Patent Description:
Next generation optical solutions utilize silicon photonics in order to achieve power control and continued miniaturization. Using silicon photonic optical modulators within transmitting optical sub-assemblies (TOSAs) for high speed data communication with greater than <NUM> gigabyte (Gb) transmission rates, one typically needs a continuous light source in the form of semiconductor lasers to be aligned to the modulator section where light is coupled from the laser to the modulator input with the help of individual lenses or lens arrays (to minimize alignment effort). Typically, the lens(es) and modulator are then hermetically sealed inside a suitable enclosure to cool the components without forming condensation. While the creation of such optical devices provides increased throughput and miniaturized structures, the energy requirements for these devices, however, remains high due to the electrical energy required to cool the laser and other components (e.g., modulator) hermetically sealed within the enclosure. Further, manufacturing requirements for perfecting height tolerances in the proper alignment of the lasers within the hermetically sealed enclosure remain strict, and in some cases manufacturing is prohibited or slowed due to these requirements.

Accordingly, a solution is needed for an optical device with increased energy efficiency that also can retain high throughput characteristics. Additionally, a solution is needed for an efficient optical communication device with high throughput that may be manufactured using lower cost components. Additionally, a solution is needed for a method of manufacturing an optical communication device that can be performed more easily yet still maintain the strict tolerances required for such devices. <CIT> relates to an optical module. According to the abstract of this document the optical module includes an optical component, a body incorporating an optical element, and a metallic sleeve having a tubular shape. The optical component includes a nonmetallic ferrule having an optical fiber insertion hole, and a metallic holder which covers part of the ferrule. In this optical module, part of the holder is inserted into the sleeve, and is positioned and welded to the sleeve. The sleeve is positioned to a tubular portion of the body and welded thereto. <CIT> relates to a modular optoelectronic package. According to the abstract of this document each functional piece for a particular optoelectronic product may be packaged individually. Each package may be equipped with one or more optical windows through which collimated beams are allowed to pass. The individual packages or modules may be mated and aligned together in such a way that the output-collimated beam of one package becomes the input-collimated beam of a second package. In this fashion, any number of individual packages may be linked together to form an optical device performing a more complex operation. <CIT> relates to a laser modulator. According to the abstract of this document an optical transmitter module comprises a single package enclosing a laser assembly and an integrated optical circuit having an input waveguide and an output waveguide. An optical fibre stub optically interconnects the laser assembly and the optical circuit, the fibre stub having one end supported to receive light from the laser assembly and the other end optically coupled to the input waveguide of the optical circuit. An output optical fibre is in optical communication with the output waveguide of the optical circuit and leads out of the package, whereby light emanating from the laser assembly is fed to the optical circuit and is there subject to data-encoding before leaving the package through the output optical fibre. <CIT> relates to a laser diode assembly. According to the abstract of this document the laser diode assembly is capable of controlling a temperature of a laser diode chip with a high accuracy. A Peltier device is mounted on a base member, and a carrier is mounted on the Peltier device. On the carrier are mounted the laser diode chip, a thermistor, and a relay block. A terminal for connecting the thermistor to an external circuit is provided so as to extend through the base member. The thermistor and the relay block are connected together by wire bonding, and the relay block and the terminal are also connected together by wire bonding. The laser diode assembly further includes a control circuit for controlling a driving current for the Peltier device contacting with the carrier so as to maintain a resistance of the thermistor fixed on the carrier at a constant value.

The components in the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding parts throughout the several views.

There is also described herein an optical communication device comprising a laser within a hermetically sealed sub·-assembly for use in an optical communications network. A thermo-electrical cooler may also reside within the hermetically sealed sub-assembly for dissipating heat generated by the laser. A window may form part of the hermetically sealed sub-assembly for communicating a light beam between the laser and an optical input situated outside the hermetically sealed sub-assembly. The optical input may be connected to an optical modulator outside the hermetically sealed sub-assembly to modulate the light beam and send a modulated optical signal to an optical communication network.

As also described herein, a laser may receive at a hermetically sealed optical sub-assembly an electrical input from an external source. In response, a laser on a sub-mount within the hermetically sealed optical sub-assembly may be fired corresponding to the electrical input. An optical modulator outside of the hermetically sealed sub-assembly may receive the output of the first laser and modulate the light and send the modulated light to an optical communication network through an optical connector that forms part of the optical communication device.

Further exemplary implementations disclosed herein include methods of manufacturing an optical communication device and hermetically sealed sub-assembly. In one example implementation, a method of manufacturing an optical communication device may include positioning a first sub-mount configured to accommodate an optical laser on a carrier wafer approximately adjacent to a first pre-defined break line in the carrier wafer. A second sub- mount is then configured to accommodate an optical modulator on the same carrier wafer approximately adjacent to a second pre-defined break line in the carrier wafer. Optionally, a jaw tool or inverted pyramid tool may then be used to align the first and second sub- mounts such that lasers/lenses on the first sub-mount and the modulator on the second sub-mount are coarsely pre- aligned with subsequent fine alignment step for lenses to maximize optical coupling between laser and modulator.

The first sub-mount can further be hermetically sealed in a sub-assembly. A window in the sub-assembly is aligned with the output of the optical laser. The optical device platform and sub-assembly may then be placed adjacent to each other such that the first and second sub-mounts are optionally passively realigned, thus allowing the laser(s) within the first sub-assembly to be aligned with the input(s) of the optical modulator.

There is also described herein, a method of manufacturing an optical communication device entailing preparing a first pre-defined break line in a submount approximate to a portion of the sub-mount that is configured to accommodate an optical laser and preparing a second pre-defined break line in the sub-mount approximate to a portion of the sub-mount that is configured to accommodate an optical modulator, The sub-mount may then be attached perpendicular to a TEC and parallel to an optical device platform (i.e., optical bench). The portion of the sub-mount between the first and second break lines may then be removed so as to allow further manufacture in accordance with methods disclosed herein.

In some optical network devices, lasers are used that require temperature control with a thermo-electrical cooler (TEC) to maintain output wavelength and/or power. To avoid condensation on temperature controlled (cooled) areas, a hermetic enclosure is utilized to enclose the electrical components, modulators, and lasers. For example, in optical device applications, a transmitter optical sub-assembly (TOSA) may be created by hermetically sealing components inside a suitable enclosure. In this way the components (which typically include lasers and optical modulators) may be cooled without forming problematic condensation within the optical device. Accordingly, the TOSA may take electrical input signals through connection leads and export the optical signals through an optical receptacle (e.g., an optical connector or patch cord is inserted into a receptacle to guide light via fiber to its final destination) by way of the hermetically sealed laser and modulator assembly enclosure.

While the creation of such an optical device provides increased throughput and miniaturized structures, the energy requirements for these devices remains high due to the electrical energy required to cool the laser and other components (e.g., modulator) hermetically sealed within the enclosure. This is in part at least because all of the components are located on the TEC and multiple short wire bonds leading to the modulator increase power consumption.

Further, because the modulator is within the hermetically enclosed structure, the electrical leads including multiple RF lines must be routed through non-conducting insulation (e.g., ceramic) from the inside of the enclosure to the connector portion while maintaining the hermeticity of the package, thus creating additional manufacturing expense and difficulty. Additionally, the final design of the connector remains high, as hermetic RF feed through is more costly compared to low cost DC feed-through (e.g., glass or metal). Furthermore, manufacturing requirements for perfecting height tolerances in the proper alignment of the lasers within the hermetically sealed enclosure remain strict, and in some cases manufacturing is prohibited or slowed due to these requirements.

In an example implementation, the optical communication device disclosed herein may have a hermetic sub-assembly of lasers and thermo-electrical coolers (TEC) integrated within a sturdy optical platform or bench which further holds optical components - e.g., isolator, optical modulator, mirrors, connectors, and electrical chips/circuits. The cost of the inventive device may be reduced over conventional designs by using TO-industry parts without compromising performance and guaranteeing the highest yield possible. In various implementations disclosed herein, multiple lasers can be placed inside the hermetic package to allow multiple channel transmissions. A window cap on the hermetic enclosure may allow the unsealed components to receive and transmit information from/to the hermetically sealed laser components. In this way, less energy is consumed by the device than conventional optical device configurations.

The present disclosure also provides methods for absorbing the large height tolerances of thermo-electrical coolers (TECs), which can be in the range of plus or minus <NUM> millimeters (mm), without compromising the stability of the optical package. Additionally, exemplary implementations disclosed herein allow for the burn-in of individual lasers to maximize yield and still allow for an arrangement of lasers on a certain pitch to be able to use lens arrays and couple light to a modulator with multiple inputs on the same pitch. The laser is on a silicon sub-mount.

In further exemplary implementations disclosed herein, the inventive optical communication device has a window forming part of the hermetically sealed assembly for communicating between the laser and an optical input situated outside the hermetically sealed assembly. The optical input and/or inputs may be coupled to an optical modulator (comprising silicon photonics) through which signal processing may be performed on the signal from the laser. An isolator to direct the laser may be either outside or within the hermetically sealed assembly. The optical communication device may also have an optical output for communication with an optical communications network. Various types of optical connectors for receiving an optical signal from the optical output and accessing the optical communications network may also be used.

The TEC that may be used in the optical communication device can be vertically or horizontally oriented within the hermetically sealed assembly. If vertically oriented, height tolerance adjustments of the laser may be made by adjusting the position of the laser vertically on the TEC. If horizontally oriented, height adjustments between the laser and the optical input may be made by varying the bottom lid of the hermetically sealed assembly or the depth of the optical modulator or depth of laser mounting. When the depth of the optical modulator or laser is varied, a spacer below the modulator or within the hermetically sealed enclosure below or above the TEC may be configured to account for height adjustments.

Optionally, the optical communication device may have multiple lasers on a single sub-mount positioned on the TEC (instead of individual lasers on a sub-mount) such that a spacer is positioned underneath the sub-mount and adjacent to the TEC to facilitate heat dissipation generated from the laser or lasers.

Exemplary implementations of the optical communication device described in the present disclosure thus provide for a reliable, flexible, and sturdy optical communication device. One implementation may have a transmitting optical sub-assembly for which low cost components from transistor outline industry (high volume) may be used, such as a standard transistor outline header (TO-header), and window cap with low cost glass/metal hermetic seal. Energy efficiency is provided by hermetically sealing limited areas, such as the cooled or uncooled laser(s) that may be used as continuous light sources. This allows for the optical modulator and connector sections of the inventive optical communication device to remain outside the hermetic package, providing advantages as described herein. This also prevents costly hermetic radio frequency (RF) feed through.

According to the various implementations, the disclosure provided herein is capable of providing advantages over the conventional TOSA connector. First, the hermetic area disclosed herein may contain direct current (DC) lines and no radio frequency (RF) signals thus allowing cheaper and easier routing than conventional designs. (This is in part because glass/metal feed-through with round pins is only effective for less than <NUM>-Gb speeds. Beyond <NUM>-Gb speeds, ceramic multi-layer has superior RF performance (less reflection/radiation and more transmission of RF signals). ) Specifically, preparing a feed-through of DC signals into the hermetic area is much cheaper and easier compared with routing RF signals because simple glass/metal seals can be used versus multiple ceramic layers mating with metal seals as required for RF routing. Second, the optical communication device may comprise, in certain implementations, lower cost standard packaging parts, such as ceramic sub-mounts, standard window caps, and/or standard pin headers. Third, the optical communication device may have a higher laser burn in yield due to the preferred individual laser on a sub-mount design described herein where individual sub-mounts may be replaced instead of replacing a multiple laser sub-mount due to a single laser failure. Fourth, the optical communication device may produce lower power consumption because it only requires that lasers within the hermetic package be cooled as opposed to electronics contained within the modulator section as required by conventional devices. Fifth, the optical communication device may produce a lower passive head load since no short wire bonds from hot to cold are required. Sixth, the optical communication device provides an elegant solution for the separation of lasers and modulator by tilting the TEC <NUM>-degress (or substantially vertical) to deal with TEC height tolerances without compromising stability or requiring more complicated design features to absorb TEC height tolerances (like shimming, laser or modulator height adjustment).

In one implementation disclosed herein, low-cost TO-header technology with multiple I/O pins can be used to allow DC routing of laser biases, along with TEC current and temperature sensor connections (e.g., connections for thermistor). The laser(s) can be mounted on individual sub-mounts. This would allow individual burn in of each laser on sub-mounts and passing dies could be used for subsequent assembly. That way burn in yield is maximized versus simultaneous burn in of several lasers on the same sub-mount which would make the whole sub-assembly fail if only one laser burn-in failed. However, it is to be understood by those of ordinary skill in the art, that the sub-assembly could use any kind of sub-mounts covering both individual or group (wafer) burn in strategies.

If the preferred individual laser sub-mounts are implemented, the shape of the sub-mounts may allow for each individual laser to be mounted on the TEC top surface to allow light emission in line with the TO-package center axis. This would also allow multiple sub-mounts with lasers to be arranged on a pitch of as little as <NUM> to match the pitch of the lens arrays and/or the modulator section pitch. To allow easy handling and burn in of individual sub-mounts, it is preferred that they have a minimum size of <NUM> to <NUM>. Also, burn in requires minimum pad size on laser sub-mounts to make a reliable electrical contact (e.g., with pogo pins). Optionally, the arrangement of several sub-mounts on the TEC top surface can be alternating (or opposing) so that all odd channels are facing one way and even channels are rotated the opposite way (i.e., <NUM> degrees). This allows the sub-assembly to maintain the desired smaller pitch (e.g., <NUM>). Otherwise, a pitch such as <NUM> would be the minimum pitch size, accordingly limiting the packaging size. In accordance with the individual sub-mount implementation, a cut out on one sub-mount side may be utilized to avoid interference with the laser wire-bond of the adjacent channel. The clearance cut on the sub-mount can easily be added before sub-mount separation by a dicing blade without adding much cost. In contrast, conventional designs use more costly reactive ion etching on silicon to create clearance cuts.

Electrical connection may be established by wire bonds from sub-mount pads to the TO-header pins (as discussed with reference to <FIG>). Layout of both sub-mount and header pins can also be carefully chosen to maintain a small footprint and still allow wire bondability. On the sub-mount backside where it makes contact with the TEC top surface, conductive epoxy can be used to electrically connect the sub-mount pad to a metalized or patterned TEC top surface and/or additional patterned substrate mounted to the TEC top surface (i.e., could be a common ground for all lasers). The electrical connection can be a <NUM>-degree bend via the conductive epoxy on the sub-mount pad close to back side to TEC top surface. This would be the lowest cost solution (without a <NUM>-degree epoxy path, wire bonds would need to replace the connection because there is limited space/access for additional pads; wrapping metal pads around edges opens up additional space to place pads but increases the cost for the sub-mount). Alternatively, as noted, sub-mounts with conductive paths wrapping around (multiple) edges could be used to have a wire-bond connection only. However, this would increase the cost of the sub-mounts.

Optionally, to increase the mechanical integrity of the laser sub-mount array on a vertically mounted thermo-electrical top surface a frame structure can be glued to the front side of the sub-mounts connecting all sub-mounts with each other and increasing the stiffness of the assembly.

Each laser can be mounted at a controlled distance to the front face of the sub-mount. A first lens can then be aligned and glued to each of the front faces of the sub-mounts to collimate or bend the laser light. This allows larger physical separation between the laser and the modulator section to accommodate the hermetic sealing with a window cap. Alternatively a lens array can be aligned and glued to the laser sub-mount front surfaces.

Accordingly, the hermetic sub-assembly comprised of a TO-header and window (lens cap) containing multiple lasers, TEC and temperature sensor (e.g., thermistor) builds a robust unit that can be easily handled and tested before being used in subsequent assembly steps. The optical sub-assembly can then be aligned and fixed (by weld, glue and/or solder) within the optical bench so that the laser signal/light may be horizontal to the optical bench. This requires a <NUM> degree tilt of the header with regards to the optical platform/bench. In this way, the optical setup is immune against any TEC height tolerances. It also allows exact alignment of laser beams in x/y/z and angle to match the optical height and position of the modulator such that the modulator height does not have to be strictly controlled.

Consistent with this disclosure, the optical bench material may be a variety of materials, including but not limited to, kovar or CuW to match the silicon coefficient of thermal expansion (CTE) and to also provide good heat sinking in case of CuW. Metal injection molding (MIM) can alternatively be used for the optical bench in order to reduce cost for higher volumes of the optical communication device. Typical metal injection molding dimensional tolerances are acceptable for the present invention.

Alternatively, ceramic could also be used as optical bench material but it is more challenging to machine to the required shape. Additionally, a hybrid of ccramic/metal or metal/metal is an option if laser welding is required, especially for a connection between the TO-header and the optical bench and the fiber optic connector/receptacle to the optical bench.

According to one implementation of the manufacture of the inventive optical communication device, isolators between the lasers and modulator would be attached to the device, followed by the placement and adhesive attachment of the modulator to the optical bench. Coarse alignment is also acceptable in the event a secondary lens (or array) is used on the modulator input side (such a secondary lens alignment would require high precision). Alternatively, a staggered layout of modulator input channels would allow larger secondary lenses and easier tooling access. Further, in another alternative implementation, all modulator inputs can be on the same line and a secondary lens array could be used.

To route the modulator output light more easily to a fiber (array) connector, it is beneficial to have the modulator output side be different than the input side to allow for an easier arrangement of components not available due to space constraints when arranging on the same side. In any event, the fiber (array) connector placement and attachment to the optical platform/bench can be either the last or second-to-last optical alignment step depending on process preferences for manufacturing the optical communication device. As noted, individual or array lenses can be used.

As further disclosed herein, the optical bench can be designed such that one or more driver integrated circuits can be mounted adjacent to the modulator or even placed directly on the modulator. Connection to a printed circuit board (PCB) can be such that wire bonds or flex connections used between an integrated circuit and PCB or alternatively a cut out on the optical bench could allow a ball grid array (BGA) attachment of the integrated circuits to the PCB.

A further aspect of an exemplary implementation of the optical communication device disclosed herein includes the heat sinking of the TEC. In a vertical orientation, the heat has to take a <NUM> degree turn from header backside to the heat sink which is typically parallel to the optical bench. By using high thermal conductivity steel for the header and an appropriate heat sink, which makes contact to the header back side (e.g., copper finger), the temperature drop within the heat sink path can be minimized to an acceptable level (e.g., adding an additional high thermal conductivity material to the header backside offers the heat a parallel path decreasing thermal resistance and temperature drop to ambient temperature).

The figures disclosed herein provide further details for the inventive optical communication device.

<FIG> illustrates a perspective view of an optical communication device <NUM> according to an implementation of the invention. The optical communication device <NUM> may comprise two main components: the optical platform/bench <NUM> and the hermetically sealed optical sub-assembly <NUM>. As shown, a modulator <NUM> (comprising silicon photonics) and a printed circuit board (PCB) <NUM> may be fixably attached to the optical communication device platform <NUM>. Additionally, an electrical integrated circuit <NUM> (e.g., a flip chip bonded via a BGA) may be bonded to the modulator <NUM>.

One or more input lenses 120A-N may reside on the modulator <NUM> to couple laser signals received from the optical sub-assembly <NUM> into the photonic modulator <NUM> for processing. A laser output lens <NUM> on the modulator <NUM> may also be used to couple the output of the photonic modulator <NUM> to an optical communication network through an optical interface <NUM> (such as the lensed fiber receptacle <NUM> shown in <FIG> or alternative receptacles (not shown)). It should be noted that additional components may be placed on the optical bench/platform <NUM>, including but not limited to passive electrical components and active driver integrated circuits, main electrical PCB <NUM>, and/or micro optics turning mirrors. The electrical connection to the PCB <NUM> (or other main electrical board) can be done by a ball grid array (BGA) or can also be done by flexible PCB or wire bond.

The optical interface <NUM> may comprise a variety of forms, including but not limited to, a lensed fiber (shown in <FIG>) or any other optical receptacle to allow a connection to an optical patch cord. Regardless of the type, the optical interface <NUM> can be attached to the optical platform (e.g., glued, soldered or welded) before or after the output lens is aligned and put into place at the modulator output side to couple maximum light into the optical interface <NUM>.

<FIG> further illustrates the hermetically sealed optical sub-assembly <NUM> according to one implementation of the invention. The sub-assembly <NUM> provides an air-tight sealed enclosure for placement of a TEC <NUM> and sub-mounted lasers 215A-N. As shown, to maximize heat dissipation and increase mechanical stability, a spacer <NUM> is incorporated underneath the lasers 215A-N. This spacer <NUM> may comprise a material, such as ceramic, or other material intended to dissipate heat from the sub-mounted lasers 215A-N. The lasers 215AN may be individually sub-mounted (as discussed with regard to <FIG>) or alternatively mounted together on a sub-mount. To direct the optical light or signal from the lasers 215A-N to the modulator <NUM>, one or more lenses (or a lens array) may be mounted adjacent to the lasers 215A-N. Metalized pads <NUM> may be used to carry current to the sub-mounted lasers 215A-N. As shown in <FIG>, there is a gap <NUM> between the TEC <NUM> and the laser sub-mount (which is made of silicon) so that the electrical pads <NUM> do not short on the TEC <NUM>. If this gap is filled with electrical conductive adhesive (like silver filled epoxy), there is a risk of electrical shortage due to overflowing epoxy. Therefore, an epoxy that has high thermal conductivity but is not electrically conductive is preferred. For example, in one exemplary implementation, an epoxy filled with ceramic particles can be used to provide a thermal, but not electrical, conductive epoxy (as discussed further with regard to <FIG>).

The temperature inside the hermetically sealed sub-assembly <NUM> may be measured by a temperature sensor like thermistor <NUM>. As further shown in <FIG>, the optical sub-assembly also comprises a window cap <NUM> that allows laser light to reach the modulator <NUM> optical signal inputs 120A-N (as shown in <FIG>). In this implementation, an isolator <NUM> is located next to the sub-mounted lasers 215A-N. However, as described herein, this isolator <NUM> alternatively may be located outside the sub-assembly.

<FIG> illustrates a cross section view of an optical communication device <NUM> according to an implementation of the invention. As shown in this implementation, the TEC <NUM> and header <NUM> are turned <NUM>-degrees to a substantially vertical position. Doing so allows for the height tolerances to be easily accounted for between the location of the modulator <NUM> and the output of the lasers 215A-N. For example, the spacer <NUM>, sub-mounted lasers 215A-N, and isolator <NUM> could be adjusted vertically to account for any variances arising between the placement of the modulator <NUM> and the lasers 215A-N. Alternatively, the sub-assembly <NUM> itself could be adjusted when placed in the optical platform <NUM> to create proper alignment between the lasers 215A-N and modulator <NUM>, if required, before being fixably attached to the optical platform.

As also shown in <FIG>, a gap <NUM> is provided between the sub-mount of the laser (i.e., silicon) and the TEC <NUM> to prevent an electrical shortage at the laser. In this configuration, heat travels from the laser (i.e., the source of the heat), down through the sub-mount, and through the spacer <NUM> to the TEC <NUM>. Alternatively, as mentioned previously, the gap <NUM> may be filled with a high thermal conductivity epoxy (e.g., 3W/mK), such as epoxy filled with ceramic particles, to improve thermal performance, thus allowing the heat to travel directly through the epoxy to the TEC <NUM>. An example illustrates the thermal efficiency gained through this approach. For example, with spacer thickness of t=<NUM>, the laser temperature may be reduced by approximately <NUM>° C and for t = <NUM>, the reduction can be approximately <NUM>° C (assuming the temperature of the laser is <NUM>° C and the ambient temperature is <NUM>° C). This is significant, as with four lasers running at 120mA each, this amounts to a TEC power savings of 40mW per <NUM>° C.

<FIG> illustrates a perspective view of an optical communication device according to another implementation of the invention. As noted, the isolator <NUM> in this implementation is shown outside of the hermetically assembled sub-assembly <NUM>. Further, this implementation illustrates that the optical communication device <NUM> may connect to an optical network through any number of interface <NUM> configurations (e.g., receptacles).

In the implementation shown in <FIG>. individual sub-mounted lasers 505A-N may be placed on a TEC in an opposing configuration to accommodate a smaller pitch as previously discussed. This configuration may be used as an alternative to the multiple lasers on a sub-mount configuration. In either case, to facilitate the exchange of laser light or signals between the sub-assembly <NUM> and the modulator inputs 120A-N, the sub-mounted lasers beneficially have lenses 510A-N to focus or collimate the laser light so that it may extend through the window cap <NUM> and reach the modulator inputs 120A-N. Alternatively, a lens array may be used in place of individual lenses.

<FIG> illustrate a preferred design and configuration for the placement of individual sub-mounted lasers 505A-N according to an implementation of the invention. In <FIG>, a single sub-mounted laser is shown. The laser on individual sub-mount design comprises a laser <NUM> with a wire bond, burn in pads <NUM> (for electrical contact during burn in needle or pin contact), and a clearance <NUM> cut to avoid contact with the wire bond of adjacent lasers. As noted previously, the clearance <NUM> may be formed by a dicing blade without adding much cost to the manufacturing process.

<FIG> further illustrates the placement of the single sub-mounted laser <NUM> on the TEC <NUM> according to an implementation of the invention. The laser on a sub-mount <NUM> may be glued or otherwise fixably attached to the TEC <NUM> and a wire bond may be extended to form an electrical connection to a pin on the header <NUM> or other pin assembly used in the hermetically sealed sub-assembly <NUM>. In accordance with <FIG>, a second sub-mounted laser <NUM> may be placed on the TEC <NUM> adjacent to and opposing the first individually sub-mounted laser <NUM>. This configuration allows for efficient routing of wire bonds 625A-N to pins on the header <NUM>. Further, as shown, this placement allows adequate clearance for using a tool <NUM> to attach the wire bonds 625A-N.

As shown in <FIG>, four sub-mounted lasers 505A-D have been placed on the TEC <NUM> according to an implementation of the invention. Each may be connected to respective pins 515A-N through wire bonds 625A-D. <FIG> illustrates the placement of four lenses on the four lasers 505A-N on individual sub-mounts on a TEC <NUM> according to a further implementation of the invention. As previously noted, a lens array could alternatively be used in place of the individual lenses.

The positioning of the lasers 505A-N in a line in an opposing manner as shown in <FIG> allows for a smaller controlled pitch. Preferably, this pitch can range from <NUM> to <NUM>, and a pitch of <NUM> is shown in <FIG>. This pitch provides advantages because it allows for denser component arrangement, smaller footprint and lower cost.

In <FIG>, an exemplary implementation of the sub-mounted laser 505A-N configuration is shown with a metal (or other material) frame <NUM> that has been optionally glued or otherwise fixably attached to the sub-mounted lasers 505A-N around the lenses 510A-N to stabilize the structure. Such stabilization allows for more stable performance over all operations, conditions and in better reliability.

<FIG> illustrate views of another optical communication device according to an implementation of the invention. In <FIG>, the optical communication device <NUM> comprises an optical bench/platform <NUM> and a hermetically sealed optical sub-assembly <NUM> similar to that shown in <FIG>. However, in <FIG>, the optical sub-assembly <NUM> design varies. Specifically, as shown in greater detail in <FIG>, the TEC <NUM> in sub-assembly <NUM> is positioned horizontal relative to the modulator <NUM>. Accordingly, sub-mounted lasers 215A-N (which may be mounted together or individually sub-mounted) are positioned on the top of the TEC <NUM> to provide heat dispersion required for the lasers. As noted previously, in some configurations the laser might not require a TEC <NUM> within the hermetically sealed sub-assembly <NUM>, in which case the lasers would be height adjusted with a spacer as required to meet alignment with the window cap <NUM> positioned between the lasers 215A-N and the inputs 120A-N to the modulator <NUM>.

As shown in <FIG>, when a TEC <NUM> is utilized, height adjustments of the TEC <NUM> in respect to platform <NUM> and/or the modulator <NUM> may be made by placing the components using a tooling component (shown by dashed line <NUM> in <FIG>) and then welding the bottom lid <NUM> with the TEC <NUM> at the preferred height to metal ring <NUM> A-N. Additionally, <FIG> illustrate that a second hermetic seal between 830A-N and <NUM> can be used to join the top metal lid <NUM> to the platform <NUM> (which, in this implementation, is multi-layer ceramic but may be any suitable material). Optionally, as shown in <FIG>, the modulator <NUM> and integrated circuit board <NUM> may be pre-adjusted height-wise by the use of a spacer <NUM>, which may be machined as a part of the platform <NUM> or added afterwards during the manufacturing process. Also the brazed metal rings <NUM> A-N used in welding should comprise ceramic with inferior RF performance. Therefore, the RF routing should go directly to the PCB as opposed to being routed via the ceramic. This may be done with wire bonds. While the isolator <NUM> is shown inside the hermetically sealed sub-assembly <NUM>, it may alternatively be located outside the hermetic enclosure <NUM> as discussed previously (if required at all). Further, as illustrated in <FIG>, the inventive optical communication device <NUM> may be manufactured without the use of a standard TO-header, although it is economically preferable to use a TO header instead of hermetic ceramic feed-through package.

The operation of the optical communication device <NUM> shown in <FIG> and <FIG> may be the same as that described previously. Specifically, a continuous light may be fired from the lasers <NUM>5A-N. While firing, the lasers 215A-N are cooled by TEC <NUM>. The laser light is passed through lenses to collimate the light adjacent to the lasers and then focused outside the hermetically sealed optical sub-assembly <NUM>, where they are coupled to the optical modulator <NUM>. As previously discussed, an isolator <NUM> may be situated inside or outside the hermetically sealed assembly <NUM>. The modulator <NUM> then modulates the laser light based on input from the PCB <NUM> and outputs the modulated signal to the optical network <NUM>.

<FIG> illustrate yet additional views of an optical communication device <NUM> according to another implementation of the invention. As shown in <FIG>, height tolerances may be adjusted in the optical sub-assembly <NUM> by adjusting distance/height between modulator <NUM> and spacer <NUM>. With subsequent locking of modulator <NUM> to spacer <NUM> (e.g., via glue, welding, or solder), the modulator <NUM> (silicon photonic chip) could be sitting on an additional carrier (not shown) which is adjusted in respect to spacer <NUM>. Especially for the locking method "welding," this is preferred since the carrier material could be weldable kovar® metal. Further, as with the implementation shown in <FIG>, a spacer <NUM> may also be used to adjust other height adjustments on the modulator <NUM> side; various shims in stepped-height tolerance variations could be used between the output of the sub-assembly <NUM> and the input(s) 120A-N to the modulator <NUM>. (Similarly, height adjustments (instead of modulator height adjustments) could likewise be done inside hermetic area <NUM> between laser sub-mount 215A-N and TEC <NUM> (not shown)). In either case as before, a window cap <NUM> is employed to allow communication between the hermetically sealed lasers 815A-N and the modulator <NUM> (which in turn may send signals to an optical network through optical interface <NUM>).

As discussed previously, the various implementations disclosed herein offer advantages over conventional designs. Such advantages include increased power performance (lower power consumption), more economical packaging designs, and potentially smaller device sizes. This list is not exclusive, but includes other advantages recognized by those of ordinary skill in the art.

The present disclosure also provides an inventive method of manufacturing the inventive optical communication device <NUM>. <FIG> illustrates a subassembly consisting of carrier <NUM>, <NUM> and <NUM>. A singulated sub-assembly is shown, but it could be part of a wafer scale assembly (i.e., a wafer of many carriers <NUM>). Carrier <NUM> has pre-defined breaks 1020A-B according to an implementation of the manufacture of the invention. Such breaks 1020A-B ensure easy separation of modulator <NUM> and laser section <NUM> in subsequent process steps. Wafer scale assembly can have cost and handling advantages. An additional advantage is pairing up of specific laser sub-mounts and modulators. The pairing can be kept throughout the whole process resulting in easier optical alignment process and better final optical coupling. For example, the modulator <NUM> and laser sub-mount <NUM> can be aligned approximately adjacent to the breaks as shown. The complete subassembly <NUM> can then be attached to the optical bench and header simultaneously and separated afterwards using pre-defined break lines 1020A-B. This manufacturing process allows sealing of the laser sub-mount portion without having the modulator in close proximity and in limited tooling access (as shown in <FIG>).

<FIG> illustrates a subassembly <NUM> with pre-defined breaks 1115A-B according to another implementation of the manufacture of the invention. Similar to the implementation shown in <FIG>, the breaks 1115A-B allow for separation of laser portion <NUM> and modulator portion <NUM> in subsequent process steps. However, in this implementation, a larger single silicon chip <NUM> encompasses both portions, eliminating the need for additional carrier <NUM>,.

As shown in <FIG>, if two separate sub-mounts are used (e.g., a laser sub-mount <NUM> and a modulator sub-mount <NUM>), a subassembly <NUM> with pre-defined breaks 1020A-B according to an implementation of the manufacture of the invention may be aligned using a tool <NUM>. In <FIG> the two sub-mounts in a first, course alignment step are placed approximately aligned with the pre-defined breaks 1020A-B. Proper height alignment between the sub-mounts is guaranteed by bond line control between subassembly <NUM> and modulator sub-mount <NUM> and between subassembly <NUM> and laser sub-mount <NUM>. However, to ensure proper side-to-side alignment, in one implementation a jaw tool <NUM> may be inserted into the space between the sub-mounts and opened as shown in <FIG> to position the two individual sub-mounts. (The jaw tool references off of the precision etched features on sub-mounts <NUM> and <NUM>). As shown, this may be performed after laser attach and burn in for laser sub-mount <NUM> but before the final placement of specific components such as the isolator the modulator and laser lenses. However, such tooling could be performed at any time prior to final attachment of the sub-mounts.

Similarly, <FIG> illustrate another method of aligning the laser sub-mount section <NUM> and modulator section <NUM>. As shown, a first tool 1705A-B may be inserted into slots 1715A-B manufactured into the sub-mount section <NUM> and modulator section <NUM>, thus providing angular alignment. At the same time, a second tool 1710A-B may be inserted into inverted pyramids 1720A-B. The combination of the second tool 1710A-B, which preferably comprises two elongated columns (e.g., conical pins in a collet used to hold the component), each ending in a pyramid or pointed shape, allows for proper lateral alignment when placed into the inverted pyramids 1720A-B. This is shown in detail in <FIG>, as second tool 1710A is pressed into the inverted pyramid slot 1720A that is machined or chemically etched into the modulator section <NUM>.

<FIG> illustrate further tooling of an optical communication device <NUM> according to an implementation of the manufacture of the invention. In <FIG>, a pre-formed tool <NUM> holds the optical platform <NUM> in place against a header <NUM> (that is stationary during the tooling process). A second tool <NUM> provides proper course alignment for placing the sub-mount or carrier wafer. In <FIG>, a subassembly <NUM> with pre-formed breaks (as discussed above with reference to <FIG>) - or alternatively a wafer <NUM> pre-formed with breaks (as discussed above with reference to <FIG>) - is positioned on top of the space next to the thermo-cooler <NUM> and on top of the optical platform <NUM>. At this point epoxy may be used to secure the sub-mount <NUM> to the spacer <NUM> and optical platform <NUM>. Curing can be performed in the fixture.

After curing, the portion of the subassembly <NUM> between the breaks is broken (i.e., cracked) under controlled conditions. This may be performed by a controlled tooling split or controlled stress exposure to a weak area of the sub-mount. Whatever the case, the middle portion of the sub-mount <NUM> (or wafer, if using a wafer configuration) can be removed or will fall away, as shown in <FIG>. Next, as illustrated in <FIG>, the tooling members <NUM>, <NUM> have been removed, along with the optical platform <NUM>, thus leaving the header <NUM> stabilized in the fixture with the TEC <NUM>, laser sub-mount <NUM>, and spacer <NUM>. With this increased access, a thermistor <NUM> may be added for heat monitoring and wire bonding may occur.

Following the completion of the wiring of the laser sub-mount <NUM> according to <FIG>, a hermetic sealing step (either projection weld or laser seam sealing) will secure the front cover <NUM> of the optical sub-assembly <NUM> to the header <NUM>. Tooling member <NUM> and tooling member <NUM> may be used during this step. As previously described, the optical sub-assembly comprises a window cap <NUM> for sending laser light/signals. At this time, the enclosure of the sub-assembly <NUM> can be hermetically sealed by soldering or welding around the joint between the front cover <NUM> and the TO-header <NUM>. After sealing <NUM> to <NUM>, tooling <NUM>, <NUM> and <NUM> are joined together again. Notably, splitting and re-joining of tooling <NUM>, <NUM> and <NUM> can be done repeatedly and precisely if designed right such that optical coupling between laser sub-mount <NUM> and modulator sub-mount <NUM> is maintained without additional active re-alignment. Finally optical bench <NUM> and header <NUM> can be joined at interface 1350A and 1350B to secure alignment permanently (attach methods could be soldering, laser welding or adhesive attach). The optical communication device <NUM> can then be removed from the clasp and additional parts (such as a PCB board and optical connector) can be added as required.

Optionally, one way of joining header <NUM> to optical bench <NUM> is to rely on tooling maintaining the optical alignment between laser sub-mount <NUM> and modulator sub-mount <NUM>. This could be advantageous during manufacturing because it is faster and less expensive due to the avoidance of additional alignment steps. However, because optical coupling could be compromised, there could be applications where this is acceptable, while other applications are less forgiving and require highest possible coupling. In those cases, after sealing of front cover <NUM> to header <NUM>, an additional active multiple access alignment step could be required between header <NUM> and optical bench <NUM> before both parts are joined at interface 1350A and 1350B.

In yet another implementation of the inventive optical communication device <NUM> shown in <FIG>, an input lens array <NUM> could be used in combination with an angled reflector <NUM> to direct the optical signals into the modulator <NUM>. The input array <NUM> receives laser light (here shown as receiving four laser beams shown as dashed lines) from the laser sub-mount. The modulator <NUM> would then modulate the light (by encoding data and multiplexing) the laser inputs and would in turn send a single light beam to the optical network. In <FIG>, the laser output lens (or lenses) <NUM> for the modulator <NUM> may be placed proximate to the optical connector <NUM>. However, as shown in <FIG>, this may also be done by using an angled reflector that bends the light <NUM> degrees and directs it to the optical interface/receptacle <NUM> that interfaces with the optical network. As such, various implementations are envisioned for processing laser signals once coupled to the modulator <NUM>, and the specific steps of processing performed by a photonic modulator <NUM> are not mandated by this disclosure. As such, the inventive optical communication device <NUM> is not limited to any specific type or method of optical processing.

<FIG> illustrate yet another tooling of an optical communication device <NUM><NUM> according to an implementation of the manufacture of the invention. In <FIG>, a pre-formed tool <NUM> holds the optical platform <NUM> in place against a header <NUM> (that is stationary during the tooling process). A second tool <NUM> provides proper course alignment for placing the sub-mount or carrier wafer.

In <FIG>, a wafer <NUM> with pre-formed breaks (as discussed above with reference to <FIG>) - or alternatively a silicon chip with pre-formed breaks (as discussed above with reference to <FIG>) - is positioned on top of the space next to the thermo-cooler <NUM> and on top of the optical platform <NUM>. As shown, the optical platform <NUM> has a pre-formed area to insert a modulator <NUM> for proper alignment. At this point epoxy may be used to secure the wafer <NUM> (with sub-mount portions) to the TEC <NUM> and optical platform <NUM>. Curing can be performed in the fixture.

After curing, the portion of the wafer <NUM> between the pre-formed breaks is cracked under controlled conditions. This may be performed by a controlled tooling split or controlled stress exposure to a weak area of the sub-mount. Whatever the case, the middle portion of the wafer <NUM> (or chip, if using a silicon sub-mount configuration) can be removed or will fall away, as shown in <FIG>. The tooling members <NUM> and <NUM> are then removed, along with the optical platform <NUM>. leaving the header <NUM> stabilized in the fixture with the TEC <NUM> and laser sub-mount portion <NUM>. With this increased access, a thermistor may be added for heat monitoring and wire bonding may occur.

Following the completion of the wiring of the laser sub-mount portion <NUM>, a hermetic sealing step (either projection or weld or laser seam sealing) will secure the front cover <NUM> of the optical sub-assembly <NUM> to the header <NUM> as shown to the right in <FIG>. Tooling member <NUM> and tooling member <NUM> may then be re-inserted as shown in <FIG>. Notably, splitting and re-joining of tooling members <NUM>, <NUM> and <NUM> can be done repeatedly and precisely if designed right such that optical coupling between sub-mount portions <NUM> and <NUM> is maintained without additional active re-alignment.

As previously described, the optical sub-assembly comprises a window cap <NUM> for sending laser light/signals. As shown in <FIG>, right side, the enclosure of the sub-assembly <NUM> can be hermetically sealed by soldering or welding around the joint between the front cover <NUM> and the TO-header <NUM>. After sealing cover <NUM> to header <NUM>, tooling members <NUM> and <NUM> and <NUM> are joined together again. Finally optical bench <NUM> and header <NUM> can be joined at their interfaces to secure alignment permanently (attach methods could be soldering, laser welding or adhesive attach). The optical communication device <NUM> can then be removed from the clasp and additional parts (such as a PCB board and optical connector) can be added as required as shown in <FIG>.

As noted, the optical communication device <NUM> may comprise a number of different implementations. <FIG> illustrates yet another example of the optical communication device <NUM> according to another implementation of the invention. In this configuration, a window cap <NUM> is again used to transmit laser light from inside the hermetically enclosed sub-assembly <NUM>. As shown in <FIG>, a lid <NUM> may be used to seal the sub-mounted lasers after they are inserted in the cover <NUM> during the manufacturing process. Electrical leads 1625A-N (e.g., made from low cost hermetic glass/metal seal) may be used to provide electrical input to the lasers, which may be part of a laser-sub-mount, such as the sub-mount portion <NUM> shown in <FIG>. A modulator portion <NUM> may then be positioned on an optical bench <NUM> outside of the sub-assembly <NUM> to receive the laser light through the window cap <NUM>. As described previously, the modulator portion <NUM> may then modulate signals using the light and utilize an interface (not shown) to access an optical network.

As shown in <FIG>, the TEC <NUM> is horizontal in this implementation, allowing height adjustments to be performed as previously noted with reference to <FIG>. However, in this specific example optical bench <NUM> can be height adjusted by moving <NUM> up or down with reference to the optical sub-assembly <NUM> and, in particular, the window cap <NUM>, which are stationary. Once the right height is found, optical bench/platform <NUM> can be permanently attached to the hermetically sealed sub-assembly <NUM> and window cap <NUM> with laser welding as indicated with arrows in <FIG>.

Further, to achieve highest optical coupling, individual lasers 120A-N can be aligned, as a last step, to the modulator <NUM> rather than using a lens array <NUM> like the one shown in <FIG>. That way optical misalignment of the multiple collimated beams to each other can be compensated and maximum coupling can be achieved. However, if applications allow for less perfect alignment conditions, then the more efficient lens array <NUM> could be used instead.

Alternatively, to recover coupling loss in instances where, for example, optical coupling shifted too much following the window cap weld, an optical flat (or window) may be used in the optical subassembly. This may be beneficial since the window in the window cap may not be perfectly aligned <NUM>-degrees, but may have some random distribution in the range of +/- <NUM> degrees. Such a situation introduces beam walk (vertically to optical beam) in the range of <NUM> to <NUM>. Accordingly, adding an optical flat and tilting it in an opposite way to the random tilt of the window may be used to beneficially recover the coupling loss due to beam walk. As such, a flat window of thickness "h" can be inserted into the collimated beam between the TO and waveguide and the flat window can be tilted and secured to shift the beam by distance "d". In addition, a secondary recovery mode could be used to recover optical tilt introduced by uncontrolled shift during the sub-assembly to platform attachment. In this optional configuration, a single/double wedge/prism could be used to recover loss and bend the collimated beam back to center (similar to that described with reference to the lens array <NUM>).

In accordance with the above description. <FIG> illustrates an example method <NUM> of using an efficient optical device. At step <NUM>, a hermetically sealed optical sub-assembly receives an electrical input. This input may be generated from an outside source or a source residing at the sub-assembly. At step <NUM>, one or more lasers are fired within the hermetically sealed optical sub-assembly. As noted herein, this laser or lasers reside on a sub-mount and are affixed to a thermo-cooler. At step <NUM>, the laser beam generated from the laser is then received outside the hermetically sealed sub-assembly at a modulator. At this point, the modulator may or may not act on the beam to generate a signal for use in an optical communication network. In either case, however, at step <NUM> the beam is directed through the modulator and output to an optical communication network. As noted, any number and type of optical connectors may provide access for the device to communicate with the optical network.

Further, in accordance with the above described manufacturing process, <FIG> provides an example method of manufacturing an optical communication device according to one implementation of the invention. At step <NUM>, a laser sub-mount is positioned on a carrier wafer adjacent to a first pre-defined break in a carrier wafer. (As noted previously, in another implementation not shown in method <NUM>, pre-defined breaks may be instead made in a single sub-mount that can carry both a laser portion and a modulator portion in lieu of using a carrier wafer. ) At step <NUM>, a modulator sub-mount is then positioned adjacent to a second pre-defined break in the carrier wafer.

In both instances, the sub-mounts may be glued or otherwise fixably attached to the carrier wafer. Further, to ensure proper alignment before or after adhesion material is applied, a jaw tool or inverted pyramid tool (as disclosed herein) may be used to align the two sub-mounts. After the modulator sub-mount is fixed, the laser-sub-mount (via the carrier wafer or in addition to the carrier wafer) is secured to a thermo-electrical cooler at step <NUM>. Likewise, at step <NUM>. the modulator sub-mount (via the carrier wafer or in addition to the carrier wafer) may be secured to an optical platform to hold the sub-assembly and modulator components in place.

Once these sub-mounts are secured, the portion of the carrier wafer between the two sub-mounts may be broken or cut away and removed at step <NUM>. As discussed herein, the modulator section may optionally then be removed to allow tooling access to the thermo-electrical cooler and laser sub-mount. In any event, as noted at step <NUM>, the laser sub-mount and at least a portion of the thermo-electrical cooler is sealed inside a hermetically sealed sub-assembly that contains a window for communicating between the laser sub-mount and modulator sub-mount. In particular, the window allows a laser beam to be fired from a laser on the hermetically sealed sub-mount and received by an input on the modulator that is not hermetically scaled. To achieve this, any of the alignment techniques disclosed herein may be used.

Claim 1:
An apparatus comprising:
a hermetically sealed component (<NUM>);
a sub-mount mounted on a spacer (<NUM>);
a laser (<NUM>) disposed within the hermetically sealed component and mounted on the sub-mount;
a thermo-electrical cooler (<NUM>) connected to the spacer (<NUM>) and disposed within the hermetically sealed component and configured to dissipate heat generated by the laser;
a gap (<NUM>) between the sub-mount and the thermo-electrical cooler; and
a window (<NUM>) forming part of the hermetically sealed component and configured to permit transmission of a light beam between the laser and an optical input (<NUM>) situated outside the hermetically sealed component,
wherein the sub-mount is made of silicon and the spacer is made of ceramic or other material intended to dissipate heat from the sub-mounted laser.