WO2024117360A1

WO2024117360A1 - Integrated optical isolator and circulator element

Info

Publication number: WO2024117360A1
Application number: PCT/KR2022/020605
Authority: WO
Inventors: 김경헌; 김승환; 박범수
Original assignee: 주식회사 포토니솔
Priority date: 2022-11-30
Filing date: 2022-12-16
Publication date: 2024-06-06
Also published as: KR20240081090A

Abstract

The present invention may provide an integrated optical isolator and circulator element, comprising: an input end optical coupler connected to an input end optical waveguide and an output end optical coupler connected to an output end optical waveguide; a first optical waveguide arm and a second optical waveguide arm connecting the input end optical coupler and the output end optical coupler; an irreversible phase shifter formed on the first optical waveguide arm and the second optical waveguide arm; an input end reversible polarization rotator positioned between the input optical coupler and the irreversible phase shifter, and an output end reversible polarization rotator positioned between the irreversible phase shifter and the output end optical coupler; and a polarization-dependent reversible phase shifter positioned between the irreversible phase shifter and the output end optical coupler, wherein the input end reversible polarization rotator and the output end reversible polarization rotator are formed on the first optical waveguide arm, and the polarization-dependent reversible phase shifter is formed on the second optical waveguide arm.

Description

Integrated optical isolator and circulator elements

The present invention relates to an integrated optical isolator and a circulator device, and more specifically, to an integrated device having an optical isolator function and an optical circulator function for all input polarized light.

Integrated optical isolators and optical circulator elements are essential for generating stable optical signals from laser diodes used in large-capacity optical transmission and reception modules, as well as photonics such as optical interposers and optical interconnects. It is an important element that is essential for integrated modules and circuit configurations.

Although various research and development results have been reported on these integrated optical isolators and optical circulator devices, they have not been developed to a level that can be mass-produced by applying them to existing silicon semiconductor processes.

For example, among conventional optical isolators and optical circulator devices, devices that form all or part of an optical interferometer using an optical waveguide made of magneto-optical material have the disadvantage of being disadvantageous in integration with other waveguide devices and operating only in horizontal or vertical polarization. In addition, devices using an irreversible phase shifter that uses silicon or other materials as an optical waveguide but attaches a magneto-optical thin film to the top have not reached the level of mass production and practical use.

The purpose of the present disclosure is to provide an integrated optical isolator and circulator element. The problem to be solved by the present disclosure is not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description of the present invention. The present disclosure will be understood more clearly by the examples. In addition, it will be appreciated that the problems and advantages to be solved by the present disclosure can be realized by the means and combinations thereof indicated in the patent claims.

As a means to solve the above-described technical problem, an integrated optical isolator and circulator device according to an embodiment of the present disclosure includes an input optical coupler connected to an input optical waveguide and an output optical coupler connected to an output optical waveguide; a first optical waveguide arm and a second optical waveguide arm connecting between the input optical coupler and the output optical coupler; an irreversible phase shifter formed on the first optical waveguide arm and the second optical waveguide arm; an input reversible polarization rotator located between the input optical coupler and the irreversible phase shifter, and an output reversible polarization rotator located between the irreversible phase shifter and the output optical coupler; and a polarization-dependent reversible phase shifter positioned between the irreversible phase shifter and the output optical coupler, wherein the input reversible polarization rotator and the output reversible polarization rotator are formed on the first optical waveguide arm, A polarization-dependent reversible phase shifter may be formed on the second optical waveguide arm.

Other aspects, features and advantages in addition to those described above will become apparent from the following drawings, claims and detailed description of the invention.

According to the problem-solving means of the present disclosure described above, it is possible to provide an integrated optical isolator and circulator device that can be easily integrated with other devices in a planar optical waveguide integrated circuit and can be mass-produced by applying to a semiconductor process.

In addition, according to the problem solving means of the present disclosure, the optical isolator and optical circulator functions can be performed with an integrated optical isolator and circulator element of the same structure for all input polarizations.

The effects of the examples are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the present invention.

Figure 1 is a diagram showing an integrated optical isolator and a circulator element according to an embodiment.

Figure 2 is a diagram showing the connection relationship between components of an integrated optical isolator and a circulator element according to an embodiment.

Figure 3 is a diagram showing a cross section of an irreversible phase shifter according to an embodiment.

Figure 4 is a cross-sectional view of a reversible polarization rotator according to an embodiment.

Figure 5 is a diagram showing a polarization-dependent reversible phase shifter according to an embodiment.

Figure 6 is a graph showing the effective refractive index distribution for each waveguide mode of a channel optical waveguide according to a change in the width of the optical waveguide according to an embodiment.

Figure 7 is a diagram showing an integrated optical isolator and circulator element having three input ports according to an embodiment.

An integrated optical isolator and circulator element, comprising: an input optical coupler connected to an input optical waveguide and an output optical coupler connected to an output optical waveguide; a first optical waveguide arm and a second optical waveguide arm connecting between the input optical coupler and the output optical coupler; an irreversible phase shifter formed on the first optical waveguide arm and the second optical waveguide arm; an input reversible polarization rotator located between the input optical coupler and the irreversible phase shifter, and an output reversible polarization rotator located between the irreversible phase shifter and the output optical coupler; and a polarization-dependent reversible phase shifter positioned between the irreversible phase shifter and the output optical coupler, wherein the input reversible polarization rotator and the output reversible polarization rotator are formed on the first optical waveguide arm, A polarization-dependent reversible phase shifter may provide an integrated optical isolator and circulator element formed on the second optical waveguide arm.

In describing the present invention, if it is judged that a detailed description of related known technology may obscure the gist of the present invention, the detailed description may be omitted, and unless otherwise defined, all terms used in this specification refer to the present invention. It has the same meaning as generally understood by those with ordinary knowledge in the relevant technical field.

Phrases such as “according to one embodiment,” “related to one embodiment,” or “according to an implementation of an embodiment” in this specification do not necessarily all refer to the same embodiment.

Since the embodiments can be subject to various changes and have various forms, some embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the embodiments to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the embodiments. The terms used in the specification are merely used to describe the embodiments and are not intended to limit the embodiments.

The terms used in the embodiments are general terms that are currently widely used as much as possible while considering the functions in the embodiments, but this is due to the intention or precedent of technicians working in the technical field to which the embodiments belong, the emergence of new technology, etc. It may vary depending on In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the relevant section. Therefore, the terms used in the embodiments should be defined based on the meaning of the term and the overall content of the embodiments, rather than simply the name of the term.

Additionally, terms including ordinal numbers such as 'first' or 'second' used in this specification may be used to describe various components, but the components should not be limited by the terms. Terms are used only to distinguish one component from another.

Additionally, some components in the drawing may be depicted with their size or proportions somewhat exaggerated. Additionally, components shown in one drawing may not be shown in other drawings.

Throughout the specification, 'examples' is an arbitrary division for easily explaining the invention in the present disclosure, and each embodiment does not need to be mutually exclusive. For example, configurations disclosed in one embodiment may be applied and/or implemented in another embodiment, and may be applied and/or implemented with changes without departing from the scope of the present disclosure.

Additionally, the terms used in this disclosure are for describing the embodiments and are not intended to limit the embodiments. In this disclosure, the singular form also includes the plural form unless otherwise specified.

Below, with reference to the attached drawings, embodiments of the present disclosure will be described in detail so that those skilled in the art can easily implement them. However, embodiments of the present disclosure may be implemented in various different forms and are not limited to the embodiments described in the present disclosure.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, the integrated optical isolator and circulator element 100 according to an embodiment includes an input optical waveguide (105a, 105b), an input optical coupler (101a), an input reversible polarization rotator (110a), and an irreversible phase. It may include a shifter 103, an output reversible polarization rotator 110b, a polarization-dependent reversible phase shifter 120, an output optical coupler 101b, and an output

optical waveguide

106a, 106b. At this time, the integrated optical isolator and circulator element 100 includes a first optical waveguide arm 102a and a second optical waveguide arm 102b connecting between the input optical coupler 101a and the output optical coupler 101b. It can be included.

The input

optical waveguides

105a and 105b are ports through which light is incident from a light source. Light is incident through one input optical waveguide 105a and travels to the integrated optical isolator and circulator element 100 and is transmitted to the output optical waveguide ( 106a). At this time, if the light traveling to the integrated optical isolator and circulator element 100 in the opposite direction through the output optical waveguide 106a is not output to the input optical waveguide 105a, the integrated optical isolator and circulator element (100) can function as an optical isolator. In addition, if light traveling through the output optical waveguide 106a through the integrated optical isolator and circulator element 100 in the opposite direction is output to the other input optical waveguide 105b, the integrated optical isolator and circulator Device 100 may function as an optical circulator.

The

optical couplers

101a and 101b are optical passive elements that have the function of distributing or splitting optical signals into two or more to propagate, or conversely, combining two or more optical signals that have been propagated into one. That is, the

optical couplers

101a and 101b can function as both an optical splitter and an optical combiner. The

optical couplers

101a and 101b have N depending on the terminal structure of the input and output terminal.

It has the shape of M. For example, if the number of optical fibers at the optical coupler input end is N and the number of optical fibers at the optical coupler output end is M, the

optical couplers

101a and 101b have N

It may have the form M.

In one embodiment, the input optical coupler 101a and the output optical coupler 101b may each be a 3dB optical coupler. In addition, the input optical coupler 101a has 2

2 form or 3

It may have a 2 shape, and the output stage optical coupler 101b has 2

2 form or 2

It can have 3 forms. The input optical coupler (101a) and the output optical coupler (101b) are each 3

2 forms and 2

Embodiments of the three types of integrated optical isolator and circulator element 100 will be described later with reference to FIG. 7.

In one embodiment, the first optical waveguide arm 102a and the second optical waveguide arm 102b are waveguides configured to allow light propagated through the input optical coupler 101a to proceed respectively and be combined at the output optical coupler 101b. It can be.

In one embodiment, the first optical waveguide arm 102a and the second optical waveguide arm 102b may be channel-type silicon optical waveguides formed on an oxide layer of a silicon on insulator (SOI) substrate. Specifically, the first optical waveguide arm 102a and the second optical waveguide arm 102b form an optical waveguide in a channel shape on a silicon substrate on the top of the SOI substrate, and an oxide film (for example, an oxide film) is formed around the upper part of the optical waveguide. , It may be created by forming an oxide film made of silicon dioxide. The first and second

optical waveguide arms

102a and 102b are formed as described above, and the

optical waveguide arms

102a and 102b include an irreversible phase shifter 103 in which the oxide film is removed on the upper part of the waveguide and a magneto-optical thin film is formed, and a reversible phase shifter 103 is provided. Elements such as

polarization rotators

110a and 110b may be integrated.

In one embodiment, the input reversible polarization rotator 110a and the output reversible polarization rotator 110b convert vertical (Transverse Electric Wave, TE) polarization into horizontal (Transvers Magnetic Wave, TM) polarization, or TM polarization into TE polarization. can do. A pair of two

reversible polarization rotators

110a and 110b may exist on the first optical waveguide arm 102a.

In one embodiment, the irreversible phase shifter 103 can irreversibly change the phase of an optical signal using a magneto-optic effect material. The magneto-optical effect of a magneto-optical material, that is, the Faraday effect, is a magneto-optical effect in which the polarization axis of an optical signal rotates under the influence of an external magnetic field, and the first optical waveguide arm 102a and the second optical waveguide arm 102b ) As the light traveling passes through the magneto-optical material of the irreversible phase shifter 103, the polarization axis may rotate by a predetermined angle. For example, the predetermined angle may be determined by the length of the irreversible phase shifter 103 and the size of the external magnetic field or residual magnetic field, or the predetermined angle may be determined by the size of the optical signal passing through the irreversible phase shifter 103. It may vary depending on the wavelength. When TE polarized light or TM polarized light passes through the irreversible phase shifter 103, the effect on the propagation speed of TE polarization is minimal, but it may have a significant effect on the propagation speed of TM polarization. Therefore, the progressing speed of each polarization can be adjusted through the polarization-dependent reversible phase shifter 120, which will be described later, so that the integrated optical isolator and circulator element 100 can perform a complete optical isolator or optical circulator function.

In one embodiment, the irreversible phase shifter 103 may be formed connected to the first optical waveguide arm 102a and the second optical waveguide arm 102b as shown in FIG. 1, but may be formed separately. It may be (not shown). For example, the irreversible phase shifter 103 includes a first irreversible phase shifter 103 formed on the first optical waveguide arm 102a and a second irreversible phase shifter formed on the second optical waveguide arm 102b. It may include a device 103. In this case, the first irreversible phase shifter 103 and the second irreversible phase shifter 103 may be separated from each other, or may be connected to each other.

In one embodiment, the phase is reversibly changed to have a positive phase value or a negative phase value compared to the phase of an optical signal traveling through a general optical waveguide depending on the type of polarization input to the polarization-dependent reversible phase shifter 120. You can. Unlike the irreversible phase shifter 103 using a magneto-optical material, the polarization-dependent reversible phase shifter 120 adjusts the width of the optical waveguide or changes the type of clad on the upper part of the optical waveguide according to the refractive index to control the passage of light. Speed can be changed.

In one embodiment, the polarization-dependent reversible phase shifter 120 transmits optical light traveling through the integrated optical isolator and circulator element 100 in the forward direction (i.e., from the input optical waveguide 105a to the output optical waveguide 106b). An optical signal propagates through the integrated optical isolator and circulator element 100 in the reverse direction (i.e., from the output optical waveguide 106a to the input optical waveguide 105a) so that constructive interference occurs in the output optical waveguide 106b. The width and length of the optical waveguide inside the polarization-dependent reversible phase shifter 120 or the refractive index of the upper clad can be adjusted so that destructive interference occurs in the input optical waveguide 105a. At this time, the light traveling through the integrated optical isolator and circulator element 100 is output only in the direction of the output optical waveguide 106a and the light cannot return to the input optical waveguide 105a, so the integrated optical isolator and circulator device The device 100 may implement a function as an optical isolator. Conversely, the optical signal traveling in the opposite direction through the integrated optical isolator and circulator element 100 causes destructive interference in one input optical waveguide 105a, but constructive interference occurs in the other input optical waveguide 106a, The width of the optical waveguide inside the polarization-dependent reversible phase shifter 120 or the refractive index of the upper clad can be adjusted. At this time, the light incident on one input optical waveguide 105a and traveling in the forward direction through the integrated optical isolator and circulator element 100 proceeds to the output optical waveguide 106b and is incident on the output optical waveguide 106b. Therefore, the light traveling in the reverse direction through the integrated optical isolator and circulator element 100 is output only to the other input optical waveguide 105b, so the integrated optical isolator and circulator element 100 can implement the function as an optical circulator. You can.

Referring to FIG. 2, the integrated optical isolator and circulator element 200 includes an input optical waveguide (205a, 205b), an input optical coupler (201a), a first optical waveguide arm (202a), and an input reversible polarization rotator (210a). , an irreversible phase shifter (203), an output-end reversible polarization rotator (210b), a second optical waveguide arm (202b), a polarization-dependent reversible phase shifter (220), an output-end optical coupler (201b), and an output-end optical waveguide (206a, 206b) includes the input

optical waveguides

105a and 105b, the input optical coupler 101a, the first optical waveguide arm 102a, and the input reversible polarization rotator of the integrated optical isolator and circulator element 100 described above in FIG. 110a), an irreversible phase shifter 103, an output reversible polarization rotator 110b, a second optical waveguide arm 102b, a polarization-dependent reversible phase shifter 120, an output optical coupler 101b, and an output optical waveguide ( It may be the same as 106a, 106b). Therefore, overlapping descriptions will be omitted.

In one embodiment, the input optical coupler 201a and the output optical coupler 201b may be connected to the input

optical waveguides

205a and 205b and the output

optical waveguides

206a and 206b, respectively.

In one embodiment, the first optical waveguide arm 202a and the second optical waveguide arm 202b may be connected between the input optical coupler 201a and the output optical coupler 201b. In particular, the first optical waveguide arm 202a may configure a first path along which light travels, and the second optical waveguide arm 202b may configure a second path along which light travels. For example, the light incident on the input

optical waveguides

205a and 205b passes through the input optical coupler 201a to the first optical waveguide arm 202a forming the first path and the second optical waveguide arm forming the second path ( It can be branched out through 202b).

In one embodiment, the irreversible phase shifter 203 may be formed in the first optical waveguide arm 202a and the second optical waveguide arm 202b.

In one embodiment, a pair of

reversible polarization rotators

210a and 210b may be formed on the first optical waveguide arm 202a. For example, the input reversible polarization rotator 210a may be located between the input optical coupler 201a and the irreversible phase shifter 203, and the output reversible polarization rotator 210b may be located between the irreversible phase shifter 203. and the output end optical coupler 201b. Accordingly, the light traveling the first path passes through a pair of reversible polarization rotators (210a, 210b) and an irreversible phase shifter (203) located between the pair of reversible polarization rotators (210a, 210b) to the output end light. You can proceed with the coupler (201b).

In one embodiment, a polarization-dependent reversible phase shifter 220 may be formed on the second optical waveguide arm 202b. For example, the polarization-dependent reversible phase shifter 220 may be located between the irreversible phase shifter 203 and the output optical coupler 201b. Accordingly, light traveling through the second path may proceed to the output optical coupler 201b through the irreversible phase shifter 203 and the polarization-dependent reversible phase shifter 220. As a result, each light traveling through the first path and the second path may be combined at the output end optical coupler 201b and output through the output end

optical waveguides

206a and 206b.

Referring to FIG. 3, the cross section of the irreversible phase shifter may represent the cross section A-A' of FIG. 1. That is, the irreversible phase shifter of FIG. 3 may be the same as the irreversible phase shifter 103 of FIG. 1 and the irreversible phase shifter 203 of FIG. 2 .

In one embodiment, the irreversible phase shifter may be formed in the channel-type first optical waveguide arm 312 formed on the oxide layer 311 of the SOI substrate. Specifically, the irreversible phase shifter may be formed by coating the magnetic thin film 314 with clad. For example, if the first optical waveguide arm 312 is a channel-type optical waveguide formed on the oxide film layer 311 of the SOI substrate and is created by forming the oxide film 313 on the optical waveguide, the irreversible phase shifter is formed on the optical waveguide. It can be created by etching a portion of the upper oxide film 313 and the first optical waveguide arm 312 and forming a magneto-optical thin film layer 314 on the etched portion. If the residual magnetic field of the magneto-optical thin film 314 is weak, an additional magnetic thin film 315 may be formed on the top.

Specifically, the irreversible phase shifter is created by coating an oxide film formed on the top of the first optical waveguide arm 312 and a mask thin film on the oxide film, and removing the upper mask layer in the area where the irreversible phase shifter is to be generated from the coated mask layer, It can be created by performing an oxide film etching process on the area from which the mask layer was removed, coating and heat treating the magneto-optical thin film 314. At this time, as described above, if the residual magnetization of the coated magneto-optical thin film 314 is low, the magnetic thin film 315 may be additionally coated and magnetized. Additionally, the residual magnetization of the magneto-optical thin film 314 or the magnetization of the additional magnetic thin film 315 may be magnetized in a direction perpendicular to the direction of optical signal propagation of the optical waveguide arm 312. Specifically, the magneto-optical thin film 314 may be coated at an inclination angle with respect to the travel direction of the first and second optical waveguide arms, and may be magnetized perpendicular to the travel direction of the first and second optical waveguide arms.

Referring to FIG. 4, the cross section of the reversible polarization rotator may represent the B-B' cross section of FIG. 1. That is, the reversible polarization rotator of FIG. 4 may be the same as the input and output

reversible polarization rotators

110a and 110b of FIG. 1 and the input and output

reversible polarization rotators

210a and 210b of FIG. 2 .

In one embodiment, the reversible polarization rotator may be formed by etching the channel-type first optical waveguide arm 412 formed on the oxide layer 411 of the SOI substrate. For example, as in FIG. 3, the first optical waveguide arm 412 is a channel-type optical waveguide 412 formed on the oxide layer 411 of the SOI substrate, and a portion of the corner of the first optical waveguide arm 412 ( After etching 416), an oxide film 413 may be formed on the optical waveguide 412.

Specifically, the reversible polarization rotator removes the upper mask layer of the area 416 to be etched to create a polarization rotator among the mask layers coated on the top of the first optical waveguide arm 412, and It can be created by performing an etching process on a portion of the waveguide, removing the mask layer, and then forming an oxide layer 413 on the top of the first optical waveguide arm 412.

In one embodiment, the polarization rotator has a structure formed by etching a portion of the edge 416 of the first optical waveguide arm 412, as well as a structure in which an asymmetric groove is formed in the first optical waveguide arm 412 and the first optical waveguide arm 412. One side of (412) may have an inclined structure, etc., and the structure of the polarization rotator is not limited to this.

The polarization-dependent reversible phase shifter of FIG. 5 may be the same as the polarization-dependent reversible phase shifter 120 of FIG. 1 and the polarization-dependent reversible phase shifter 220 of FIG. 2 .

Referring to FIG. 5, the polarization-dependent reversible phase shifter includes one or

more input ports

525a and 525b, an input polarization splitter 521a, a high-speed optical waveguide 524, a low-speed optical waveguide 523, and an output polarization splitter ( 521b) and one or

more output ports

526a and 526b.

In one embodiment, the input polarization splitter 521a may separate light traveling through the second optical waveguide arm into TE polarization and TM polarization. Specifically, the input polarization splitter 521a can separate TE polarization and TM polarization by using the principle that the propagation constants of TE polarization and TM polarization are different depending on the characteristics of the optical waveguide. At this time, the TM polarization and TE polarization separated by the input polarization splitter 521a may propagate to the high-speed optical waveguide 524 or the low-speed optical waveguide 523, respectively.

The high-speed optical waveguide 524 is an optical waveguide in which the relative speed of light is higher than that of a general optical waveguide and the propagation speed of one polarization is higher than the propagation speed of the other polarization, and is comprised of the first optical waveguide arm and the second optical waveguide arm. When the waveguide width is narrower than the width of a general optical waveguide or has an upper clad with a low effective refractive index, it has a negative phase value compared to the phase of the optical signal passing through the general optical waveguide, thereby increasing the speed of light travel. For example, to form the high-speed optical waveguide 524, the waveguide width can be narrowed, or the upper clad can be changed to a material with a low effective refractive index. Likewise, the low-speed optical waveguide 523 is an optical waveguide in which the relative traveling speed of light is lower than that of a general optical waveguide and the traveling speed of polarization on one side is opposite, and the general optical waveguide of the first optical waveguide arm and the second optical waveguide arm When the waveguide has a width wider than the width or has an upper clad with a high effective refractive index, it has a positive phase value compared to the phase of an optical signal passing through a general optical waveguide, slowing down the speed of light. For example, to form the low-speed optical waveguide 523, the waveguide width can be made wider, or the upper clad can be changed to a material with a high effective refractive index.

Meanwhile, in order to change the effective refractive index of the high-speed optical waveguide 524 and/or the low-speed optical waveguide 523, a method of applying heat or irradiating a laser to the existing clad material on the upper part of the

optical waveguides

523 and 524 can be utilized. You can.

In one embodiment, the output terminal polarization splitter 521b may output the combined TE polarization and TM polarization transmitted through the high-speed optical waveguide 524 and the low-speed optical waveguide 523. At this time, which optical waveguide the TE polarization and TM polarization travel through among the high-speed optical waveguide 524 and the low-speed optical waveguide 523 depends on the positions of the

input ports

525a and 525b of the input terminal polarization splitter 521a. For example, the polarization-dependent reversible phase shifter of FIG. 5 represents an embodiment in which an optical signal is input to the input terminal polarization splitter 521a through the upper input port 525a.

At this time, in the input terminal polarization splitter 521a, TE polarization proceeds in a straight line and is input to the low-speed optical waveguide 523, but TM polarization crosses and is input to the high-speed optical waveguide 524. At this time, the input polarization splitter 521a may further include an intermediate optical waveguide that allows TM polarization to traverse. Likewise, TM polarized light that has passed through the high-speed optical waveguide 524 can be output from the output port 526a by crossing through the intermediate optical waveguide at the output end polarization splitter 521b. However, the split polarization path may vary depending on the structure of the input polarization splitter 521a, and the output port of the merged polarization may vary depending on the structure of the output polarization splitter 521b.

FIG. 6 is a graph showing the effective refractive index distribution for each waveguide mode of a channel optical waveguide with respect to a change in the width of the optical waveguide according to an embodiment.

Referring to FIG. 6, it can be seen that the effective refractive index changes depending on the width of the optical waveguide used in the polarization-dependent reversible phase shifter. In one embodiment, when the optical waveguide width is 300 nm and the lateral inclination is 80 degrees, when the optical waveguide width changes at a wavelength of 1310 nm, looking at the modes and effective refractive index changes within the optical waveguide, in the case of a single-mode optical waveguide, the optical waveguide width is 230 nm. Below, it can be seen that the effective refractive index of TE polarized light and TM polarized light is relatively small, and the effective refractive index of TM polarized light is larger than that of TE polarized light. When the optical waveguide width is wider than 230 nm, the effective refractive index value may increase, and it can be seen that the effective refractive index of TE polarized light is greater than that of TM polarized light. The optical isolator and All polarized light encountering the optical waveguide at the output end of the circulator element causes constructive interference, and conversely, light traveling in the opposite direction causes destructive interference at the optical waveguide at the input end. Depending on the degree of phase change in the reversible polarization rotator located in the first optical waveguide arm, the selection of the input ports (525a, 525b) and output ports (526a, 526b) of the polarization-dependent reversible phase shifter may also be changed.

Referring again to FIG. 2, an operational embodiment of the integrated optical isolator and circulator element 200 is shown assuming that TE polarized light or TM polarized light is input to the input

optical waveguides

205a and 205b according to the above-described embodiment. Explain. When TE polarized light is input to the input end optical waveguide 205a, the TE polarized light is branched through the input end optical coupler 201a to the first path of the first optical waveguide arm 202a and the second path of the second optical waveguide arm 202b. 2 routes will be followed. TE polarization traveling through the first path is converted into TM polarization through the input polarization rotator 210a, passes through the irreversible phase shifter 203, slows down, and is converted back into TE polarization through the output polarization rotator 210b. converted. That is, the TE polarized light that has traveled the first path arrives at the output optical coupler 201b at a reduced travel speed. The TE polarized light traveling the second path is not affected by the traveling speed as it passes through the irreversible phase shifter 203, so its speed is faster than the TE polarized light traveling the first path. TE polarized light passing through the irreversible phase shifter 203 of the second path is input to the polarization-dependent reversible phase shifter 220 (specifically, the upper input port of the polarization-dependent reversible phase shifter 220), According to the above-described embodiment, a low-speed optical waveguide is used, thereby slowing down the speed. That is, the TE polarization that travels the second path slows down like the TE polarization that travels the first path, and is combined at the output end optical coupler 201b.

Similarly, when TM polarized light is input to the input optical waveguide 205a, the TM polarized light is split through the input optical coupler 201a and passes through the first path of the first optical waveguide arm 202a and the second optical waveguide arm 202b. The second path is proceeded. TM polarization traveling through the first path is converted into TE polarization through the input polarization rotator 210a, is not affected by the traveling speed while passing through the irreversible phase shifter 203, and is returned to TM through the output polarization rotator 210b. converted to polarized light. That is, the TM polarized light traveling the first path arrives at the output optical coupler 201b without being affected by the traveling speed. The TM polarization traveling through the second path slows down as it passes through the irreversible phase shifter 203, making it slower than the TM polarization traveling through the first path. The TM polarized light that has passed through the irreversible phase shifter 203 of the second path is input to the polarization-dependent reversible phase shifter 220 (specifically, the upper input port of the polarization-dependent reversible phase shifter 220), According to the above-described embodiment, the speed is increased by using a high-speed optical waveguide. That is, the TM polarized light that travels the second path has the same traveling speed as the TM polarized light that travels the first path, and is combined at the output end optical coupler 201b.

As such, the integrated optical isolator and circulator element 200 according to an embodiment of the present invention can perform optical isolator and optical circulator functions regardless of input polarization, such as TE polarization and TM polarization.

Referring to FIG. 7, for the configuration of an integrated optical isolator and circulator device according to another embodiment, the input

optical waveguides

705a, 705b, 705c and the output

optical waveguides

706a, 706b, 706c are three optical waveguides. It can be done. Meanwhile, elements other than the input optical waveguides (705a, 705b, 705c) and the output optical waveguides (706a, 706b, 706c), such as input and output optical couplers (701a, 701b), first and second optical waveguide arms ( 702a, 702b), a pair of polarization rotators (710a, 710b), an irreversible phase shifter (703), and a polarization-dependent reversible phase shifter (720) are connected to the input and output optical couplers (201a, 201b) of FIG. It may be the same as the first and second optical waveguide arms (202a, 202b), a pair of polarization rotators (210a, 210b), the irreversible phase shifter (203), and the polarization-dependent reversible phase shifter (220).

In one embodiment, the input optical coupler 701a and the output optical coupler 701b each have 3

2 forms and 2

It can have 3 forms. At this time, one of the three

optical waveguides

705a and 706a may be a bridge-type optical waveguide. For example, the input optical coupler 701a is tapered so that the three

input ports

705a, 705b, and 705c are divided into a first optical waveguide arm 702a and a second optical waveguide arm 702b. You can. Likewise, the output end optical coupler 701b may be configured to be tapered so that the first optical waveguide arm 702a and the second optical waveguide arm 702b are divided into three

output ports

706a, 706b, and 706c. .

In one embodiment, the integrated optical isolator and circulator device uses a multimode interferometer structure, uses a Mach-Zehnder interferometer structure, uses an asymmetric directional coupler, uses a directional coupler consisting of a curved optical waveguide, or uses a multi-level optical coupler. By using a directional coupler or a directional coupler composed of an optical waveguide with a groove, an input optical waveguide (705a, 705b, 705c) and an output optical waveguide (706a, 706b, 706c) having three optical waveguides can be formed. there is.

Unless there is an explicit order or statement to the contrary regarding the steps constituting the method according to the invention, the steps may be performed in any suitable order. The present invention is not necessarily limited by the order of description of the above steps. The use of all examples or illustrative terms in the present invention is simply for explaining the present invention in detail, and the scope of the present invention is not limited by the examples or illustrative terms unless limited by the claims. Additionally, those skilled in the art will recognize that various modifications, combinations and changes may be made depending on design conditions and factors within the scope of the appended claims or their equivalents.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and the scope of the patent claims described below as well as all scopes equivalent to or equivalently changed from the scope of the claims are within the scope of the spirit of the present invention. It will be said to belong to

Claims

an input optical coupler connected to the input optical waveguide and an output optical coupler connected to the output optical waveguide;

a first optical waveguide arm and a second optical waveguide arm connecting between the input optical coupler and the output optical coupler;

an irreversible phase shifter formed on the first optical waveguide arm and the second optical waveguide arm;

an input reversible polarization rotator located between the input optical coupler and the irreversible phase shifter, and an output reversible polarization rotator located between the irreversible phase shifter and the output optical coupler; and

It includes a polarization-dependent reversible phase shifter located between the irreversible phase shifter and the output optical coupler,

The input reversible polarization rotator and the output reversible polarization rotator are formed on the first optical waveguide arm,

The polarization-dependent reversible phase shifter is formed on the second optical waveguide arm.
According to claim 1,

The irreversible phase shifter,

A magneto-optical thin film is coated on the top of the first and second optical waveguide arms to irreversibly change the phase of light traveling through the first and second waveguide arms,

The magneto-optical thin film is,

An integrated optical isolator and circulator element coated at a predetermined inclination angle with respect to the traveling direction of the first and second optical waveguide arms and magnetized perpendicular to the traveling direction of the first and second optical waveguide arms. .
According to claim 2,

The irreversible phase shifter,

a first irreversible phase shifter formed on the first optical waveguide arm; and

A second irreversible phase shifter formed on the second optical waveguide arm,

An integrated optical isolator and circulator device, wherein the first and second irreversible phase shifters are separated from each other.
According to claim 1,

The polarization-dependent reversible phase shifter,

an input polarization splitter that separates the light traveling through the second optical waveguide arm into TE (Transverse Electric Wave) polarization and TM (Transverse Magnetic Wave) polarization;

a high-speed optical waveguide that increases the propagation speed of TE polarization or TM polarization separated from the input polarization splitter;

a low-speed optical waveguide that reduces the propagation speed of TE polarization or TM polarization separated from the input polarization splitter; and

an output-stage polarization splitter that combines TE polarization and TM polarization transmitted through the high-speed optical waveguide and the low-speed optical waveguide and outputs the output;

An integrated optical isolator and circulator element comprising a.
According to claim 4,

The high-speed optical waveguide,

Having a waveguide width narrower than the width of the second optical waveguide arm, or having an upper clad with a low effective refractive index,

The low-speed optical waveguide,

An integrated optical isolator and circulator element having a waveguide width wider than the width of the second optical waveguide arm or having an upper clad with a high effective refractive index.
According to claim 1,

The input optical waveguide and the output optical waveguide are:

An integrated optical isolator and circulator element consisting of two or three optical waveguides.