A multi-port interferometer and a split-beam polarimetric detector

Abstract

The application discloses a kind of multi-port interferometer and split-amplitude polarization detector, belong to integrated photonic device field, multi-port interferometer includes multimode waveguide, two input ports and M output ports, etching has round hole on the multimode waveguide, wherein, M=4 or 6;With the same polarization state light is respectively input from the two input ports, after the regulation and interference of multimode waveguide, output M road light to different projection polarization state projection.The application also provides a kind of split-amplitude polarization detector, including light polarization beam splitter rotator, multi-port interferometer, M light detector and polarization state calculation module;The application can simultaneously reduce the volume of interferometer and polarization detector, reduce system complexity and improve integration.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of integrated photonic devices, and more particularly, relates to a multi-port interferometer and a split-amplitude polarization detector. BACKGROUND

[0002] Polarization reflects the vector characteristics of the optical field and can carry very rich information. The polarization detector is an instrument for measuring the polarization state of light and plays a crucial role in many fields such as polarization imaging, optical sensing, optical communication, etc.

[0003] The polarization detector can be divided into two categories according to the measurement method: one is a time-splitting polarization detector, which measures the polarization state of the light by adjusting the polarization-related device to process and measure the light to be measured. The Stokes parameters of the light to be measured are calculated by multiple detection results, thereby completing the measurement of the polarization state. This method requires at least four detections, and the measurement speed is slow. The other is a split-amplitude polarization detector, which splits the light to be measured and adjusts the polarization of each light to achieve simultaneous measurement of four Stokes parameters. However, this type of polarization detector requires multiple on-chip devices for multi-channel light splitting, resulting in a large system. At the same time, the signal-to-noise ratio of the input to the detector is low. In particular, the interferometer for achieving polarization adjustment in this type of polarization detector is composed of multiple discrete components, making the interferometer large in size and the system complex, which is not conducive to on-chip integration. SUMMARY

[0004] In view of the defects of the prior art and the need for improvement, the present application provides a multi-port interferometer and a split-amplitude polarization detector, which aims to reduce the size of the interferometer and the split-amplitude polarization detector, reduce the system complexity, and improve the integration.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present application, a multi-port interferometer is provided, comprising a multi-mode waveguide, two input ports and M output ports, and a circular hole is etched on the multi-mode waveguide, wherein M = 4 or 6.

[0006] Two lights with the same polarization state are input from the two input ports respectively, and after the regulation and interference of the multi-mode waveguide, M lights are output to project different polarization states.

[0007] When M = 4, the arrangement of the circular holes satisfies that the four different projection polarization states are not coplanar on the Poincare sphere.

[0008] When M = 6, the arrangement of the circular holes satisfies that the six different projection polarization states form three groups of orthogonal projection polarization states, and the three groups of orthogonal projection polarization states are not coplanar on the Poincare sphere.

[0009] Further, when M = 6, the transmission matrix A of the multi-port interferometer is:

[0010]

[0011] Further, the arrangement matrix B of the etched circular holes on the multi-mode waveguide is:

[0012]

[0013] wherein 1 represents an etched circular hole, and 0 represents a non-etched circular hole.

[0014] Further, when M = 4, the transmission matrix C of the multi-port interferometer is:

[0015]

[0016] Further, the size of the multi-port interferometer is not more than 10um x 10um.

[0017] Further, the etched circular holes on the multi-mode waveguide are symmetrically distributed.

[0018] According to a second aspect of the present application, a split amplitude type polarization detector is provided, comprising: a light polarization beam splitting rotator, a multi-port interferometer, M light detectors, and a polarization state calculation module; the multi-port interferometer is the multi-port interferometer of any one of the first aspect;

[0019] The light polarization beam splitting rotator is used to decompose the input light to be measured into a pair of orthogonal polarized light, and convert the orthogonal polarized light into the same polarization state.

[0020] The M light detectors are respectively used to detect the light intensity of the M paths of light projected to different projection polarization states output by the multi-port interferometer.

[0021] The polarization state calculation module is used to calculate the Stokes parameters of the input light to be measured according to the light intensity of the M paths of light projected to different projection polarization states, and obtain the polarization state of the input light to be measured.

[0022] Further, the light polarization beam splitting rotator, the multi-port interferometer, the M light detectors, and the polarization state calculation module are integrated on the same chip.

[0023] Further, the two beams of light of the same polarization state are the same horizontal polarization state.

[0024] Further, when M = 6, the light intensity of the 6 paths of light projected to different projection polarization states and the Stokes parameters of the input light to be measured satisfy:

[0025]

[0026] wherein, (S0, S1, S2, S3) TI1 to I6 are currents of the light projected to different projection polarization states, is an inverse matrix of a polarization analysis matrix W A is: A

[0027]

[0028] Overall, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0029] (1) Compared with the existing interferometer composed of multiple discrete devices, the interferometer designed by the present application is only one device. A series of circular holes with a specific regular arrangement are etched on a multimode waveguide, so that two beams of light with the same polarization state are subjected to regulation and interference by the multimode waveguide, and M beams of light projected to different projection polarization states are output. When M = 4, the arrangement of the circular holes etched on the multimode waveguide satisfies that the 4 different projection polarization states are not coplanar on the Poincare sphere. When M = 6, the arrangement of the circular holes etched on the multimode waveguide satisfies that the 6 different projection polarization states form three sets of orthogonal projection polarization states, and the three sets of orthogonal projection polarization states are not coplanar on the Poincare sphere. Through the interferometer of the present application, specific amplitude and phase regulation of two input light beams is realized. The present application designs the multi-port interferometer based on the reverse idea, which realizes the function of multiple devices with only one device, reduces the size of the interferometer, reduces the system complexity, and improves the integration of the system.

[0030] (2) Further, based on the above idea, the present application also designs a preferred two-in-six-out multi-port interferometer, which has the advantages of small size, simple structure and easy on-chip integration.

[0031] (3) Based on the multi-port interferometer designed by the present application, the present application also designs a split-amplitude polarization detector. The light intensity of the M beams of light projected to different projection polarization states output from the multi-port interferometer is detected, the M beams of light projected to different projection polarization states are converted into M beams of electrical signals, and then the polarization state of the input light to be measured is obtained. The measurement method is simple, and the size of the split-amplitude polarization detector is reduced, the system complexity is reduced, and the integration of the system is improved.

[0032] In summary, the present application solves the problems of system complexity, large size and low measurement accuracy in the polarization detector composed of traditional discrete devices. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a split-amplitude polarization detector structure diagram provided by an embodiment of the present application.

[0034] ​Figure 2 This is a schematic diagram of the structure of the two-input six-output multi-port interferometer provided in Embodiments 1 and 2 of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment provides an amplitude-splitting polarization detector, including: an optical polarization beam splitter rotator, a multi-port interferometer, M photodetectors, and a polarization state calculation module;

[0038] An optical polarization beam splitter is used to decompose the input light to be tested into a pair of orthogonally polarized beams and convert the orthogonally polarized beams into the same horizontal polarization state for output.

[0039] A multi-port interferometer is used to control and interfere two beams of light with the same horizontal polarization state through a multimode waveguide, and output light with different projected polarization states in the M-direction.

[0040] M photodetectors are used to detect the light intensity of M paths projected to different projection polarization states, and convert the M paths of light projected to different projection polarization states into M electrical signals.

[0041] The polarization state calculation module is used to calculate the Stokes parameters of the input light under test based on the current of the M-channel electrical signals, and obtain the polarization state of the input light under test.

[0042] The multi-port interferometer includes a multimode waveguide, which has two input ports and M output ports. Circular holes are etched on the multimode waveguide, where M = 4 or 6.

[0043] When M=4, the arrangement of the etched circular holes on the multimode waveguide satisfies the following: the four different projected polarization states are not coplanar on the Bonga sphere.

[0044] When M=6, the arrangement of the circular holes etched on the multimode waveguide satisfies the following: the six different projected polarization states are orthogonally formed into three sets of orthogonally projected polarization light, and the three sets of orthogonally projected polarization states are not coplanar on the Bonga sphere.

[0045] As a preferred option, the optical polarization beam splitter rotator, multi-port interferometer, M photodetectors, and polarization state calculation module are integrated on the same chip, improving the integration of the polarization detector.

[0046] Preferably, the multi-port interferometer has a size of no more than 10um x 10um.

[0047] In this embodiment, the optical polarization beam splitter rotator splits the input light of the polarization state to be measured into 0° linearly polarized light and 90° linearly polarized light. Assuming that the Jones vector J of the input light to be measured is:

[0048]

[0049] wherein A x and A y are the electric field intensities of the 0° linearly polarized light and the 90° linearly polarized light respectively, and δ is the phase difference between the two orthogonal polarized lights, then the light intensity of the first light output by the optical polarization beam splitter rotator is A x , the light intensity of the second light is A y , and the phase difference between the two is δ.

[0050] When M = 6, the multi-port interferometer is a two-in-six-out multi-port interferometer. The transmission matrix A of the two-in-six-out multi-port interferometer is set as:

[0051]

[0052] wherein (a i b i ) represents one projection polarization state of the input light to be measured, and i = 1, 2, … or 6.

[0053] The light fields E i received by the six light detectors are respectively:

[0054]

[0055] It can be seen that J i = (a i b i ), that is, J i can be regarded as one projection polarization state of the input light to be measured, is the conjugate of J i , and E i can be regarded as the light field after the input light to be measured is projected to J i .

[0056] The currents generated by the six light signals detected by the six detectors are:

[0057]

[0058] wherein I i represents the current generated by the i-th light signal, and R is the responsivity of the six light detectors.

[0059] Therefore, the circular hole arrangement of the multi-port interferometer only needs to satisfy that the 6 different projection polarization states obtained after the transmission matrix of the interferometer is passed by the input light are orthogonal to form three groups of orthogonal projection polarization states, and the three groups of orthogonal projection polarization states are not coplanar on the Poincare sphere, so that the measurement of the polarization state of the input light can be completed.

[0060] In the embodiment of the application, the transmission matrix A of the two-in-six-out multi-port interferometer is configured as:

[0061]

[0062] At this time, the six projection polarization states after passing through the transmission matrix of the two-in-six-out multi-port interferometer are three pairs of orthogonal polarization states, forming a spherical-t design on the Poincare sphere, and having optimal polarization measurement accuracy; the six pieces of light projected on the six polarization states are output, the currents I1 to I6 of the six light detectors are read, the projection light intensity of the input light to be measured on the three pairs of orthogonal polarization states is obtained, and the Stokes parameters (S0, S1, S2, S3) of the input light can be calculated. T .

[0063] The calculation formula of the Stokes parameters of the input light from the current of the light detector is as follows

[0064]

[0065] Among them, is the inverse matrix of the polarization analysis matrix W A , so that the Stokes parameters of the input light are obtained, and the polarization state measurement is completed, and the polarization analysis matrix W A is:

[0066]

[0067] As shown in Figure 2 , based on the transmission matrix designed in the embodiment of the application, the arrangement matrix B of the circular holes etched on the multi-mode waveguide is:

[0068]

[0069] Among them, in the arrangement matrix B of the circular holes, 1 represents etching a circular hole, and 0 represents not etching a circular hole.

[0070] As a preferred, the circular holes on the multi-port interferometer designed based on the above principle are symmetrically distributed up and down.

[0071] Similarly, when the multi-port interferometer is a two-in-four-out multi-port interferometer, the principle is similar to that of the two-in-six-out multi-port interferometer, and the transmission matrix C of the two-in-four-out multi-port interferometer designed in the embodiment of the application is:

[0072]

[0073] Example 2

[0074] like Figure 2 As shown, this embodiment provides a multi-port interferometer, including a multimode waveguide, two input ports and M output ports, with circular holes etched on the multimode waveguide, wherein M = 4 or 6;

[0075] Two beams of light with the same polarization state are input from two input ports respectively. After being modulated and interfered by a multimode waveguide, light with different projected polarization states in the M-direction is output.

[0076] When M=4, the arrangement of the circular holes satisfies the following condition: the four different projection polarization states are not coplanar on the Bonga sphere;

[0077] When M=6, the arrangement of the circular holes satisfies the following: the six different projected polarization states are orthogonal to form three sets of orthogonal projected polarization states, and the three sets of orthogonal projected polarization states are not coplanar on the Bonga sphere.

[0078] Specifically, when M=6, the multiport interferometer is a 2-input 6-output multiport interferometer, and the transmission matrix A of this 2-input 6-output multiport interferometer is set as follows:

[0079]

[0080] Among them, (a i b i ) represents a projected polarization state of input light with the same polarization state, i = 1, 2, ... or 6.

[0081] When the arrangement of the circular apertures satisfies the condition that six different projected polarization states are pairwise orthogonal to form three sets of orthogonal projected polarization states, and the three sets of orthogonal projected polarization states are not coplanar on the Bonga sphere, based on the reverse design, the transmission matrix A of the multi-port interferometer is designed as follows:

[0082]

[0083] Correspondingly, the arrangement matrix B of the circular holes etched on the multimode waveguide is:

[0084]

[0085] In this context, 1 represents etching the round hole, and 0 represents not etching the round hole.

[0086] Specifically, when M=4, and the arrangement of the circular holes satisfies that the four different projected polarization states are not coplanar on the Bonga sphere, the transmission matrix C of the multiport interferometer is:

[0087]

[0088] The specific amplitude and phase control of two input lights is realized by the multi-port interferometer. The multi-port interferometer is designed based on reverse idea, the function of multiple devices is realized by only one device, the volume of the interferometer is reduced, the system complexity is reduced, and the integration of the system is improved.

[0089] Those skilled in the art can understand that the above description is only preferred embodiments of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A multi-port interferometer, characterized in that, It includes a multimode waveguide, two input ports and M output ports, and circular holes are etched on the multimode waveguide, wherein M = 4 or 6; Two beams of light with the same polarization state are input from the two input ports respectively. After being modulated and interfered by the multimode waveguide, light with different projection polarization states in the M-direction is output. When M=4, the arrangement of the circular holes satisfies the following: the four different projected polarization states are not coplanar on the Bonga sphere; When M=6, the arrangement of the circular holes satisfies the following: the six different projected polarization states are orthogonal to form three sets of orthogonal projected polarization states, and the three sets of orthogonal projected polarization states are not coplanar on the Bonga sphere.

2. The multi-port interferometer according to claim 1, characterized in that, When M=6, the transmission matrix A of the multi-port interferometer is:

3. The multi-port interferometer according to claim 2, characterized in that, The arrangement matrix B of the circular holes etched on the multimode waveguide is: In this context, 1 represents etching the round hole, and 0 represents not etching the round hole.

4. The multi-port interferometer according to claim 1, characterized in that, When M=4, the transmission matrix C of the multi-port interferometer is:

5. The multi-port interferometer according to claim 1, characterized in that, The size of the multiport interferometer does not exceed 10um × 10um.

6. The multi-port interferometer according to claim 1, characterized in that, The circular holes etched on the multimode waveguide are symmetrically distributed vertically.

7. An amplitude-divided polarization detector, characterized in that, include: The system comprises an optical polarization beam splitter rotator, a multi-port interferometer, M photodetectors, and a polarization state calculation module; the multi-port interferometer is the multi-port interferometer described in any one of claims 1-6. The optical polarization beam splitter is used to decompose the input light to be tested into a pair of orthogonally polarized lights and convert the orthogonally polarized lights into the same polarization state; The M photodetectors are used to detect the light intensity of the M-path projection polarization states output by the multi-port interferometer. The polarization state calculation module is used to calculate the Stokes parameters of the input light to be tested based on the light intensity projected under different polarization states of the M-path, and to obtain the polarization state of the input light to be tested.

8. The amplitude-divided polarization detector according to claim 7, characterized in that, The optical polarization beam splitter rotator, multi-port interferometer, M photodetectors, and polarization state calculation module are integrated on the same chip.

9. The amplitude-divided polarization detector according to claim 7, characterized in that, The two beams of light with the same polarization state are in the same horizontal polarization state.

10. The amplitude-divided polarization detector according to claim 7, characterized in that, When M=6, the light intensity projected onto the six paths to different projection polarization states satisfies the following relationship with the Stokes parameters of the input light to be measured: Among them, (S0 S1 S2 S3) T Here, I represents the Stokes parameters of the input light to be measured, and I1 to I6 represent the currents of the six lights projected onto different projection polarization states. The polarization analysis matrix W A The inverse matrix, the polarization analysis matrix W A for:

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