CN-122029464-A - Polarizing beam splitter using asymmetric power splitting and multipath interferometry

Abstract

A polarizing beamsplitter includes an input port, a first output port, and a second output port, and a polarizing beamsplitter coupled between the input port and the first output port and the second output port. The input port is adapted to receive polarization multiplexed guided wave optical signals including Transverse Electric (TE) optical signals and Transverse Magnetic (TM) optical signals. The polarizing beam splitting area comprises a pattern of at least two materials having different refractive indices. The pattern is shaped to de-multiplex the TE optical signal and the TM optical signal by directing a majority of a first power of the TE optical signal received at the input port to the second output port via asymmetric power splitting while directing a majority of a second power of the TM optical signal received at the input port to the first output port via multipath interferometry.

Inventors

• Y-K.R.Wu

Assignees

• X开发有限责任公司

Dates

Publication Date

20260512

Application Date

20240919

Priority Date

20231002

Claims (20)

1. 1. A polarizing beam splitter, comprising: an input port adapted to receive polarization multiplexed guided wave optical signals including Transverse Electric (TE) optical signals and Transverse Magnetic (TM) optical signals; a first output port and a second output port, and A polarized beam splitting region coupled between the input port and the first and second output ports, wherein the polarized beam splitting region comprises a pattern of at least two materials having different refractive indices, wherein the pattern is shaped to demultiplex the TE optical signal and the TM optical signal by directing a majority of a first power of the TE optical signal received at the input port to the second output port via asymmetric power splitting while directing a majority of a second power of the TM optical signal received at the input port to the first output port via multipath interferometry.
2. 2. The polarizing beam splitter of claim 1, wherein the at least two materials comprise silicon and silicon dioxide.
3. 3. The polarizing beam splitter of claim 1, wherein the input port comprises an interface between a single mode waveguide and the polarizing beam splitting region, and wherein the TE optical signal and the TM optical signal are fundamental polarization modes TE0 and TM0 of the single mode waveguide, respectively.
4. 4. The polarizing beam splitter of claim 1, wherein the polarizing beam splitting region comprises a planar waveguide having a pattern disposed within the planar waveguide as a two-dimensional pattern of the at least two materials.
5. 5. The polarizing beam splitter of claim 1, wherein the pattern comprises: A first irregularly shaped channel formed of a high refractive index material surrounded by a low refractive index material, the first irregularly shaped channel extending between the input port and the second output port.
6. 6. The polarizing beam splitter of claim 5 wherein the first irregularly shaped channel comprises an S-shaped curved shape that is not blocked by the low index material.
7. 7. The polarizing beam splitter of claim 5, wherein the first irregularly shaped channel forms a TE path from the input port to the second output port, the TE path being shaped to selectively direct the majority of the first power of the TE optical signal to the second output port.
8. 8. The polarizing beam splitter of claim 1, wherein the pattern is shaped to selectively direct the majority of the second power of the TM optical signal to the first output port via a plurality of TM paths extending from the input port to the first output port, the TM paths defined by a high refractive index material surrounded by a low refractive index material.
9. 9. The polarizing beam splitter of claim 8, wherein the plurality of TM paths comprises: a main TM path including a plurality of scattering locations formed by islands of the low refractive index material dispersed within the high refractive index material; a secondary TM path passing through the high refractive index material, and A tertiary TM path through the high refractive index material, the tertiary TM path being blocked in at least one location by the low refractive index material, Wherein the primary TM path, the secondary TM path, and the tertiary TM path direct the majority of the second power of the TM optical signal received at the input port to the first output port via the multi-path interferometry.
10. 10. The polarizing beam splitter of claim 1, wherein the pattern comprises a reverse design pattern defined by iterative minimization of a loss function that sums transmission loss, reflection loss, and crosstalk loss.
11. 11. A method of demultiplexing a polarization dependent optical signal, the method comprising: Receiving Transverse Electric (TE) and Transverse Magnetic (TM) optical signals multiplexed on a common waveguide at an input port of a polarizing beam splitting region, wherein the polarizing beam splitting region comprises a pattern of at least two materials having different refractive indices; Directing a majority of a first power of a TM optical signal received at the input port to a first output port coupled to the polarization beam splitting region using multipath interferometry, and A majority of the second power of the TE optical signal received at the input port is directed using asymmetric power splitting to a second output port coupled to the polarized beam splitting area, Wherein the pattern causes the multipath interferometry and the asymmetric power splitting on the TM optical signal and the TE optical signal, respectively, simultaneously when the input port is simultaneously stimulated by the TM optical signal and the TE optical signal.
12. 12. The method of claim 11, wherein the input port is disposed on a first side of the polarized beam splitting area, wherein the first output port and the second output port are disposed on a second side of the polarized beam splitting area opposite the first side, and wherein the first output port and the second output port are physically offset from each other along the second side.
13. 13. The method of claim 11, wherein the pattern comprises an irregular pattern of the at least two materials.
14. 14. The method of claim 13, wherein the polarization beam splitting region comprises a planar waveguide having a pattern disposed within the planar waveguide as a two-dimensional pattern of the at least two materials.
15. 15. The method of claim 13, wherein the irregular pattern comprises: A first irregularly shaped channel formed of a high refractive index material surrounded by a low refractive index material, the first irregularly shaped channel extending between the input port and the second output port.
16. 16. The method of claim 15, wherein the first irregularly shaped channel comprises an S-shaped curved shape that is not blocked by the low refractive index material.
17. 17. The method of claim 15, wherein the first irregularly shaped channel forms a TE path from the input port to the second output port, the TE path selectively directing the majority of the first power of the TE optical signal to the second output port.
18. 18. The method of claim 11, wherein the pattern selectively directs the majority of the second power of the TM optical signal to the first output port via a plurality of TM paths extending from the input port to the first output port, the TM paths defined by a high refractive index material surrounded by a low refractive index material.
19. 19. The method of claim 18, wherein the plurality of TM paths comprises: a main TM path including a plurality of scattering locations formed by islands of the low refractive index material dispersed within the high refractive index material; a secondary TM path passing through the high refractive index material, and A tertiary TM path through the high refractive index material, the tertiary TM path being blocked in at least one location by the low refractive index material, Wherein the primary TM path, the secondary TM path, and the tertiary TM path direct the majority of the second power of the TM optical signal received at the input port to the first output port via the multi-path interferometry.
20. 20. The method of claim 11, wherein the pattern comprises a reverse design pattern defined by iterative minimization of a loss function that sums transmission loss, reflection loss, and crosstalk loss.

Description

Polarizing beam splitter using asymmetric power splitting and multipath interferometry Cross Reference to Related Applications The present application claims priority from U.S. application Ser. No. 18/375,717, filed on Ser. No. 2/10/2023, the contents of which are incorporated herein by reference. Technical Field The present disclosure relates generally to photonic devices and in particular, but not exclusively, to polarizing beam splitters. Background Artificial Intelligence (AI) and Machine Learning (ML) applications are expected to place high demands on the data bandwidth of future XPUs (e.g., central processing units, graphics processing units, tensor processing units, etc.). In fact, the data bandwidth is expected to be the bottleneck for future XPU developments. In particular, board-to-board interconnects and chip-to-chip interconnects will need to support ever-increasing bandwidth. Optical interconnect technology is expected to meet this increasing bandwidth demand. However, although the optical interconnect provides a high bandwidth, the conventional design has a problem in that the data bandwidth density (i.e., the data bandwidth per unit area) is low. In order to increase the data bandwidth density of optical interconnects, it is desirable to shrink the physical size of photonic integrated circuits. Polarizing Beam Splitters (PBS) are fundamental building blocks for high-speed optical interconnects because they enable polarization multiplexing. A PBS is an optical filter that splits an incident light beam into two separate beams having different polarizations. In an ideal scene, these individual beams are perfectly polarized and the polarization is orthogonal. In the context of guided wave light (e.g., optical fibers), the incident light may include Transverse Electric (TE) and Transverse Magnetic (TM) polarizations, while in the context of single mode waveguides (e.g., single mode optical fibers), the light may include only fundamental spatial modes TE0 and TM0 for the respective polarizations. The TE0 and TM0 signals may increase the bandwidth of the guided light by encoding different data channels on orthogonal polarization modes TE0 and TM0. The physical size of a conventional PBS is about 100 um x 8 um. A PBS that is capable of significantly reducing these physical dimensions while maintaining the desired functional characteristics (e.g., polarization crosstalk and isolation, insertion/transmission loss, back reflection, etc.) would help meet the higher data bandwidth density requirements expected in future XPU developments. Disclosure of Invention Drawings Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Not all instances of an element may be labeled to avoid obscuring the drawings where appropriate. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles described. Fig. 1 is a functional block diagram illustrating a Polarizing Beam Splitter (PBS) according to an embodiment of the present disclosure. Fig. 2 shows details of a PBS having a reverse-engineered polarization beam splitting region, according to an embodiment of the present disclosure. Fig. 3A and 3B illustrate a Transverse Electric (TE) path through a polarization beam splitting region that directs a majority of the power of a TE optical signal to an output port 2 of a PBS via asymmetric power splitting, according to an embodiment of the present disclosure. Fig. 4A and 4B illustrate a Transverse Magnetic (TM) path through a polarized beam splitting area that directs a majority of the power of a TM optical signal to output port 1 via multipath interferometry according to an embodiment of the present disclosure. Fig. 5A is a graph illustrating transmission loss of a PBS according to an embodiment of the present disclosure. Fig. 5B is a graph showing the retroreflective loss of a PBS according to an embodiment of the present disclosure. Fig. 5C is a graph illustrating crosstalk loss of a PBS according to an embodiment of the present disclosure. Fig. 6 is a flowchart illustrating an operation of a PBS to de-multiplex TE and TM optical signals according to an embodiment of the present disclosure. Fig. 7A shows an illustrative simulation environment for simulating operation of a PBS being designed in accordance with an embodiment of the present disclosure. Fig. 7B shows an operational simulation of a PBS according to an embodiment of the present disclosure. Fig. 7C illustrates a concomitant simulation (back propagation) of performance loss errors through a simulated environment including a PBS, according to an embodiment of the present disclosure. Fig. 8A is a flowchart illustrating example time steps for reverse-engineering the operation of a PBS and accompanying simulations, according to an embodiment of