Integrated polarization controller system

Abstract

An integrated photonic system is disclosed that includes a polarization controller for a photonic system that incorporates integrated photonics for effecting polarization effects in an optical signal. An integrated photonic assembly separates, controls and combines polarized components of an optical signal using a polarized beam splitter combiner, at least one phase shifter and at least one beam splitter.

Description

Technical Field

[0001] The present invention relates to photonics systems and, in particular, to a polarization controller for a photonics system incorporating integrated photonics for achieving polarization effects in optical signals. Summary of the invention

[0002] According to a first aspect, an integrated photonic system is provided, comprising: a photonic chip, which includes a polarization controller having a polarization side port and at least one component side port, the polarization controller including: a polarization splitter rotator (PSR) having first, second and third ports, the PSR coupled above the polarization side port via its first port; a first group of waveguides coupled to the second port and the third port of the PSR; a first phase shifter coupled along a first waveguide in the first group of waveguides; and a first beam splitter having a first group of ports and a second group of ports, the first beam splitter coupled to the PSR via its first group of ports and on the first group of waveguides, and the first beam splitter coupled to at least one port of the second group of ports of the first beam splitter via the at least one component side port of the polarization controller.

[0003] In some embodiments, the first beam splitter comprises a 2:1 beam splitter. In some embodiments, the first beam splitter comprises a 2:2 beam splitter.

[0004] In some embodiments, the first phase shifter is configured to apply a phase shift that optimizes an optical signal emitted from at least one of the at least one component-side port of the polarization controller.

[0005] In some embodiments, the first phase shifter is configured to apply a phase shift that generates an optical signal having a selected polarization state emitted from the polarization-side port of the polarization controller.

[0006] In some embodiments, the first phase shifter is tunable.

[0007] Some embodiments also provide at least one power detection element coupled along at least one component side port of the polarization controller, and wherein the controller, the at least one power detection element and the tunable first phase shifter are included in a feedback loop for tuning a first phase shift of the first phase shifter.

[0008] Some embodiments also provide: a second group of waveguides coupled to the first group of ports of the first beam splitter; a second phase shifter coupled along a first waveguide in the second group of waveguides; a second beam splitter having a first group of ports and a second group of ports, the second beam splitter coupled to the first group of waveguides via its first group of ports and coupled to the second group of waveguides via its second group of ports, the second beam splitter coupled to the PSR on the first group of waveguides and coupled to the first beam splitter on the second group of waveguides.

[0009] In some embodiments, the first beam splitter comprises a 2:1 beam splitter and the second beam splitter comprises a 2:2 beam splitter. In some embodiments, the first beam splitter comprises a 2:2 beam splitter and the second beam splitter comprises a 2:2 beam splitter.

[0010] In some embodiments, the first phase shifter and the second phase shifter are configured to apply a phase shift that optimizes an optical signal emitted from at least one of the at least one component-side port of the polarization controller.

[0011] In some embodiments, the first phase shifter and the second phase shifter are configured to apply a phase shift that produces an optical signal having a selected polarization state emitted from the polarization side port of the polarization controller.

[0012] In some embodiments, the first phase shifter and the second phase shifter are tunable.

[0013] Some embodiments are also provided with at least one power detection element coupled along at least one component side port of the polarization controller and a controller, and wherein the controller, the at least one power detection element and the tunable first phase shifter and the second phase shifter are included in a feedback loop for tuning the phase shift of the tunable first and second phase shifters.

[0014] In some embodiments, the at least one power detection element includes at least one photodetector coupled to at least one of the at least one component side ports of the polarization controller via a tap, and wherein the controller controls at least one electrical control signal sent to the tunable first phase shifter and the second phase shifter in response to a signal from the at least one photodetector.

[0015] In some embodiments, the at least one power detection element includes a photodetector coupled to a port of the at least one component side port of the polarization controller, and wherein the controller controls at least one electrical control signal sent to the tunable first phase shifter and the second phase shifter in response to a signal from the photodetector.

[0016] In some embodiments, the first phase shifter is configured to apply a phase shift to generate a circularly polarized sensing light signal transmitted from the polarization side port of the polarization controller, and to output a linearly polarized light signal on one of the at least one component side ports of the polarization controller, wherein the linearly polarized light signal has an optical power proportional to the circularly polarized measurement light signal received at the polarization side port of the polarization controller, and the transmitted circularly polarized sensing light signal has an opposite handedness to the received circularly polarized measurement light signal.

[0017] In some embodiments, the first phase shifter and the second phase shifter are configured to apply a phase shift for generating a circularly polarized sensing light signal transmitted from the polarization side port of the polarization controller, and for outputting a linearly polarized light signal at one of the at least one component side ports of the polarization controller, wherein the linearly polarized light signal has an optical power proportional to the circularly polarized measurement light signal received at the polarization side port of the polarization controller, and the transmitted circularly polarized sensing light signal has an opposite handedness to the received circularly polarized measurement light signal.

[0018] Some embodiments are further provided with a driver for driving the phase shift of the tunable first and second phase shifters in at least one of a rapid and random manner to generate an optical signal effectively having a scrambled polarization state.

[0019] The above and additional aspects and embodiments of the present invention will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments and / or aspects with reference to the accompanying drawings, a brief description of which will be provided below. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other advantages of the present invention will become apparent upon reading the following detailed description and referring to the accompanying drawings.

[0021] Figure 1 is a schematic block diagram of an integrated photonic system including a type I integrated polarization controller with a single component side port according to an embodiment.

[0022] Figure 2 is a schematic block diagram of an integrated photonic system including a type I integrated polarization controller with two component side ports according to an embodiment.

[0023] Figure 3 is a schematic block diagram of an integrated photonic system including a type II integrated polarization controller with a single component side port according to an embodiment.

[0024] Figure 4is a schematic block diagram of an integrated photonic system including a type II integrated polarization controller with two component side ports according to an embodiment.

[0025] Figure 5 is a schematic block diagram of an integrated photonic system including a controllable type-II integrated polarization controller with a single component side port and feedback according to an embodiment.

[0026] Figure 6 is a schematic block diagram of an integrated photonic system including a controllable type-II integrated polarization controller having one component-side port for feedback according to an embodiment.

[0027] Figure 7 is a schematic block diagram of an integrated photonic system including a Type I or Type II integrated polarization controller implemented in a circularly polarized reflective sensor according to an embodiment.

[0028] Figure 8 is a schematic block diagram of an integrated photonic system including a type II integrated polarization controller implemented as a polarization scrambler according to an embodiment.

[0029] Although the present invention is susceptible to various modifications and alternative forms, specific embodiments or implementations have been shown by way of example in the accompanying drawings and will be described in detail herein. However, it should be understood that the present invention is not intended to be limited to the specific forms disclosed. On the contrary, the present invention will cover all modifications, equivalents and alternatives that fall within the scope of the invention defined by the appended claims. DETAILED DESCRIPTION

[0030] Photonic systems use many structural and functional elements to guide, emit, manipulate or otherwise use photon signals in their desired applications. In many such systems, the polarization state of light is utilized in any way depending on the environment or applied to useful applications. In modern silicon photonics, integrating as much structure and functionality as possible into on-chip devices has advantages over free-space components, including but not limited to optimization of size, cost, and optical performance. Whether in light detection and ranging (LIDAR) or any other optoelectronic application, the use and control of the polarization state of light can be complex and / or bulky, sometimes involving large birefringent blocks or wave plates, etc., and the conversion between on-chip polarization optical elements and free-space polarization optical elements can introduce undesirable insertion losses.

[0031] The present invention describes an on-chip solution for converting, controlling and utilizing the polarization state of light, avoiding or mitigating the problems associated with polarization controllers consisting solely of free-space optical elements.

[0032] Now refer to Figure 1An integrated photonic system 1000 including a type I integrated polarization controller according to an embodiment is discussed.

[0033] Many variations of the on-chip solution described below can be used for optical signals transmitted in either direction or in both directions simultaneously. Therefore, rather than structurally characterizing any of the various device ports as input or output, various aspects of the devices and structures are described as "polarization sides" or "component sides." As will become clear below, "polarization side" will refer to the side or direction of the device that receives or transmits polarized optical signals, and "component side" will refer to the side or direction of the device that receives or transmits a component of a polarized optical signal (in the form of a linearly polarized signal).

[0034] The integrated photonic system 1000 includes an integrated polarization controller 1010, which includes a polarization controller for converting polarizations having orthogonal components (e.g., having equal amplitudes) into polarizations having orthogonal components (e.g., having equal amplitudes). x and E y (TE and TM) into any polarization state in a single component direction (e.g. E x For example, a linearly polarized optical signal (e.g., from the x-axis) at 45° (which may be a "diagonal" or "anti-diagonal" polarization state, right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), or any elliptical polarization state formed by a combination of TE and TM with equal amplitude and phase difference other than ±π / 2, 0, or π) can be converted to a linear polarization state, such as TE, with approximately the same power as the original optical signal.

[0035] Regarding the structure, starting from the polarization side of the system 1000, the first port of the transmitter 1100 is used as the polarization side port of the integrated polarization controller 1010. The transmitter 1100 can be any free space to chip converter that supports two polarization components (TE and TM), such as a grating or an inverted cone. The second port of the transmitter 1100 is coupled to a single polarization side port of a polarization beam splitter rotator (PSR) 1200, which is coupled to the first set of ports on the polarization side of the 2:1 beam splitter 1420 via its component side ports on the first set of waveguides 1001, 1003. The first component side port of the PSR is coupled to the first waveguide 1001, and the second component side port of the PSR is coupled to the second waveguide 1003. A phase shifter 1320 is coupled along the first waveguide 1001. The first waveguide 1001 is coupled to a first port of a 2:1 beam splitter 1420, and the second waveguide 1003 is coupled to a second port of the 2:1 beam splitter 1420. The component side of the 2:1 beam splitter 1420 is coupled via a second set of ports (consisting of a single third port) to a component side port 1009 of an integrated polarization controller 1010, represented here as a waveguide coupled to other optical components using polarization converted optical signals.

[0036] Regarding the function, at the transmitter 1100, the original optical signal of the original polarization state is input to the integrated polarization controller 1010. After passing through the transmitter 1100, the optical signal enters the polarization beam rotator (PSR) 1200, which separates the orthogonal polarization components of the optical signal, rotates one of them, and outputs them on separate component side ports. y The component (TM) is rotated 90° into TE polarization and is output from the first component side port of the PSR 1200 along the first waveguide 1001 as a first component optical signal “TM as TE”. xThe component (TE) is output as a second component optical signal "TE" from the second component side port of the PSR 1200 along the second waveguide 1003. Due to the unequal effective refractive index that generally affects the TM and TE components, the TE and TM polarization components of the optical signal experience different phase shifts when passing through the transmitter 1100 and the PSR 1200. This will be reflected in the phases of the first and second component optical signals emitted from the PSR 1200. For the purpose of operating the polarization controller 1010, the absolute phase of the optical signal passing through the first set of waveguides 1001, 1003 is not important, only the relative phase difference Δθ between the optical signal passing through the first waveguide 1001 and the optical signal passing through the second waveguide 1003 is important. This relative phase difference Δθ depends not only on the phase shift caused by the transmitter 1100 and the PSR 1200, but also on the original phase difference between the orthogonal polarization components of the original optical signal. The first component optical signal "TM as TE" passes through a phase shifter 1320 coupled along the first waveguide 1001 that applies a phase shift of Δφ in the first component optical signal. The phase-shifted first component optical signal is emitted from the phase shifter 1320, passes through the remaining portion of the first waveguide 1001, and enters the 2:1 beam splitter 1420 via its first port. The second component optical signal passes through the second waveguide 1003 and enters the 2:1 beam splitter 1420 via its second port. The 2:1 beam splitter 1420 effectively adds the optical signals received on its first set of ports to produce a final output optical signal output from the third port of the 2:1 beam splitter and on the component side port 1009. In order to optimize the output power of the final output optical signal, the optical signals input to the 2:1 beam splitter should be in phase, or have any phase difference that optimizes the power according to the internal configuration of the 2:1 beam splitter 1420. To achieve this, the phase shift Δφ of the phase shifter 1320 is appropriately selected. In some embodiments, for example when the 2:1 beam splitter is a Y-branch beam splitter, the phase shift Δφ is selected to be an integer multiple of 2π minus the relative phase difference Δθ to optimize the output power. It should be noted that in some embodiments, the phase shift Δφ of the phase shifter 1320 is selected to optimize other aspects of the final output optical signal, such as, for example, the signal strength of the modulated signal, the eye-opening, and / or the bit error rate.

[0037] It should be noted that in some embodiments, instead of using separate transmitter 1100 and PSR 1200, a single transmitter is used that also functions as a polarization beam splitter rotator. In these embodiments, the two component side ports of the single transmitter are directly coupled to the first and second waveguides 1001 and 1003.

[0038] It should be noted that the relative phase of the first component optical signal “TM as TE” emitted from the transmitter 1100 and PSR 1200 on the first waveguide 1001 can lead or follow the phase of the second component optical signal “TE” emitted from the transmitter 1100 and PSR1200 on the second waveguide 1003.

[0039] Since only the relative phase difference is relevant (and not the absolute phase), in some embodiments, the phase shifter 1320 is positioned along the second waveguide 1003 and its phase shift Δφ is appropriately chosen.

[0040] Although the first component optical signal passing through the first waveguide 1001 has been characterized as "TM as TE", and the second component optical signal passing through the second waveguide has also been characterized as "TE", as long as the optical signals emitted from the transmitter 1100 and / or PSR 1200 are in the same (parallel) linear polarization state supported by both the first and second waveguides 1001, 1003, they can be appropriately phase-shifted by the phase shifter 1320 and combined in the 2:1 beam splitter 1420. For example, in some cases, the transmitter 1100 and PSR 1200 can split and rotate the polarization components so that the E of the incident optical signal is x The component (TE) is rotated 90° to become TM polarization and output as “TE as TM”, and the E of the incident optical signal y The component (TM) is output as "TM", and these two signals pass through waveguides 1001, 1003 that support "TM" mode transmission.

[0041] In some embodiments where the polarization of the original optical signal is known, the phase shifter 1320 is a fixed passive element.

[0042] In some embodiments, to handle various polarization states (orthogonal components with equal amplitudes), phase shifter 1320 is tunable and the polarization controller includes active control of phase shifter 1320 and optionally includes devices such as taps and photodiodes (similar to the following combined Figure 5 Various elements for power monitoring (such as those described above) are used to provide feedback to a controller for tuning the phase shift Δφ.

[0043] The phase shifter 1320 of this embodiment and other embodiments can be implemented using a variety of different technologies, including but not limited to: thermo-optic, electro-optic, carrier injection, carrier depletion, liquid crystal or MEMS. Generally, thermo-optic technology is better due to its low optical loss.

[0044] In some embodiments, the polarization controller 1010 is reversed so that the first port of the transmitter 1100 is used as the output of the polarization controller 1010, and the component side port 1009 is used as the input of the polarization controller 1010. In this case, a linearly polarized optical signal, such as "TE", is launched into the component side port 1009, the signal is split, and a relative phase difference Δφ is introduced by the phase shifter 1320 so that once rotated and recombined in the PSR 1200 and the transmitter 1100, the optical signal emitted from the transmitter 1100 has a desired polarization, such as any optical signal that is linearly polarized at 45° (e.g., from the x-axis), in a "diagonal" or "anti-diagonal" polarization state, or right-hand circular polarization (RHCP), or left-hand circular polarization (LHCP), or any elliptical polarization state formed by a combination of TE and TM of equal amplitude and a phase difference other than ±π / 2, 0, or π. Therefore, the phase shift Δφ is determined taking into account both the desired polarization state of the output and the relative phase difference Δθ introduced by the transmitter 1100 and the PSR 1200 .

[0045] Typically, the polarization controller 1010 uses a combination of the transmitter 1100 and / or the PSR 1200 to split two orthogonal polarization components (of the same amplitude) of the incident optical signal and rotate one to be parallel to the other, and uses a phase shifter 1320 to control the relative phase of the two component optical signals before combining them in a 2:1 beam splitter, and optionally (or simultaneously) is also capable of performing the opposite operation.

[0046] In some embodiments of a Type I polarization controller, the 2:1 beam splitter may be replaced by a 2:2 beam splitter that, for example, ignores one path, including, for example, a multi-mode interferometer (MMI) or a directional coupler.

[0047] This is what we will discuss now. Figure 2 An example of an integrated photonic system 2000 including a type I integrated polarization controller according to an embodiment is shown.

[0048] The integrated photonic system 2000 includes an integrated polarization controller 2010, which includes a controller for converting any polarization state having orthogonal components (e.g., E x and E y (TE and TM)) into a polarization state with substantially all incident power in a single component direction (e.g., E xFor example, an optical signal that is linearly polarized at 45° (e.g., from the x-axis) (in a "diagonal" or "anti-diagonal" polarization state, right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), or any elliptical polarization state formed by a combination of TE and TM of equal amplitude and a phase difference other than ±π / 2, 0, or π) can be converted to a linear polarization state, such as TE, with approximately the same power as the original optical signal.

[0049] Starting from the polarization side of the system 2000, the first port of the transmitter 2100 is used as the polarization side port of the integrated polarization controller 2010. The transmitter 2100 can be any free space to chip converter that supports two polarization components (TE and TM) such as a grating or an inverted cone. The second port of the transmitter 2100 is coupled to a single polarization side port of a polarization beam splitter rotator (PSR) 2200, which is coupled to the first set of ports on the polarization side of the 2:2 beam splitter 2420 via its component side ports on the first set of waveguides 2001, 2003. The first component side port of the PSR 2200 is coupled to the first waveguide 2001, and the second component side port of the PSR 2200 is coupled to the second waveguide 2003. A phase shifter 2320 is coupled along the first waveguide 2001. The first waveguide 2001 is coupled to a first port of a 2:2 beam splitter 2420, and the second waveguide 2003 is coupled to a second port of the 2:2 beam splitter 2420. The component side of the 2:2 beam splitter 2420 is coupled via a second set of ports (consisting of a third and a fourth port) to two component side ports 2009a, 2009b of an integrated polarization controller 2010, represented here as waveguides (one or both of which are coupled to other optical components using polarization-converted optical signals), respectively.

[0050] At the transmitter 2100, the original optical signal of the original polarization state is input to the integrated polarization controller 2010. After passing through the transmitter 2100, the optical signal enters the polarization beam rotator (PSR) 2200, which splits the orthogonal polarization components of the optical signal, rotates one of them, and outputs them on separate component side ports. The Ey component (TM) of the incident optical signal is rotated 90° to TE polarization and is output from the first component side port of the PSR 2200 along the first waveguide 2001 as a first component optical signal "TM as TE". The Ey component (TM) of the incident optical signal is rotated 90° to TE polarization and is output from the first component side port of the PSR 2200 along the first waveguide 2001 as a first component optical signal "TM as TE". xThe component (TE) is output from the second component side port of the PSR 2200 along the second waveguide 2003 as a second component optical signal "TE". Due to the unequal effective refractive index that generally affects the TM and TE components, the TE and TM polarization components of the optical signal experience different phase shifts when passing through both the transmitter 2100 and the PSR 2200. This will be reflected in the phases of the first and second component optical signals emitted from the PSR 2200. For the operation of the polarization controller 2010, the absolute phase of the optical signal passing through the first set of waveguides 2001, 2003 is not important, only the relative phase difference Δθ between the optical signal passing through the first waveguide 2001 and the optical signal passing through the second waveguide 2003 is important. This relative phase difference Δθ depends not only on the phase shift caused by the transmitter 2100 and the PSR 2200, but also on the original phase difference between the orthogonal polarization components of the original optical signal. The first component optical signal "TM as TE" passes through the phase shifter 2320 coupled along the first waveguide 2001, which applies a phase shift of Δφ in the first component optical signal. The phase-shifted first component optical signal emerges from the phase shifter 2320, passes through the rest of the first waveguide 2001, and enters the 2:2 beam splitter 2420 via the first port of the 2:2 beam splitter 2420. The second component optical signal passes through the second waveguide 2003, and enters the 2:2 beam splitter 2420 via the second port of the 2:2 beam splitter 2420. The 2:2 beam splitter 2420 effectively adds the optical signals received on its first set of ports to produce a final output optical signal output from one of the ports of its second set of ports (i.e., one of the third or fourth ports of the 2:2 beam splitter 2420) and on one of the component-side ports 2009a, 2009b. The other of the third or fourth ports of the 2:2 beam splitter coupled to the other of the component side ports 2009a, 2009b generates an optical signal that is the difference between the two optical signals received at the first set of ports 2420 of the 2:2 beam splitter. In order to optimize the output power of the final output optical signal, the optical signals input to the 2:2 beam splitter should be in phase, or should have any phase difference that optimizes the power appearing on the intended component side ports 2009a, 2009b, depending on the internal structure of the 2:2 splitter 2420 (and which of the component side ports 2009a, 2009b is used as the "output"). For example, the 2:2 beam splitter 2420 can cause an even-mode input optical signal to optimize the power on one of the two component side ports 2009a and 2009b while minimizing the power on the other of the two component side ports 2009a and 2009b. In this case, the same 2:2 splitter may cause the odd-mode input optical signal to optimize the power on the other of the two component side ports 2009a and 2009b while minimizing the power on one of the two component side ports 2009a and 2009b.It should be noted that although in some embodiments only one of the two component side ports 2009a and 2009b is used as the desired output of the final output optical signal and the optical signal at the other of the two component side ports 2009a and 2009b is abandoned or discarded, the optical signals at both component side ports 2009a and 2009b are used in some embodiments and in some cases are used for different purposes (similar to combining). Figure 6 and Figure 7 described embodiments).

[0051] In order to achieve the appropriate relative phase difference for optimizing the output power, the phase shift Δφ of the phase shifter 2320 is appropriately selected. In some embodiments, the phase shift Δφ is selected to be an integer multiple of 2π minus the relative phase difference Δθ, while in other embodiments (odd mode optimized output), the phase shift Δφ is selected to be an integer multiple of π minus the relative phase difference Δθ plus 2π to optimize the output power. It should be noted that in some embodiments, the phase shift Δφ of the phase shifter 2320 is selected to optimize other aspects of the final output optical signal, such as, for example, the signal strength, eye opening, and / or bit error rate of the modulated signal.

[0052] In some embodiments, rather than using separate transmitters 2100 and PSRs 2200, a single transmitter or coupler is used that also functions as a polarization beam splitter rotator. In these embodiments, the two component side ports of the coupler are directly coupled to the first and second waveguides 2001 and 2003.

[0053] The relative phase of the first component optical signal "TM as TE" emitted from the transmitter 2100 and PSR 2200 on the first waveguide 2001 can lead or follow the phase of the second component optical signal "TE" emitted from the transmitter 2100 and PSR 22000 on the second waveguide 2003. In some embodiments, the phase shifter 2320 is positioned along the second waveguide 2003 and its phase shift Δφ is appropriately selected.

[0054] As long as the optical signals emerging from the transmitter 2100 and / or PSR 2200 are in the same (parallel) linear polarization state supported by both the first and second waveguides 2001 and 2003, they can be appropriately phase shifted by the phase shifter 2320 and combined in the 2:2 beam splitter 2420. For example, in some cases, the transmitter 2100 and PSR 2200 can split and rotate the polarization components so that the E of the incident optical signal is x The component (TE) is rotated 90° to TM polarization and output as “TE as TM”, and the E of the incident optical signal y The component (TM) output is "TM", and both signals pass through waveguides 2001 and 2003 that support "TM" mode transmission.

[0055] In some embodiments where the polarization of the original optical signal is known, the phase shifter 2320 is a fixed passive element.

[0056] In some embodiments, to handle various polarization states (orthogonal components with equal amplitudes), phase shifter 2320 is tunable and the polarization controller includes active control of phase shifter 2320 and optionally includes devices such as taps and photodiodes (similar to the following combined Figure 5 Various elements for power monitoring (such as those described above) are used to provide feedback to the controller for tuning the phase shift Δφ.

[0057] In some embodiments (such as the following combination Figure 7 ), the polarization controller 2010 is inverted so that the first port of the transmitter 2100 is used as the output of the polarization controller 2010, and the component side ports 2009a, 2009b are used as the input of the polarization controller 2010. In this case, a linearly polarized optical signal, such as "TE", is launched into one component side port (e.g., 2009a), the signal is split, and a relative phase difference is introduced by the phase shifter 2320 so that once rotated and recombined in the PSR 2200 and the transmitter 2100, the optical signal emitted from the transmitter 2100 has a desired polarization, such as 45° linear polarization (e.g., from the x-axis), or "diagonal" or "anti-diagonal" polarization state, or right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP), or any optical signal of any elliptical polarization state formed by a combination of TE and TM with equal amplitude and a phase difference of ±π / 2, 0, π. The phase shift Δφ is determined taking into account both the desired polarization state of the output and the relative phase difference Δθ introduced by the transmitter 2100 and the PSR 2200 .

[0058] In some embodiments (such as the following combination Figure 7 As described above, the polarization controller 2010 is used for both forward and reverse directions. In this case, the first port of the transmitter 2100 is used as the input and output of the polarization controller 2010, and one of the component side ports 2009a and 2009b is used as the other input of the polarization control device 2010, while the other of the component side ports 2009a and 2009b is used as the other output of the polarization controller. In this case, a linearly polarized optical signal, such as "TE", is transmitted to one component side port, such as the component side port 2009b, the signal is branched and a relative phase difference is introduced by the phase shifter 2320, so that once rotated and recombined in the PSR 2200 and the transmitter 2100, the optical signal emitted from the transmitter 2100 has a desired polarization, such as right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP), which can be used for analyzing material samples (such as Figure 7 ), the optical signal assumes the opposite (LHCP or RHCP) circular polarization state when reflected back to the polarization controller 2010. Due to the opposite handedness of the returning optical signal (described below), after passing through the polarization controller 2010 in the opposite direction, it emerges as a "TE" optical signal on the component side port 2009a.

[0059] The polarization controller 2010 uses a combination of the transmitter 2100 and / or the PSR 2200 to split the two orthogonal polarization components (with the same amplitude) of the incident optical signal and rotate one to be parallel to the other, and uses a phase shifter 2320 to control the relative phase of the two component optical signals before combining them in a 2:2 beam splitter, and is also capable of performing reverse operations alternately or simultaneously.

[0060] Combination of the above Figure 1 and Figure 2 The discussed Type I polarization controllers 1010 and 2010, although illustrated as receiving or generating optical signals of polarization states having orthogonal components of equal amplitude, can also be used with optical signals of other polarization states, thereby changing the degree of power loss in the generated optical signal. In order to process optical signals of any polarization state, a Type II integrated polarization controller as described below can be used.

[0061] Reference Figure 3 , an integrated photonic system 3000 including a type II integrated polarization controller according to an embodiment will now be discussed.

[0062] As above Figure 1 and Figure 2 As noted in the embodiments of , the 2:1 beam splitter and the 2:2 beam splitter effectively add the first and second component optical signals they receive to produce an output optical signal, and generally the in-phase inputs of similar amplitude optimize the output power at the component side port of the polarization controller which serves as its output. If the phase or amplitude is not matched, the output power will not be optimized. This is why Type I polarization controllers are best suited for optical signals with polarization components of equal amplitude. In order to allow operation in any polarization state, with any phase difference for the polarization components and with any amplitude ratio, instead of using a single 2:1 or 2:2 beam splitter at the output of the polarization controller, a variable beam splitter is used.

[0063] The integrated photonic system 3000 includes an integrated polarization controller 3010, which includes a controller for converting any polarization state having orthogonal components (e.g., E x and E y (TE and TM)) into a polarization state with substantially all incident power in a single component direction (e.g., E xFor example, a linear, circular, or elliptically polarized optical signal can be converted into a specific linear polarization state, such as TE, which has approximately the same power as the original optical signal.

[0064] Starting from the polarization side of the system 3000, the first port of the transmitter 3100 is used as the polarization side port of the integrated polarization controller 3010. The transmitter 3100 can be any free space to chip converter that supports two polarization components (TE and TM) such as a grating or an inverted cone. The second port of the transmitter 3100 is coupled to a single polarization side port of a polarization beam splitter rotator (PSR) 3200, which is coupled to the first set of ports on the polarization side of the 2:2 beam splitter 3420 via its component side ports on the first set of waveguides 3001 and 3003. The first component side port of the PSR 3200 is coupled to the first waveguide 3001, and the second component side port of the PSR 3200 is coupled to the second waveguide 3003. A first phase shifter 3320 is coupled along the first waveguide 3001. The first waveguide 3001 is coupled to a first port of a 2:2 beam splitter 3420, and the second waveguide 3003 is coupled to a second port of the 2:2 beam splitter 3420. The component side of the 2:2 beam splitter 3420 is coupled to a first group of ports on the polarization side of a 2:1 beam splitter 3440 on a second group of waveguides 3005 and 3007 via a second group of ports (composed of third and fourth ports). The 2:2 beam splitter 3420 is coupled to a third waveguide 3005 via its third port, and to a fourth waveguide 3007 via its fourth port. A second phase shifter 3340 is coupled along the third waveguide 3005. The third waveguide 3005 is coupled to a first port of a 2:1 beam splitter 3440, and the fourth waveguide 3007 is coupled to a second port of the 2:1 beam splitter 3440. The component side of the 2:1 beam splitter 3440 is coupled via a second set of ports (consisting of a single third port) to a component side port 3009 of an integrated polarization controller 3010 represented here as a waveguide coupled to other optical components using polarization converted optical signals.

[0065] At the transmitter 3100, the original optical signal of the original polarization state is input to the integrated polarization controller 3010. After passing through the transmitter 3100, the optical signal enters the polarization beam splitter rotator (PSR) 3200, which splits the orthogonal polarization components of the optical signal, rotates one of them, and outputs them on separate component side ports. y The component (TM) is rotated 90° into TE polarization and is output from the first component side port of the PSR 3200 along the first waveguide 3001 as a first component optical signal “TM as TE”. xThe component (TE) is output as a second component optical signal "TE" from the second component side port of the PSR 3200 along the second waveguide 3003. Since the effective refractive index that generally affects the TM and TE components is unequal, the TE and TM polarization components of the optical signal experience different phase shifts when passing through both the transmitter 3100 and the PSR 3200. This will be reflected in the phases of the first and second component optical signals emitted from the PSR 3200. For the operation of the polarization controller 3010, the absolute phase of the optical signal passing through the first set of waveguides 3001 and 3003 is not important, only the relative phase difference Δθ between the optical signal passing through the first waveguide 3001 and the optical signal passing through the second waveguide 3003 is important. This relative phase difference Δθ depends not only on the phase shift caused by the transmitter 3100 and the PSR 3200, but also on the original phase difference between the orthogonal polarization components of the original optical signal. The first component optical signal "TM as TE" passes through a first phase shifter 3320 coupled along the first waveguide 3001, which applies a first phase shift of Δφ1 in the first component optical signal. The phase-shifted first component optical signal exits the first phase shifter 3320, passes through the remaining portion of the first waveguide 3001, and enters the 2:2 beam splitter 3420 via a first port of the 2:2 beam splitter 3420. The second component optical signal passes through the second waveguide 3003, and enters the 2:2 beam splitter 3420 via a second port of the 2:2 beam splitter 3420. The 2:2 beam splitter 3420 effectively adds the optical signals received at its first set of ports to generate an optical signal output from one port of its second set of ports, and the optical signal generated at the other port of its second set of ports is the difference between the two optical signals received at the first set of ports of the 2:2 beam splitter 3420. To ensure that the optical signals arriving at the 2:1 beam splitter 3440 have equal power, the optical signals input to the 2:2 beam splitter 3420, regardless of their relative power, should be phased by ±90° (±π / 2), or any phase difference that equalizes the power of the signals emitted on the second set of waveguides 3005 and 3007, depending on the internal structure of the 2:2 beam splitter 3420. This ensures that the two optical signals emitted from the 2:2 beam splitter 3420, i.e., one is the sum of the optical signals input to the 2:2 beam splitter 3420, and the other is the difference of the optical signals input to the 2:2 beam splitter 3420, have the same power.

[0066] In order to achieve such an appropriate relative phase difference for equalizing the output power from the 2:2 beam splitter 3420, the first phase shift Δφ1 of the first phase shifter 3320 is appropriately selected, that is, appropriately selected to provide a relative phase difference of ±90° (±π / 2). In some embodiments, the first phase shift Δφ1 is selected to be an integer multiple of 2π minus an additional relative phase difference Δθ offset by ±90° (±π / 2).

[0067] The third and fourth component optical signals of equal power are emitted from the 2:2 beam splitter 3420 on the third and fourth waveguides 3005 and 3007, respectively. The third and fourth component optical signals emitted from the 2:2 beam splitter 3420 on the third and fourth waveguides 3005 and 3007 will have a relative phase difference Δθ2 depending on the relative amplitudes of the optical signals input to the 2:2 beam splitter 3420. The third component optical signal passing through the third waveguide 3005 passes through a second phase shifter 3340 coupled along the third waveguide 3005 that applies a second phase shift of Δφ2 in the third component optical signal. The phase-shifted third component optical signal is emitted from the phase shifter 3340, passes through the remaining portion of the third waveguide 3005, and enters the 2:1 beam splitter 3440 via the first port of the 2:1 beam splitter 3440. The fourth component optical signal passes through the fourth waveguide 3007 and enters the 2:1 beam splitter 3440 via the second port of the 2:1 beam splitter 3440. The 2:1 beam splitter 3440 effectively adds the optical signals received on its first set of ports to produce a final output optical signal output from its third port and on the component side port 3009. In order to optimize the output power of the final output optical signal, the optical signals input to the 2:1 beam splitter 3440 should be in phase, or have any phase difference that optimizes the power according to the internal structure of the 2:1 beam splitter 3440. To achieve this, the second phase shift Δφ2 of the second phase shifter 3340 is appropriately selected, and in some embodiments, the second phase shift Δφ2 is selected to be an integer multiple of 2π minus the second relative phase difference Δθ2 to optimize the output power. It should be noted that in some embodiments, the second phase shift Δφ2 of the phase shifter 3340 is selected to optimize other aspects of the final output optical signal, such as, for example, the signal strength of the modulation signal, the eye opening, and / or the bit error rate.

[0068] In some embodiments, rather than using separate transmitters 3100 and PSR 3200, a single transmitter is used that also functions as a polarization beam splitter rotator. In these embodiments, the two component side ports of the single transmitter are directly coupled to the first and second waveguides 3001 and 3003. The relative phase of the first component optical signal "TM as TE" emitted from the transmitter 3100 and PSR 3200 on the first waveguide 3001 can lead or follow the phase of the second component optical signal "TE" emitted from the transmitter 3100 and PSR 3200 on the second waveguide 3003. In some embodiments, one or both of the first and second phase shifters 3320 and 3340 are positioned along the second and fourth waveguides 3003 and 3007, respectively, and their phase shifts Δφ1 and Δφ2 are appropriately selected.

[0069] As long as the optical signals emerging from the transmitter 3100 and / or PSR 3200 are in the same (parallel) linear polarization state supported by the first and second waveguides 3001 and 3003, they can be appropriately phase-shifted by the first phase shifter 3320 and manipulated by the remaining elements of the polarization controller 3010. For example, in some cases, the transmitter 3100 and PSR 3200 can separate and rotate the polarization components so that the E of the incident optical signal is x The component (TE) is rotated 90° to TM polarization and output as “TE as TM”, and the E of the incident optical signal y The component (TM) is output as "TM", and both signals pass through waveguides 3001, 3003 that support "TM" mode transmission.

[0070] In some embodiments where the polarization of the original optical signal is known, phase shifters 3320 and 3340 are fixed passive elements.

[0071] In some embodiments, phase shifters 3320 and 3340 are tunable to handle arbitrary polarization states, and the polarization controller includes active control of phase shifters 3320 and 3340, and optionally includes devices such as taps and photodiodes (similar to the following combined Figure 5 Various elements for power monitoring (such as those described above) are used to provide feedback to the controllers for tuning the phase shifts Δφ1, Δφ2.

[0072] In some embodiments, the polarization controller 3010 is reversed so that the first port of the transmitter 3100 is used as the output of the polarization controller 3010, and the component side port 3009 is used as the input of the polarization controller 3010. In this case, a linearly polarized optical signal, such as "TE", is launched into the component side port 3009, the signal is split, and a relative phase difference Δφ2 is introduced by the second phase shifter 3340, so that once split by the 2:2 beam splitter 3420 and another relative phase difference Δφ1 is introduced by the first phase shifter 3320, and once rotated and recombined in the PSR 3200 and the transmitter 3100, the optical signal emitted from the transmitter 3100 has a desired polarization, such as any arbitrary linear, circular or elliptical polarization state. Therefore, the phase shifts Δφ1, Δφ2 are determined by considering both the desired polarization state of the output and the relative phase difference Δθ introduced by the transmitter 3100 and the PSR 3200.

[0073] Typically, the polarization controller 3010 uses a combination of the transmitter 3100 and / or the PSR 3200 to separate two orthogonal polarization components of an arbitrarily polarized incident optical signal, and rotates one to be parallel to the other, and uses a first phase shifter 3320 to control the relative phases of the two component optical signals so that they have a relative phase difference of ±90° (±π / 2) before passing through a 2:2 beam splitter 3420, emits optical signals with equal power from the 2:2 beam splitter 3420, and uses a second phase shifter 3340 to further phase shift one of the signals by Δφ2 before combining them in a 2:1 beam splitter 3440 for output so that they are in phase, and is also capable of (alternatively or simultaneously) performing the opposite operation.

[0074] In some embodiments of a Type II polarization controller, the 2:1 beam splitter may be replaced by a component-side 2:2 beam splitter (eg, one output is omitted) comprising, for example, a multi-mode interferometer (MMI) or a directional coupler.

[0075] This is the basis for the discussion now. Figure 4 The illustrated embodiment has an example of an integrated photonic system 4000 including a Type II integrated polarization controller.

[0076] The integrated photonic system 4000 includes an integrated polarization controller 4010, which includes a controller for converting any polarization state having orthogonal components (e.g., E x and E y (TE and TM)) into a polarization state with substantially all incident power in a single component direction (e.g., E x For example, a linear, circular, or elliptically polarized optical signal can be converted into a specific linear polarization state, such as TE, which has approximately the same power as the original optical signal.

[0077] Starting from the polarization side of the system 4000, the first port of the transmitter 4100 is used as the polarization side port of the integrated polarization controller 4010. The transmitter 4100 can be any free space to chip converter that supports two polarization components (TE and TM) such as a grating or an inverted cone. The second port of the transmitter 4100 is coupled to a single polarization side port of a polarization beam splitter rotator (PSR) 4200, which is coupled to the first set of ports on the polarization side of the polarization side 2:2 beam splitter 4420 via its component side ports on the first set of waveguides 4001 and 4003. The first component side port of the PSR 4200 is coupled to the first waveguide 4001, and the second component side port of the PSR 4200 is coupled to the second waveguide 4003. A first phase shifter 4320 is coupled along the first waveguide 4001. The first waveguide 4001 is coupled to the first port of the polarization-side 2:2 beam splitter 4420, and the second waveguide 4003 is coupled to the second port of the polarization-side 2:2 beam splitter 4420. The component side of the polarization-side 2:2 beam splitter 4420 is coupled to the first group of ports on the polarization side of the component-side 2:2 beam splitter 4440 on the second group of waveguides 4005 and 4007 via the second group of ports (composed of the third and fourth ports). The polarization-side 2:2 beam splitter 4420 is coupled to the third waveguide 4005 via its third port, and to the fourth waveguide 4007 via its fourth port. A second phase shifter 4340 is coupled along the third waveguide 4005. The third waveguide 4005 is coupled to the first port of the component-side 2:2 beam splitter 4440, and the fourth waveguide 4007 is coupled to the second port of the component-side 2:2 beam splitter 4440. The component side of the component-side 2:2 splitter 4440 is coupled via a second set of ports (consisting of the third and fourth ports) to two component-side ports 4009a and 4009b of the integrated polarization controller 4010, represented here as waveguides, respectively, one or both of which are coupled to other optical elements that use polarization-converted optical signals.

[0078] At the transmitter 4100, the original optical signal of the original polarization state is input to the integrated polarization controller 4010. After passing through the transmitter 4100, the optical signal enters the polarization beam rotator (PSR) 4200, which splits the orthogonal polarization components of the optical signal, rotates one of them, and outputs them on separate component side ports. y The component (TM) is rotated 90° into TE polarization and is output from the first component side port of the PSR 4200 along the first waveguide 4001 as a first component optical signal “TM as TE”. xThe component (TE) is output as a second component optical signal "TE" from the second component side port of the PSR 4200 along the second waveguide 4003. Due to the unequal effective refractive index that generally affects the TM and TE components, the TE and TM polarization components of the optical signal experience different phase shifts when passing through both the transmitter 4100 and the PSR 4200. This will be reflected in the phases of the first and second component optical signals emitted from the PSR 4200. For the operation of the polarization controller 4010, the absolute phase of the optical signal passing through the first set of waveguides 4001, 4003 is not important, only the relative phase difference Δθ between the optical signal passing through the first waveguide 4001 and the optical signal passing through the second waveguide 4003 is important. This relative phase difference Δθ depends not only on the phase shift caused by the transmitter 4100 and the PSR 4200, but also on the original phase difference between the orthogonal polarization components of the original optical signal. The first component optical signal "TM as TE" passes through the first phase shifter 4320 coupled along the first waveguide 4001 to apply a first phase shift of Δφ1 in the first component optical signal. The phase-shifted first component optical signal emerges from the first phase shifter 4320, passes through the remaining portion of the first waveguide 4001, and enters the polarization-side 2:2 beam splitter 4420 via the first port of the 2:2 beam splitter 4420. The second component optical signal passes through the second waveguide 4003, and enters the polarization-side 2:2 beam splitter 4420 via the second port of the 2:2 beam splitter 4420. The 2:2 beam splitter 4420 effectively adds the optical signals received on its first set of ports to generate an optical signal output from one of its ports of the second set of ports, and the other port of its second set of ports generates an optical signal that is the difference between the two optical signals received on the first set of ports of the polarization-side 2:2 beam splitter 4420. In order to ensure that the optical signals arriving at the component-side 2:2 beam splitter 4440 have equal powers, the optical signals input to the polarization-side 2:2 beam splitter 4420 should have a phase difference of ±90° (±π / 2) or any phase difference that equalizes the powers of the signals output on the second set of waveguides 4005 and 4007, regardless of their relative powers, depending on the internal structure of the 2:2 beam splitter 4420. This ensures that the two optical signals output from the polarization-side 2:2 beam splitter 4420 (i.e., one is the sum of the optical signals input to the polarization-side 2:2 beam splitter 4420, and the other is the difference of the optical signals output to the polarization-side 2:2 beam splitter 4420) have the same power.

[0079] In order to achieve the appropriate relative phase difference for balancing the output power from the polarization-side 2:2 beam splitter 4420, the first phase shift Δφ1 of the first phase shifter 4320 is appropriately selected, that is, a relative phase difference of ±90° (±π / 2) is selected. In some embodiments, the first phase shift Δφ1 is selected to be an integer multiple of 2π minus an additional relative phase difference Δθ offset by ±90° (±π / 2).

[0080] The third and fourth component optical signals of equal power are emitted from the polarization side 2:2 beam splitter 4420 on the third waveguide 4005 and the fourth waveguide 4007, respectively. Depending on the relative amplitudes of the optical signals input to the polarization side 2:2 beam splitter 4420, the third and fourth component optical signals emitted from the polarization side 2:2 beam splitter 4420 to the third and fourth waveguides 4005 and 4007 will have a relative phase difference Δθ2. The third component optical signal passing through the third waveguide 4005 passes through the second phase shifter 4340 coupled along the third waveguide 3005, which applies a second phase shift of Δφ2 in the third component optical signal. The phase-shifted third component optical signal is emitted from the phase shifter 4340, passes through the remaining portion of the third waveguide 4005, and enters the component side 2:2 beam splitter 4440 via the first port of the 2:2 beam splitter 4440. The fourth component optical signal passes through the fourth waveguide 4007 and enters the component-side 2:2 beam splitter 4440 via the second port of the 2:2 beam splitter 4440. The component-side 2:2 beam splitter 4440 effectively adds the optical signals received on its first set of ports to produce a final output optical signal output from one of the ports of its second set of ports (i.e., one of the third or fourth ports of the component-side 2:2 beam splitter 4440) and on one of the component-side ports 4009a and 4009b. The other of its third or fourth ports coupled to the other of the component-side ports 4009a and 4009b produces an optical signal that is the difference between the two optical signals received on the first set of ports of the component-side 2:2 beam splitter 4440.

[0081] In order to optimize the output power of the final output optical signal, the optical signal input to the component-side 2:2 beam splitter 4440 should be in phase, or have any phase difference that optimizes the power according to the internal structure of the component-side 2:2 beam splitter 444. To achieve this, the second phase shift Δφ2 of the second phase shifter 4340 is appropriately selected, and in some embodiments, the second phase shift Δφ2 is selected to be an integer multiple of 2π minus the second relative phase difference Δθ2 to optimize the output power. It should be noted that in some embodiments, the second phase shift Δφ2 of the phase shifter 4340 is selected to optimize other aspects of the final output optical signal, such as the signal strength, eye opening and / or bit error rate of the modulated signal.

[0082] In some embodiments, instead of using separate transmitters 4100 and PSR 4200, a single transmitter is used that also functions as a polarization beam splitter rotator. In these embodiments, the two component side ports of the single transmitter are directly coupled to the first and second waveguides 4001 and 4003. The relative phase of the first component optical signal "TM as TE" emitted from the transmitter 4100 and PSR 4200 on the first waveguide 4001 can lead or follow the phase of the second component optical signal "TE" emitted from the transmitter 4100 and PSR 4200 on the second waveguide 4003. In some embodiments, one or both of the first and second phase shifters 4320 and 4340 are positioned along the second and fourth waveguides 4003 and 4007, respectively, and their phase shifts Δφ1 and Δφ2 are appropriately selected.

[0083] As long as the optical signals emerging from the transmitter 4100 and / or PSR 4200 are in the same (parallel) linear polarization state supported by the first and second waveguides 4001 and 4003, they can be appropriately phase-shifted by the first phase shifter 4320 and manipulated by the remaining elements of the polarization controller 4010. For example, in some cases, the transmitter 4100 and PSR 4200 can split and rotate the polarization components so that the E of the incident optical signal is x The component (TE) is rotated 90° to TM polarization and output as “TE as TM”, and the E of the incident optical signal y The component (TM) output is "TM", and both signals pass through waveguides 4001, 4003 that support "TM" mode transmission.

[0084] In some embodiments where the polarization of the original optical signal is known, phase shifters 4320 and 4340 are fixed passive elements.

[0085] In some embodiments, to handle arbitrary polarization states, phase shifters 4320 and 4340 are tunable, and the polarization controller includes active control of phase shifters 4320 and 4340, and optionally includes devices such as taps and photodiodes (similar to the following combined Figure 5 Various elements for power monitoring (such as those described above) are used to provide feedback to the controllers for tuning the phase shifts Δφ1, Δφ2.

[0086] In some embodiments (such as the following combination Figure 7), the polarization controller 4010 is inverted so that the first port of the transmitter 4100 is used as the output of the polarization controller 4010, and the component side ports 4009a and 4009b are used as the input of the polarization controller 4010. In this case, a linearly polarized optical signal, such as "TE", is transmitted into one component side port (e.g., 4009a), the signal is branched, and a relative phase difference Δφ2 is introduced by the second phase shifter 4340, so that once it is branched by the polarization side 2:2 beam splitter 4420 and after another relative phase difference Δφ1 is introduced by the first phase shifter 4320, once it is rotated and recombined in the PSR 4200 and the transmitter 4100, the optical signal emitted from the transmitter 4100 has a desired polarization, such as any arbitrary linear, circular or elliptical polarization state. Therefore, the phase shifts Δφ1, Δφ2 are determined by considering both the desired polarization state of the output and the relative phase difference Δθ introduced by the transmitter 4100 and the PSR 4200.

[0087] In some embodiments (such as the following combination Figure 7 As described above), the polarization controller 4010 is used for both forward and reverse directions. In this case, the first port of the transmitter 4100 is used as the input and output of the polarization controller 4010, and one of the component side ports 4009a and 4009b is used as the other input of the polarization controller 4010, while the other of the component side ports 4009a and 4009b is used as the other output of the polarization controller. In this case, a linearly polarized optical signal, such as "TE", is transmitted to one component side port, such as the component side port 4009b, the signal is branched, and a relative phase difference is introduced by the second phase shifter 4340, so that once it is branched by the polarization side 2:2 beam splitter 4420 and after another relative phase difference Δφ1 is introduced by the first phase shifter 4320, and once it is rotated and recombined in the PSR 4200 and the transmitter 4100, the optical signal emitted from the transmitter 4100 has a desired polarization, such as right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP) (as in Figure 7 In the example of (which can be used to analyze material samples), the optical signal assumes the opposite (LHCP or RHCP) circular polarization state when reflected back to the polarization controller 4010. Due to the opposite handedness of the returning optical signal (as described below), after passing through the polarization controller 4010 in the opposite direction, it emerges as a "TE" optical signal on the component side port 4009a.

[0088] Typically, the polarization controller 4010 uses a combination of a transmitter 4100 and / or a PSR 4200 to split two orthogonal polarization components of an incident optical signal of arbitrary polarization, and rotates one to be parallel to the other, and uses a first phase shifter 4320 to control the relative phases of the two component optical signals so that they have a relative phase difference of ±90° (±π / 2) before passing through a polarization-side 2:2 beam splitter 4420 (optical signals with equal power are emitted from the 2:2 beam splitter 4420), and before combining them in a component-side 2:2 beam splitter 4440 for output, one of them is further phase-shifted by Δφ2 using a second phase shifter 4440 so that they are in phase or have a relative phase with optimized power, and the reverse operation can also be performed.

[0089] Now refer to Figure 5 The invention describes an embodiment including a method capable of feedback control such as Figure 3 An integrated photonic system 5000 of a Type II integrated polarization controller 5010 is shown.

[0090] Such as Figure 3 and Figure 4 The type II integrated polarization controller shown is well suited to processing optical signals of any arbitrary polarization state. However, in the case of receiving an optical signal whose polarization state is unknown (such as the output from an optoelectronic circuit or device using a single-mode (non-polarization maintaining) optical fiber), the phase shift provided by the first and second phase shifters should be adjusted in response to the polarization of the original optical signal. In order to achieve this, some form of detection and feedback control should be implemented.

[0091] Starting from the polarization side of the system 5000, the first port of the coupler 5100 is used as the polarization side port of the integrated polarization controller 5010 and receives the original optical signal from, for example, a single mode (SM) fiber 5110. The coupler 5100 can be a dual polarization fiber coupler or any free space to chip converter that supports two polarization components (TE and TM) such as a grating or an inverted taper. The second port of the coupler 5100 is coupled to a single polarization side port of a polarization beam rotator (PSR) 5200, which is coupled to the first set of ports on the polarization side of the 2:2 beam splitter 5420 via its component side ports on the first set of waveguides 5001 and 5003. The first component side port of the PSR 5200 is coupled to the first waveguide 5001, and the second component side port of the PSR 5200 is coupled to the second waveguide 5003. A first tunable phase shifter 5320 is coupled along the first waveguide 5001. The first waveguide 5001 is coupled to a first port of a 2:2 beam splitter 5420, and the second waveguide 5003 is coupled to a second port of the 2:2 beam splitter 5420. The component side of the 2:2 beam splitter 5420 is coupled to a first group of ports on the polarization side of a 2:1 beam splitter 5440 on a second group of waveguides 5005 and 5007 via a second group of ports (composed of a third and a fourth port). The 2:2 beam splitter 5420 is coupled to a third waveguide 5005 via its third port, and to a fourth waveguide 5007 via its fourth port. A second tunable phase shifter 5340 is coupled along the third waveguide 5005. The third waveguide 5005 is coupled to a first port of a 2:1 beam splitter 5440, and the fourth waveguide 5007 is coupled to a second port of the 2:1 beam splitter 5440. The component side port of the 2:1 beam splitter 5440 is coupled to a component side port 5009 of an integrated polarization controller 5010, represented here as a waveguide coupled to other optical components using polarization converted optical signals. An optical tap 5009c is coupled to the component side port 5009 of the integrated polarization controller 5010. A light detecting element such as a photodiode 5510 is coupled to the tap 5009c. The photodiode 5510 is electrically coupled to a controller 5500, which itself is electrically coupled to first and second tunable phase shifters 5320 and 5340.

[0092] Figure 5 The integrated polarization controller 5010 is roughly similar to Figure 3The embodiment shown works in the same manner, however, additional elements provide detection, feedback and control to optimize the power or some other aspect of the output signal. An optical tap 5009c coupled to the component side port 5009 of the integrated polarization controller 5010 is used to tap a small amount of the output optical signal (e.g., 1%). A photodiode 5510 is used to measure the intensity of the output optical signal passing through the output 5009 using the light received on the tap 5009c and thereby measure its power. The controller 5500 receives an electrical signal from the photodiode 5510 indicating the amount of light measured. In response to the measurement, the controller 5500 determines what first phase shift and second phase shift should be applied by the first phase shifter 5320 and the second phase shifter 5340, or how much one or both of them should be adjusted. The controller 5500 then sends an electrical control signal to the first phase shifter 5320 and the second phase shifter 5340 to appropriately adjust one or both of them. When the polarization state of the original optical signal is completely unknown, such as when an optoelectronic circuit coupled to the SM fiber 5110 is started up, when its operation is interrupted, or when the polarization state changes dramatically and instantaneously, a control loop can be systematically used to search for and find the optimal settings of the first phase shifter 5320 and the second phase shifter 5340. The control loop can also be used to fine-tune or continuously adjust the first phase shifter 5320 and the second phase shifter 5340 to maintain optimal power when the polarization state of the original optical signal drifts, shifts, or otherwise changes slowly.

[0093] Now refer to Figure 6 Description of the invention includes a device such as a controller capable of being controlled based on feedback from one of its component side ports according to an embodiment. Figure 4 An integrated photonic system 6000 of a Type II integrated polarization controller 6010 is shown.

[0094] Combined with Figure 5 As with the discussed embodiments, in the case of receiving an optical signal whose polarization state is unknown, detection and feedback control are used to adjust the phase shift provided by the first and second phase shifters in response to the polarization of the original optical signal.

[0095] Starting from the polarization side of the system 6000, the first port of the coupler 6100 is used as the polarization side port of the integrated polarization controller 6010 and receives the original optical signal from, for example, a single mode (SM) fiber 6110. The coupler 6100 can be a dual polarization fiber coupler or any free space to chip converter that supports two polarization components (TE and TM) such as a grating or an inverted taper. The second port of the coupler 6100 is coupled to a single polarization side port of a polarization beam splitter rotator (PSR) 6200, which is coupled to the first group of ports on the polarization side of the polarization side 2:2 beam splitter 6420 via its component side ports on the first group of waveguides 6001, 6003. The first component side port of the PSR 6200 is coupled to the first waveguide 6001, and the second component side port of the PSR 6200 is coupled to the second waveguide 6003. A first tunable phase shifter 6320 is coupled along the first waveguide 6001. The first waveguide 6001 is coupled to a first port of a polarization-side 2:2 beam splitter 6420, and the second waveguide 6003 is coupled to a second port of the polarization-side 2:2 beam splitter 6420. The component side of the polarization-side 2:2 beam splitter 6420 is coupled to a first group of ports on the polarization side of a component-side 2:2 beam splitter 6440 on a second group of waveguides 6005 and 6007 via a second group of ports (consisting of a third and a fourth port). The polarization-side 2:2 beam splitter 6420 is coupled to a third waveguide 6005 via its third port, and to a fourth waveguide 6007 via its fourth port. A second tunable phase shifter 6340 is coupled along the third waveguide 6005. The third waveguide 6005 is coupled to a first port of the component-side 2:2 beam splitter 6440, and the fourth waveguide 6007 is coupled to a second port of the component-side 2:2 beam splitter 6440. The component side of the component side 2:2 beam splitter 6440 is coupled to two component side ports 6009a and 6009b of the integrated polarization controller 6010, represented here as waveguides, via a second set of ports (consisting of the third and fourth ports), respectively, and one of the two component side ports 6009a is coupled to other optical elements that utilize the polarization converted optical signal. The other component side port 6009b (the light from which would otherwise be discarded) is coupled to a light detection element such as a photodiode 6510. The photodiode 6510 is electrically coupled to the controller 6500, which itself is electrically coupled to the first tunable phase shifter 6320 and the second tunable phase shifter 6340.

[0096] Figure 6 The integrated polarization controller 6010 is roughly similar to Figure 4The embodiment shown works in the manner of the embodiment shown, however, additional elements provide detection, feedback and control to optimize the power or some other aspects of the output signal. The photodiode 6510 is used to measure the intensity of the output optical signal passing through the other component side port 6009b, thereby measuring its power. Due to the internal structure of the component side 2:2 beam splitter 6440, the intensity of the light emitted from the other component side port 6009b (which would otherwise be discarded) provides information about the intensity of the output optical signal emitted from one component side port 6009a of the polarization controller 6010 for outputting the optical signal. In particular, when the light intensity measured at the photodiode 6510 is minimized, the power at the component side port 6009a used as the output is optimized. The controller 6500 receives an electrical signal indicating the measured amount of light from the photodiode 6510. In response to the measurement, the controller 6500 determines what kind of first phase shift and second phase shift should be applied by the first phase shifter 6320 and the second phase shifter 6340, or how much one or both of them should be adjusted. The controller 6500 then sends electrical control signals to the first phase shifter 6320 and the second phase shifter 6340 to appropriately adjust one or both of them. When the polarization state of the original optical signal is completely unknown, such as when the optoelectronic circuit coupled to the SM fiber 6110 is started, when its operation is interrupted, or when the polarization state changes dramatically in an instant, the control loop can be systematically used to search and find the optimal settings of the first phase shifter 6320 and the second phase shifter 6340. The control loop can also be used to fine-tune or continuously adjust the first phase shifter 6320 and the second phase shifter 6340 to maintain optimal power when the polarization state of the original optical signal drifts, shifts, or otherwise changes slowly.

[0097] In some embodiments, in addition to the photodiode coupled to the other component side port 6009b of the polarization controller 6010, an additional tap coupled to one component side port 6009a with its own photodiode is also electrically coupled to the controller 6500 for feedback control. In other embodiments, both component side ports 6009a and 6009b are coupled to taps with their own photodetectors, which are coupled to the controller 6500, so that both component side ports 6009a and 6009b can be used for optical signal output or input (e.g., as Figure 7 The use of two detection elements to monitor power and / or phase can provide more information for improved control of the first phase shifter 6320 and the second phase shifter 6340. Additional taps and photodiodes can be provided along the waveguides 6001, 6003, 6005, and 6007 for additional power monitoring, thereby enabling more efficient and / or more accurate adjustment of the control loop. For example, monitoring the equal power emitted on the second set of waveguides 6005, 6007 can be used directly to adjust the first phase shifter 6320.

[0098] It should be noted that Figure 5 or Figure 6 The polarization controller shown or any other variation with feedback and control loops can be used as a polarizer. When an original optical signal with an arbitrary or unknown polarization state is input, the phase shifter of the polarization controller can be adjusted until the power of one of its component side port outputs is maximized. The drive voltage or other electrical control signal used to drive the phase shifter indicates the phase shift applied to the optical signal that causes the maximum power. The original polarization state of the original optical signal can be inferred from these phase shifts. In a similar manner to the above, additional power monitoring of the power in waveguides 6001, 6003, 6005, 6007 and 6009a and / or 6009b with taps and photodiodes can be used to directly infer the input polarization state, and reduce or completely eliminate the need to track the tuning or drive voltage or other electrical control signals of the first and / or second phase shifters.

[0099] Figure 7 The following shows that Figure 2 and Figure 4 An example of the application of an integrated photonic system 7000 of a Type I or Type II polarization controller, with or without a tap and associated controller, in a circularly polarized reflectance sensor is shown.

[0100] For discussion Figure 7 In the sensor system 7000, the “polarization side” of the device may also be referred to as the “sensing side” of the device, and the “component side” of the device may also be referred to as the “device side” of the device.

[0101] The sensing side port 7109 serves as the input and output of the integrated polarization controller 7010. It transmits a sensing light signal as described below, and simultaneously receives a reflected light signal after interacting with the material sample as described below. The polarization controller 7010 includes Figure 2 Type I polarization controller or Figure 4 All components of a Type II polarization controller and are used as Figure 2 Type I polarization controller or Figure 4 A type II polarization controller, optionally with a configuration similar to Figure 5 The controller is shown along with one or more taps and photodiodes. The device-side input and device-side output of the polarization controller 7010 are shown here as waveguides 7009a and 7009b.

[0102] The linearly polarized light signal (such as E xOr TE) is input to the device side input port 7009b. After passing through the polarization controller 7010, it is emitted as an output via the sensing side port 7109 as a circularly polarized light signal (e.g., right-hand circularly polarized (RHCP)). The RHCP sensing signal passes through an optional collimating lens 7120 and passes through a material sample to be measured (optional) 7130. A reflector 7140 such as a mirror is optionally placed behind the material sample 7130. The RHCP light signal is reflected by the mirror 7140, and after reflection, after passing through the material sample 7130 and the lens 7120 for the second time, it becomes left-handed circularly polarized (LHCP) returned as a measurement light signal at the sensing side port 7109 of the polarization controller 7010. After passing through the polarization controller 7010 in the other direction, it is emitted as a linearly polarized light signal (e.g., E x The optical signal 7130 or TE) is emitted from the device side output 7009a. Since the power of the output optical signal is generally proportional to the power of the received measurement optical signal, the measurement of the power of the output optical signal reveals information about the material sample 7130 and / or the mirror 7140.

[0103] It should be noted that if the material sample 7130 is composed of a birefringent material, the analysis may involve tuning the polarization controller 7010 to produce polarization states that are not LHCP or RHCP upon exiting the sensing side port 7109, but have such properties once they have passed through the material sample 71300. In this case, the handedness of the circularly polarized light will be reversed once it is reflected from the mirror 7140.

[0104] In some embodiments, such as in sensing and spectroscopy applications, the material sample 7130 is primarily transmissive and the light measured by the system 7000 consists primarily of light that passes through the sample 7130 and is reflected back from the mirror 7140 .

[0105] In some embodiments, such as in LIDAR applications, the reflector 7140 is not a mirror but a diffuse reflector, and is not a specular reflector, and the target material itself is the reflector 7140 , so there is no separate material sample 7130 between the reflector 7140 and the polarization controller 7010 .

[0106] It should be understood that any one of the device side ports 7009a, 7009b can be used as an input while the other is used as an output. It should also be understood that LHCP or RHCP signals can be emitted from the polarization controller 7010, and due to its construction, the optical signals of opposite handedness will automatically be converted and output as linearly polarized signals, such as TE, on the device side output 7009a.

[0107] Figure 8 The following shows that Figure 4An example of application of the integrated photonic system 8000 of the type II polarization controller in a polarization scrambler is shown.

[0108] A polarization scrambler generates an optical signal having a rapidly and / or randomly varying polarization state. The generated scrambled optical signal is useful for testing and measurement of optical devices and / or for any application utilizing an effectively depolarized optical signal.

[0109] For discussion Figure 8 In the scrambler system 8000, the "polarization side" of the device may also be referred to as the "output side" of the device, and the "component side" of the device may also be referred to as the "input side" of the device.

[0110] Starting from the polarization side of the system 8000, the first port of the coupler 8100 is used as the output of the integrated polarization controller 8010 and launches the scrambled optical signal into, for example, a single mode (SM) fiber 8110 or free space. The coupler 8100 can be a dual polarization fiber coupler or any free space to chip converter that supports two polarization components (TE and TM) such as a grating or an inverted taper. The second port of the coupler 8100 is coupled to a single output side port of a polarization beam splitter rotator (PSR) 8200, which is coupled to the first set of ports on the output side of the 2:2 beam splitter 8420 via its input side port on the first set of waveguides 8001, 8003. The first input side port of the PSR 8200 is coupled to the first waveguide 8001, and the second input side port of the PSR 8202 is coupled to the second waveguide 8003. A first tunable phase shifter 8320 is coupled along the first waveguide 8001. The first waveguide 8001 is coupled to a first port of a 2:2 beam splitter 8420, and the second waveguide 8003 is coupled to a second port of the 2:2 beam splitter 8420. The input side of the 2:2 beam splitter 8420 is coupled to a first group of ports on the output side of a 2:1 beam splitter 8440 on a second group of waveguides 8005, 8007 via a second group of ports (composed of a third and a fourth port). The 2:2 beam splitter 8420 is coupled to a third waveguide 8005 via its third port, and to a fourth waveguide 8007 via its fourth port. A second tunable phase shifter 8340 is coupled along the third waveguide 8005. The third waveguide 8005 is coupled to a first port of a 2:1 beam splitter 8440, and the fourth waveguide 8007 is coupled to a second port of the 2:1 beam splitter 8440. The input side port of the 2:1 beam splitter 8440 is coupled to the input side port 8009 of the integrated polarization controller 8010, shown here as a waveguide coupled to other optical components supplying the original optical signal. The driver 8500 is electrically coupled to the first tunable phase shifter 8320 and the second tunable phase shifter 8340.

[0111] Figure 8 The integrated polarization controller 8010 is roughly similar to Figure 3 The illustrated embodiment operates in the same manner, however, additional elements provide control of the phase shifters 8320 and 8340, and the optical signal passes through the polarization scrambler 8000 in the opposite direction.

[0112] For example, E x The linearly polarized optical signal of TE or TE is input to the input side port 8009. The driver 8500 controls the phase shifters 8320 and 8340 by applying an electrical signal that applies a random and / or rapidly changing phase shift to the optical signal passing through the phase shifter. After passing through the polarization controller 8010, the outgoing optical signal is a scrambled polarization optical signal with a random and / or rapidly changing polarization state.

[0113] In some embodiments, fast phase shifters, such as carrier modulation or Pockels effect modulation phase shifters, are used for phase shifters 8320 and 8340 to achieve faster scrambling.

[0114] It should be understood that Figure 5 , Figure 6 , Figure 7 and Figure 8 The feedback, control and drive circuits shown may include processors, memory, interfaces and / or other components that are either external to the integrated polarization controller or implemented in the same integrated platform as the integrated polarization controller, including, for example, integrated within the same substrate or chip, integrated on or co-located on a common substrate or platform, or electrically and / or optically coupled across multiple platforms including integrated polarization controllers in the same device or multiple devices.

[0115] While specific embodiments and applications of the present invention have been shown and described, it will be understood that the invention is not limited to the precise construction and composition disclosed herein and that various modifications, variations and variations will be apparent from the foregoing description without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. An integrated photonic system, include: An optoelectronic chip comprising a polarization controller having a polarization side port and at least one component side port, the polarization controller comprising: a polarization splitter rotator (PSR) having a first port, a second port, and a third port, wherein the PSR is coupled to the polarization side port through its first port; a first set of waveguides coupled to the second port and the third port of the PSR; a first phase shifter coupled along a first waveguide of the first set of waveguides; and A first beam splitter having a first set of ports and a second set of ports, the first beam splitter being coupled to the PSR through its first set of ports and on the first set of waveguides, and being coupled to at least one of the second set of ports of the first beam splitter through the at least one component-side port of the polarization controller.

2. The integrated photonic system of claim 1, wherein the first beam splitter comprises a 2:1 beam splitter.

3. The integrated photonic system of claim 1, wherein the first beam splitter comprises a 2:2 beam splitter.

4. The integrated photonic system of claim 1, wherein the first phase shifter is configured to apply a phase shift that optimizes an optical signal exiting at least one of the at least one component-side port of the polarization controller.

5. The integrated photonic system of claim 1, wherein the first phase shifter is configured to apply a phase shift that produces an optical signal having a selected polarization state emitted from the polarization-side port of the polarization controller.

6. The integrated photonic system of claim 1, wherein the first phase shifter is tunable.

7. The integrated photonic system according to claim 6, further comprising: include: At least one power detection element is coupled along at least one component side port of the polarization controller, and wherein the controller, the at least one power detection element and the tunable first phase shifter are included in a feedback loop for tuning a first phase shift of the first phase shifter.

8. The integrated photonic system according to claim 1, further comprising: include: a second set of waveguides coupled to the first set of ports of the first beam splitter; a second phase shifter coupled along a first waveguide in the second set of waveguides; a second beamsplitter having a first set of ports and a second set of ports, the second beamsplitter coupled to the first set of waveguides through its first set of ports and to the second set of waveguides through its second set of ports, the second beamsplitter coupled to the PSR on the first set of waveguides and coupled to the first beamsplitter on the second set of waveguides.

9. The integrated photonic system of claim 8, wherein the first beam splitter comprises a 2:1 beam splitter and the second beam splitter comprises a 2:2 beam splitter.

10. The integrated photonic system of claim 8, wherein the first beam splitter comprises a 2:2 beam splitter and the second beam splitter comprises a 2:2 beam splitter.

11. The integrated photonic system of claim 8, wherein the first phase shifter and the second phase shifter are configured to apply a phase shift that optimizes an optical signal exiting at least one of the at least one component-side port of the polarization controller.

12. The integrated photonic system of claim 8, wherein the first phase shifter and the second phase shifter are configured to apply a phase shift that produces an optical signal having a selected polarization state emitted from the polarization-side port of the polarization controller.

13. The integrated photonic system of claim 8, wherein the first phase shifter and the second phase shifter are tunable.

14. The integrated photonic system according to claim 13, further comprising: include: controller and at least one power detection element coupled along at least one component side port of the polarization controller, and The controller, the at least one power detection element, and the first and second tunable phase shifters are included in a feedback loop for tuning the phase shifts of the first and second tunable phase shifters.

15. An integrated photonic system according to claim 14, wherein the at least one power detection element includes at least one photodetector coupled to at least one of the at least one component-side ports of the polarization controller via a tap, and wherein the controller controls at least one electrical control signal sent to the tunable first phase shifter and the second phase shifter in response to a signal from the at least one photodetector.

16. An integrated photonic system according to claim 15, wherein the at least one power detection element includes a photodetector coupled to a port of the at least one component side port of the polarization controller, and wherein the controller controls at least one electrical control signal sent to the tunable first phase shifter and the second phase shifter in response to a signal from the photodetector.

17. An integrated photonic system according to claim 3, wherein the first phase shifter is constructed to apply a phase shift to generate a circularly polarized sensing light signal transmitted from the polarization side port of the polarization controller, and to output a linearly polarized light signal on one of the at least one component side ports of the polarization controller, the linearly polarized light signal having an optical power proportional to the circularly polarized measurement light signal received at the polarization side port of the polarization controller, and the transmitted circularly polarized sensing light signal has an opposite handedness to the received circularly polarized measurement light signal.

18. The integrated photonic system according to claim 10, in, The first phase shifter and the second phase shifter are configured to apply a phase shift for generating a circularly polarized sensing light signal transmitted from the polarization side port of the polarization controller, and for outputting a linearly polarized light signal at one of the at least one component side ports of the polarization controller, wherein the linearly polarized light signal has an optical power proportional to the circularly polarized measurement light signal received at the polarization side port of the polarization controller, and the transmitted circularly polarized sensing light signal has an opposite handedness to the received circularly polarized measurement light signal.

19. The integrated photonic system according to claim 13, further comprising: include: A driver is used to drive the phase shift of the first and second tunable phase shifters in at least one of a rapid and random manner to generate an optical signal that effectively has a scrambled polarization state.

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