided by the carrier to align the optical subassembly with the planar optical waveguide output. In particular, the optical subassembly is operably configured to provide a low transmission loss for light traveling from the planar optical waveguide output to the optical fiber.

Claims

1. An optical subassembly for non-reciprocal coupling of light from a planar optical waveguide output to an optical fiber, the optical subassembly comprising: a carrier configured to support the optical subassembly; the optical fiber fixed to the optical subassembly; a focusing optical system consists of two foci with one focus operably coincident with the optical fiber; an optical isolator operably configured to transmit light unidirectionally between two foci; an input boundary provided by the carrier to align the optical subassembly with the planar optical waveguide output; and wherein the optical subassembly is operably configured to provide a low transmission loss for the light travelling from the planar optical waveguide output to the optical fiber.

2. The optical subassembly as claimed in claim 1, wherein the planar optical waveguide output is anyone of a silicon photonic (SIP) circuit output and a photonic integrated circuit (PIC) output.

3. The optical subassembly as claimed in claim 1, wherein the focusing optical system comprises at least one focusing element.

4. The optical subassembly as claimed in claim 1, wherein the input boundary is further configured to align an input focus with an optical subassembly boundary.

5. The optical subassembly as claimed in claim 1, wherein one of two foci coincident with the optical fiber.

6. The optical subassembly as claimed in claim 1, wherein the optical isolator is a free-space optical isolator.

7. The optical subassembly as claimed in claim 6, wherein the optical isolator is positioned between the two foci that transmit light in one direction operate bases on magneto-optic effect.

8. The optical subassembly as claimed in claim 1, wherein the focusing optical system further comprises a C-lens, a GRIN-lens or a lensed fiber.

9. The optical subassembly as claimed in claim 1, wherein the optical subassembly further comprises a light transmitting window with a light input plane and a hollow tube.

10. The optical subassembly as claimed in claim 3, wherein the at least one focusing element of the focusing optical system—is configured with a light transmitting window.

11. The optical subassembly as claimed in claim 1, wherein the carrier is in anyone shape selected from a hollow tube, a U-shape, an L-shape, and alike shape carrier.

12. The optical subassembly as claimed in claim 1, wherein the focusing optical system magnifies a mode size of the planar optical waveguide output to optimize a coupling efficiency to the optical fiber.

13. The optical subassembly as claimed in claim 1, wherein the optical subassembly with a 3-micrometer mode field diameter silicon photonic (SIP) planer waveguide has a coupling efficiency of about 71% for 1311 nm light with standard SFM28 fiber.

14. An assembly process of an optical subassembly for nonreciprocal coupling of light from a planar optical waveguide output of a silicon photonic (SIP) to an optical fiber, comprising: fixing a focusing optical components of an optical subassembly to a carrier; aligning a diverging light source to an input boundary of the optical subassembly; adjusting position of the diverging light source and an angle of incident for light power to pass through a first focus and a second focus of a focusing optical system; placing an optical isolator between two foci of the focusing optical system; fixing the optical fiber to the carrier wherein an optical fiber input coincident with the second focus of the focusing optical system; and wherein the optical subassembly is operably configured to provide a low transmission loss for light travel from the planar optical waveguide output to the optical fiber.

15. The assembly process as claimed in claim 14, wherein the assembly process further comprises: focusing the diverging light source to an optical fiber facet center by at least one focusing element of the focusing optical system; magnifying a mode size of the planar optical waveguide output to an output waveguide of the optical fiber; and wherein the focusing optical system magnifies a mode size of the planar optical waveguide output to optimize a coupling efficiency to the optical fiber.

16. The assembly process as claimed in claim 14, wherein the assembly process further comprises: connecting at least one focusing element of the focusing optical system with a light-transmitting window at a light exit side; and supporting the optical subassembly on a hollow tube.

17. The assembly process as claimed in claim 14, wherein the focusing optical system further comprises a C-lens, a GRIN-lens or a lensed fiber.

18. The assembly process as claimed in claim 14, wherein the optical isolator is a free-space optical isolator.

19. The assembly process as claimed in claim 14, wherein the carrier is in anyone shape selected from a hollow tube, a U-shape, an L-shape, and alike shape carrier.

20. The assembly process as claimed in claim 14, wherein the optical subassembly with a 3-micrometer mode field diameter silicon photonic (SIP) planer waveguide has a coupling efficiency of about 71% for 1311 nm light with standard SFM28 fiber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] So that the manner in which the above recited features of the present invention is be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0025] FIG. I is a photonic integrated circuit (PIC) mode size converter in accordance with one prior art;

[0026] FIG. II is a mode size converter having a first end and a second end in accordance with another prior art;

[0027] FIG. 1 illustrates a pictorial representation of an optical subassembly for nonreciprocal coupling of light in accordance with one embodiment of the present invention;

[0028] FIG. 2 illustrates a pictorial representation of an optical subassembly for nonreciprocal coupling of light in accordance with another embodiment of the present invention;

[0029] FIG. 3 illustrates a pictorial representation of an optical subassembly for nonreciprocal coupling of light in accordance with yet another embodiment of the present invention;

[0030] FIG. 4 illustrates a pictorial representation of an optical subassembly for nonreciprocal coupling of light in accordance with yet another embodiment of the present invention;

[0031] FIG. 5 illustrates a pictorial representation of an optical subassembly having a light input plane provided by a light-transmitting window in accordance with yet another embodiment of the present invention;

[0032] FIG. 6 illustrates a pictorial representation of an optical subassembly having a light input plane provided by a light-transmitting window in accordance with yet another embodiment of the present invention; and

[0033] FIG. 7 is a flow chart illustrating an assembly process of an optical subassembly for nonreciprocal coupling of light from a planar optical waveguide output of a silicon photonic (SiP) to an optical fiber.

ELEMENT LIST

[0034] 101—First focusing lens [0035] 102—Second focusing lens [0036] 103—Optical Isolator [0037] 104—Input boundary [0038] 105—Input focus [0039] 106—Fiber [0040] 107—Carrier [0041] 108—Light transmitting window [0042] 109—Fiber capillary [0043] 110—Assembly body

DETAILED DESCRIPTION

[0044] Various embodiments of the present invention provide an optical subassembly for non-reciprocal coupling of light from a planar optical waveguide output to an optical fiber and an assembly process thereof.

[0045] The principles of the present invention and their advantages are best understood by referring to FIG. 1 to FIG. 7. In the following detailed description of illustrative or exemplary embodiments of the disclosure, specific embodiments in which the disclosure may be practiced are described in sufficient detail to enable those skilled in the art to practice the disclosed embodiments.

[0046] The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and equivalents thereof. References within the specification to “one embodiment,” “an embodiment,” “embodiments,” or “one or more embodiments” are intended to indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure.

[0047] FIG. 1 illustrates a pictorial representation of an optical subassembly for nonreciprocal coupling of light in accordance with one embodiment of the present invention. In particular, the optical subassembly (100) includes the first focusing lens (101), second focusing lens (102), optical isolator (103), input boundary (104), input focus (105), optical fiber (106) and a carrier (107). In particular, the optical subassembly is operably configured to provide a low transmission loss for light traveling from the planar optical waveguide output to the optical fiber. Moreover, the optical subassembly is further configured to perform a unidirectional transmission of light.

[0048] In particular, the focusing optical system formed by first focusing lens (101) and second focusing lens (102) is operably configured to collect and focus the light to the optical fiber (106), the optical fiber (106) is fixed to the optical subassembly (100), the optical isolator (103) is operably configured between two foci of the optical focusing system to provide an unidirectional transmission of the light, the carrier (107) is configured to support the optical subassembly (100), the input focus (105) is configured to align with the input boundary (104) provided by the carrier (107).

[0049] In accordance with an embodiment of the present invention, the focusing optical system further includes the first focusing lens (101) and a second focusing lens (102). Particularly, the first focusing lens (101) and a second focusing lens (102) forms an optical coupling assembly. Moreover, the optical focusing assembly is operably configured to collect and focus the light to the optical fiber (106). Furthermore, the optical coupling assembly provides a focus location for the input focus to align in the same plane with the optical subassembly boundary.

[0050] In accordance with an embodiment of the present invention, one of the two foci coincident with a fiber optical input.

[0051] In accordance with an embodiment of the present invention, the optical planar waveguide output is anyone of a silicon photonic (SiP) output and a photonic integrated circuit (PIC) output. In particular, the mode size of planar optical waveguide output is magnified to matched with that of the optical fiber by the first focusing lens (101) and the second focusing lens (102).

[0052] In accordance with an embodiment of the present invention, the optical isolator is a free-space optical isolator. In particular, the optical isolator is positioned between two foci of the focusing optical system for providing a nonreciprocal unidirectional transmission of the light.

[0053] In one or more embodiments of the present invention, the optical isolator operates on the magneto-optic effect with either polarizers or a birefringent optics in order to prevent light travelling in backward direction.

[0054] In accordance with an embodiment of the present invention, the optical subassembly further comprises a light-transmitting window with a light input plane and a hollow tube. In particular, at least one focusing element of the focusing optical system is configured with the light-transmitting window. Moreover, the focusing element is selected from the first focusing lens and the second focusing lens.

[0055] In accordance with an embodiment of the present invention, the input boundary is further configured to align the input focus with an optical subassembly boundary. Also, the input boundary provides a reference plane for an optical subassembly boundary to align with the planar optical waveguide.

[0056] FIG. 2 illustrates a pictorial representation of an optical subassembly for nonreciprocal coupling of light in accordance with another embodiment of the present invention. In particular, the optical subassembly (200) includes the first focusing lens (101), second focusing lens (102), optical isolator (103), input boundary (104), input focus (105), optical fiber (106) and carrier (107). Moreover, the optical fiber input is in contact with the second focusing lens (102) of the focusing optical system. Furthermore, the second focusing lens (102) is anyone of a lensed fiber, a C-lens and a GRIN-lens. Subsequently, the second focusing lens (102) aligns to optical fiber (106) in three axis alignment. Also, the second focusing lens (102) is configured to the optical fiber input.

[0057] FIG. 3 illustrates a pictorial representation of an optical subassembly for nonreciprocal coupling of light in accordance with yet another embodiment of the present invention. In particular, the optical subassembly (300) includes the first focusing lens (101), optical isolator (103), input boundary (104), input focus (105), optical fiber (106) and a carrier (107). Moreover, the first focusing lens (101) of the focusing optical system is configured for collecting and focusing the light to the optical fiber (106). Moreover, the beam passing the optical isolator (103) is a conventional latched garnet isolator. Furthermore, the first focusing lens (101) of the focusing optical system and an optical fiber (106) are in contact with the optical isolator (103) to provide non-reciprocal coupling of the light from a planar optical waveguide output to an optical fiber (106).

[0058] FIG. 4 illustrates a pictorial representation of an optical subassembly for non-reciprocal coupling of light in accordance with yet another embodiment of the present invention. In particular, the optical sub assembly (400) includes the first focusing lens (101), optical isolator (103), input boundary (104), input focus (105), optical fiber (106) and a carrier (107). Moreover, the first focusing lens (101) of the focusing optical system and an optical fiber (106) are in contact with the optical isolator (103) to provide non-reciprocal coupling of the light from a planar optical waveguide output to an optical fiber (106).

[0059] FIG. 5 illustrates a pictorial representation of an optical subassembly having a light input plane provided by a light-transmitting window in accordance with yet another embodiment of the present invention. In particular, the optical subassembly (500) includes the first focusing lens (101), optical isolator (103), input boundary (104), input focus (105), optical fiber capillary (109), a carrier (107) and light transmitting window (108). Moreover, the first focusing lens (101) of the focusing optical system is in contact with the light exit side of the light transmitting window (108). Furthermore, a single focusing element of the focusing optical system is configured with the light transmitting window (108). Also, the optical subassembly (500) allows better control in the focusing lens angle and enhances the stability of coupling from a planar output waveguide to the optical fiber.

[0060] FIG. 6 illustrates a pictorial representation of an optical subassembly having a light input plane provided by a light-transmitting window in accordance with yet another embodiment of the present invention. In particular, the optical subassembly (600) includes the first focusing lens (101), optical isolator (103), input boundary (104), input focus (105), optical fiber capillary (109), a carrier (107), light transmitting window (108) and an assembly body (110). The single focusing lens of the focusing optical system in contact with the light exit side of the light transmitting window (108). Moreover, the optical subassembly (600) is supported on a hollow tube provide better mechanical support and stability for fiber. Subsequently, the single focusing lens in contact with the light exit side of the transmitting window enhances stability of coupling.

[0061] FIG. 7 is a flow chart illustrating an assembly process of an optical subassembly for nonreciprocal coupling of light from a planar optical waveguide output of a silicon photonic (SIP) to an optical fiber. The assembly process 700 starts at step 705 and proceeds to step 710. At step 705, focusing optical components of the optical subassembly are fixed to target position on the carrier. And at step 710, a diverging light source is aligned to the input boundary of the optical subassembly.

[0062] Step 710 proceeds to step 715. At step 715, the position of the diverging light source and angle of incident is adjusted so that most optical power pass through first focus and second focus of the focusing optical system.

[0063] Step 715 proceeds to step 720. At step 720, an optical isolator is positioned between two foci of the optical subassembly.

[0064] Step 720 proceeds to step 725. At step 725, a fiber is fixed to the carrier so that the optical fiber input coincident with the second focus of the optical subassembly.

[0065] In particular, the optical subassembly is operably configured to provide a low transmission loss for light travel from the planar optical waveguide output to the optical fiber.

[0066] In accordance with an embodiment of the present invention, the assembly process further includes focusing the diverging light source to an optical fiber facet center by at least one focusing element of the focusing optical system and magnifying the mode size of the planar optical waveguide output to an output waveguide of the optical fiber. In particular, the focusing optical system magnifies a mode size of the planar optical waveguide output to optimize coupling efficiency to the optical fiber.

[0067] In accordance with an embodiment of the present invention, the assembly process further includes focusing a diverging light source to an optical fiber facet center by a second focusing lens (102) and magnifying a mode size of planar output waveguide to an output waveguide of the optical fiber by a first focusing lens (101) and the second focusing lens (102) of the focusing optical system.

[0068] In accordance with an embodiment of the present invention, the assembly process further includes collecting and focusing a diverging light source to an optical fiber facet center only by a first focusing lens (101) and magnifying a mode size of planar optical waveguide output to an output waveguide of the optical fiber by configuring working distances of the first focusing lens (101) of the focusing optical system.

[0069] In accordance with an embodiment of the present invention, the assembly process further includes connecting at least one focusing element selected from the first focusing lens (101) and the second focusing lens (102) of the focusing optical system with the light-transmitting window at a light exit side and supporting the optical subassembly on a hollow tube.

[0070] In one or more embodiments of the present invention, the optical isolator may be positioned between photonic integrated circuit (PIC) output and the first focusing element to provide the same effect by matching the target performance. Since output from a photonic integrated circuit (PIC) is a polarized light, simple optical isolator made of latched garnet plate sandwiched between two polarizers can be used.

[0071] In an embodiment of the present invention, when the emission point of the output planar waveguide is located at the edge of the photonic integrated circuit (PIC) then a simple butt-joint with the optical subassembly boundary provides focusing of the light. In particular, a predetermined distance of the photonic integrated circuit (PIC) output from the edge is accommodated by the optical subassembly by shifting the input focus at a predetermined distance.

[0072] In accordance with an embodiment of the present invention, the photonic integrated circuit (PIC) output is positioned with respect to the input of optical subassembly for coupling in the communication photonic packaging. With the planer structure of photonic integrated circuit (PIC) and input boundary of the optical subassembly, optical alignment is reduced to x/y/z 3-axis from original x/y/z/pitch/roll/yaw 6-degree alignment.

[0073] In one or more embodiments of the present invention, for high volume production the optical isolator by planner process includes cutting into a rectangle dice and focusing the light beam to pass through to an output fiber facet center by the focusing optical system.

[0074] In accordance with an embodiment of the present invention, the optical subassembly further comprises a diverging light source. In particular the light output from planar waveguides is a diverging light source with mode size diameter in few micrometers. Moreover, the light source is positioned at the input focus of the optical subassembly such that a portion of the light is collected and focus to the fiber input with reduced divergence angle based on the arrangement of the optical assembly.

[0075] In accordance with an embodiment of the present invention, the carrier (107) is in anyone shape selected from a hollow tube, U-shape, an L-shape, and alike shape carrier.

[0076] It is understandable that the above mentioned hollow tube is one of a possible structure to improve the carrier support for the focuser of the focusing optical system, but other shape or complex structure, such as carrier is a hollow tube, in U-shape, L-shape, with additional guiding, alignment features, steps can be added to realize the same optical function of the focuser/focusing optical system in this invention.

[0077] In accordance with an embodiment of the present invention, the optical subassembly with a 3-micrometer mode field diameter silicon photonic (SIP) waveguide has a coupling efficiency of about 71% for 1311 nm to SMF28.

[0078] Thus, the embodiments of the present invention provide an optical subassembly for non-reciprocal coupling of light from a planar optical waveguide output to an optical fiber and an assembly process thereof. The optical subassembly integrates light coupling and optical isolation function for photonic integrated circuit (PIC) coupling to the optical fiber in single subassembly. Moreover, the optical subassembly product is compact in size, cost effective, with a simple assembly process with photonic integrated circuit (PIC) without compromising the coupling efficiency. Furthermore, the focusing element combines coupling optical assembly and free space isolator in a single optical subassembly device to deliver light from a photonic integrated circuit (PIC) to the optical fiber.

[0079] Although some features and examples herein have been described in language specific to structural features or methodological steps, it is to be understood that the subject matter herein is not necessarily limited to the specific features or steps described. Any process descriptions, elements or blocks in the flow diagrams described herein or depicted in the attached figures should be understood as potentially representing modules, segments, or portions of code that include one or more executable instructions for implementing specific logical functions or elements in the process. Alternate implementations are included within the scope of the examples described herein in which elements or functions can be deleted, or executed out of order from that shown or discussed, including substantially synchronously or in reverse order, depending on the functionality involved as would be understood by those skilled in the art.

[0080] It should be emphasized that many variations and modifications can be made to the above-described examples, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims. Moreover, in the claims, any reference to a group of items provided by a preceding claim clause is a reference to at least some of the items in the group of items, unless specifically stated otherwise. This document expressly envisions alternatives with respect to each and every one of the following claims individually, in any of which claims any such reference refers to each and every one of the items in the corresponding group of items. Furthermore, in the claims, unless otherwise explicitly specified, an operation described as being “based on” a recited item can be performed based on only that item, or based at least in part on that item. This document expressly envisions alternatives with respect to each and every one of the following claims individually, in any of which claims any “based on” language refers to the recited item(s), and no other(s). Additionally, in any claim using the “comprising” transitional phrase, a recitation of a specific number of components is not limited to embodiments including exactly that number of those components, unless expressly specified. However, such a claim does describe both embodiments that include exactly the specified number of those components and embodiments that include at least the specified number of those components.