Optical ring modulator with photonic crystal

Abstract

The present disclosure relates to an optical ring modulator with photonic crystals. Embodiments of the present disclosure provide an optical ring modulator. The optical ring modulator includes a waveguide including a first semiconductor material having a first doping type, and a second semiconductor material adjacent to the first semiconductor material and having a second doping type. A P-N junction is located between the first semiconductor material and the second semiconductor material. A plurality of photonic crystal layers have an upper surface substantially coplanar with an upper surface of the waveguide structure, wherein each photonic crystal layer is embedded within the first semiconductor material or the second semiconductor material.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure generally relate to structures for propagating and processing optical signals. More specifically, the present disclosure relates to optical ring modulators with embedded photonic crystals. BACKGROUND

[0002] The rise of networked devices with links to data centers, such as the “Internet of Things” (IoT), has been accompanied by a large number of signal processing elements in integrated circuits (ICs). The ICs can be modified, adapted, to accommodate the various components needed to transport light from one component to another. Various ICs formed to include photonic devices and microcircuits are referred to as “photonic integrated circuits” (PICs). PIC dies often include optical components located at the surface or edge of the PIC die to transport light to or from optical devices (e.g., waveguides and grating couplers) within the PIC die. Various optical components such as photonic waveguides, photonic transmitters and receivers, etc. can relay signals through optical transport.

[0003] Propagation of information in the photonic domain from one component to another often requires the use of an optical modulator, such as a ring modulator. A ring modulator is an optical ring resonator used to tune the resonant wavelength in an optical signal. An optical resonator refers to a component formed by an optical waveguide shaped into a circle and placed in close proximity to another waveguide (bus). When light passes through the bus waveguide, a small fraction of the optical power is coupled to the ring waveguide structure via a coupling mechanism. The coupled power can be adjusted by the distance between the bus waveguide and the ring itself. The optical power can accumulate in the ring to such a level that even a small fraction of the light is transmitted back to the bus waveguide, destructively interfering with the light propagating on the bus waveguide.

[0004] An optical modulator can be formed within a PIC die by embedding a P-N junction in the bus waveguide to change the effective refractive index of the material through which the light propagates. As a result, the optical modulator changes the wavelength at which resonance occurs and the effective optical length. The resonant wavelength shifts according to the bias voltage applied to the P-N junction, thereby defining the efficiency of the modulator. Higher wavelength resonance shifts result in higher extinction ratios (ER) and lower insertion losses (IL). SUMMARY

[0005] Some aspects of the present disclosure provide an optical ring modulator comprising: a waveguide structure comprising: a first semiconductor material having a first doping type, and a second semiconductor material adjacent to the first semiconductor material and having a second doping type opposite to the first doping type, the first semiconductor material and the second semiconductor material defining a P-N junction within the waveguide structure; and a plurality of photonic crystal structures, each photonic crystal structure embedded within the first semiconductor material or the second semiconductor material of the waveguide structure and having an upper surface substantially coplanar with an upper surface of the waveguide structure.

[0006] Further aspects of the present disclosure provide an optical ring modulator comprising: a waveguide structure comprising: a waveguide structure comprising: a first semiconductor material having a first doping type, and a second semiconductor material adjacent to the first semiconductor material and having a second doping type opposite to the first doping type, the first semiconductor material and the second semiconductor material defining a P-N junction within the waveguide structure; a first photonic crystal layer on an upper surface of the first semiconductor material; a first plurality of semiconductor pillars having the first doping type, each semiconductor pillar of the first plurality of semiconductor pillars embedded within the first photonic crystal layer and having a top surface substantially coplanar with a top surface of the first photonic crystal layer; a second photonic crystal layer on an upper surface of the second semiconductor material; and a second plurality of semiconductor pillars having the second doping type, each semiconductor pillar of the first plurality of semiconductor pillars embedded within the second photonic crystal layer and having a top surface substantially coplanar with a top surface of the second photonic crystal layer.

[0007] Other aspects of the present disclosure provide an optical ring modulator comprising: a waveguide structure comprising: a first semiconductor material having a first doping type, and a second semiconductor material adjacent to the first semiconductor material and having a second doping type opposite to the first doping type, the first semiconductor material and the second semiconductor material defining a P-N junction within the waveguide structure; a first plurality of photonic crystal pillars within the first semiconductor material, each photonic crystal pillar of the first plurality of photonic crystal pillars having a bottom surface substantially coplanar with a bottom surface of the first semiconductor material; a first photonic crystal layer on the first plurality of photonic crystal pillars and within a recessed region of the first semiconductor material; a second plurality of photonic crystal pillars within the second semiconductor material, each photonic crystal pillar of the second plurality of photonic crystal pillars having a bottom surface substantially coplanar with a bottom surface of the second semiconductor material; and a second photonic crystal layer on the second plurality of photonic crystal pillars and within a recessed region of the second semiconductor material. BRIEF DESCRIPTION OF DRAWINGS

[0008] These and other features of the present disclosure will be more readily understood from the following detailed description of the various aspects of the present disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the present disclosure, in which:

[0009] Figure 1 A plan view of a waveguide and an optical ring modulator with a photonic crystal material according to embodiments of the present disclosure is shown.

[0010] Figure 2 A perspective view of a portion of an optical ring modulator with a photonic crystal post according to embodiments of the present disclosure is shown.

[0011] Figure 3 A cross-sectional view of a portion of an optical ring modulator with a photonic crystal post according to embodiments of the present disclosure taken along view line 3-3 of Figure 2

[0012] Figure 4 A perspective view of a portion of an optical ring modulator with a photonic crystal post and a photonic crystal layer according to embodiments of the present disclosure is shown.

[0013] Figure 5 A cross-sectional view of a portion of an optical ring modulator with a photonic crystal post and a photonic crystal layer according to embodiments of the present disclosure taken along view line 5-5 of Figure 4

[0014] A perspective view of a portion of an optical ring modulator with a semiconductor post according to embodiments of the present disclosure is shown. Figure 6

[0015] A cross-sectional view of a portion of an optical ring modulator with a semiconductor post according to embodiments of the present disclosure taken along view line 7-7 of Figure 7 Figure 6 A perspective view of a portion of an optical ring modulator with a photonic crystal layer and a photonic crystal post located between portions of a P-N junction according to embodiments of the present disclosure is shown.

[0016] Figure 8 A cross-sectional view of a portion of an optical ring modulator with a photonic crystal layer and a photonic crystal post located between portions of a P-N junction according to embodiments of the present disclosure taken along view line 9-9 of

[0017] Figure 9 Figure 8 A cross-sectional view of a portion of an optical ring modulator with a photonic crystal layer and a photonic crystal post located between portions of a P-N junction according to embodiments of the present disclosure taken along view line 9-9 of

[0018] Figure 10 A perspective view of a portion of an optical ring modulator with interdigitated semiconductor material according to embodiments of the present disclosure is shown.​​​

[0019] Figure 11 The following is illustrated according to an embodiment of the present disclosure. Figure 10 The first cross-sectional view of a portion of an optical ring modulator with interlaced semiconductor materials, taken by view line 11-11.

[0020] Figure 12 The following is illustrated according to an embodiment of the present disclosure. Figure 10 The second cross-sectional view of a portion of an optical ring modulator with intersecting semiconductor materials, taken by view line 12-12.

[0021] It should be noted that the accompanying drawings of this disclosure are not necessarily drawn to scale. The drawings are intended to depict only typical aspects of this disclosure and should therefore not be considered as limiting the scope of this disclosure. In the drawings, the same reference numerals denote the same elements between the figures. Detailed Implementation

[0022] In the following description, reference is made to the accompanying drawings, which form part of this specification, and specific exemplary embodiments in which the present teachings may be practiced are illustrated by way of example. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present teachings, and it should be understood that other embodiments may be used and modifications may be made without departing from the scope of the present teachings. Therefore, the following description is merely illustrative.

[0023] This disclosure relates to an optical ring modulator for processing optical signals. Embodiments of this disclosure can be implemented on a photonic integrated circuit (PIC) die. The PIC die may include a semiconductor wafer configured to include photonic elements (e.g., optical waveguides, photodiodes, thermal phase-shifting elements, ring filters, etc.) for transmitting and / or processing photonic signals, as well as electronic components (e.g., wires, vias, transistors, and other devices). The PIC die may include signal modulation hardware, such as a Mach-Zehnder modulator (MZM) for filtering optical signals to determine the phase shift between them. Such components can process optical signals to be multiplexed, demultiplexed, and / or otherwise prepared for transmission to other parts of the PIC die for processing.

[0024] Embodiments of the present disclosure can include, for example, optical ring modulators formed from a semiconductor material and photonic crystals arranged in layers or pillars within the semiconductor material. The semiconductor material can include two oppositely doped semiconductor materials, defining a P-N junction at a physical interface between the two semiconductor materials. When a voltage is applied across the two semiconductor materials, for example, through a conductive contact to both semiconductor materials, the P-N junction forms a diode. The semiconductor material of the optical ring modulator, which can be arranged in a ring, receives light from a waveguide during operation of a PIC die. The light will pass through the semiconductor material and change the carrier concentration across the P-N junction, changing the effective refractive index and optical length of the ring.

[0025] Embodiments of the present disclosure overcome certain technical limitations of semiconductor-based optical ring modulators by increasing the interaction between the photonic signal and the P-N junction as the photonic signal passes through the ring structure. In an example of a ring modulator (e.g., having a radius of approximately ten micrometers (pm)), the photonic signal must travel the entire length of the ring at least once. Embodiments of the present disclosure increase the mode interaction between the photonic signal and the P-N junction by embedding photonic crystal structures configured to slow down light within the optical ring modulator. More specifically, embodiments of the present disclosure include a plurality of photonic crystal structures, such as pillars or other articles, embedded within two oppositely doped semiconductor materials.

[0026] The photonic crystal material can include any crystalline material having optical nanostructures that affect the motion of photons passing therethrough, such as by reflecting incident light. Crystalline silicon dioxide (Si02) is one type of photonic crystal suitable for use in embodiments of the present disclosure, although other crystalline materials (e.g., various types of silicon nanocrystals) can be used in additional implementations. Each photonic crystal structure in the optical ring modulator can have an upper surface that is substantially coplanar with an upper surface of a respective region of the semiconductor material. The upper surface can be a top surface of the material, or simply an upper surface of the semiconductor material that is horizontally between portions of the material coupled to an electrical contact or P-N junction. Regardless of how formed and distributed, the photonic crystal material can direct optical modes toward the P-N junction, where they would otherwise travel away from the P-N junction within the optical ring modulator before being directed back.

[0027] Figure 1A plan view of an optical ring modulator 100 is shown in accordance with various embodiments of the present disclosure. The optical ring modulator 100 can be used as an optical filter, for example, to tune an optical signal as it passes from one region of a PIC die to another to ensure that encoded data is accurately transmitted and without significant noise, signal loss, etc. The waveguides 102 can comprise any now known or later developed optical transmission medium, including various silicon-based and / or nitride-based optical transmission materials. According to one example, the waveguides 102 can comprise silicon nitride (Si3N4) or other materials with the same or similar properties. The waveguides 102 can be optically aligned with the optical ring modulator 100 to adjust the amount of light coupled to the optical ring modulator 100. In Figure 1 In the example of FIG. 1, the waveguides 102 receive light from and output light to one waveguide 102. It should be appreciated that additional implementations can include multiple waveguides 102, each configured to send and receive optical signals to and from the optical ring modulator 100.

[0028] The optical ring modulator 100 can shift the phase of an optical signal. An optical ring modulator is a set of interconnected waveguides, one of which takes the form of a closed loop between a waveguide carrying an input optical signal and a waveguide transmitting an output optical signal. The desired wavelength band of the optical ring modulator 100 can be referred to as a “resonant wavelength,” while rejected wavelengths can be referred to as “non-resonant wavelengths.” During operation, light of the resonant wavelength passes from the waveguides 102 through the loop and increases its intensity in multiple round trips through the closed loop (“ring”). The transmitted optical signal can experience constructive interference as it passes through the closed loop before being output to an output “bus” waveguide, which can be the same as or different from the waveguides 102 and which functions as a detector waveguide. It should be appreciated that the optical ring modulator 100 optionally can include non-looped filtering elements, but which perform substantially the same filtering function on a selected wavelength before it is output from the optical ring modulator 100 to a bus waveguide such as the waveguides 102.

[0029] To implement the optical filtering functionality described herein, the optical ring modulator 100 includes electrically active semiconductor materials that are arranged to form P-N diode junctions when a voltage is applied. For example, the optical ring modulator 100 can include a first semiconductor material 104 having a first doping type and a second semiconductor material 106 having a second doping type opposite the first doping type. The first semiconductor material 104 can define an inner ring of the optical ring modulator 100 and the second semiconductor material 106 can define an outer ring of the optical ring modulator 100, or vice versa. The semiconductor materials 104, 106 can include, but are not limited to, silicon, germanium, silicon germanium, silicon carbide, and those consisting essentially of one or more III-V compound semiconductors having a composition defined by the chemical formula Al X1 Ga X2 In X3 As Y1 P Y2 N Y3 Sb Y4 where X1, X2, X3, Y1, Y2, Y3, and Y4 represent relative proportions that are each greater than or equal to zero and X1+X2+X3+Y1+Y2+Y3+Y4 = 1 (1 being the total relative molar amount). Other suitable substrates include II-VI compound semiconductors having a composition Zn A1 Cd A2 Se B1 Te B2 where A1, A2, B1, and B2 are relative proportions that are each greater than or equal to zero and A1+A2+B1+B2 = 1 (1 being the total molar amount). In addition, portions of the materials 104, 106 can be strained.

[0030] The first semiconductor material 104 and the second semiconductor material 106 can each include a dopant. The dopant within each semiconductor material 104, 106 can have an opposite polarity with respect to the other such that the physical interface between the materials 104, 106 defines a P-N junction. According to one example, the first semiconductor material 104 can have a P-type doping, while the second semiconductor material 106 can have an N-type doping. When referring to a dopant, a P-type dopant refers to an element that is introduced into a semiconductor material to create free holes by "accepting" an electron from a semiconductor atom and thus "releasing" a hole. The acceptor atom must have one less valence electron than the host semiconductor. P-type dopants suitable for use in the semiconductor materials 104, 106 can include, but are not limited to: boron (B), indium (In), and gallium (Ga). Boron (B) is the most common acceptor in silicon technology. Other alternatives include In and Ga. Ga has a high diffusivity in silicon dioxide (Si02), and thus, the oxide cannot be used as a mask during Ga diffusion. An N-type dopant is an element that is introduced into a semiconductor material to create free electrons, for example, by "donating" an electron to the semiconductor. The N-type dopant must have one more valence electron than the semiconductor. Common N-type donors in silicon (Si) include, for example, phosphorus (P), arsenic (As), and / or antimony (Sb). Doping of each semiconductor material 104, 106 can be achieved via direct ion implantation and / or various other techniques known in the art. Processing techniques for doping the various materials in the optical modulator 100 are well known in the art and thus are not described in detail. Moreover, while the first semiconductor material 104 and the second semiconductor material 106 can have a vertically extending physical interface due to the contact with each other along the respective sidewalls, in further implementations, all or a portion of the physical interface can extend horizontally.

[0031] To induce an electro-active diode junction between each semiconductor material 104, 106 of the optical ring modulator 100, a voltage source 108 can be electrically coupled to the optical ring modulator 100. More specifically, a cathode terminal of the voltage source 108 can be coupled to the first semiconductor material 104, while an anode terminal of the voltage source 108 can be coupled to the second semiconductor material 106. As described herein, the coupling of the voltage source 108 to the semiconductor materials 104, 106 can be achieved through conductive contacts to the semiconductor materials 104, 106.

[0032] The optical ring modulator 100 differs from conventional optical filter devices, ring modulators, and the like in that it includes a plurality of photonic structures 110 distributed throughout the first semiconductor material 104 and the second semiconductor material 106, rather than being confined within a single portion of the materials 104, 106 and / or as a continuous region of photonic crystal material. The photonic crystal structures 110 can be formed, for example, by removing targeted portions of the semiconductor materials 104, 106 (e.g., by etching with a mask) and depositing a photonic crystal material within the etched openings to create a number of different photonic crystal structures 110 throughout the optical ring modulator 100. A variety of types of photonic crystal structures 110 can be formed in this manner, such as photonic crystal layers, photonic crystal pillars, and / or other types of shapes. The size and shape of the photonic crystal structures 110 can be selected based on the wavelength of light to be transmitted through the optical ring modulator 100, the technical application, and / or other factors. During operation, the photonic crystal structures 110 can redirect errant light within the optical ring modulator 100 toward the P-N junction between the semiconductor materials 104, 106, thereby increasing the interaction between the transmitted light and the P-N junction.

[0033] As a general recommendation, the Applicant has determined that a higher percentage of the photonic crystal structures 110 in the mass of the optical ring modulator 100 is associated with a higher "group index" of the optical ring modulator 100 (i.e., the speed of light in a vacuum relative to the mode of the speed of light within the medium). A higher group index generally indicates a lower speed of light, and thus a greater interaction between the P-N junction between the semiconductor materials 104, 106 and the optical signal. In various embodiments of the present disclosure (several examples of which are described herein), the photonic crystal structures 110 can be formed within and / or distributed throughout the optical ring modulator 100 to provide a greater or lesser influence on the propagation of light within the optical ring modulator 100.

[0034] Reference is now made to Figure 2 and 3 wherein Figure 2 a partial perspective view is provided, Figure 3 a cross-sectional view is provided along the view line 3-3 Figure 2A cross-sectional view in the plane X-Z of the intercept is discussed with respect to an example configuration of the optical ring modulator 100. As previously described, the optical ring modulator 100 can include a first semiconductor material 104 and a second semiconductor material 106 having opposite doping types. A set of electrically conductive contacts 112 can be formed on the semiconductor materials 104, 106. Each contact 112 can be formed at a respective location, such as a terminal region 113 of the first semiconductor material 104 or the second semiconductor material 106. Application of a voltage (e.g., from a voltage source 108 Figure 1 )) to the terminal regions 113 of the semiconductor materials 104, 106 will electrically drive operation of the optical ring modulator 100. The first semiconductor material 106 can include a first intermediate region 114 having a higher doping concentration than the terminal regions 113 of the first semiconductor material 104 underlying the contacts 112. The first semiconductor material 104 can also include a first depletion region 116 having a higher doping concentration than the rest of the first semiconductor material 104, including the first intermediate region 114. In a similar configuration, the second semiconductor material 106 can include a second intermediate region 118 having a higher doping concentration than the terminal regions 113 underlying the contacts 112 adjacent thereto. The second semiconductor material 106 can thus also include a second depletion region 120 having a higher doping concentration than the rest of the second semiconductor material 106, including the second intermediate region 118. A physical interface between each depletion region 116, 120 of the highly doped material can form a P-N junction 122 within the optical ring modulator 100 to change the effective refractive index of a waveguide therein.

[0035] To increase interaction between an optical signal within the optical ring modulator 100 and the P-N junction 122, a photonic crystal structure 110 in the form of photonic crystal pillars 110a Figure 1 ) can be distributed throughout each semiconductor material 104, 106 of the optical ring modulator 100. According to one example, a number of photonic crystal pillars 110a can be formed within each intermediate region 114, 118 of each semiconductor material 104, 106. The photonic crystal pillars 110a can have an upper surface that is substantially coplanar with an upper surface of the adjacent intermediate region 114, 118. In Figure 2 、 3In the example of FIG. 1, the upper surfaces of the photonic crystal pillars 110a and the intermediate regions 114, 118 can be substantially coplanar with the top surfaces of the semiconductor materials 104, 106, but this need not be the case in all implementations. Each photonic crystal pillar 110a can have substantially the same vertical thickness as the intermediate region 114, 118 in which it is located. However, this need not be the case in all instances. The presence of the photonic crystal pillars 110a can divert light within the optical ring modulator 100 toward the P-N junction 122 to increase optical interaction with the electrical diode induced within the depletion regions 116, 120.

[0036] The distribution of the photonic crystal pillars 110a can be controlled to further increase optical interaction between signals within the optical ring modulator 100 and the P-N junction 122. The distribution of the photonic crystal pillars 110a can be defined based on, for example, a pitch diameter ratio of the photonic crystal pillars 110a and / or other physical properties relative to the first and / or second semiconductor materials 104, 106. The diameter (only Figure 3 ) represented by reference symbol "d" indicates the total horizontal width of one photonic crystal pillar 110a along the X-axis at its upper surface. The physical parameter "pitch" (only Figure 3 ) represented by reference symbol "a" refers to the sum of the diameter of one photonic crystal pillar 110a and the horizontal width of the portion of the semiconductor material 104, 106 adjacent thereto located between two photonic crystal pillars 110a. According to one example, the diameter d of each photonic crystal pillar 110a can be approximately two hundred nanometers (nm) and the pitch a can be approximately four hundred nanometers. In this case, the pitch diameter ratio between each pair of photonic crystal pillars 110a in the optical ring modulator 100 can be approximately 2: 1. These physical parameters of the photonic crystal pillars 110a can be suitable for selected wavelengths, such as light having a wavelength of approximately 1560 nm, due to the effective wavelength classification diversion. In various applications, such wavelength classifications can include, for example, the original band (1260-1360 nm wavelength) and the conventional band (1530 nm-1565 nm wavelength).

[0037] In the example of FIG. 1, the upper surfaces of the photonic crystal pillars 110a and the intermediate regions 114, 118 can be substantially coplanar with the top surfaces of the semiconductor materials 104, 106, but this need not be the case in all implementations. Each photonic crystal pillar 110a can have substantially the same vertical thickness as the intermediate region 114, 118 in which it is located. However, this need not be the case in all instances. The presence of the photonic crystal pillars 110a can divert light within the optical ring modulator 100 toward the P-N junction 122 to increase optical interaction with the electrical diode induced within the depletion regions 116, 120. Figure 4 and 5 In further implementations illustrated in the example of FIG. 1, the optical ring modulator 100 can be provided with photonic crystal pillars 110a and other types of photonic crystal structures simultaneously. Figure 4 A partial perspective view is provided in FIG. 2, Figure 5 A cross-sectional view is provided in FIG. 3 along Figure 4The image shows a cross-sectional view in plane XZ taken by line 5-5. The upper surfaces of the intermediate regions 114, 118 may be recessed in the vertical direction relative to the upper surfaces of the adjacent depletion regions 116, 120 and the remainder of the semiconductor materials 104, 106. In this configuration, the depletion regions 116, 120 may respectively define raised portions of the first semiconductor material 104 and the second semiconductor material 106. A PN junction 122 may be defined along the physical interface between the depletion regions 116, 120 of the semiconductor materials 104, 106. A photonic crystal pillar 110a may be formed within the intermediate regions 114, 118 such that the top surface of the photonic crystal pillar 110a is substantially coplanar with the recessed upper surfaces of the intermediate regions 114, 118. Here, each semiconductor material 104, 106 may include a photonic crystal layer 110b located in the horizontal direction between the depletion regions 116, 120 and the remainder of the semiconductor materials 104, 106. Photonic crystal layer 110b in Figure 4 The dashed lines in the middle are used to better illustrate the positions of the central regions 114, 118 and the photonic crystal pillar 110a below them.

[0038] The photonic crystal layer 110b may have the same composition as the photonic crystal pillar 110a, or it may be formed from a different photonic crystal material. During fabrication, the photonic crystal layer 110b can be formed by recessing target portions of the semiconductor materials 104, 106, depositing a layer of crystalline material (e.g., silicon dioxide discussed elsewhere herein), and planarizing the deposited material onto the top surfaces of the semiconductor materials 104, 106. Although both the semiconductor crystal pillar 110a and the semiconductor crystal layer 110 are present, the optical ring modulator 100 can operate in substantially the same manner as in other embodiments discussed herein. However, adding the photonic crystal layer 110b can further increase the group refractive index of the optical ring modulator 100 to a higher level than possible in embodiments that only include the photonic crystal pillar 110a.

[0039] Figure 6 and 7 An optical ring modulator 100 with different configurations of semiconductor and photonic crystal materials is shown. Similar to other examples discussed herein, Figure 6 A partial perspective view of the optical ring modulator 100 is provided, while Figure 7 Provided along Figure 6 The view is a cross-sectional view taken in the plane XZ by line 7-7. In such an example, the photonic crystal layer 110b can be coupled with... Figure 4 and 5 An arrangement similar to the one shown and described is formed in the recessed portions of the semiconductor materials 104 and 106. Although Figure 6 and 7The photonic crystal column 110a is omitted in the text. Figures 2-5 However, they may still exist in other locations within the optical ring modulator 100 and / or Figures 2-5 The same location shown.

[0040] According to the example, the optical ring modulator 100 may include a plurality of semiconductor pillars 124, each semiconductor pillar 124 formed within a corresponding portion of the photonic crystal layer 110b and on corresponding portions of the first semiconductor material 104 and the second semiconductor material 106. The semiconductor pillars 124 may be formed of doped semiconductor materials and may have the same doping type and / or concentration as the underlying portions of the semiconductor materials located within the intermediate regions 114, 118. In the example implementation, the semiconductor pillars 124 above the first intermediate region 114 may have a first doping type (e.g., P-type doping), while the semiconductor pillars 124 above the second intermediate region 118 may have the opposite second doping type (e.g., N-type doping).

[0041] Semiconductor pillars 124 can be formed within the photonic crystal layer 110b, for example, by removing selected portions of the photonic crystal layer 110b and forming doped semiconductor material within the opening, for example, via deposition and / or epitaxial growth. Additionally or alternatively, semiconductor pillars 124 can be formed by removing other portions of the semiconductor material and replacing the removed portions with the photonic crystal layer 110b, such that the remaining semiconductor material forms the semiconductor pillars 124. Regardless of how the semiconductor pillars 124 are formed, they can all have a vertical thickness substantially equal to that of adjacent portions of the photonic crystal layer 110b. Therefore, all semiconductor pillars 124 can have an upper surface substantially coplanar with the upper surface of the photonic crystal layer 110b and the upper surfaces of the semiconductor materials 104, 106 and the depletion regions 116, 118.

[0042] Figure 8 and 9 Features of an optical ring modulator 100 in another implementation are shown. Figure 8 A partial perspective view of the optical ring modulator 100 is provided, while Figure 9 Provided along Figure 8 The view is a cross-sectional view taken in plane XZ by line 9-9. In this case, each of the first semiconductor material 104 and the second semiconductor material 106 of the optical ring modulator 100 may have at least one photonic crystal layer 110b located therein. In addition, the photonic crystal pillar 110a (only Figure 9 ) and / or semiconductor pillar 124 (only) Figure 9 These pillars may or may not be located within semiconductor materials 104 and 106. Possible locations of these pillars are... Figure 9The image is shown in dashed lines. When included, the photonic crystal pillar 110a can be located within the intermediate regions 114 and 118. When included, the semiconductor pillar 124 can be located within the photonic crystal layer 110b.

[0043] Regardless of whether it includes photonic crystal pillar 110a or semiconductor pillar 124, the optical ring modulator 100 may include a set of inserted photonic crystal pillars 110c. Figure 8 Two are shown in the diagram. The inserted photonic crystal pillar 110c can be located directly between the oppositely doped portions of the first semiconductor material 104 and the second semiconductor material 106. In some implementations, the inserted photonic crystal pillar can be located directly between the first depletion region 116 and the second depletion region 120, and thus can be positioned along the Y-axis relative to the PN junction 122 ( Figure 8 The photonic signals are adjacent in the horizontal direction. By including inserted photonic crystal pillars 110c within the optical ring modulator 100 to generate staggered PN junctions 122, the group refractive index of the optical ring modulator 100 can further increase the interaction between the photonic signals and each PN junction 122.

[0044] Figures 10-12 Another implementation of the optical ring modulator 100 is shown, wherein portions of the oppositely doped material are adjacent to each other in the circumferential direction (i.e., along the Y-axis) rather than in the radial direction (i.e., along the X-axis). Figure 10 A partial perspective view of this configuration is shown. Figure 11 Provided along Figure 10 The first cross-sectional view in the XZ plane, intercepted by view line 11-11. Figure 12 Provided along Figure 10 The view in Figures 12-12 A second cross-sectional view in the XZ plane. In such a configuration, each XZ cross-section of the optical ring modulator 100 may include only one type of doped semiconductor material, such as the first semiconductor material 104 (…). Figure 10 , 11 ) or second semiconductor material 106 ( Figure 10 , 12 ).

[0045] exist Figures 10-12 In the example, the first semiconductor material 104 and the second semiconductor material 106 are radially (i.e., Figures 10-12The first semiconductor material 104 and the second semiconductor material 106 can be interleaved with one another in the X-axis direction (e.g., in the X-Z cross-section of the optical ring modulator 100). The interleaving of the first semiconductor material 104 and the second semiconductor material 106 can be such that P-N junctions 122 are formed at the physical interfaces between the interleaved semiconductor materials. A photonic crystal layer 110b can be located alongside the first semiconductor material 104 and the second semiconductor material 106 to assist the travel of a photonic signal in the optical ring modulator 100 toward the P-N junctions 122 in substantially the same manner as discussed for other examples herein. In each X-Z cross-section of the optical ring modulator 100, the first semiconductor material 104 or the second semiconductor material 106 can be adjacent to an inactive region 130 composed of non-doped semiconductor material, insulating material, and / or other structures that prevent current from bypassing the P-N junctions 122 Figure 10 The interleaving of the first semiconductor material 104 and the second semiconductor material 106 can continue across the circumference of the optical ring modulator 100 as the optical ring modulator 100 is ring-shaped. Although various features of the optical ring modulator 100 can be described herein as additional or alternative embodiments, it should be understood that any of the features described differently in some examples (e.g., the photonic crystal columns 110a, the photonic crystal layer 110b, the intervening photonic crystal columns 110c, the semiconductor columns 124, etc.) can be changed to be used in other examples in any conceivable combination.

[0046] Embodiments of the present disclosure can provide various technical and commercial advantages, some of which are described herein by way of example. Various embodiments of the present disclosure provide photonic crystal structures (e.g., columns and / or layers proximate to P-N junctions) in an optical ring modulator. Such photonic crystal structures are effective for increasing the optical interaction between a photonic signal and an electro-active P-N junction for optical filtering (e.g., by increasing the group refractive index of the optical modulator structure). Various embodiments of the present disclosure can be implemented in a ring modulator to improve the modulation efficiency of the structure over the entire length of the ring. During operation, these effects can provide a total insertion loss (i.e., insertion loss measured on a power-time curve of a digital signal) that can be less than about one decibel (dB) as compared to an insertion loss of at least about 4.5 dB for a typical working optical modulator in which photonic crystal structures are absent. Conversely, the inclusion of photonic crystal structures in the modulator can significantly increase the extinction ratio (i.e., the ratio between two optical power levels of a digital signal in the modulator) to more than about twenty dB as compared to a significantly smaller extinction ratio (e.g., about 4.5 dB) that is achieved in a conventional ring modulator.

[0047] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. "Optional" or "optionally" means that the subsequently described event or circumstance can or can not occur, and that the description includes instances where the event occurs and instances where it does not.

[0048] Approximating language can be used herein for the purpose of conveying a statistical probability range. Thus, a stated value of, for example, 10% or 90% is intended to convey a statistical probability range of 10% to 90%, unless otherwise expressly stated. Approximating language can be applied to any quantitative representation that involves measurement of a variable that can vary or can not vary. Such a representation is inherently inexact, and it typically involves some implicit statistical distribution rather than a specific value. Thus, use of terms such as "about," "substantially," and "approximately" can permit for variation in a value or value range that still generally falls within the notion of the term so described. Unless otherwise expressly stated, all numerical designations, including numerical ranges, are approximations and should be so considered to account for natural variations occurring in measurements. In one embodiment, the numerical ratings are based on a scale of 1 to 10, with 1 being the lowest rating and 10 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 1 to 5, with 1 being the lowest rating and 5 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 1 to 4, with 1 being the lowest rating and 4 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 1 to 3, with 1 being the lowest rating and 3 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 1 to 2, with 1 being the lowest rating and 2 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 1, with 1 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 2, with 2 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 3, with 3 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 4, with 4 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 5, with 5 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 6, with 6 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 7, with 7 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 8, with 8 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 9, with 9 being the highest rating. In another embodiment, the numerical ratings are based on a scale of 10, with 10 being the highest rating.

[0049] All devices or steps plus functional elements of corresponding structures, materials, acts, and equivalents of the following claims in which are intended to include any structure, material, or act for performing the functions in combination with other claimed The description of the disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or to limit the disclosure to the forms disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. Embodiments were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others skilled in the art to understand various embodiments with various modifications being suited to the particular use contemplated.

Claims

1. An optical ring modulator, comprising: a waveguide structure, comprising: a first semiconductor material having a first doping type, and a second semiconductor material adjacent to the first semiconductor material and having a second doping type opposite the first doping type, the first semiconductor material and the second semiconductor material defining a P-N junction within the waveguide structure; and a plurality of photonic crystal structures, each photonic crystal structure embedded within the first semiconductor material or the second semiconductor material of the waveguide structure and having an upper surface substantially coplanar with an upper surface of the waveguide structure, wherein the plurality of photonic crystal structures includes an intervening photonic crystal post directly between the first semiconductor material and the second semiconductor material.

2. The optical ring modulator of claim 1, wherein the first semiconductor material is adjacent to the second semiconductor material in a horizontal direction.

3. The optical ring modulator of claim 2, wherein the first semiconductor material and the second semiconductor material are interleaved with one another throughout a circumference of the optical ring modulator.

4. The optical ring modulator of claim 1, further comprising: a first plurality of semiconductor posts having the first doping type, each semiconductor post of the first plurality of semiconductor posts embedded within the first semiconductor material above a first photonic crystal structure of the plurality of photonic crystal structures and having a top surface substantially coplanar with a top surface of the first semiconductor material; and a second plurality of semiconductor posts having the second doping type, each semiconductor post of the second plurality of semiconductor posts embedded within the second semiconductor material above a second photonic crystal structure of the plurality of photonic crystal structures and having a top surface substantially coplanar with a top surface of the second semiconductor material.

5. The optical ring modulator of claim 1, further comprising a set of semiconductor posts within at least one of the plurality of photonic crystal structures, each semiconductor post of the set of semiconductor posts having an upper surface substantially coplanar with the upper surface of the plurality of photonic crystal structures and substantially coplanar with a top surface of the waveguide structure.

6. The optical ring modulator of claim 1, wherein the intervening photonic crystal post is between a portion of the first semiconductor material and a portion of the second semiconductor material in a horizontal direction and adjacent to the P-N junction.

7. The optical ring modulator of claim 1, wherein the plurality of photonic crystal structures includes a plurality of photonic crystal posts distributed throughout the first semiconductor material and the second semiconductor material, and wherein a pitch diameter ratio between two photonic crystal posts of the plurality of photonic crystal posts is 2:

1.

8. The optical ring modulator of claim 1, wherein the first semiconductor material and the second semiconductor material comprise silicon (Si), and the plurality of photonic crystal structures comprise crystalline silicon dioxide (Si02).

9. An optical ring modulator, comprising: a waveguide structure, comprising: ​ a first semiconductor material having a first doping type, and a second semiconductor material adjacent to the first semiconductor material and having a second doping type opposite the first doping type, the first semiconductor material and the second semiconductor material defining a P-N junction within the waveguide structure; a first photonic crystal layer on an upper surface of the first semiconductor material; a first plurality of semiconductor pillars having the first doping type, each semiconductor pillar of the first plurality of semiconductor pillars embedded within the first photonic crystal layer and having a top surface substantially coplanar with a top surface of the first photonic crystal layer; a second photonic crystal layer on an upper surface of the second semiconductor material; a second plurality of semiconductor pillars having the second doping type, each semiconductor pillar of the first plurality of semiconductor pillars embedded within the second photonic crystal layer and having a top surface substantially coplanar with a top surface of the second photonic crystal layer; and a third plurality of photonic crystal pillars directly between the first semiconductor material and the second semiconductor material.

10. The optical ring modulator of claim 9, wherein the first semiconductor material is adjacent to the second semiconductor material in a horizontal direction.

11. The optical ring modulator of claim 9, wherein: the first semiconductor material and the second semiconductor material each include a raised portion having a top surface substantially coplanar with a top surface of the first photonic crystal layer or the second photonic crystal layer, and an interface between the first semiconductor material and the second semiconductor material is between the raised portion of the first semiconductor material and the raised portion of the second semiconductor material.

12. The optical ring modulator of claim 11, wherein each photonic crystal pillar of the third plurality of photonic crystals is between a portion of the raised portion of the first semiconductor material and a portion of the raised portion of the second semiconductor material, with no photonic crystal pillars between other portions of the interface between the first semiconductor material and the second semiconductor material.

13. The optical ring modulator of claim 9, wherein a pitch diameter ratio between two semiconductor pillars of the first plurality of semiconductor pillars or the second plurality of semiconductor pillars is 2:

1.

14. The optical ring modulator of claim 9, wherein the first semiconductor material and the second semiconductor material comprise silicon (Si), and the third plurality of photonic crystal pillars comprise crystalline silicon dioxide (Si02).

15. An optical ring modulator, comprising: a waveguide structure including: a first semiconductor material having a first doping type, and a second semiconductor material adjacent to the first semiconductor material and having a second doping type opposite the first doping type, the first semiconductor material and the second semiconductor material defining a P-N junction within the waveguide structure; a first plurality of photonic crystal pillars within the first semiconductor material, each photonic crystal pillar of the first plurality of photonic crystal pillars having a bottom surface that is substantially coplanar with a bottom surface of the first semiconductor material; a first photonic crystal layer on the first plurality of photonic crystal pillars and within a recessed region of the first semiconductor material; a second plurality of photonic crystal pillars within the second semiconductor material, each photonic crystal pillar of the second plurality of photonic crystal pillars having a bottom surface that is substantially coplanar with a bottom surface of the second semiconductor material; a second photonic crystal layer on the second plurality of photonic crystal pillars and within a recessed region of the second semiconductor material; and a third plurality of photonic crystal pillars directly between the first semiconductor material and the second semiconductor material.

16. The optical ring modulator of claim 15, wherein the first semiconductor material is horizontally adjacent to the second semiconductor material.

17. The optical ring modulator of claim 15, wherein: the first semiconductor material and the second semiconductor material each include a raised portion having a top surface that is substantially coplanar with a top surface of the waveguide structure, and an interface between the first semiconductor material and the second semiconductor material is between the raised portion of the first semiconductor material and the raised portion of the second semiconductor material.

18. The optical ring modulator of claim 17, wherein each photonic crystal pillar of the third plurality of photonic crystal pillars is between a portion of the raised portion of the first semiconductor material and a portion of the raised portion of the second semiconductor material, wherein there are no photonic crystal pillars between other portions of the interface between the first semiconductor material and the second semiconductor material.

19. The optical ring modulator of claim 15, wherein a pitch diameter ratio between two semiconductor pillars of the first plurality of photonic crystal pillars or the second plurality of photonic crystal pillars is 2:

1.

20. The optical ring modulator of claim 15, wherein the first semiconductor material and the second semiconductor material comprise silicon (Si), and the first plurality of photonic crystal pillars or the second plurality of photonic crystal pillars comprise crystalline silicon dioxide (Si02).

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