Patent Description:
Optical communications use modulated light beams to convey information through optical fibers, free space, or waveguides. A beam of light can be modulated either directly by modulating current to a light source, or externally by using an optical modulator to modulate a continuous-wave light beam produced by the light source. External modulation has advantages in that it can handle higher power and frequencies; however, the required components can be larger, more complex, and more expensive. <CIT> discloses an optical device including a first substrate, having first and second surfaces, and a second substrate having a third surface. The first substrate includes: a laser unit, having an active layer and emitting light into the first substrate from the active layer; a reflecting mirror, having a plane obliquely intersecting an optical axis of light emitted from the laser unit, and being formed on the first surface so as to reflect the light toward the second surface; and a convex lens, being formed in a region on the second surface, the region including an optical axis of the light reflected by the reflecting mirror. The second substrate is provided with a grating coupler and an optical waveguide on the third surface, the optical waveguide having light incident on the grating coupler propagating therethrough. <CIT> discloses an optical package including a semiconductor laser, a wavelength conversion device and a MEMS-actuated mirror oriented on a base module to form a folded optical pathway between an output of the semiconductor laser and an input of the wavelength conversion device. An optical assembly is located in a mechanical positioning device and the mechanical positioning device is disposed on the base module along the optical pathway such that the beam of the semiconductor laser passes through the optical assembly, is reflected by the MEMS-actuated mirror back through the optical assembly and into the waveguide portion of the wavelength conversion device. The MEMS-actuated mirror is operable to scan the beam of the semiconductor laser over the input of the wavelength conversion device. The optical assembly may be adjusted along the optical pathway with the mechanical positioning device to focus the beam into the waveguide portion of the wavelength conversion device.

The claimed subject-matter is defined in independent claims <NUM> and <NUM>.

This disclosure generally relates to an integrated optical assembly for coupling a beam of light into a photonic integrated circuit (PIC) using an adjustable mirror. The assembly can include the laser light source, optical components such as a lens and an optical isolator, the mirror, and a PIC having an optical grating coupler for coupling the laser into the PIC. The PIC can include a waveguide to receive the light from the grating coupler. The PIC can additionally include power splitters, monitor photodiodes, and a modulator for modulating the light.

A grating coupler is an optical device that can couple light traveling in free space or an optical fiber into a waveguide (or vice-versa). The grating coupler is a diffractive element with a limited optical bandwidth over which it can efficiently couple light into or out of the waveguide. Furthermore, optical grating couplers with large mode field diameters may have even narrower bandwidths. Process variations in the fabrication of the grating coupler can result in variation of the center wavelength from one grating coupler to another. In addition, the angle of incidence of light impinging on the grating coupler also affects the center wavelength; e.g., a steeper angle of incidence may result in a shorter center wavelength. Process variations in the assembly can also affect the angle of incidence of light on the grating coupler. Such process variations can include, for example and without limitation, position of the light source, lens, mirror, and grating coupler. In addition, the wavelength of light generated by the light source itself may vary. For example and without limitation, optical communication systems using wavelength-division multiplexing may employ wavelengths ranging from <NUM> to <NUM>.

An integrated optical assembly can compensate for the variations in processes and light wavelength by taking advantage of the relationship between center wavelength of the grating coupler and the angle of incidence of light impinging on the grating coupler. For example, instead of a fixed reflector such as a prism, mirror, or polished fiber tip, the integrated optical assembly can include an adjustable mirror for redirecting the laser onto the grating coupler. The adjustable mirror can be a microelectromechanical system (MEMS) mirror that can be adjusted using, for example, electrostatic actuators controlled by a controller using feedback from a monitor photodiode on the PIC. In some implementations, the mirror can include other small form-factor mirrors; for example, the mirror can include a reflective surface glued or otherwise affixed to one or more laser-cut sheet metal shims. In some implementations, the mirror can remain free to move for the service life of the assembly such that future adjustments can be made.

Use of a MEMS mirror allows for miniaturization of the integrated optical assembly. The size of the entire integrated optical assembly can be on the order of a few millimeters in its longest dimension. This can make the integrated optical assembly appropriate for use in, for example, a data communications transceiver. In addition, the presence of the MEMS mirror allows the other components to be fixed to each other in a mass production environment, with alignment adjustments to be made using the mirror. This allows for a simpler fabrication process with wider tolerances, which can reduce the overall cost of the device.

<FIG> is a graph <NUM> of an example relationship of loss versus wavelength for light coupling into an optical grating coupler. Optical grating couplers can be used to couple light traveling in free space or an optical fiber into a waveguide, and vice-versa. Optical grating couplers are therefore useful in optical communications for coupling light into and out of photonic integrated circuits (PICs) in optical transmitters, receivers, and transceivers. An optical grating coupler may include surface features such as lines or ridges that create an interface suitable for receiving or emitting an optical signal. Such an optical grating coupler is a resonant device; therefore, it will couple optical signals of a certain bandwidth around a center wavelength. The center wavelength and bandwidth are functions of the dimensions of the surface features of the optical grating coupler.

The graph <NUM> illustrates an example relationship of loss versus wavelength for coupling light into an optical grating coupler. The wavelength at which the grating coupler is most efficient-i.e., least lossy-is referred to as the center wavelength. The grating coupler can couple light with a reasonable efficiency across a finite bandwidth (BW) around the center wavelength. The bandwidth can be defined as a range of wavelengths of light over which coupling loss is less than, for example, 1dB, 3dB, or 6dB greater than the coupling loss at the center wavelength.

<FIG> is a graph <NUM> of example relationships of loss versus wavelength for coupling light into three different optical grating couplers. Because optical grating couplers are resonant devices with a center wavelength that depends on its surface features, process variations in the fabrication of optical grating couplers can result in variation of the center wavelength from one optical grating coupler to another. The graph <NUM> illustrates example relationships of loss versus wavelength for optical grating couplers <NUM>, <NUM>, and <NUM>. For example, grating coupler <NUM> has a center wavelength <NUM>, grating coupler <NUM> has a center wavelength <NUM>, and grating coupler <NUM> has a center wavelength <NUM>. Thus, even though optical grating couplers may be manufactured for a particular wavelength, process variation can result in optical grating couplers having center wavelengths that vary from the desired wavelength. For example, the pitch or spacing of the surface features can affect the resonant behavior of the optical grating coupler, and thus the center wavelength. Without a way to compensate for the center wavelength variation among optical grating couplers, the devices employing them may not operate as efficiently as they could.

<FIG> is a graph <NUM> of an example relationship of optimum wavelength versus angle of incidence for coupling light into an optical grating coupler. The graph <NUM> shows that the center wavelength for optimum coupling of light into an optical grating coupler can vary based on the angle of incidence. For example, at an angle of incidence of <NUM> degrees from normal to the surface of the optical grating coupler, the optimum (center) wavelength for efficient coupling of light will be approximately <NUM>. At an angle of incidence of <NUM> degrees, the optimum wavelength will be approximately <NUM>. This relationship between angle of incidence and center wavelength can lead to an additional source of variation in center wavelength among devices. For example, the relative positioning of the optical grating coupler, light source, lens, and mirror can affect the angle of incidence, and thus the center wavelength of the system. Slight variations in the alignment of the lens from device to device can result in variations in the angle of incidence of the beams of light on the respective optical grating couplers. The variation in the angle of incidence among devices should, all things being equal, result in a corresponding variation in the center wavelength of each device, even though each device is manufactured to operate at the same center wavelength.

The graph <NUM> shows, however, that the relationship between the angle of incidence and the optimum wavelength behaves substantially linearly. This relationship can therefore be exploited to adjust the angle of incidence and potentially compensate for variations in grating coupler surface features and the relative positions of system components. For example, the system can include a moveable mirror or reflector. The mirror angle can be adjusted to set the angle of incidence of light impinging on the grating coupler. The mirror angle can therefore be adjusted to set the angle of incidence in a manner that tunes the center wavelength of the system to the desired wavelength. For example, in some implementations, the wavelength of the light beam is <NUM>. Using the example measurements in the graph <NUM>, the center wavelength of the system can be set to <NUM> by adjusting the mirror such that the angle of incidence of light on the optical grating coupler is roughly <NUM> degrees. The exact angle of incidence for efficient coupling of light into the optical grating coupler may depend on the dimensions of the grating coupler surface features. Similarly, the mirror angle to achieve the desired angle of incidence may depend on the relative position of other components of the integrated optical assembly. In both cases, the angle of the mirror can be used to optimize the angle of incidence for efficient coupling at the center wavelength. The graph <NUM> represents just one example of a relationship between angle of incidence and optimum wavelength. Other grating couplers will exhibit different relationships depending on their geometry and physical properties.

<FIG> is a block diagram of an integrated optical assembly <NUM>, according to illustrative implementations. The assembly <NUM> includes an optics mount <NUM> and a photonic integrated circuit (PIC) <NUM>. The optics mount <NUM> has disposed thereon a light source <NUM>, a lens <NUM>, and, in some implementations, an optical isolator <NUM>. The PIC <NUM> includes an optical grating coupler <NUM>. The assembly <NUM> includes a microelectromechanical system (MEMS) mirror <NUM> mounted to either or both of the optics mount <NUM> and the PIC <NUM>. The integrated optics assembly <NUM> can function as an externally modulated laser, providing a modulated optical signal <NUM>. A controller <NUM> can execute certain operations of the integrated optical assembly <NUM> such as controlling a position of a reflective portion of the mirror <NUM>. For example and without limitation, the controller <NUM> can be used to adjust or optimize light coupling over the lifetime of the device, including adjusting to compensate for thermal expansion or contraction of components of the integrated optical assembly <NUM>.

In some implementations, the optics mount <NUM> can include silicon or be fabricated from one or more silicon blocks or wafers. In some implementations, the optics mount <NUM> can include an antireflective (AR) coating <NUM> on a top and/or bottom side in regions passing a light beam <NUM>. The AR coating can include a multi-layer hard oxide coating that includes silicon dioxide (SiO2) and hafnium dioxide (HfO2). The light source <NUM> can be mounted to the optics mount <NUM> with solder <NUM>; for example, gold/tin solder. The lens <NUM> and optical isolator <NUM> can be mounted to the optics mount <NUM> with a layer of epoxy <NUM>. The optics mount <NUM> can itself be mounted to the PIC <NUM> with a layer of epoxy <NUM>. The epoxy can be of a type having high transparency. For example, in some implementations, the epoxy can be a UV-curable optical path link up epoxy.

In some implementations, the optics mount <NUM> can be between approximately <NUM> and <NUM> long. In some implementations, the optics mount <NUM> can be approximately <NUM> long. In some implementations, the optics mount <NUM> can be between approximately <NUM> to <NUM> wide. In some implementations, the optics mount <NUM> can be approximately <NUM> wide. In some implementations, the optics mount <NUM> can be between approximately <NUM> to <NUM> tall. In some implementations, the optics mount <NUM> can be approximately <NUM> tall. In some implementations, the optics mount <NUM> can include two wafers: the first wafer extending the length of the optics mount <NUM>, and a second wafer under the region of the light source <NUM> to align the output of the light source <NUM> with the axis of the lens <NUM>. In some implementations, the first wafer can be between approximately <NUM> and <NUM>. In some implementations, the first wafer can be approximately <NUM> tall. In some implementations, the second wafer can be between approximately <NUM> and <NUM> tall. In some implementations, the second wafer can be approximately <NUM> tall. The lens <NUM> and optical isolator <NUM> can extend above the height of the first wafer of the optics mount <NUM>. In some implementations, the lens <NUM> and optical isolator <NUM> can add between approximately <NUM> and <NUM> in height above the first wafer of the optics mount <NUM>. In some implementations, the lens <NUM> and optical isolator <NUM> can add approximately <NUM> in height above the first wafer of the optics mount <NUM>.

In some implementations, the PIC <NUM> can be between approximately <NUM> and <NUM> tall. In some implementations, the PIC <NUM> can be approximately <NUM> tall. In some implementations, the PIC <NUM> can be less than or equal to <NUM> tall. In some implementations, the PIC <NUM> can be between approximately <NUM> and <NUM> long. In some implementations, the PIC <NUM> can be approximately <NUM> long. In some implementations, the PIC <NUM> can be between approximately <NUM> and <NUM> wide. In some implementations, the PIC <NUM> can be approximately <NUM> wide. These dimensions of the components of the integrated optical assembly <NUM> can allow it to fit into a typical data communications transceiver module.

The light source <NUM> can produce a continuous-wave beam of light <NUM> with a narrow bandwidth. In some implementations, the light source <NUM> can be a laser diode in die form. In some implementations, the diode die can be mounted p-side down. In some implementations, the diode die can be mounted p-side up. The light source <NUM> can be soldered to electrical contacts or pads on the surface of the optics mount <NUM>. The electrical contacts can provide electrical current to the light source <NUM>. In some implementations, the light source <NUM> can be a distributed feedback laser. A distributed feedback laser is a type of laser with an active region that includes a diffraction grating. The grating can reflect light at a particular wavelength to form the resonator. Distributed feedback lasers can be susceptible to interference from external light, however. For example, any light reflected back from the optical grating coupler can interfere with the laser and cause it to become unstable. Therefore, in some implementations, the optics mount <NUM> can include an optical isolator <NUM>. The optical isolator <NUM> can pass the light beam <NUM> in a first direction, but block any light from passing in the reverse direction back toward the light source <NUM>. For example, the optical isolator <NUM> can block light reflecting back from the interface between free space and the optics mount <NUM>, the interface between the optics mount <NUM> and the PIC <NUM>, and/or the surface of the grating coupler <NUM> and redirected by the mirror <NUM> back towards the light source <NUM>. In some implementations, the optical isolator can be a latching garnet Faraday rotator-based micro-optical isolator.

The lens <NUM> can include a lens or a lens assembly for focusing the light beam <NUM> onto the grating coupler <NUM> either directly or indirectly (via one or more reflections). The lens can be mounted on the optics mount <NUM> using epoxy <NUM>. In some implementations, the lens <NUM> can be mounted on the optics mount <NUM> indirectly via one or more brackets or mounts.

The mirror <NUM> redirects the light beam <NUM> towards the optical grating coupler <NUM>. The mirror <NUM> includes a controllable element that can adjust the tilt or position of a reflective portion of the mirror to set the desired angle of incidence of the light beam <NUM> on the optical grating coupler <NUM>. The mirror <NUM> is a microelectromechanical system (MEMS) mirror. The mirror <NUM> can include one or more actuators that can adjust the tilt or position of the reflective portion of the mirror <NUM> based on a supplied voltage or current. In some non-claimed implementations, the tilt or position of the reflective portion can be adjusted about one axis. According to the invention, the tilt or position of the reflective portion is adjusted about two orthogonal or nearly orthogonal axes. Tilting of the reflective portion may be substantially rotational, but may also include a degree of incidental vertical or lateral movement due to interactions between actuators and supporting elements. The reflective portion of the mirror <NUM> can receive the light beam <NUM> via free space (i.e., air or other gas), and redirect it through the same. When the beam of light <NUM> enters the optics mount <NUM>, however, it can experience refraction due to the change in refractive index. For example, the refractive index of air is very close to <NUM>, while the refractive index of silicon can be approximately <NUM>. In some implementations, the anti-reflective (AR) coating <NUM> can include one or more layers of materials with indices of refraction between that of silicon and air; for example, the multi-layer hard oxide coating described previously. The angle of the mirror <NUM> as well as its position relative to the optical grating coupler <NUM> can be set to take into account this refraction and ensure the light beam <NUM> focuses on the optical grating coupler <NUM>. The mirror <NUM> is described in more detail below with regard to <FIG>.

The PIC <NUM> includes the optical grating coupler <NUM>, which receives the light beam <NUM> from the mirror <NUM>. The PIC <NUM> can include a modulator for modulating the continuous wave light beam <NUM> coupled into the optical grating coupler <NUM>. The modulated signal can exit the PIC <NUM> as the optical signal <NUM> conveying data across an optical link. The PIC <NUM> and its components are described in detail below with regard to <FIG>.

The controller <NUM> can include programmable logic such as a field-programmable gate array (FPGA), a microcontroller, or a microprocessor. The controller <NUM> can be integral with, or external to the integrated optical assembly <NUM>. The controller <NUM> can include a memory and interfaces for interacting with other components of the integrated optical assembly <NUM>. The controller <NUM> can include interfaces for receiving commands and transmitting status information via display, audio, input, and networking devices. The controller <NUM> can aid in performing adjustment or calibration operations involving positioning of the mirror <NUM>. In some implementations, the controller <NUM> can include drivers (not shown) for providing analog voltage signals to the mirror <NUM> for controlling the position of the reflective portion of the mirror <NUM>. In some implementations, the drivers for providing the analog voltage signals can be physically separate from the controller <NUM>, and either adjacent to or integrated with the mirror <NUM>. In some implementations, the drivers can include digital-to-analog convertor (DAC) for converting a digital signal from the controller <NUM> into an analog voltage suitable for controlling the position of the reflective portion of the mirror <NUM>. In some implementations, the drivers can include voltage amplifiers for amplifying relatively low-voltage (e.g., several volts) control and/or logic signals from the controller <NUM> to the relatively higher voltage (e.g., tens of volts) used to control electrostatic actuators of the mirror <NUM>. In some implementations, the drivers can include current amplifiers for actuating magnetic actuators. The current amplifier can convert digital or analog voltages into currents adequate for magnetic actuation of the reflective portion of the mirror <NUM> (e.g., tens or hundreds of milliamps).

<FIG> is a block diagram of a photonic integrated circuit (PIC) <NUM> for use in an integrated optical assembly <NUM>, according to illustrative implementations. In the assembly <NUM>, the PIC <NUM> can be positioned underneath the optics mount <NUM>. The outline <NUM> represents the outline of the optics mount <NUM> relative to the PIC <NUM> in this example implementation. Electrical connections are omitted for clarity.

The PIC <NUM> can receive the light beam <NUM> at the optical grating coupler <NUM>. The optical grating coupler <NUM> couples the light beam <NUM> into the waveguide <NUM>. The waveguide <NUM> conveys the light to the modulator <NUM>, which modulates the continuous-wave light to create and optical signal that can be used to transmit data. The waveguide <NUM> receives the modulated optical signal from the output of the modulator <NUM> and conveys it to an edge coupler <NUM> adjacent to a side of the PIC <NUM>. The edge coupler <NUM> can transmit the optical signal <NUM> into another medium; for example, an optical fiber or another waveguide external to the PIC <NUM>.

In some implementations, the PIC <NUM> can include means for measuring the amplitude of light coupled into the optical grating coupler <NUM>. For example, the PIC <NUM> can include a monitor photodiode <NUM>. The monitor photodiode <NUM> can include a light-sensitive device such as a photodiode, which can convert an optical signal received from a tap on the waveguide <NUM> or <NUM> to an electrical signal that varies in relation to the amplitude of the optical signal. In some implementations, the modulator <NUM> can have two output waveguides. In such implementations, each output waveguide can have a separate monitor photodiode <NUM>. The signals of the respective monitor photodiodes <NUM> can be summed. The controller <NUM> can receive the electrical signal[s] and use it to determine the efficiency of coupling light into the optical grating coupler <NUM>. The controller <NUM> can further provide voltages or currents to set a position of the mirror <NUM>. Using the electrical signal from the monitor photodiode <NUM> as feedback, the controller <NUM> can adjust the position of the mirror <NUM> to achieve a certain angle of incidence of the light beam <NUM> on the optical grating coupler <NUM>. The controller can adjust mirror <NUM> position, and by extension the angle of incidence, to increase the efficiency of coupling light into the optical grating coupler <NUM>.

In some implementations, the integrated optical assembly <NUM> can include a tap on the waveguide output of the modulator <NUM>. An additional grating coupler or edge coupler can receive light from the tap and direct it to an external monitor photodiode. The controller <NUM> can receive an electrical signal from the external monitor photodiode and use it to determine the efficiency of coupling of the light beam <NUM> into the PIC <NUM>.

In some implementations, the integrated optical assembly <NUM> can include one or more additional monitor photodiodes on the optics mount <NUM>. This additional monitor photodiode can be positioned adjacent to the light source <NUM> to provide direct measurements of performance that are decoupled from mechanical shifts of intermediary components such as the lens <NUM>, isolator <NUM>, and mirror <NUM>, as well as changes in alignment between the optics mount <NUM> and the PIC <NUM>. These measurements can be helpful to, for example, monitor the health of the light source <NUM> to detect degradation of output power over time. The additional monitor photodiode can be used in place of external monitor photodiodes during the burn-in manufacturing step of the optics mount <NUM> assembly process.

<FIG> is a diagram of a two-axis microelectromechanical system (MEMS) mirror assembly <NUM> for use in an integrated optical assembly, according to an illustrative implementation. The mirror assembly <NUM> includes three main components: a mirror platform <NUM>, a gimbal <NUM>, and a mirror substrate <NUM>. The mirror platform <NUM>, gimbal <NUM>, and mirror substrate <NUM> are disposed above a base substrate (not shown). The mirror platform <NUM> can include a reflective surface and/or coating on its upper side. The mirror assembly <NUM> includes actuators for moving the components. In the implementation shown in <FIG>, the mirror assembly <NUM> can be actuated in two dimensions. The actuators 520a and 520b (collectively "actuators <NUM>") can move the mirror platform <NUM> with respect the gimbal <NUM>, and the actuators 525a and 525b (collectively "actuators <NUM>") can move the gimbal <NUM> and the mirror platform <NUM> with respect to the mirror substrate <NUM>.

In some implementations, the actuators <NUM> and <NUM> can apply torque to their inner component. For example, the actuators <NUM> can apply torque to rotate the mirror platform <NUM> to cause rotation in the X-Z plane (i.e., about the Y-axis), and the actuators <NUM> can apply torque to rotate the gimbal <NUM> to cause rotation in the Y-Z plane (i.e., about the X-axis). In this manner, the actuators <NUM> and the actuators <NUM> can move the mirror platform <NUM> about a first axis and a second axis, respectively, where the axes are substantially orthogonal to each other.

In some implementations, the actuators <NUM> and <NUM> can be vertical comb-drive electrostatic actuators. Each actuator <NUM> and <NUM> can have a first part and a second part; for example, the actuators <NUM> can have a left side and a right side, and the actuators <NUM> can have a top side and a bottom side, as oriented in the drawing. A first voltage applied to the first part of the actuator can cause the actuator to move the mirror platform <NUM> in a first direction. In some implementations, the first direction can be a rotational direction about an axis of motion of the mirror platform <NUM>. A second voltage applied to the second part of the actuator can cause the actuator to move the mirror platform in a second direction opposite the first direction. For example, the first voltage applied to the first part of the actuators 520a may cause the mirror platform <NUM> to move clockwise around the Y-axis, and the second voltage applied to the second part of the actuators 520a may cause the mirror platform <NUM> to move counterclockwise around the Y-axis.

<FIG> is a diagram of a non-claimed single-axis microelectromechanical system (MEMS) mirror assembly <NUM> for use in an integrated optical assembly, according to an illustrative implementation. The mirror assembly <NUM> includes a mirror platform <NUM> suspended in or over a cavity defined in a mirror substrate <NUM> by a torsion beam <NUM>. The torsion beam <NUM> allows the mirror platform <NUM> to move rotationally in one dimension; i.e., the Y-Z plane. The mirror platform <NUM> can include a reflective layer or surface on its top side. The mirror platform <NUM> can rotate relative to the mirror substrate <NUM> under the influence of one or more actuators (not shown). In some implementations, the mirror platform <NUM> can be positioned with the aid of one or more external drivers. An external driver may include an electrostatic, piezo, thermal, or magnetic actuator. The actuators can receive a control voltage or current and set a position of the mirror platform <NUM>. In some implementations, the mirror assembly <NUM> can be miniaturized. For example, the mirror assembly <NUM> can be embodied in a discrete device having dimensions less than a millimeter in the x, y, and z directions. In some implementations, the mirror assembly <NUM> can be a discrete device having dimensions less than <NUM> in the x, y, and z directions.

In some implementations, the mirror platform <NUM> can be positioned via means external to the mirror assembly <NUM>. For example, a rod or hook can be used to adjust the position of the mirror platform <NUM> while coupling of light into the PIC <NUM> is monitored. In some implementations, the mirror platform <NUM> can be moved using magnetic forces.

<FIG> is a flowchart of an example method <NUM> of manufacturing an integrated optical assembly, according to an illustrative implementation. The method <NUM> includes providing an optics mount having disposed thereon a light source for providing a beam of light and a lens configured to focus the beam of light (stage <NUM>). The method <NUM> includes providing a photonic integrated circuit (PIC) having disposed thereon a grating coupler for receiving the beam of light and coupling the beam of light into a waveguide (stage <NUM>). The method <NUM> includes providing a microelectromechanical systems (MEMS) mirror configured to receive the beam of light from the lens and redirect it towards the grating coupler (stage <NUM>). The method <NUM> includes assembling the optics mount, the MEMS mirror, and the PIC into the integrated optical assembly (stage <NUM>). In some implementations, the method <NUM> includes calibrating he position of the MEMS mirror to increase coupling of the beam of light into the waveguide (stage <NUM>).

The method <NUM> includes providing an optics mount having disposed thereon a light source for providing a beam of light and a lens configured to focus the beam of light (stage <NUM>). The optics mount can be similar to the optics mount <NUM> described with respect to <FIG>. Likewise, the light source can be similar to the light source <NUM>, and the lens can be similar to the lens <NUM>. The light source <NUM> can be bonded or otherwise mounted to the optics mount <NUM> using a solder <NUM> or adhesive. The lens <NUM> can be fixed to the optics mount <NUM> via a combination of an adhesive and/or a bracket or mount. The light source <NUM> and lens <NUM> are arranged such that the light source <NUM> can direct a beam of light towards the lens <NUM>.

The method <NUM> includes providing a photonic integrated circuit (PIC) having disposed thereon a grating coupler for receiving the beam of light and coupling the beam of light into a waveguide (stage <NUM>). The PIC can be similar to the PIC <NUM> described with respect to <FIG> and <FIG>. Likewise, the grating coupler can be similar to the optical grating coupler <NUM>.

The method <NUM> includes providing a microelectromechanical systems (MEMS) mirror configured to receive the beam of light from the lens and redirect it towards the grating coupler (stage <NUM>). The mirror can be similar to the mirror <NUM> described with respect to <FIG>, including the mirror assemblies <NUM> and <NUM> described with respect to <FIG>. The mirror <NUM> can be mounted or attached to the optics mount <NUM>. In some implementations, the mirror <NUM> or <NUM> can include one or more actuators for adjusting a position of the MEMS mirror to affect an angle of incidence of the beam of light on the grating coupler <NUM>.

The method <NUM> includes assembling the optics mount, the MEMS mirror, and the PIC into the integrated optical assembly (stage <NUM>). The optics mount <NUM> and the PIC <NUM> can be joined and bonded using an adhesive such as epoxy or solder balls applied via a solder shooter, or by mechanical fasteners such as bolts or clamps. The mirror <NUM> can be joined to the optics mount <NUM> and/or the PIC <NUM>. The mirror <NUM> can be fixed in position such that it can receive the light beam <NUM> from the light source <NUM> and lens, and redirect the light beam <NUM> through the optics mount <NUM> to the optical grating coupler <NUM> on the PIC <NUM>. During the assembly stage, it is important to properly align the optics mount <NUM> and the PIC <NUM> in the X-Y plane to achieve alignment between the light beam <NUM> and the optical grating coupler <NUM>, which may be as small as several micrometer in each dimension. In some implementations, a focused spot size of the light beam <NUM> can be approximately <NUM> in diameter. In some implementations, alignment may be performed visually by activating the light source <NUM> and observing the point of incidence of the light beam <NUM>. In some implementations, alignment may be performed using feedback from the monitor photodiode <NUM> to measure optical coupling.

In some implementations, the method <NUM> includes calibrating the position of the MEMS mirror to increase coupling of the beam of light into the waveguide (stage <NUM>). In some implementations, the light source <NUM> can be activated, and the mirror <NUM> adjusted to direct the light beam <NUM> onto the optical grating coupler <NUM>. A position and/or tilt of a reflective portion of the mirror <NUM> can be adjusted to set an angle of incidence of the light beam <NUM> on the optical grating coupler <NUM>. The angle of incidence can be adjusted to increase coupling of the light beam <NUM> into the grating coupler <NUM>.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular implementations. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable sub-combination.

References to "or" may be construed as inclusive so that any terms described using "or" may indicate any of a single, more than one, and all of the described terms. The labels "first," "second," "third," and so forth are not necessarily meant to indicate an ordering and are generally used merely to distinguish between like or similar items or elements.

Claim 1:
An integrated optical assembly (<NUM>) comprising:
an optics mount (<NUM>) having disposed thereon a light source (<NUM>) for providing a beam of light (<NUM>) and a lens (<NUM>) configured to focus the beam of light;
a photonic integrated circuit PIC (<NUM>) mechanically coupled to the optics mount and having disposed thereon a grating coupler (<NUM>) for receiving the beam of light and coupling the beam of light into a waveguide (<NUM>); and
a microelectromechanical systems MEMS mirror (<NUM>) configured to receive the beam of light from the lens and redirect it towards the grating coupler, wherein a position of a reflective portion of the MEMS mirror is adjustable to affect an angle of incidence of the beam of light on the grating coupler, characterized in that the MEMS mirror (<NUM>) can rotate about two axes and the axes are substantially orthogonal to each other.