Patent Application
20130064494
The present disclosure is directed, in general, to an optical communication system and more specifically, an optical receiver, and, methods of manufacturing the same.
This section introduces aspects that may be helpful to facilitating a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light. The statements of this section are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Some optical circuit packages include planar lightwave circuits and moisture or organic vapor sensitive electro-optic devices. Because they are moisture sensitive, it is sometimes desirable to enclose the moisture or organic vapor sensitive electro-optic device in a hermetically sealed package. Because the refractive index of the planar lightwave circuits is sensitive to temperature, it is sometimes desirable to replace a portion of its optical path with a refractive-index-compensation material.
One embodiment of the disclosure is an optical circuit package. The package comprises a substrate having a planar surface and an interferometric planar lightwave circuit located on the planar surface of the substrate. A refractive-index-compensation material is incorporated into a portion of the planar lightwave circuit such that an optical path through the planar lightwave circuit passes through the refractive-index-compensation material. The package also comprises a moisture or organic vapor sensitive electro-optic device located on the substrate. An inner hermetic can is located on the substrate, wherein the inner hermetic can encapsulates the portion of the planar lightwave circuit incorporating the refractive-index-compensation material. An outer hermetic can is located on or around the substrate, wherein the outer hermetic can encloses the planar lightwave circuit, the moisture or organic vapor sensitive electro-optic device and the inner hermetic can.
Another embodiment is a method of manufacturing an optical circuit package. The method comprises forming an interferometric planar lightwave circuit located on a planar surface of a substrate. A refractive-index-compensation material is incorporated into a portion of the planar lightwave circuit located such that an optical path through the planar lightwave circuit passes through the refractive-index-compensation material. A moisture or organic vapor sensitive electro-optic device is placed on the substrate. An inner hermetic can is formed on the substrate so as to encapsulate the portion of the planar lightwave circuit incorporating the refractive-index-compensation material. An outer hermetic can is formed on or around the substrate so as to enclose the planar lightwave circuit, the moisture or organic vapor sensitive electro-optic device and the inner hermetic can.
The embodiments of the disclosure are best understood from the following detailed description, when read with the accompanying FIGUREs. Some features in the figures may be described as, for example, “top,” “bottom,” “vertical” or “lateral” for convenience in referring to those features. Such descriptions do not limit the orientation of such features with respect to the natural horizon or gravity. Various features may not be drawn to scale and may be arbitrarily increased or reduced in size for clarity of discussion. Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
The description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof. Additionally, the term, “or,” as used herein, refers to a non-exclusive or, unless otherwise indicated. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.
The present disclosure benefits from the discoveries made when manufacturing optical devices where a refractive-index-compensation material was incorporated into an arrayed waveguide grating and then the arrayed waveguide grating and avalanche photodiode detectors on the substrate were hermetically sealed inside an enclosure, referred to herein as a hermetic can, located on the substrate. The hermetic can is designed to prevent the penetration of water vapor present in the surrounding atmosphere, and thereby protect the avalanche photodiode detectors from damage from moisture.
Surprisingly, it was found that the avalanche photodiode detectors in optical devices still rapidly (e.g., within weeks or months) broke down from exposure to moisture. It was discovered that the avalanche photodiode detectors broke down due to exposure to moisture released from the refractive-index-compensation material incorporated into the arrayed waveguide grating. That is, the refractive-index-compensation material contained amounts of water or volatile organic compounds that were detrimental to the avalanche photodiode detectors.
In certain embodiments of the present disclosure, the problem of preventing exposure of the avalanche photodiode detector to moisture released by the refractive-index-compensation material was addressed by forming a hermetic can around the portion of the arrayed waveguide grating having the refractive-index-compensation material. Thus, an inner hermetic can encapsulates at least the portion of the arrayed waveguide grating having the refractive-index-compensation material, and, an outer hermetic can encloses both the arrayed waveguide grating and the avalanche photodiode detectors.
It was realized, as part of the present disclosure, that the above described solution could apply to any interferometric planar lightwave circuit and any moisture or organic vapor sensitive electro-optic device, and not just arrayed waveguide grating and avalanche photodiode detectors, respectively.
One embodiment of the present disclosure is an optical circuit package. Some embodiments of an optical circuit package can be configured as an optical transmitter component, or, an optical receiver component, or both, in a communication system, such as an optical transceiver system.
With continuing reference to
The term interferometric planar lightwave circuit, as used herein refers to any optical circuit with two or more optical paths that interfere with each other. Non-limiting examples include an arrayed waveguide grating, Mach-Zender interferometer, a ring resonator or similar devices whose interference effects can be altered by temperature, until compensated for, e.g., by incorporating the refractive-index-compensation material 210 as discussed herein.
The term moisture or organic vapor sensitive electro-optic device, a used here refers to any electro-optic device that could be incorporated on an optical circuit package and whose function can be damaged or function compromised by the presence of moisture or organic vapors. Non-limiting examples include avalanche photodiode detectors, lasers, PIN photodiodes or similar devices familiar to one of ordinary skill.
Although the illustrative example package 100 is discussed below in context of the planar lightwave circuit 110 being or including an arrayed waveguide grating, and, the moisture or organic vapor sensitive electro-optic device 120 being or including avalanche photodiode detectors, the package 100 could include different combinations of different embodiments of circuits 110 and devices 120.
The term refractive-index-compensation material 210, as used herein, refers to a material whose refractive index changes in a direction with increasing temperature that is opposite to the direction of change in the effective refractive index of the waveguide material that the arrayed waveguide grating 110 is composed of. For example, consider an embodiment of the package 100 where the arrayed waveguide grating 110 includes a waveguide material whose effective refractive index increases with increasing temperature (e.g., silica glass). In such an embodiment, the refractive-index-compensation material would be a material whose refractive index decreases with increasing temperature (e.g., a resin material than includes epoxy groups or silicone groups).
One of ordinary skill in the art would understand how to adjust the amount of refractive-index-compensation material 210 incorporated into the arrayed waveguide grating 110, and the optical path 215 so as to compensate for the extent of the temperature-related change in the effective refractive index that the arrayed waveguide grating 110 would otherwise have.
As further illustrated in
As also illustrated for the example package shown in
As further illustrated in
As illustrated in
In some cases, such as illustrated in
In some embodiments the walls 220 can include a solder and the lid 225 can includes a silicon material. For instance, the walls 220 can be made of a lead-tin solder alloy and the lid 225 can be made of silicon layer micro-machined to fit onto the walls 220, and to include a cavity 330, in some cases. In other embodiments, however, one or both the walls 220 and lid 225 of the inner hermetic can 125 can be made of a metal or metal alloy (e.g., solder), or, a glass material (e.g., silica glass).
Similarly, as shown in
Some embodiments of the package 100 can further include one or more fiber couplers 170 located on the substrate 105. At least one of the fiber couplers 170 can be optically coupled to the arrayed waveguide grating 110 and the one or more fiber couplers can be enclosed by the outer hermetic can 125 (except for a facet that is coupled to an optical fiber outside of the package). As illustrated some of the fiber couplers 170 can be optically coupled to the second free-space propagation region 152 of the arrayed waveguide grating 110 via waveguides 175 located on the substrate 105. One of ordinary skill in the art would appreciate how the arrayed waveguide grating can be configured to connect an optical data signal carried in an optical output from the fiber couplers 170 and transferred to arrayed waveguide grating via a set waveguides 175 optically connecting the fiber couplers 170 to the arrayed waveguide grating 110.
Another embodiment of the disclosure is a method of manufacturing an optical circuit package.
With continuing reference to
In some embodiments, forming an arrayed waveguide grating 110 (or other planar lightwave circuits) on the planar surface 107 of the substrate 105 (step 405) can include a step 430 of patterning a lower cladding layer 320, a core layer 325, and an upper cladding layer 315 to form a first free-space propagation region 150, a second free-space propagation region 152 and a plurality of single mode waveguide portions 155 of the arrayed waveguide grating 110. These waveguide portions 150, 152, 155 can be continuously connected to each other through the material layers 315, 320, 325 that the arrayed waveguide grating 110 is formed from. One skilled in the art would be familiar with techniques such as chemical vapor depositing or flame hydrolysis, or re-melting procedures, to form the cladding layers 315, 320 (e.g., composed of silicon oxides) or the core layer 325 (e.g., composed of silicon). In some cases the patterning step 430 the lower cladding layer, the core layer, and the upper cladding layer can also form waveguides 140 that connect the first free-space propagation region 150 to the avalanche photodiode detector 120, and/or form other waveguides 175 that connect an external optical fiber to the second free-space propagation region 152.
In other embodiments, the arrayed waveguide grating 110 and other light guiding components of the package 100 can be formed in step 405 by depositing and patterned other types of waveguide materials such as indium phosphide (InP), organic polymer core and cladding materials, or other materials familiar to those skilled in the art.
In some cases, the step 415 of placing the plurality of avalanche photodiode detectors 120 (or other moisture or organic vapor sensitive electro-optic devices) on the substrate 105 includes placing pre-formed avalanche photodiode detectors 120 on the substrate 105 with the aid of micro-manipulators, and then soldering the avalanche photodiode detectors 120 in place. In some cases it is desirable to place the avalanche photodiode detectors on the substrate in step 415 after forming the inner hermetic can 125 is step 420 to avoid exposing the avalanche photodiode detectors to any moisture released from the refractive-index-compensation material 210.
In some embodiments of the method 400, incorporating the refractive-index-compensation material 210 into the portion of the arrayed waveguide grating (or other planar lightwave circuit; step 410) includes a step 440 of forming a trench 310 and a step 445 of filling the trench 310 with the refractive-index-compensation material 210. In some cases, forming the trench 310 in step 440 can include masking and the etching (e.g., a dry etch process) the upper and lower cladding layers 150, 152 and core layer 155 in a single or a series of etching processes. In some cases, filling the trench 310 in step 445 can include spin-coating of the refractive-index-compensation material 210 on the substrate 105 or other filling procedures well know to those skilled in the art.
In some embodiments, forming the inner hermetic can 125 (step 420) includes a step 450 of forming walls 220 on the substrate 105 and around the portion 115 of the arrayed waveguide grating 110 (or other planar lightwave circuit) that incorporates the refractive-index-compensation material 210. In some cases, for instance, the walls 220 can be formed in step 450 by depositing a perimeter line of solder around the portion 115 of the arrayed waveguide grating 110 via conventional solder deposition tools. In such cases the walls 220 can be made of solder.
In some embodiments, forming the inner hermetic can 125 (step 420) also includes a step 452 of placing a lid 225 on the walls 220 and a step 454 of sealing the lid 225 to the walls 220. For instance, as part of step 452 the micro-manipulators can be used to place the lid 225 on the walls 220 and, in step 454, the walls 220 and/or lid 225 can be heated so as to form an-air tight seal.
In some cases, step 454, or steps 452 and 454, are performed while the package 110 is in a moisture-free environment, although this is not necessary, because the arrayed waveguide grating portion 115 incorporating the refractive-index-compensation material 210 is atmospherically isolated from the rest of the package 100 including the avalanche photodiode detectors 120 (or other moisture or organic vapor sensitive electro-optic device) by the inner hermetic can 120. That is, in some cases step 454, or steps 452 and 454, can be performed with the optical circuit package 110 located in a moisture-containing environment.
In some embodiments forming the inner hermetic can 125 (step 420) includes a step 456 of includes micro-machining a material layer (e.g., a metal, silicon, silica glass or similar material) to form the lid 225. In some cases as part of step 456 the lid 225 is formed to include a cavity 330, that is configured to enclose a portion 335 of the refractive-index-compensation material 210 located above a surface 340 of the arrayed waveguide grating 110.
In some embodiments of the method 400, forming an outer hermetic can 130 (step 425) includes a step 460 of forming walls 160 that surround the interferometric planar lightwave circuit 110 (e.g. an arrayed waveguide device) or other and moisture or organic vapor sensitive electro-optic device 120 (e.g., avalanche photo detectors) and step 462 of placing a cap 165 on the walls 160, with the optical circuit package 110 located in a moisture-free environment, and a step 464 of sealing the cap 165 to the walls 160 while still in the moisture-free environment. For instance, the walls 160 formed in step 460 can include depositing a line of solder and placing the cap 165 on the walls 160 and then sealing the cap 165 to the walls 160, similar to that discussed in the context of steps 450, 452, and 454, respectively. The moisture-free environment can be formed by placing the package 100 in a chamber with an atmosphere of pure nitrogen, helium, argon or similar gas having a low moisture content, performing steps 462 and 464 with the package 100 in the chamber.
Although the embodiments have been described in detail, those of ordinary skill in the art should understand that they could make various changes, substitutions and alterations herein without departing from the scope of the disclosure.
