Polarization rotating reflector

Abstract

The present invention discloses a polarization rotation reflector and a polarization-independent interferometer comprising: an optical coupler having a 50:50 distribution ratio; first and second input optical waveguides connected to one end of the optical coupler; first and second connecting optical waveguides connected to the other end of the optical coupler; and a loop-shaped optical waveguide connected to the first and second connecting optical waveguides, wherein the loop-shaped optical waveguide comprises a core portion penetrating the center, stress-applying portions adjacent to both sides of the core portion, and a cladding portion surrounding the core portion and the stress-applying portions, wherein the cross-section of the first end of the loop-shaped optical waveguide has a shape formed by rotating the cross-section of the second end of the loop-shaped optical waveguide by 90 degrees.

Description

Technology Field

[0001] The present invention relates to a polarization rotating reflector, and more specifically, to a polarization rotating reflector that rotates the polarization of incident light by 90 degrees and reflects it with a simple structure, and to a polarization-independent interferometer including the same. Background Technology

[0002] In the information society, the rapid development of computer and internet technologies necessitates technologies capable of rapidly processing large volumes of information in various forms. Existing technologies, which rely on electronic technology based on copper wiring, are showing limitations in terms of transmission volume and speed. To meet the demands of an ultra-high-speed information and communication society, the development of optical communication technology capable of accommodating massive information capacities is essential.

[0003] To develop optical communication technology, research is being conducted on optical devices that change the polarization state without magneto-optical materials or magnets, unlike Faraday mirrors that rotate and reflect the polarization of incident light using the magneto-optic Faraday effect. The problem to be solved

[0004] The present invention aims to provide a polarization rotation reflector that rotates the polarization of incident light by 90 degrees and reflects it with a simple structure, and a polarization-independent interferometer including the same.

[0005] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0006] A polarizing rotating reflector according to the present invention comprises an optical coupler having a 50:50 distribution ratio, first and second input optical waveguides connected to one end of the optical coupler, first and second connecting optical waveguides connected to the other end of the optical coupler, and a loop-shaped optical waveguide connected to the first and second connecting optical waveguides, wherein the loop-shaped optical waveguide comprises a core portion penetrating the center, stress-applying portions adjacent to both sides of the core portion, and a cladding portion surrounding the core portion and the stress-applying portions, and the cross-section of the first end of the loop-shaped optical waveguide may have a shape obtained by rotating the cross-section of the second end of the loop-shaped optical waveguide by 90 degrees. Effects of the invention

[0007] The polarization rotating reflector according to the present invention can reflect incident light by rotating its polarization by 90 degrees with a simple structure and can be manufactured at a low cost, so it can be used in polarization-independent interferometers. Brief explanation of the drawing

[0008] FIG. 1 is a plan view illustrating a polarizing rotating reflector according to embodiments of the present invention. FIG. 2 is a conceptual diagram illustrating the structure and cross-section of a polarizing rotating reflector according to embodiments of the present invention. FIGS. 3 and FIGS. 4a are plan views illustrating a polarizing rotating reflector according to embodiments of the present invention. Figure 4b is a cross-sectional view of Figure 4a taken along the line I-I'. FIGS. 5 and 6 are plan views illustrating a polarization-independent interferometer including a polarization rotation reflector according to embodiments of the present invention. Specific details for implementing the invention

[0009] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0010] The present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and subject to various modifications and changes. The description of the embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. In the attached drawings, the components are depicted enlarged from their actual size for convenience of explanation, and the proportions of each component may be exaggerated or reduced.

[0011] The terms used in this specification are for describing embodiments and are not intended to limit the invention. Furthermore, unless otherwise defined, the terms used in this specification may be interpreted in the sense commonly known to those skilled in the art.

[0012] In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used in this specification, 'comprises' and / or 'comprising' do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements.

[0013] Although terms such as "first," "second," etc., have been used in this specification to describe various areas, concepts, etc., these areas and concepts should not be limited by such terms. These terms are used merely to distinguish one specific area or concept from another area or concept. Accordingly, a part referred to as the first part in one embodiment may be referred to as the second part in another embodiment. The embodiments described and illustrated herein also include their complementary embodiments. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0014] Hereinafter, embodiments of a pulse laser device according to the present invention will be described in detail with reference to FIGS. 1 to 5.

[0016] FIG. 1 is a plan view illustrating a polarizing rotating reflector according to embodiments of the present invention. FIG. 2 is a conceptual diagram illustrating the structure and cross-section of a polarizing rotating reflector according to embodiments of the present invention.

[0017] Referring to FIGS. 1 and 2, the polarization rotating reflector according to the present invention may include a first input optical waveguide (110), a second input optical waveguide (120), an optical coupler (200), a first connecting optical waveguide (310), a second connecting optical waveguide (320), and a loop-type optical waveguide (500).

[0018] The first and second input optical waveguides (110, 120) may be connected to one end of the optical coupler (200), and one end of each of the first and second connecting optical waveguides (310, 320) may be connected to the other end of the optical coupler (200). The other end of each of the first and second connecting optical waveguides (310, 320) may be connected to either one of the first and second ends (EP1, EP2) of the loop optical waveguide (500). The optical coupler (200) may be, for example, a DC (directional coupler) or a 2X2 MMI (multi-mode interference device) having a 50:50 distribution ratio.

[0019] The first and second input optical waveguides (110, 120), the first and second connecting optical waveguides (310, 320), and the loop optical waveguide (500) may be, for example, optical fibers. Referring to FIG. 2, the loop optical waveguide (500) may be a polarization maintaining fiber (PMF) that is twisted by 90 degrees and includes a core portion (CR) penetrating the center, stress applying parts (SAPs) adjacent to both sides of the core portion (CR), and a cladding portion (CL) surrounding the core portion (CR) and the stress applying parts (SAPs).

[0020] A polarization-maintaining optical fiber (PMF) is a birefringence optical fiber in which the effective refractive index differs depending on the polarization component of the light propagating through the core (CR). Due to this birefringence, the incident light exhibits different propagation characteristics depending on the polarization component, thereby suppressing energy exchange between the two polarizations. Consequently, the incident light maintains its initial polarization state even as it propagates. The polarization-maintaining optical fiber (PMF) has a fast axis (FA) and a slow axis (SA) passing through the center of the core (CR). The stress-applying sections (SAP) of the polarization-maintaining optical fiber (PMF) are provided symmetrically on the slow axis (SA) with respect to the fast axis (FA).

[0021] The first section (CS1) of the loop-type optical waveguide (500) may have a high-speed axis (FA) parallel to the ground and a low-speed axis (SA) perpendicular to the ground. The second section (CS2) of the loop-type optical waveguide (500) may have a low-speed axis (SA) parallel to the ground and a high-speed axis (FA) perpendicular to the ground. In other words, the second section (CS2) of the loop-type optical waveguide (500) may have a shape obtained by rotating the first section (CS1) by 90 degrees. In other words, the low-speed axis (SA) of the first section (CS1) may be orthogonal to the low-speed axis (SA) of the second section (CS2), and the high-speed axis (FA) of the first section (CS1) may be orthogonal to the high-speed axis (FA) of the second section (CS2).

[0022] Referring again to FIG. 1, the cross-section of the first end (EP1) of the loop-type optical waveguide (500) may be the same as the first cross-section (CS1), and the cross-section of the second end (EP2) of the loop-type optical waveguide (500) may be the same as the second cross-section (CS2). The length (L) of the loop-type optical waveguide (500) may be determined by the following [Equation 1].

[0023] [Mathematical Formula 1]

[0024]

[0025] Here, λ is the wavelength of light incident on the polarizing rotating reflector, and n s is the mode refractive index experienced by light that is incident on the first end (EP1) through the first connected optical waveguide (310), rotates clockwise, and arrives at the second end (EP2), and n f is the mode refractive index experienced by light that enters the second end (EP2) through the second connected optical waveguide (320), rotates counterclockwise, and arrives at the first end (EP1), where i is an integer.

[0026] The light that enters the first end (EP1) through the first connected optical waveguide (310), rotates clockwise, and arrives at the second end (EP2), and the light that enters the second end (EP2) through the second connected optical waveguide (320), rotates counterclockwise, and arrives at the first end (EP1), can each be in a polarization state that is rotated 90 degrees from the initial polarization state.

[0028] FIG. 3 is a plan view illustrating a polarizing rotating reflector according to embodiments of the present invention. For convenience of explanation, descriptions of matters substantially identical to those with reference to FIG. 1 and FIG. 2 are omitted, and the differences are described in detail.

[0029] Referring to FIG. 3, each of the first and second ends (EP1, EP2) of the loop optical waveguide (500) can be connected and coupled with an optical link (10) comprising a first input optical waveguide (110), a second input optical waveguide (120), an optical coupler (200), a first connecting optical waveguide (310), and a second connecting optical waveguide (320).

[0031] FIG. 4a is a plan view illustrating a polarizing rotating reflector according to embodiments of the present invention. FIG. 4b is a cross-sectional view of FIG. 4a taken along the line I-I'. For convenience of explanation, descriptions of matters substantially identical to those with reference to FIG. 1 and FIG. 2 are omitted, and the differences are described in detail.

[0032] Referring to FIGS. 4a and 4b, each of the first and second ends (EP1, EP2) of a loop-type optical waveguide (500) can be connected and coupled to an optical integrated circuit chip (20) comprising a first input optical waveguide (110), a second input optical waveguide (120), an optical coupler (200), a first connecting optical waveguide (310), and a second connecting optical waveguide (320), which is integrated on a substrate (100) having an upper surface parallel to the first direction (D1) and the second direction (D2) and orthogonal to the third direction (D3). The first direction (D1), the second direction (D2), and the third direction (D3) may be directions orthogonal to each other, for example.

[0033] At this time, the first input optical waveguide (110), the second input optical waveguide (120), the optical coupler (200), the first connecting optical waveguide (310), and the second connecting optical waveguide (320) may be, for example, silicon optical waveguides provided on the substrate (20). The first and second ends (EP1, EP2) of the loop-type optical waveguide (500) may be connected and coupled to the optical integrated circuit chip (20), for example, through a V-groove block (400). The V-groove block (400) may be a block having V-shaped grooves (GR) on its upper surface. The grooves (GR) of the V-groove block (400) may support and secure the first and second ends (EP1, EP2) of the loop-type optical waveguide (500).

[0035] FIG. 5 is a plan view illustrating a polarization-independent interferometer including a polarization-rotating reflector according to embodiments of the present invention. For convenience of explanation, descriptions of matters substantially identical to those with reference to FIG. 1 and FIG. 2 are omitted, and the differences are described in detail.

[0036] Referring to FIG. 5, the polarization-independent interferometer according to the present invention may include a polarization-rotating reflector (PRR). More specifically, the polarization-independent interferometer according to the present invention may include an optical waveguide into which an input light (IL) is input, optical waveguides into which first and second output lights (OL1, OL2) are output, an optical circulator (CC), a first optical coupler (210), first and second input optical waveguides (110, 120), a second optical coupler (220), first and second connecting optical waveguides (310, 320), and a loop-type optical waveguide (500). The first and second input optical waveguides (110, 120), the second optical coupler (220), the first and second connecting optical waveguides (310, 320), and the loop optical waveguide (500) can form a polarization rotating reflector (PRR) as described with reference to FIGS. 1 and 2.

[0037] An optical waveguide into which the input light (IL) is input and an optical waveguide into which the first output light (OL2) is output can be connected to one end of the first optical coupler (210). An optical circulator (CC) may be an optical element designed to direct a signal entering through one port to another adjacent port in a counterclockwise (or clockwise) direction. At least a portion of the first input optical waveguide (110) may be bent into a semicircular shape.

[0038] In the polarization-independent interferometer according to the present invention, the light traveling to the second optical coupler (220) may have its polarization state changed after rotating the loop-type optical waveguide (500) (e.g., the TE component becomes the TM component, and the TM component becomes the TE component). Accordingly, the phase difference between the two paths of light returning to the first optical coupler (210) can be constant regardless of the polarization state of the incident light (IL) (i.e., polarization-independent), and the first and second output lights (OL1, OL2) can operate stably by being insensitive to the input polarization.

[0040] FIG. 6 is a plan view illustrating a polarization-independent interferometer including a polarization-rotating reflector according to embodiments of the present invention. For convenience of explanation, descriptions of matters substantially identical to those with reference to FIG. 1, 2 and 5 are omitted, and the differences are described in detail.

[0041] Referring to FIG. 6, the polarization-independent interferometer according to the present invention may include a first polarization-rotating reflector (PRR1) and a second polarization-rotating reflector (PRR2). The first and second polarization-rotating reflectors (PRR1, PRR2) may each be connected to a first optical coupler (210) through a first input optical waveguide (110) or a second input optical waveguide (120). The lengths of the first input optical waveguide (110) and the second input optical waveguide (120) may differ from each other. In other words, the polarization-independent interferometer according to the present invention may be an asymmetric interferometer comprising first and second input optical waveguides (110, 120) of different lengths.

[0042] More specifically, the first polarization rotating reflector (PRR1) may include a second optical coupler (220), a first connecting optical waveguide (311), a second connecting optical waveguide (321), and a first loop-type optical waveguide (510), and the second polarization rotating reflector (PRR2) may include a third optical coupler (230), a third connecting optical waveguide (312), a fourth connecting optical waveguide (322), and a second loop-type optical waveguide (520). The second and third optical couplers (220, 230) may each be connected to the first optical coupler (210) through the first input optical waveguide (110) or the second input optical waveguide (120).

[0044] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 An optical integrated circuit chip comprising: an optical coupler; first and second input optical waveguides connected to one end of the optical coupler; first and second connecting optical waveguides connected to the other end of the optical coupler; and a loop-shaped optical waveguide connected to the first and second connecting optical waveguides, wherein the loop-shaped optical waveguide comprises a core portion penetrating the center, stress-applying portions adjacent to both sides of the core portion, and a cladding portion surrounding the core portion and the stress-applying portions, wherein the cross-section of the first end of the loop-shaped optical waveguide has a shape obtained by rotating the cross-section of the second end of the loop-shaped optical waveguide by 90 degrees, and a substrate for mounting the optical coupler, the first and second input optical waveguides, and the first and second connecting optical waveguides; and a polarizing rotating reflector further comprising a V-groove block provided adjacent to the optical integrated circuit chip and mounting the first end and the second end of the loop-shaped optical waveguide. Claim 2 In claim 1, the stress-applying parts are arranged vertically within the cross-section of the first end and are arranged horizontally within the cross-section of the second end, forming a polarization rotation reflector. Claim 3 In claim 2, the stress-applying parts are a polarizing rotating reflector that is continuously twisted from the first end to the second end. Claim 4 delete Claim 5 A polarizing rotating reflector according to claim 1, further comprising an optical fiber link connected to the first end of the loop-type optical waveguide and the second end. Claim 6 In claim 1, the optical coupler is a polarizing rotating reflector having a 50:50 distribution ratio. Claim 7 A polarizing rotating reflector according to claim 1, wherein the first cross section of the loop-shaped optical waveguide has a high-speed axis parallel to the ground and a low-speed axis perpendicular to the ground, and the second cross section of the loop-shaped optical waveguide has the high-speed axis perpendicular to the ground and a low-speed axis parallel to the ground. Claim 8 In claim 1, each of the first and second input optical waveguides, the first and second connecting optical waveguides, and the loop-type optical waveguide comprises a polarizing rotating reflector including an optical fiber. Claim 9 Input and output optical waveguides; a first optical coupler connected to one side of the input and output optical waveguides; and a polarization rotating reflector connected to the other side of the first optical coupler, wherein the polarization rotating reflector comprises: an optical coupler; first and second input optical waveguides connected to one end of the optical coupler; and first and second connecting optical waveguides connected to the other end of the optical coupler. An optical integrated circuit chip comprising: a loop-shaped optical waveguide connected to the first and second connected optical waveguides, wherein the loop-shaped optical waveguide comprises a core portion penetrating the center, stress-applying portions adjacent to both sides of the core portion, and a cladding portion surrounding the core portion and the stress-applying portions, wherein the cross-section of the first end of the loop-shaped optical waveguide has a shape obtained by rotating the cross-section of the second end of the loop-shaped optical waveguide by 90 degrees, and a substrate for mounting the optical coupler, the first and second input optical waveguides, and the first and second connected optical waveguides; and a polarization-independent interferometer further comprising a V-groove block provided adjacent to the optical integrated circuit chip and mounting the first end and the second end of the loop-shaped optical waveguide. Claim 10 In claim 9, a polarization-independent interferometer further comprising an optical circulator connected to the end of the input optical waveguide.

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