Patent Description:
<CIT> discloses an integrated optical element and in which an optical waveguide having favorable characteristics such as polarization dependence is integrated with an optical semiconductor element. The integrated optical element comprises a silicon bench having an element mount surface; an optical circuit element; and an optical semiconductor element. The optical circuit element includes an optical waveguide in which a grating is formed, and a substrate different from the silicon bench, and the optical semiconductor element constitutes an external resonator together with the grating. The optical circuit element and the optical semiconductor element are fixed onto the element mount surface of the silicon bench via a bonding material, while being apart from the silicon bench at a predetermined distance.

<CIT> discloses a device including a substrate. The device may include a carrier mounted to the substrate. The device may include a transmitter photonic integrated circuit (PIC) mounted on the carrier. The transmitter PIC may include a plurality of lasers that generate an optical signal when a voltage or current is applied to one of the plurality of lasers. The device may include a first microelectromechanical structure (MEMS) mounted to the substrate. The first MEMS may include a first set of lenses. The device may include a planar lightwave circuit (PLC) mounted to the substrate. The PLC may be optically coupled to the plurality of lasers by the first set of lenses of the first MEMS. The device may include a second MEMS, mounted to the substrate, that may include a second set of lenses, which may be configured to optically couple the PLC to an optical fiber.

<CIT> discloses a transmitting optical module that includes multi-laser diode (LDs) and a planar lightwave circuit (PLC) to multiplex optical beams each output from the optical sources. The PLC is mounted on a carrier through a WG carrier in upside down arrangement. The LDs are also mounted on the carrier through an LD carrier. The LDs and the PLC are optical coupled with two lenses each having respective optical axes offset from the other such that the optical coupling of the optical beam inputting the PLC becomes a maximum.

<CIT> discloses an optical module, a manufacturing method of an optical module, and an optical device.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention which is defined by the appended claims.

Various embodiments of a hybrid multi-wavelength source (MWS) and associated methods are disclosed herein. The hybrid MWS is designed and configured to supply continuous wave (CW) laser light having multiple wavelengths. The hybrid MWS is a device that emits multiple wavelengths of CW laser light that are usable in a wavelength-division multiplexing (WDM) system for transmission into a single optical fiber. Hybrid integration of the MWS disclosed herein refers to combining different devices made on separate substrates into a single package.

It should be understood that the term "wavelength" as used herein refers to the wavelength of electromagnetic radiation. And, the term "light" as used herein refers to electromagnetic radiation within a portion of the electromagnetic spectrum that is usable by optical data communication systems. In some embodiments, the portion of the electromagnetic spectrum includes light having wavelengths within a range extending from about <NUM> nanometers to about <NUM> nanometers (covering from the O-Band to the C-Band, inclusively, of the electromagnetic spectrum). However, it should be understood that the portion of the electromagnetic spectrum as referred to herein can include light having wavelengths either less than <NUM> nanometers or greater than <NUM> nanometers, so long as the light is usable by an optical data communication system for encoding, transmission, and decoding of digital data through modulation/de-modulation of the light. In some embodiments, the light used in optical data communication systems has wavelengths in the near-infrared portion of the electromagnetic spectrum. Also, the term "laser beam" as used herein refers to a beam of CW light generated by a laser device. It should be understood that a laser beam may be confined to propagate in an optical waveguide, such as (but not limited to) an optical fiber or an optical waveguide within a planar lightwave circuit (PLC). In some embodiments, the laser beam is polarized. And, in some embodiments, the light of a given laser beam has a single wavelength, where the single wavelength can refer to either essentially one wavelength or can refer to a narrow band of wavelengths that can be identified and processed by an optical data communication system as if it were a single wavelength.

<FIG> shows a top view of an example hybrid MWS <NUM>, in accordance with some embodiments of the present invention. <FIG> shows a vertical cross-section view of the example hybrid MWS <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments of the present invention. The hybrid MWS <NUM> includes a substrate <NUM>, a laser array chip <NUM>, a PLC <NUM>, and an optical fiber alignment device <NUM>. The substrate <NUM> includes a first area 101A for receiving the laser array chip <NUM>. The substrate <NUM> also includes a second area 101B elevated relative to the first area 101A. The second area 101B is separated from the first area 101A by a trench <NUM> that has a bottom surface at a lower elevation within the substrate <NUM> than the first area 101A. The substrate <NUM> includes a third area 101C next to the second area 101B. The third area 101C has a lower elevation within the substrate <NUM> than the second area 101B.

The laser array chip <NUM> is disposed in the first area 101A. In some embodiments, the laser array chip <NUM> is an InP chip. However, in other embodiments, the laser array chip <NUM> is a chip other than InP. The laser array chip <NUM> has optical outputs facing toward the second area 101B. The PLC <NUM> is disposed in the second area 101B. The PLC <NUM> has optical inputs facing toward and aligned with respective optical outputs of the laser array chip <NUM>. The PLC <NUM> has optical outputs facing toward the third area 101C. The optical fiber alignment device <NUM> is disposed in the third area 101C. The optical fiber alignment device <NUM> is configured to receive a number of optical fibers <NUM>, such that optical cores of the number of optical fibers <NUM> respectively align with the optical outputs of the PLC <NUM>.

In some embodiments, the laser array chip <NUM> is attached to the substrate <NUM> by flip-chip bonding, which includes disposing a ball grid array (BGA) <NUM> between the laser array chip <NUM> and respective conductive pads exposed on the substrate <NUM> surface. The BGA <NUM> provides for electrical connectivity between electrical circuitry in the laser array chip <NUM> and electrical circuitry within the substrate <NUM>. In some embodiments, the substrate <NUM> includes a plurality of electrically conductive structures electrically connected to a plurality of electrically conductive pads exposed within the first area 101A of the substrate <NUM>. The plurality of electrically conductive pads is configured to receive the BGA <NUM>. In some embodiments an epoxy underfill material <NUM> is disposed within the first area 101A between the laser array chip <NUM> and the substrate <NUM>, and between solder balls of the BGA <NUM>. In some embodiments, the trench <NUM> within the substrate <NUM> is configured to facilitate deposition of the epoxy underfill material <NUM>. It should be understood that flip-chip attachment of the laser array chip <NUM> to the substrate <NUM> using the BGA <NUM> is one of many different ways that the laser array chip <NUM> can be attached to the substrate <NUM> and electrically connected to circuitry within the substrate <NUM>. In other embodiments, the laser array chip <NUM> is attached to the substrate <NUM> using essentially any known electronic packaging process, which can optionally include disposition of bumps, solder, under-fill, and/or other component(s), between the laser array chip <NUM> and the substrate <NUM>, and can include bonding techniques such as mass reflow, thermal-compression bonding (TCB), wire-bonding, or essentially any other suitable bonding technique. For example, in some embodiments, instead of using the BGA <NUM>, the laser array chip <NUM> is attached to the substrate <NUM> using controlled collapse chip connection bumps.

The PLC <NUM> and the optical fiber alignment device <NUM> are attached to the substrate <NUM> by an optical index-matched epoxy material <NUM>, such that a layer of the optical index-matched epoxy material <NUM> exists between the substrate <NUM> and each of the PLC <NUM> and the optical fiber alignment device <NUM>. The optical index-matched epoxy material <NUM> has an optical index of refraction that is substantially the same as an optical index of refraction of optical waveguides within the PLC <NUM> and laser array chip <NUM>. Also, in some embodiments, the optical index-matched epoxy material <NUM> has an optical index of refraction that is substantially the same as an optical index of refraction of optical cores of the optical fibers <NUM>. In some embodiments, the optical index-matched epoxy material <NUM> is disposed to fill the trench <NUM> within the substrate <NUM>. In some embodiments, the laser array chip <NUM> is slightly spaced apart from the PLC <NUM>, such that the optical index-matched epoxy material <NUM> is disposed within a gap between the laser array chip <NUM> and the PLC <NUM>. Also, in some embodiments, the PLC <NUM> is slightly spaced apart from the optical fibers <NUM> secured within the optical fiber alignment device <NUM>, such that the optical index-matched epoxy material <NUM> is disposed within a gap between the PLC <NUM> and the optical cores of the optical fibers <NUM>. And, more specifically, the optical index-matched epoxy material <NUM> is disposed within a gap between the PLC <NUM> and the optical fiber alignment device <NUM>.

In some embodiments, a stiffener structure <NUM> is disposed on the substrate <NUM> to extend around a union of the first area 101A and the second area 101B of the substrate <NUM>, without encroaching within the third area 101C of the substrate. In some embodiments, the stiffener structure <NUM> has a top surface at a substantially same elevation above the substrate <NUM> as a top surface of the laser array chip <NUM>. However, in some embodiments, the top surface of the stiffener structure <NUM> and the top surface of the laser array chip <NUM> are at different elevations above the substrate <NUM>. In various embodiments, the stiffener structure <NUM> is formed of a rigid material, such as aluminum or some other material that is chemically, thermally, and mechanically compatible with the interfacing materials of the hybrid MWS <NUM>. In various embodiments, the stiffener structure <NUM> is attached to the substrate <NUM> using an adhesive material, such as an epoxy material. Also, in some embodiments, a thermal interface material (TIM) <NUM> is disposed across top surfaces of the stiffener structure <NUM>, the laser array chip <NUM>, and the PLC <NUM>. In some embodiments, the TIM <NUM> is a thermal adhesive. In some embodiments, the TIM <NUM> is Master Bond EP30TC by Master Bond Inc. In some embodiments, the TIM <NUM> is a metal or metal alloy, such as Indium (In), Indium-Lead (InPb), among other materials. It should be understood that in various embodiments, the TIM <NUM> is essentially any adhesive thermal interface material that is used in semiconductor packaging to enhance thermal coupling between components. Also, in some embodiments, a lid structure <NUM> is disposed on the TIM <NUM>. The lid structure <NUM> is configured to cover the laser array chip <NUM> and the PLC <NUM>. The lid structure <NUM> is also configured to extend over the stiffener structure <NUM>. In various embodiments, the lid structure <NUM> is formed of a high thermal conductivity material, such as copper, or aluminum, or copper alloy, or aluminum alloy, among others.

<FIG> shows a more detailed top view arrangement of the laser array chip <NUM> and the PLC <NUM>, in accordance with some embodiments. <FIG> shows a side view of the laser array chip <NUM> as seen from the perspective of the PLC <NUM>, referenced as View B-B in <FIG>, in accordance with some embodiments. <FIG> shows a side view of the PLC <NUM> as seen from the perspective of the laser chip array <NUM>, referenced as View C-C in <FIG>, in accordance with some embodiments. The laser array chip <NUM> is configured to generate and output a plurality of laser beams, i.e., (N) laser beams. In some embodiments, (N) is eight. However, in other embodiments, (N) can be either less than eight or greater than eight. The plurality of laser beams have different wavelengths (λ<NUM>-λN) relative to each other, where the different wavelengths (λ<NUM>-λN) are distinguishable to an optical data communication system. In some embodiments, the laser array chip <NUM> includes a plurality of lasers DFB-<NUM> to DFB-N for respectively generating the plurality (N) of laser beams, where each laser DFB-<NUM> to DFB-N generates and outputs a laser beam at a respective one of the different wavelengths (λ<NUM>-λN). Each of the plurality of lasers DFB-<NUM> to DFB-N is optically connected to transmit its particular wavelength of CW laser light to a respective one of the optical outputs L-O1 to L-ON of the laser array chip <NUM>, such that the different wavelengths (λ<NUM>-λN) of CW laser light generated by the plurality of lasers DFB-<NUM> to DFB-N are respectively provided to the different optical output L-O1 to L-ON of the laser array chip <NUM> for transmission from the laser array chip <NUM>. In some embodiments, each of the plurality of lasers DFB-<NUM> to DFB-N is a distributed feedback laser configured to generate CW laser light at a particular one of the different wavelengths (λ<NUM>-λN). The distributed feedback laser is a type of diode laser that has a single-wavelength emission spectrum or a "single longitudinal mode. " In some embodiments, the plurality of lasers DFB-<NUM> to DFB-N generate CW laser light having wavelengths within the O-band, or within a range extending from <NUM> nanometers to <NUM> nanometers. In some embodiments, the distributed feedback of the plurality of lasers DFB-<NUM> to DFB-N is centered at <NUM> nanometers for use with SiGe photodetectors. It should be understood that in other embodiments, any of the plurality of lasers DFB-<NUM> to DFB-N can be configured to generate CW laser light at wavelength(s) of either less than <NUM> nanometers or greater than <NUM> nanometers.

In some embodiments, the PLC <NUM> includes a dielectric core and cladding in a single layer on a silicon or glass substrate. The PLC <NUM> includes an interior configuration of optical waveguides configured to route light received through optical input ports PLC <NUM> to optical output ports of the PLC <NUM> in a prescribed manner. In some embodiments, the PLC <NUM> includes nitride waveguides. However, in other embodiments, the PLC <NUM> can be implemented using essentially any material that is suitable to form optical waveguides. The PLC <NUM> is configured to receive the plurality of laser beams of CW light of the different wavelengths (λ<NUM>-λN) from the laser array chip <NUM> at a corresponding plurality (N) of optical input ports PLC-I1 to PLC-IN of the PLC <NUM>, such that each of the plurality (N) of optical inputs PLC-I1 to PLC-IN of the PLC <NUM> receives a different wavelength of CW laser light. The PLC <NUM> is configured to distribute a portion of the CW laser light received at each of the optical inputs PLC-I1 to PLC-IN of the PLC <NUM> to each of a plurality (M) of optical output ports PLC-O1 to PLC-OM of the PLC <NUM>, such that the different wavelengths (λ<NUM>-λN) of CW laser light received through the plurality (N) of optical inputs of the PLC <NUM> are collectively transmitted through each of the plurality (M) of optical outputs PLC-O1 to PLC-ON of the PLC <NUM>. In some embodiments, (M) is sixteen. However, in other embodiments, (M) is either less than sixteen or greater than sixteen. In this manner, the PLC <NUM> operates to distribute the plurality (N) of laser beams such that all of the different wavelengths (λ<NUM>-λN) of the plurality (N) of laser beams are provided to each of the plurality (M) of optical output ports PLC-O1 to PLC-OM of the PLC <NUM>. Therefore, it should be understood that the PLC <NUM> operates to provide light at all of the different wavelengths (λ<NUM>-λN) of the plurality (N) of laser beams to each one of the optical output ports PLC-O1 to PLC-OM of the PLC <NUM>. In this manner, the PLC <NUM> functions as an NxM optical multiplexing device. Also, the optical power transmitted at a given wavelength through any one of the plurality (M) of optical output ports PLC-O1 to PLC-OM of the PLC <NUM> is approximately equal to the optical power received at the given wavelength through the corresponding one of the optical inputs PLC-I1 to PLC-IN of the PLC <NUM> divided by (M). Therefore, it should be understood that the optical output power of the configuration of the laser array chip <NUM> and PLC <NUM> scales with the number (M) of output channels, rather than with the number (N) of generated CW laser wavelengths. In some embodiments, the PLC <NUM> is configured as a star coupler.

The optical fiber alignment device <NUM> is configured to receive the plurality (M) of optical fibers <NUM> and respectively align the optical cores of the plurality (M) of optical fibers <NUM> to the plurality (M) of optical output ports PLC-O1 to PLC-OM of the PLC <NUM>. In some embodiments, the optical fiber alignment device <NUM> is a v-groove array that includes a plurality (M) of v-grooves, where each v-groove is configured to receive and align one of the plurality (M) of optical fibers <NUM>. However, it should be understood that in other embodiments, the optical fiber alignment device <NUM> can be configured in a manner that does not include v-grooves, so long as the optical fiber alignment device <NUM> is configured to receive the plurality (M) of optical fibers <NUM> and respectively align the optical cores of the plurality (M) of optical fibers <NUM> to the plurality (M) of optical output ports PLC-O1 to PLC-OM of the PLC <NUM>. In various embodiments, the optical fiber alignment device <NUM> is formed of a material that is chemically, thermally, and mechanically compatible with the interfacing materials and components of the hybrid MWS <NUM>. For example, in some embodiments, the optical fiber alignment device <NUM> is formed of aluminum, plastic, or another suitable material.

In some embodiments, the laser array chip <NUM> is secured to the substrate <NUM> before the PLC <NUM> is secured to the substrate <NUM>. In these embodiments, the PLC <NUM> has to be optically aligned with the laser array chip <NUM> so that the plurality of optical input ports PLC-I1 to PLC-IN of the PLC <NUM> respectively optically align with the plurality of optical output ports L-O1 to L-ON of the laser array chip <NUM>. In some embodiments, the laser array chip <NUM> and the PLC <NUM> are collectively configured to provide for active alignment of the PLC <NUM> to the laser array chip <NUM> through operation of the laser array chip <NUM> after the laser array chip <NUM> is disposed in the first area 101A of the substrate <NUM>. In some embodiments, the laser array chip <NUM> includes a first alignment laser DFB-A1 configured and connected to provide CW laser light to a first alignment optical output L-AO1 on the laser array chip <NUM>. The first alignment optical output L-AO1 faces toward the second area 101B of the substrate <NUM> when the laser array chip <NUM> is attached to the substrate <NUM> within the first area 101A of the substrate <NUM>. In some embodiments, the first alignment optical output L-AO1 is positioned at a first side of the plurality (N) of lasers DFB-<NUM> to DFB-N, such as shown in <FIG>. The laser array chip <NUM> also includes a first alignment photodetector PD-A1 optically connected to a first alignment optical input L-AI1 on the laser array chip <NUM>. The first alignment optical input L-AI1 faces toward the second area 101B of the substrate <NUM> when the laser array chip <NUM> is attached to the substrate <NUM> within the first area 101A of the substrate <NUM>. In some embodiments, the first alignment optical input L-AI1 is positioned next to the first alignment optical output L-AO1, such as shown in <FIG>.

The PLC <NUM> includes a first alignment waveguide WG-<NUM> configured to extend from a first alignment optical input PLC-AI1 on the PLC <NUM> to a first alignment optical output PLC-AO1 on the PLC <NUM>, such that light entering the first alignment optical input PLC-AI1 on the PLC <NUM> is conveyed through the first alignment waveguide WG-<NUM> and through the first alignment optical output PLC-AO1 on the PLC <NUM>. The PLC <NUM> is configured so that both the first alignment optical input PLC-AI1 and the first alignment optical output PLC-AO1 of the PLC <NUM> face toward the first area 101A when the PLC <NUM> is positioned within the second area 101B on the substrate <NUM>. The PLC <NUM> is properly aligned with the laser array chip <NUM> when the first alignment optical input PLC-AI1 of the PLC <NUM> is optically aligned with the first alignment optical output L-AO1 of the laser array chip <NUM>, and when the first alignment optical output PLC-AO1 of the PLC <NUM> is optically aligned with the first alignment optical input L-AI1 of the laser array chip <NUM>, such that CW laser light transmitted from the first alignment laser DFB-A1 travels through the first alignment waveguide WG-<NUM> and back into the laser array chip <NUM> for detection by the first alignment photodetector PD-A1. In this manner, during active alignment of the PLC <NUM> to the laser array chip <NUM>, the laser array chip <NUM> is operated so that the first alignment laser DFB-A1 operates to transmit CW laser light through the first alignment optical output L-AO1, while the first alignment photodetector PD-A1 operates to detect light received through the first alignment optical input L-AI1. Detection of light by the first alignment photodetector PD-A1 indicates that the PLC <NUM> is properly aligned with the laser chip array <NUM>.

In some embodiments, to provide for even better optical alignment between the PLC <NUM> and the laser array chip <NUM>, the laser array chip <NUM> includes a second alignment laser DFB-A2 configured and connected to provide CW laser light to a second alignment optical output L-AO2 on the laser array chip <NUM>. The second alignment optical output L-AO2 faces toward the second area 101B of the substrate <NUM> when the laser array chip <NUM> is attached to the substrate <NUM> within the first area 101A of the substrate <NUM>. In some embodiments, the second alignment optical output L-AO2 is positioned at a second side of the plurality (N) of lasers DFB-<NUM> to DFB-N, such as shown in <FIG>. The laser array chip <NUM> also includes a second alignment photodetector PD-A2 optically connected to a second alignment optical input L-AI2 on the laser array chip <NUM>. The second alignment optical input L-AI2 faces toward the second area 101B of the substrate <NUM> when the laser array chip <NUM> is attached to the substrate <NUM> within the first area 101A of the substrate <NUM>. In some embodiments, the second alignment optical input L-AI2 is positioned next to the second alignment optical output L-AO2, such as shown in <FIG>.

The PLC <NUM> includes a second alignment waveguide WG-<NUM> configured to extend from a second alignment optical input PLC-AI2 on the PLC <NUM> to a second alignment optical output PLC-AO2 on the PLC <NUM>, such that light entering the second alignment optical input PLC-AI2 on the PLC <NUM> is conveyed through the second alignment waveguide WG-<NUM> and through the second alignment optical output PLC-AO2 on the PLC <NUM>. The PLC <NUM> is configured so that both the second alignment optical input PLC-AI2 and the second alignment optical output PLC-AO2 of the PLC <NUM> face toward the first area 101A when the PLC <NUM> is positioned within the second area 101B on the substrate <NUM>. The PLC <NUM> is properly aligned with the laser array chip <NUM> when the second alignment optical input PLC-AI2 of the PLC <NUM> is optically aligned with the second alignment optical output L-AO2 of the laser array chip <NUM>, and when the second alignment optical output PLC-AO2 of the PLC <NUM> is optically aligned with the second alignment optical input L-AI2 of the laser array chip <NUM>, such that CW laser light transmitted from the second alignment laser DFB-A2 travels through the second alignment waveguide WG-<NUM> and back into the laser array chip <NUM> for detection by the second alignment photodetector PD-A2. In this manner, during active alignment of the PLC <NUM> to the laser array chip <NUM>, the laser array chip <NUM> is operated so that the first alignment laser DFB-A1 operates to transmit CW laser light through the first alignment optical output L-AO1, while the first alignment photodetector PD-A1 operates to detect light received through the first alignment optical input L-AI1. Also, the laser array chip <NUM> is operated so that the second alignment laser DFB-A2 operates to transmit CW laser light through the second alignment optical output L-AO2, while the second alignment photodetector PD-A2 operates to detect light received through the second alignment optical input L-AI2. Detection of light by both the first alignment photodetector PD-A1 and the second alignment photodetector PD-A2 indicates that the PLC <NUM> is properly aligned with the laser chip array <NUM>. Detection of strong photocurrent signals by both the first alignment photodetector PD-A1 and the second alignment photodetector PD-A2 indicates that the PLC <NUM> is properly aligned with the laser chip array <NUM> with respect to coordinates in the x, y, and z directions, and with respect to roll in the y-z plane, yaw in the x-y plane, and pitch in the x-z plane.

<FIG> shows an alternate embodiment of the hybrid MWS <NUM> in which discrete lasers DFB-<NUM> to DFB-N are disposed on the substrate <NUM>, rather than having the lasers DFB-<NUM> to DFB-N integrally formed within the laser array chip <NUM>, in accordance with some embodiments. The configuration of <FIG> is the same as that of <FIG>, with the exception of having discrete lasers DFB-<NUM> to DFB-N instead of the laser array chip <NUM>. Also, in the embodiment of <FIG>, if the integrated active alignment between the PLC <NUM> and the lasers DFB-<NUM> to DFB-N is implemented, then the alignment lasers DFB-A1 and DFB-A2 will also be discretely disposed on the substrate <NUM>, and the alignment photodetectors PD-A1 and PD-A2 will also be discretely disposed on the substrate <NUM>. In this embodiment, the position and orientation on the substrate <NUM> of each discrete laser DFB-<NUM> to DFB-N is carefully controlled. Also, the position and orientation on the substrate <NUM> of each discrete alignment laser DFB-A1 and DFB-A2 and each discrete photodetector PD-A1 and PD-A2 is carefully controlled. In some embodiments, the substrate <NUM> is formed to include a number of positioning and aligning structures to facilitate proper positioning and alignment on the substrate <NUM> of the lasers DFB-<NUM> to DFB-N, the alignment lasers DFB-A1 and DFB-A2, and the alignment photodetectors PD-A1 and PD-A2.

<FIG> describe an example assembly process flow for manufacturing the hybrid MWS <NUM>, in accordance with some embodiments. <FIG> shows a top view of the substrate <NUM>, in accordance with some embodiments. <FIG> shows a vertical cross-section view of the substrate <NUM>, referenced as View A-A in<FIG>, in accordance with some embodiments. The first area 101A is where the laser array chip <NUM> is to be disposed. The second area 101B is where the PLC <NUM> is to be disposed. The third area 101C is where the optical fiber alignment device <NUM> is to be disposed. The trench <NUM> is formed between the first area 101A and the second area 101B. In some embodiments, the trench extends along a full length of the side of the laser array chip <NUM> that faces toward the PLC <NUM>, i.e., that faces toward the second area 101B. The bottom of the trench <NUM> is at a lower elevation with the substrate <NUM> than the first area 101A. Also, the second area 101B is at a higher elevation on the substrate <NUM> than the first area 101A. It should be understood that the second area 101B forms a mesa-like structure upon which the PLC <NUM> is disposed. Also, when the PLC <NUM> is disposed within the second area 101B, a portion of the PLC <NUM> will extend over and above a portion of the trench <NUM>, and a portion of the PLC <NUM> will extend over and above a portion of the third area 101C. Also, the elevation of the third area 101C within the substrate <NUM> is lower than the elevation of the second area 101B.

It should be understood that the specific elevation of the second area 101B is set so that the optical inputs PLC-I1 to PLC-IN can be optically aligned with the optical outputs L-O1 to L-ON of the laser array chip <NUM>. Therefore, the specific elevation of the second area 101B within the substrate <NUM> relative to the first area 101A is dependent upon the specific configurations of the laser array chip <NUM> and the PLC <NUM>. Similarly, the specific elevation of the third area 101C is set so that the optical cores of the optical fibers <NUM> can be optically aligned with the optical outputs PLC-O1 to PLC-OM of the PLC <NUM> when the optical fibers <NUM> are positioned in the optical fiber alignment device <NUM>. Therefore, the specific elevation of the third area 101C within the substrate <NUM> relative to the second area 101B is dependent upon the specific configurations of the PLC <NUM> and the optical fiber alignment device <NUM>.

The substrate <NUM> is an electronic packaging substrate. In some embodiments, the substrate <NUM> is formed of a dielectric material. In some embodiments, the substrate <NUM> is formed of an organic material. In some embodiments, the substrate <NUM> is formed of a ceramic material. In some embodiments, the substrate <NUM> is formed of aluminum oxide (Al<NUM>O<NUM>), or aluminum nitride (AIN), or a similar ceramic material. In some embodiments, the substrate <NUM> is an Indium-Phosphide (III-V) substrate. It should be understood that in various embodiments, the substrate <NUM> can be formed of essentially any other type of substrate material upon which electronic devices and/or optical-electronic devices and/or optical waveguides and/or optical fiber(s)/fiber ribbon(s) can be mounted. Also, it should be understood that the substrate <NUM> can be configured to include electrical circuitry in the form of conductive lines/structures formed and routed in one or more levels within the substrate <NUM>, with conductive lines/structures in different levels of the substrate <NUM> electrically connected by one or more conductive via structures as needed to form a prescribed electrical circuit configuration.

<FIG> shows a top view of the BGA <NUM> disposed on the substrate <NUM>, in accordance with some embodiments. <FIG> shows a vertical cross-section view of the BGA <NUM> disposed on the substrate <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments. It should be understood that the particular arrangement of the BGA <NUM> shown in <FIG> is provided by way of example and in no way limits the possible configuration of the BGA <NUM> in various embodiments. Also, as previously mentioned, the BGA <NUM> is one example of various possible ways in which the laser array chip <NUM> can be physically and electrically connected to the substrate <NUM>. Therefore, it should be understood that while the BGA <NUM> technique is used in some embodiments, use of the BGA <NUM> technique is not required in all embodiments.

<FIG> shows a top view of the laser array chip <NUM> disposed on the BGA <NUM>, in accordance with some embodiments. <FIG> shows a vertical cross-section view of the laser array chip <NUM> disposed on the BGA <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments. In some embodiments, the laser array chip <NUM> is configured so that the flip-chip manufacturing technique is utilized to connected the laser array chip <NUM> to the BGA <NUM> or other connection mechanism. It should be understood that the individual solder balls of the BGA <NUM> are disposed on corresponding exposed electrical pads on the substrate <NUM>. Similarly, each solder ball of the BGA <NUM> also contacts a corresponding exposed electrical pad on the laser array chip <NUM>. Then, when the solder balls of the BGA <NUM> are reflowed, each solder ball of the BGA <NUM> becomes fused with its corresponding electrical pad on the substrate <NUM> and with its corresponding electrical pad on the laser array chip <NUM>.

<FIG> shows a vertical cross-section view of the underfill epoxy <NUM> disposed between the laser array chip <NUM> and the substrate <NUM> and between the solder balls of the BGA <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments. During application of the underfill epoxy <NUM>, the trench <NUM> acts as a reservoir to enable the fabricator to control the flow of the underfill epoxy <NUM>.

<FIG> shows a top view of the PLC <NUM> disposed on the substrate <NUM>, in accordance with some embodiments. <FIG> shows a vertical cross-section view of the PLC <NUM> disposed on the substrate <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments. In some embodiments, the PLC <NUM> is positioned on the substrate <NUM> such that a small gap exists between the PLC <NUM> and the laser array chip <NUM>. This small gap allows for movement of the PLC <NUM> relative to the laser array chip <NUM> during the process of actively aligning the PLC <NUM> to the laser array chip <NUM>. As previously discussed, the alignment lasers DFB-A1 and/or DFB-A2 along with their corresponding photodetectors PD-A1 and PD-A2 are operated to actively align the PLC <NUM> to the laser array chip <NUM>. Therefore, at this stage of hybrid MWS <NUM> assembly process, power is supplied to the laser array chip <NUM>. In some embodiments, power is supplied to the laser array chip <NUM> through circuitry within the substrate <NUM>. Also, it should be appreciated that by using the integrated alignment lasers DFB-A1 and/or DFB-A2 and the integrated photodetectors PD-A1 and/or PD-A2 on the laser array chip <NUM> in conjunction with the loopback alignment waveguides WG-<NUM> and WG-<NUM> on the PLC <NUM>, it is not necessary for the alignment tool (the tool used to position the PLC <NUM> on the substrate <NUM>) to have a laser or a photodetector for alignment purposes.

<FIG> shows a vertical cross-section view of the optical index-matched epoxy <NUM> disposed between the PLC <NUM> and the substrate <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments. In some embodiments, the trench <NUM> facilitates disposal of the optical index-matched epoxy <NUM> between the PLC <NUM> and the substrate <NUM>, and between the PLC <NUM> and the laser array chip <NUM>. Also, it should be appreciated that the mesa-like structure corresponding to the second area 101B of the substrate <NUM> serves to reduce a thickness of the optical index-matched epoxy <NUM> bond layer between the PLC <NUM> and the substrate <NUM>.

<FIG> shows a top view of the optical fiber alignment device <NUM> disposed on the substrate <NUM>, in accordance with some embodiments. <FIG> shows a vertical cross-section view of the optical fiber alignment device <NUM> disposed on the substrate <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments. In some embodiments, the optical fibers <NUM> are attached to the optical fiber alignment device <NUM> before the optical fiber alignment device <NUM> is attached to the substrate <NUM>. In these embodiments, one or more of the lasers DFB-<NUM> to DFB-N of the laser array chip <NUM> can be operated to provide for a light source for active alignment of the optical fiber alignment device <NUM> with the PLC <NUM>. In these embodiments, at least some of the optical fibers <NUM> attached to the optical fiber alignment device <NUM> are optically connected to a photodetector device to provide for detection of light transmission through the optical fibers <NUM>, which indicates proper optical alignment of the optical fibers <NUM> with the optical output ports PLC-O1 to PLC-ON of the PLC <NUM>, which in turn indicates proper positioning and alignment of the optical fiber alignment device <NUM> relative to the substrate <NUM>. <FIG> shows a vertical cross-section view of the optical index-matched epoxy <NUM> disposed between the optical fiber alignment device <NUM> and the substrate <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments.

<FIG> shows a top view of the stiffener structure <NUM> disposed on the substrate <NUM>, in accordance with some embodiments. <FIG> shows a vertical cross-section view of the stiffener structure <NUM> disposed on the substrate <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments. An elevation of a top surface of the stiffener structure <NUM> above the substrate <NUM> is at least as high as an elevation of a top surface of the laser array chip <NUM> above the substrate <NUM> and an elevation of a top surface of the PLC <NUM> above the substrate <NUM>. The stiffener structure <NUM> is configured to provide rigidity and mechanical strength to the hybrid MWS <NUM>. The stiffener structure <NUM> is also configured to provide a mounting structure for the lid <NUM>. In some embodiments, the stiffener structure <NUM> is configured to extend around a union of the first area 101A and the second area 101B of the substrate <NUM> without encroaching within the third area 101C of the substrate <NUM>.

<FIG> shows a top view of the TIM <NUM> disposed on the stiffener structure <NUM>, the laser array chip <NUM>, and the PLC <NUM>, in accordance with some embodiments. <FIG> shows a vertical cross-section view of the TIM <NUM> disposed on the stiffener structure <NUM>, the laser array chip <NUM>, and the PLC <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments. <FIG> shows a top view of the lid <NUM> disposed on the TIM <NUM>, in accordance with some embodiments. <FIG> shows a vertical cross-section view of the lid <NUM> disposed on the TIM <NUM>, referenced as View A-A in <FIG>, in accordance with some embodiments. In this embodiment, the TIM <NUM> functions as an adhesive to secure the lid <NUM> to the stiffener structure <NUM>, the laser array chip <NUM>, and the PLC <NUM>.

<FIG> shows a flowchart of a method for manufacturing the hybrid MWS <NUM>, in accordance with some embodiments. The method includes an operation <NUM> for forming the substrate <NUM> to include the first area 101A for receiving a chip. In some embodiments, the substrate is formed of a dielectric material. In some embodiments, the substrate is formed of a ceramic material. In some embodiments, the substrate is formed of aluminum oxide, or aluminum nitride, or a similar ceramic material. The method also includes an operation <NUM> for forming the substrate <NUM> to include the second area 101B elevated relative to the first area 101A. The method also includes an operation <NUM> for forming the substrate <NUM> to include the trench <NUM> between the first area 101A and the second area 101B. The trench <NUM> has a bottom at a lower elevation within the substrate <NUM> than the first area 101A. In some embodiments, the trench <NUM> is formed to extend along the full length of the side of the laser array chip <NUM> that faces toward the PLC <NUM>. The method also includes an operation <NUM> for forming the substrate <NUM> to include the third area 101C next to the second area 101B. The third area 101C has a lower elevation within the substrate <NUM> than the second area 101B. The method also includes an operation <NUM> for disposing the laser array chip <NUM> in the first area 101A, such that the optical outputs L-O1 to L-ON of the laser array chip <NUM> face toward the second area 101B. The method also includes an operation <NUM> for disposing the PLC <NUM> in the second area 101B, such that the optical inputs PLC-I1 to PLC-IN of the PLC <NUM> face toward and align with respective optical outputs L-O1 to L-ON of the laser array chip <NUM>, and such that optical outputs PLC-O1 to PLC-OM of the PLC <NUM> face toward the third area 101C. The method also includes an operation <NUM> for disposing the optical fiber alignment device <NUM> in the third area 101C. The optical fiber alignment device <NUM> is configured to receive the number of optical fibers <NUM>, such that optical cores of the number of optical fibers <NUM> respectively align with the optical outputs PLC-O1 to PLC-OM of the PLC <NUM>.

The method also includes positioning the PLC <NUM> so that the optical inputs PLC-I1 to PLC-IN of the PLC <NUM> respectively receive CW laser light from the optical outputs L-O1 to L-ON of the laser array chip <NUM>, such that each of the optical inputs PLC-I1 to PLC-IN of the PLC <NUM> receives a different wavelength of CW laser light. In some embodiments, the method includes operating the laser array chip <NUM> to perform active alignment of the PLC <NUM> to the laser array chip <NUM> after the laser array chip <NUM> is disposed in the first area 101A on the substrate <NUM> and is connected to the substrate <NUM>.

In some embodiments, the method includes operating the first alignment laser DFB-A1 on the laser array chip <NUM> to transmit CW laser light through the first alignment optical output L-AO1 on the laser array chip <NUM>. Also, in these embodiments, the method includes operating the first alignment photodetector PD-A1 on the laser array chip <NUM> to detect when the CW laser light enters the first alignment optical input L-AI1 on the laser array chip <NUM>, by way of having traveled through the first alignment waveguide WG-<NUM> on the PLC <NUM>. Also, in these embodiments, the method includes aligning the PLC <NUM> on the substrate <NUM> relative to the laser array chip <NUM> so that the CW laser light transmitted through the first alignment optical output L-AO1 on the laser array chip <NUM> enters the first alignment optical input PLC-AI1 on the PLC <NUM> and travels through the first alignment waveguide WG-<NUM> to exit the first alignment optical output PLC-AO1 on the PLC <NUM> and enter the first alignment optical input L-AI1 on the laser array chip <NUM> and be detected by the first alignment photodetector PD-A1.

In some embodiments, the method further includes operating the second alignment laser DFB-A2 on the laser array chip <NUM> to transmit CW laser light through the second alignment optical output L-AO2 on the laser array chip <NUM>. In these embodiments, the method also includes operating the second alignment photodetector PD-A2 to detect when the CW laser light enters the second alignment optical input L-AI2 on the laser array chip <NUM>. Also, in these embodiments, the method includes aligning the PLC <NUM> on the substrate <NUM> relative to the laser array chip <NUM> so that the CW laser light transmitted through the second alignment optical output L-AO2 on the laser array chip <NUM> enters the second alignment optical input PLC-AI2 on the PLC <NUM> and travels through the second alignment waveguide WG-<NUM> to exit the second alignment optical output PLC-AO2 on the PLC <NUM> and enter the second alignment optical input L-AI2 on the laser array chip <NUM> and be detected by the second alignment photodetector PD-A2.

Also, in some embodiments, the operation <NUM> for disposing the laser array chip <NUM> in the first area 101A of the substrate <NUM> includes flip-chip connecting of the laser array chip <NUM> to the substrate <NUM> using the BGA <NUM> or other connection mechanism. Also, in these embodiments, the method includes disposing the BGA <NUM> on the plurality of electrically conductive pads exposed at the surface of the substrate <NUM>. Also, in some embodiments, the method includes disposing the epoxy underfill material <NUM> within the first area 101A on the substrate <NUM> between the laser array chip <NUM> and the substrate <NUM>, and between solder balls of the BGA <NUM>. In some embodiments, the method includes using the trench <NUM> to facilitate deposition of the epoxy underfill material <NUM>.

Also, in some embodiments, the method includes disposing the index-matched epoxy material <NUM> between the PLC <NUM> and the substrate <NUM>. Also, in some embodiments, the method includes disposing the index-matched epoxy material <NUM> to fill the trench <NUM> in the substrate <NUM> and the gap between the laser array chip <NUM> and the PLC <NUM>. Also, in some embodiments, the method includes disposing the index-matched epoxy material <NUM> between the optical fiber alignment device <NUM> and the substrate <NUM>. Also, in some embodiments, the method includes disposing the index-matched epoxy material <NUM> to fill the gap between the PLC <NUM> and the optical fiber alignment device <NUM>.

Also, in some embodiments, the method includes attaching the stiffener structure <NUM> to the substrate <NUM>, such that the stiffener structure extends around a union of the first area 101A and the second area 101B on the substrate <NUM> without encroaching within the third area 101C on the substrate <NUM>. Also, in some embodiments, the method includes disposing the TIM <NUM> across top surfaces of the stiffener structure <NUM>, the laser array chip <NUM>, and the PLC <NUM>. Also, in some embodiments, the method includes positioning the lid structure <NUM> on the TIM <NUM>, such that the lid structure <NUM> covers the laser array chip <NUM> and the PLC <NUM>, and such that the lid structure <NUM> also extends over the stiffener structure <NUM>.

<FIG> shows a diagram of the hybrid MWS <NUM> indicating where optical losses occur, in accordance with some embodiments. For each wavelength of light generated by a corresponding one of the plurality of lasers DFB-<NUM> to DFB-N in the laser array chip <NUM>, a first optical loss L1 occurs at the interface between the laser array chip <NUM> and the PLC <NUM>. In some embodiments, the first optical loss L1 is less than or equal to about <NUM> dB. For each wavelength of light, a second optical loss L2 occurs as the light travels through the PLC <NUM> to the plurality (M) of optical outputs PLC-O1 to PLC-OM of the PLC <NUM>. In some embodiments, the second optical loss L2 is less than or equal to about <NUM> dB. Also, for each wavelength of light, a third optical loss L3 occurs at the interface between the PLC <NUM> of the optical fiber <NUM>-x. In some embodiments, the third optical loss L3 is less than or equal to about <NUM> dB.

<FIG> shows a modified laser array chip 103A coupled to the PLC <NUM>, in accordance with some embodiments. The modified laser array chip 103A includes semiconductor optical amplifiers SOA-<NUM> to SOA-N respectively disposed to amplify the CW laser light generated by the lasers DFB-<NUM> to DFB-N. Each of SOA-<NUM> to SOA-N is configured to generate an amplified version of the CW laser light received from the respective one of the lasers DFB-<NUM> to DFB-N and provide the amplified version of the CW laser light to the respective optical output L-O1 to L-ON of the laser array chip <NUM>. In various embodiments, the modified laser array chip 103A can be implemented in the hybrid MWS <NUM> in place of the laser array chip <NUM>.

<FIG> shows a modified hybrid MWS 100A, in accordance with some embodiments. The modified hybrid MWS 100A is like the hybrid MWS <NUM>, with the exception that an array of SOAs <NUM> is disposed between the PLC <NUM> and the optical fibers <NUM>-<NUM> to <NUM>-M, which are attached to the optical fiber alignment device <NUM>. The array of SOAs <NUM> includes SOA-<NUM> to SOA-M respectively positioned to receive light from the optical outputs PLC-O1 to PLC-OM of the PLC <NUM>. Each of SOA-<NUM> to SOA-M is configured to amplify the received light and transmit the amplified light into the optical core of the respective one of the optical fibers <NUM>-<NUM> to <NUM>-M. The array of SOAs <NUM> is positioned on the substrate <NUM> and secured to the substrate <NUM> by the optical index-matched epoxy <NUM>. As compared to the SOA implementation in the modified laser array chip 103A of <FIG>, the array of SOAs <NUM> provides for separate optimization of the lasers DFB-<NUM> to DFB-N and the SOA-<NUM> to SOA-N. Also, as compared to the SOA implementation in the modified laser array chip 103A of <FIG>, the array of SOAs <NUM> provides more gain from each of SOA-<NUM> to SOA-N and lower optical insertion loss through the PLC <NUM>.

<FIG> shows the modified hybrid MWS 100A implemented within a pre-amplified receiver, in accordance with some embodiments. The optical fibers <NUM>-<NUM> to <NUM>-M are optically connected to respective optical transmitters Tx-<NUM> to Tx-M. Each of the optical transmitters Tx-<NUM> to Tx-M is optically connected to an optical data communication link, as indicated by arrows <NUM>. An array of SOAs <NUM> is optically connected to receive the optical signals from the optical transmitters Tx-<NUM> to Tx-M, by way of the optical data communication link, as indicated by arrows <NUM>. Each of SOA-<NUM> to SOA-M amplifies the optical signal that it receives and transmits the amplified optical signal to through a respective optical fiber <NUM>-<NUM> to <NUM>-M to a respective optical receiver Rx-<NUM> to Rx-M. Use of the modified hybrid MWS 100A in the pre-amplified receiver of <FIG> provides extra gain from the unsaturated array of SOAs <NUM> and can improve link margin to +<NUM> dB or better.

<FIG> shows a modified hybrid MWS 100B that includes the modified laser array chip 103A of <FIG> and optical fiber interfaces for the optical inputs and optical outputs of the PLC <NUM>, in accordance with some embodiments. The PLC <NUM> is disposed on a substrate <NUM>. The substrate <NUM> is disposed on the substrate <NUM>. Respective optical fibers IF-<NUM> to IF-N are secured to the substrate <NUM> and are respectively optically connected to the optical inputs PLC-I1 to PLC-IN of the PLC <NUM>. Also, respective optical fibers OF-<NUM> to OF-M are secured to the substrate <NUM> and are respectively optically connected to the optical outputs PLC-O1 to PLC-OM of the PLC <NUM>. Also, in some embodiments, optical fibers IF-A1 and OF-A1 are optically connected to the first alignment optical input PLC-AI1 and the first alignment optical output PLC-AO1 of the PLC <NUM>, respectively. The optical fibers IF-A1 and OF-A1 are secured to the substrate <NUM>. Also, in some embodiments, optical fibers IF-A2 and OF-A2 are optically connected to the second alignment optical input PLC-AI2 and the second alignment optical output PLC-AO2 of the PLC <NUM>, respectively. The optical fibers IF-A2 and OF-A2 are secured to the substrate <NUM>. Use of optical fiber interfaces for the optical inputs and optical outputs of the PLC <NUM> serve to reduce the optical losses through the PLC <NUM>. Also, use of optical fiber interfaces for the optical inputs and optical outputs of the PLC <NUM> makes it easer to implement optical isolators, if needed.

<FIG> shows a modified hybrid MWS 100C that includes implementation of the PLC <NUM> in conjunction with a praseodymium-doped fiber amplifier (PDFA) <NUM> and a 1xM optical splitter <NUM>, in accordance with some embodiments. The PLC <NUM> is implemented on a substrate <NUM>. The substrate <NUM> is attached to the substrate <NUM>. Optical fibers IF-<NUM> to IF-N are optically connected to the optical inputs PLC-I1 to PLC-IN of the PLC <NUM>. The optical fibers IF-<NUM> to IF-N are attached to the substrate <NUM>. Each optical fiber IF-<NUM> to IF-N receives CW laser light from a respective one of the lasers DFB-<NUM> to DFB-N in the laser array chip <NUM>. The PLC <NUM> is implemented with the number (M) of optical outputs equal to one. A first end of an optical fiber <NUM> is optically connected to the optical output PLC-O1 of the PLC <NUM>. A second end of the optical fiber <NUM> is optically connected to an optical input of the PDFA <NUM>. The optical fiber <NUM> is attached to the substrate <NUM>. A first end of an optical fiber <NUM> is optically connected to an optical output of the PDFA <NUM>. A second end of the optical fiber <NUM> is optically connected to an optical input of the 1xM optical splitter <NUM>. The optical fiber <NUM> is attached to the substrate <NUM>. The number (M) of optical fibers OF-<NUM> to OF-M are respectively optically connected to the (M) optical outputs of the 1xM optical splitter <NUM>. The optical fibers OF-<NUM> to OF-M are attached to the substrate <NUM>. The optical cores of the optical fibers <NUM>-<NUM> to <NUM>-M are aligned to optically couple with the optical cores of the optical fibers OF-<NUM> to OF-M, respectively.

It is not intended to be exhaustive or to limit the invention.

Claim 1:
A multi-wavelength source (<NUM>), comprising:
a substrate (<NUM>) including a first area (101A) for receiving a chip and a second area (101B) elevated relative to the first area (101A), the second area (101B) separated from the first area (101A) by a trench (<NUM>) having a bottom at a lower elevation within the substrate (<NUM>) than the first area (101A), the substrate (<NUM>) including a third area (101C) next to the second area (101B), the third area (101C) having a lower elevation within the substrate (<NUM>) than the second area (101B);
a laser array chip (<NUM>) disposed in the first area (101A), the laser array chip (<NUM>) having optical outputs facing toward the second area (101B), wherein the laser array chip (<NUM>) is configured to output multiple wavelengths of continuous wave laser light;
a planar lightwave circuit (<NUM>) disposed in the second area (101B), the planar lightwave circuit (<NUM>) having optical inputs facing toward and aligned with respective optical outputs of the laser array chip (<NUM>), the planar lightwave circuit (<NUM>) having optical outputs facing toward the third area (101C); and
an optical fiber alignment device (<NUM>) disposed in the third area (101C), the optical fiber alignment device (<NUM>) configured to receive a number of optical fibers (<NUM>) such that optical cores of the number of optical fibers (<NUM>) respectively align with the optical outputs of the planar lightwave circuit (<NUM>).