OPTOELECTRONIC DEVICE AND MANUFACTURING METHOD THEREOF

An optoelectronic device includes a first substrate, a second substrate, a photonic integrated circuit, and a laser diode. The second substrate is over the first substrate. The photonic integrated circuit is disposed on the first substrate and includes a first waveguide channel, a second waveguide channel, and a patterned structure. The first waveguide channel and the second waveguide channel are coupled to the patterned structure. The laser diode is disposed on the second substrate and configured to emit a light beam toward the patterned structure.

BACKGROUND

Field of Disclosure

The present disclosure relates to an optoelectronic device and a manufacturing method thereof.

Description of Related Art

As process technology advances, requirements for data transmission and calculation rates increase. Therefore, the semiconductor industry is facing the challenge of integrating more complex circuits into unit area. However, the data transmission bandwidth of traditional electronic integrated circuits (EIC) is limited. As a result, how to integrate optical components into electronic integrated circuits has become a critical issue to be solved by those in the industry, to convert electrical signals into optical signals for data transmission to increase data transmission bandwidth.

SUMMARY

An aspect of the disclosure is to provide an optoelectronic device and a manufacturing method of an optoelectronic device that may efficiently solve the aforementioned problems.

According to an embodiment of the disclosure, an optoelectronic device includes a first substrate, a second substrate, a photonic integrated circuit, and a laser diode. The second substrate is over the first substrate. The photonic integrated circuit is disposed on the first substrate and includes a first waveguide channel, a second waveguide channel, and a patterned structure. The first waveguide channel and the second waveguide channel are coupled to the patterned structure. The laser diode is disposed on the second substrate and configured to emit a light beam toward the patterned structure.

In an embodiment of the disclosure, a first axis of the first waveguide channel and a second axis of the second waveguide channel extend and intersect in the patterned structure.

In an embodiment of the disclosure, an included angle between the first axis of the first waveguide channel and the second axis of the second waveguide channel is between about 80 degrees and about 100 degrees.

In an embodiment of the disclosure, the laser diode is disposed over the patterned structure so that the light beam emitted by the laser diode is incident perpendicularly to the first substrate.

In an embodiment of the disclosure, the patterned structure includes a plurality of island-shaped units in a central area of the patterned structure, and a first axis of the first waveguide channel and a second axis of the second waveguide channel extend and intersect in the central area.

In an embodiment of the disclosure, a shortest diameter of any one of the island-shaped units or a pitch between any two adjacent ones of the island-shaped units is less than an operation wavelength of the light beam.

In an embodiment of the disclosure, the patterned structure further includes a multipronged unit between the central area and the first waveguide channel. The multipronged unit has a backbone and a prong connected to the backbone. The backbone is adjacent to the first waveguide channel. The prong is adjacent to the central area.

In an embodiment of the disclosure, the patterned structure includes a plurality of linear units in a diagonal area of the patterned structure. The diagonal area is at a side of the patterned structure that is away from the first waveguide channel. Each of the linear units has a normal vector substantially parallel to a first axis of the first waveguide channel.

In an embodiment of the disclosure, a shortest diameter of any one of the linear units or a pitch between any two adjacent ones of the linear units is less than an operation wavelength of the light beam.

In an embodiment of the disclosure, a gap between a light-emitting window of the laser diode and the patterned structure is between about 500 nm and about 100 μm.

In an embodiment of the disclosure, any side length of an outer edge of the patterned structure is between about 0.8 times and about 5 times a diameter of a light-emitting window of the laser diode.

According to another embodiment of the disclosure, a manufacturing method of an optoelectronic device includes providing a first substrate. The first substrate includes a photonic integrated circuit thereon. The photonic integrated circuit includes a first waveguide channel, a second waveguide channel, and a patterned structure. The first waveguide channel and the second waveguide channel are coupled to the patterned structure. The manufacturing method further includes providing a second substrate including a laser diode. The manufacturing method further includes docking the first substrate and the second substrate so that a light-emitting window of the laser diode faces the patterned structure of the photonic integrated circuit.

In an embodiment of the disclosure, docking the first substrate and the second substrate so that the laser diode is disposed over the patterned structure of the photonic integrated circuit. The laser diode is configured to emit a light beam perpendicularly to the first substrate.

In an embodiment of the disclosure, the patterned structure of the photonic integrated circuit includes a plurality of island-shaped units in a central area of the patterned structure. A shortest diameter of any one of the island-shaped units or a pitch between any two adjacent ones of the island-shaped units is less than an operation wavelength of the light beam emitted by the laser diode.

In an embodiment of the disclosure, a first axis of the first waveguide channel and a second axis of the second waveguide channel extend and intersect in the central area.

In an embodiment of the disclosure, an included angle between the first axis of the first waveguide channel and the second axis of the second waveguide channel is between about 80 degrees and about 100 degrees.

In an embodiment of the disclosure, the island-shaped units are configured to scatter the light beam in a plurality of different directions.

In an embodiment of the disclosure, the patterned structure further includes a multipronged unit between the central area and the first waveguide channel. The multipronged unit has a backbone and a prong connected to the backbone. The multipronged unit is configured to receive the light beam passing through the prong and partially guide the light beam to the backbone so that the light beam is shaped and coupled to the first waveguide channel.

In an embodiment of the disclosure, the patterned structure includes a plurality of linear units in a diagonal area of the patterned structure. The diagonal area is at a side of the patterned structure that is away from the first waveguide channel. A shortest diameter of any one of the linear units or a pitch between any two adjacent ones of the linear units is less than an operation wavelength of a light beam emitted by the laser diode.

In an embodiment of the disclosure, each of the linear units has a normal vector substantially parallel to a first axis of the first waveguide channel to block the light beam incident to the linear units and partially reflect the light beam to the first waveguide channel.

Accordingly, in the optoelectronic device and the manufacturing method of the optoelectronic device of the present disclosure, the substrate provided with the photonic integrated circuit is docked with the substrate provided with the laser diode. The photonic integrated circuit includes two waveguide channels and a patterned structure that promotes light coupling to the two waveguide channels. Therefore, higher optical coupling efficiency that is polarization independent may be achieved. To be more specific, the included angle between the two waveguide channels is deliberately selected so that the light beams coupled to the two waveguide channels are substantially equal in quantity. In addition, the patterned structure is a sub-wavelength structure and includes units with different shapes and characteristic lengths. Thus, the sub-wavelength structure may match the mode of the incident laser light more effectively, while reducing energy loss and maintaining a more stable optical coupling efficiency in a wider wavelength range.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments, and thus may be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein. Therefore, it should be understood that there is no intent to limit example embodiments to the particular forms disclosed, but on the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.

Reference is made toFIG.1A.FIG.1Ais a perspective view of an optoelectronic device10according to some embodiments of the present disclosure. The optoelectronic device10includes a first substrate100and a second substrate200docked with each other. As shown inFIG.1A, the second substrate200may be disposed over the first substrate100. A photonic integrated circuit101is disposed on a surface of the first substrate100facing the second substrate200. A laser diode is disposed on a surface of the second substrate200facing the first substrate100. The laser diode is configured to emit a light beam toward the patterned structure130. It should be understood that in order to show the relative positions between the components, the concrete structure of the laser diode is omitted inFIG.1A, and only a light-emitting window240of the laser diode is shown for illustration. The structure of the laser diode will be described in detail with other figures in following paragraphs.

The photonic integrated circuit101on the first substrate100may include a first waveguide channel110, a second waveguide channel120, and a patterned structure130, as shown inFIG.1A. The first waveguide channel110extends in a direction X. The second waveguide channel120extends in a direction Y. Each of the first waveguide channel110and the second waveguide channel120has one end coupled to the patterned structure130. The other ends of the first waveguide channel110and the second waveguide channel120may be coupled to other optical elements, such as optical fibers, respectively, but this disclosure is not limited thereto. The patterned structure130includes microstructures with different geometric and optical properties. Detailed features of the patterned structure130will be described in following paragraphs.

As shown inFIG.1A, the optoelectronic device10further includes a pad210, a pad220, and a pad230disposed on the surface of the second substrate200facing the first substrate100. In some embodiments, the pad220and the pad230are electrically connected to the laser diode. In some embodiments, the pad230serves as an anode of the laser diode, and the pad220serves as a cathode of the laser diode to provide electrical signals to drive the laser diode. In some embodiments, the pad210may be in a floating state and serves as a spacer together with the pad220and the pad230to maintain the gap between the first substrate100and the second substrate200. Thereby, the distance of the light-emitting window240relative to the patterned structure130may be adjusted. In some embodiments, the pad210may be made of a different material than the pad220and the pad230.

Reference is made toFIG.1B.FIG.1Bis an enlarged partial view ofFIG.1A. As shown inFIG.1B, the light-emitting window240is disposed directly over the patterned structure130. For example, a central axis of the light-emitting window240may be substantially aligned with a center of the patterned structure130. The light-emitting window240has a diameter D. The laser diode emits a light beam L1 toward the patterned structure130through the light-emitting window240. The light beam L1 is diverted and scattered by the microstructures of the patterned structure130to form a light beam L2 and a light beam L3 coupled to the first waveguide channel110and the second waveguide channel120, respectively. In some embodiments, an overall outer edge of the patterned structure130is approximately quadrangular, as shown inFIG.1B. Any side length of the outer edge of the quadrangular (such as a side length S1 and a side length S2) is between about 0.8 times and about 5 times the diameter D of the light-emitting window240of the laser diode.

Reference is made toFIG.2.FIG.2is a side view of the optoelectronic device10taken along a line A-A′ shown inFIG.1Aaccording to some embodiments of the present disclosure. As shown inFIG.2, the pad210, the pad220, and the pad230are disposed between the first substrate100and the second substrate200to separate the first substrate100and the second substrate200. In some embodiments, the pad210, the pad220, and the pad230disposed on the second substrate200may be respectively connected to pads of the first substrate100through solder bumps260. For example, a thickness of the solder bumps260is deliberately selected such that a gap G1 between the light-emitting window240and the patterned structure130along a direction Z is between about 500 nm and about 100 μm. In some embodiments, the optoelectronic device10may further include a dielectric layer (not shown) disposed between the first substrate100and the second substrate200and covering each pad to protect the connection.

Reference is made toFIG.3.FIG.3is a partial cross-sectional view of the second substrate200of the optoelectronic device10taken along a line B-B′ ofFIG.1Aaccording to some embodiments of the present disclosure. As aforementioned, the laser diode250is disposed on the surface of the second substrate200facing the first substrate100. For the sake of clarity, inFIG.3, the second substrate200is shown in the bottom part of the figure, and the light-emitting window240of the laser diode250is positioned upward. In some embodiments, as shown inFIG.3, the laser diode250may be a laser element such as a vertical cavity surface emitting laser (VCSEL) or a laser element that guides a light beam toward the first substrate100so that the light beam has the shown light transmission mode through secondary optical structures. The laser diode250includes a first reflective layer251, a second reflective layer252, and a light-emitting layer253disposed between the first reflective layer251and the second reflective layer252. In some embodiments, each of the first reflective layer251and the second reflective layer252has a plurality of stacked compound semiconductor material layers to form different types of distributed Bragg reflectors (DBR). The first reflective layer251is coupled to the pad220used as the cathode, and the second reflective layer252is coupled to the pad230used as the anode. In some embodiments, the light-emitting layer253is a multiple quantum well (MQW) structure. In some embodiments, the first reflective layer251, the second reflective layer252, and the light-emitting layer253may include a same material and may be doped with different doping species or doping concentrations so that they have different electrical properties. In addition, as shown inFIG.3, the pad230may surround and define the light-emitting window240. The light-emitting window240has a diameter D. It should be noted that the pad210, the pad220, and the pad230shown inFIG.3may be portions extended from the pad210, the pad220, and the pad230shown inFIG.1AandFIG.2. Therefore, the pad210, the pad220, and the pad230shown inFIG.3may have different relative positional relationships than the pad210, the pad220, and the pad230shown inFIG.1AandFIG.2. For example, a height of a top surface of the pad230may be greater than heights of top surfaces of the pad220and the pad230shown inFIG.3. In some other embodiments, the laser diode250may be a laser element formed based on prior arts and configured to emit a light beam perpendicularly to the first substrate100, but the present disclosure is not limited thereto.

Reference is made toFIG.4AandFIG.4B.FIG.4AandFIG.4Bare top views of the first waveguide channel110, the second waveguide channel120, and the patterned structure130according to some embodiments of the present disclosure. The first waveguide channel110, the second waveguide channel120, and the patterned structure130shown inFIG.4AandFIG.4Bare the same, but for the sake of clarity, different auxiliary lines are drawn for explanation.

As aforementioned, the patterned structure130has an outer edge that is approximately quadrangular. As shown inFIG.4A, the first waveguide channel110and the second waveguide channel120extend into the quadrangular outer edge of the patterned structure130and are coupled to the patterned structure130.

In greater detail, the patterned structure130has a central area CA, a diagonal area DA1, and a diagonal area DA2. The central area CA is disposed at the center of the quadrangular outer edge of the patterned structure130. The diagonal area DA1 and the diagonal area DA2 are disposed at two opposite corners of the outer edge of the quadrangular. The diagonal area DA1 is disposed at a side of the patterned structure130that is away from the second waveguide channel120. The diagonal area DA2 is disposed at a side of the patterned structure130that is away from the first waveguide channel110. As shown inFIG.4A, the diagonal area DA1 and the diagonal area DA2 are substantially symmetrical. A first axis A1 of the first waveguide channel110and a second axis A2 of the second waveguide channel120extend and intersect in the central area CA of the patterned structure130and form an included angle θ. In some embodiments, the included angle θ is between about 80 degrees and about 100 degrees. For example, the included angle θ may be substantially 90 degrees. In such case, the light beams coupled to the first waveguide channel110and the second waveguide channel120are substantially equal in quantity. In addition, the first axis A1 of the first waveguide channel110extends toward the diagonal area DA2, and the second axis A2 of the second waveguide channel120extends toward the diagonal area DA1.

Reference is made toFIG.4B. The patterned structure130includes units with different shapes and characteristic lengths, such as island-shaped units131, multipronged units132, linear units133, and partition units134. These units are disposed in different areas of the patterned structure130and have different light-guiding properties. In some embodiments, these units can be obtained by inverse design according to desired optical coupling characteristics of the optoelectronic device10.

Furthermore, in some embodiments, a shortest diameter of any pattern of these units or the pitch between any two adjacent units is less than an operation wavelength of the light beam emitted by the laser diode. Taking this embodiment as an example, if the operation wavelength of the light beam is about 1300 nm, the shortest diameter of any pattern of the units or the pitch between any two adjacent units can be designed to be less than about half of the operation wavelength, such as less than about 650 nm. However, this disclosure is not limited to this. The shortest diameter of any pattern of the units or the pitch between any two adjacent units may also be between about 150 nm and about 300 nm as needed. To be more specific, the patterned structure130is a sub-wavelength structure. The sub-wavelength structure may match the mode of the incident laser light more effectively and reduce reflection and scattering, thereby reducing energy loss during the optical coupling process. In addition, the sub-wavelength structure may maintain higher optical coupling efficiency over a wider wavelength range. This is important for multi-wavelength or broad-spectrum applications to ensure stable performance across a wide range of wavelengths. For example, a 1 dB bandwidth of the patterned structure130formed according toFIG.4Bexceeds about 20 nm.

To be more specific, as shown inFIG.4B, the patterned structure130includes the island-shaped units131in the central area CA. The island-shaped units131have approximately circular contours. In other words, characteristic lengths of the island-shaped unit131in the direction X and the direction Y are similar. In some embodiments, the arrangement of the island-shaped units131may be periodic, semi-periodic, or non-periodic. In addition, as aforementioned, in the central area CA, the shortest diameter D1 of the patterns of the island-shaped units131or the pitch P1 between two adjacent island-shaped units131is less than the operation wavelength of the light beam.

As shown inFIG.4B, the patterned structure130includes multipronged units132between the central area CA and the waveguide channel (i.e., the first waveguide channel110or the second waveguide channel120). Each of the multipronged units132has a backbone and at least one prong connected to the backbone. One end of the backbone faces the waveguide channel, and the other end of the backbone faces the central area CA. A direction of the prongs intersects with a direction of the backbone. For example, a multipronged unit132-1has a backbone132aand two prongs132bconnected to the backbone. One end of the backbone132afaces the second waveguide channel120, and the other end faces the central area CA. The two prongs132bare adjacent to the central area CA and their directions intersect with the direction of the backbone132a, forming a Y-shaped unit. On the other hand, a multipronged unit132-2has a backbone132c, two prongs132dconnected to the backbone and adjacent to the second waveguide channel120, and a prong132econnected to the backbone and adjacent to the central area CA. Similarly, directions of the two prongs132dand the prong132eintersect with the direction of the backbone132c.

As shown inFIG.4B, the patterned structure130includes the linear units133in the diagonal area DA1 and the diagonal area DA2. The linear units133have approximately elongated contours. In other words, characteristic lengths of the linear units133in the direction X are significantly different from characteristic lengths of the linear units133in the direction Y. For example, the characteristic lengths of the linear units133in the diagonal area DA1 in the direction X is at least twice the characteristic lengths in the direction Y. In addition, reference is made toFIG.4AandFIG.4B. Each of the linear units133in the diagonal area DA1 has a normal vector n1 that is substantially parallel to the second axis A2 of the second waveguide channel120, and each of the linear units133in the diagonal area DA2 has a normal vector n2 that is substantially parallel to the first axis A1 of the first waveguide channel110. In some embodiments, an included angle between the normal vector n1 and the normal vector n2 is between about 80 degrees and about 100 degrees. Moreover, as aforementioned, the shortest diameter D2 of the patterns of the linear units133in the diagonal area DA1 and the diagonal area DA2 or the pitch P2 between two adjacent linear units133is less than the operation wavelength of the light beam.

As shown inFIG.4B, the patterned structure130includes the partition units134between the first waveguide channel110and the second waveguide channel120and between the two waveguide channels and the central area CA. In some embodiments, an included angle between a direction of the partition units134and the first axis A1 of the first waveguide channel110as well as an included angle between the direction of the partition units134and the second axis A2 of the second waveguide channel120are between about 40 degrees and about 50 degrees, respectively.

In some embodiments, as shown inFIG.4B, a transition zone exists between two adjacent areas of the patterned structure130. The characteristics of the units in one area gradually change over the transition zone into the characteristics of the units in another adjacent area. Therefore, the units in the transition zone can have some of the light-guiding properties of the units in both areas. For example, the units between the central area CA and the diagonal area DA1 inFIG.4Bhave irregular contours combining the approximately circular contours of the island-shaped units131and the approximately elongated contours of the linear units133, such as approximately jagged contours. These units have the function of scattering incident light while blocking and reflecting the incident light.

By arranging the units with different shapes and characteristic lengths to scatter, block, or guide the light beam, the patterned structure130may improve the coupling efficiency of the light beam into the two waveguide channels. In greater detail, since the light-emitting window240is disposed directly over the patterned structure130, the light beam will first be received by the central area CA after emitted by the laser diode. Then, the island-shaped units131in the central area CA are configured to divert and scatter the light beam in different directions. For example, the light beam is split into different light portions scattered along a positive direction of the direction Y, a negative direction of the direction X, a negative direction of the direction Y, and a positive direction of the direction X. After a first light portion is diverted by the island-shaped units131, the first light portion propagates toward the second waveguide channel120along the positive direction of the direction Y. Then, the multipronged unit132-1and the multipronged unit132-2receive the first light portion through the prongs adjacent to the central area CA, guide the first light portion to the backbones and the prongs adjacent to the first waveguide channel110, thereby performing beam shaping. The shaped first light portion is coupled to the second waveguide channel120. Similarly, a second light portion is coupled to the first waveguide channel110along the negative direction of the direction X. On the other hand, after a third light portion is diverted by the island-shaped units131, the third light portion propagates toward the diagonal area DA1 along the negative direction of the direction Y. Then, the linear units133in the diagonal area DA1 block the third light portion to prevent light leakage. Since the normal vector n1 of the linear units133in the diagonal area DA1 is substantially parallel to the second axis A2 of the second waveguide channel120, the third light portion may be partially reflected and pass through the central area CA again toward the second waveguide channel120. Also, the third light portion is shaped and coupled to the second waveguide channel120through the multipronged units132. Similarly, the fourth light portion propagates along the positive direction of the direction X. Then, the fourth light portion is blocked and partially reflected by the linear units133in the diagonal area DA2, shaped through the multipronged units132, and coupled to the first waveguide channel110. During the process of light transmission and coupling, the partition units134are configured to prevent the light portions guided to the first waveguide channel110and the light portions guided to the second waveguide channel120from interfering with each other.

Reference is made toFIG.5.FIG.5is a graph of optical coupling efficiency versus polarization angle of the optoelectronic device10according to some embodiments of the present disclosure. As shown inFIG.5, the thin solid line represents the optical coupling efficiency of the first waveguide channel110. The dotted line represents the optical coupling efficiency of the second waveguide channel120. The thick solid line represents the sum of the optical coupling efficiencies of the two waveguide channels. It can be seen that in an embodiment where the included angle θ between the first axis A1 and the second axis A2 is substantially 90 degrees, the sum of the optical coupling efficiencies of the first waveguide channel110and the second waveguide channel120can reach similar values when the light beams have different polarization angles. Therefore, the optoelectronic device10according to some embodiments of the present disclosure can achieve higher overall optical coupling efficiency that is polarization independent.

The following paragraphs describe the manufacturing method of the optoelectronic device according to some embodiments of the present disclosure.

First, a first substrate is provided. As aforementioned, a photonic integrated circuit is disposed on a surface of the first substrate. The photonic integrated circuit includes a first waveguide channel, a second waveguide channel, and a patterned structure. In some embodiments, the first waveguide channel, the second waveguide channel, and the patterned structure are formed through an etching process. The first waveguide channel and the second waveguide channel are coupled to the patterned structure. In some embodiments, a first axis of the first waveguide channel and a second axis of the second waveguide channel extend and intersect in the patterned structure. In some embodiments, an included angle between the first axis of the first waveguide channel and the second axis of the second waveguide channel is between about 80 degrees and about 100 degrees. In some embodiments, the patterned structure has microstructures as previously described. In some embodiments, the patterned structure is a sub-wavelength structure.

Next, a second substrate is provided. The second substrate is provided with a laser diode and pads electrically connected to the laser diode. In some embodiments, the laser diode may be a vertical cavity surface emitting laser (VCSEL). In some other embodiments, the laser diode may be a laser element formed using prior arts. The present disclosure is not limited thereto.

Then, the first substrate and the second substrate are docked together so that the light-emitting window of the laser diode faces the patterned structure of the photonic integrated circuit, thereby forming the optoelectronic device10of the present disclosure. In some embodiments, docking the first substrate with the second substrate includes flipping the second substrate or the first substrate so that the surface of the first substrate provided with the photonic integrated circuit faces the surface of the second substrate where the light-emitting window is disposed. In some embodiments, docking the first substrate with the second substrate such that the laser diode is disposed directly over the patterned structure of the photonic integrated circuit. For example, a central axis of the light-emitting window of the laser diode may be substantially aligned to a center of the patterned structure with tolerances within 1 μm. The laser diode is configured to emit a light beam perpendicularly to the first substrate. The patterned structure is configured to couple the light beam emitted by the laser diode to the first waveguide channel and the second waveguide channel.

Accordingly, in the optoelectronic device and the manufacturing method of the optoelectronic device of the present disclosure, the substrate provided with the photonic integrated circuit is docked with the substrate provided with the laser diode. The photonic integrated circuit includes two waveguide channels and a patterned structure that promotes light coupling to the two waveguide channels. Therefore, higher optical coupling efficiency that is polarization independent may be achieved. To be more specific, the included angle between the two waveguide channels is deliberately selected so that the light beams coupled to the two waveguide channels are substantially equal in quantity. In addition, the patterned structure is a sub-wavelength structure and includes units with different shapes and characteristic lengths. Thus, the sub-wavelength structure may match the mode of the incident laser light more effectively, while reducing energy loss and maintaining a more stable optical coupling efficiency in a wider wavelength range.