An optical waveguide delay line

Abstract

The present invention discloses an optical waveguide delay line, which includes a structure in which delay units and optical switch units are arranged alternately between an input channel and an output channel, and phase change materials are distributed on the delay units along the waveguide length direction; or includes a single micro-ring structure or a cascaded structure of multiple micro-rings composed of phase shifters and tunable couplers, and the phase change materials are distributed on the phase shifters of a single micro-ring or a cascaded structure of multiple micro-rings; or includes a Bragg grating structure, and the phase change materials are distributed at intervals in the waveguide length direction to form a Bragg grating; the phase change materials can be embedded in the waveguide or tiled on the waveguide surface; electrodes are located directly above the phase change materials and are used to change the phase state of the phase change materials. The optical waveguide delay line of the present invention has zero static power consumption, a compact structure, and can achieve non-volatile tunability; the introduction of phase change materials greatly reduces the integrated optical waveguide structure. By tuning the physical length or resonant wavelength or reflection wavelength of the optical signal passing through, the tunability of the delay time is achieved.

Description

Technical Field

[0001] The present invention relates to integrated optical waveguide devices, and particularly to an optical waveguide delay line. Background Art

[0002] With the development of integrated optical waveguide technology, the demand for high-performance optical waveguide devices in the fields of optical communication and optical computing is increasing day by day. The tunability of traditional optical waveguide devices usually utilizes a weak tuning mechanism, and the refractive index change provided by the weak tuning mechanism is small. A relatively large size is required to accumulate the required phase transformation, which results in a relatively large device size and high power consumption, restricting the scalability of tunable delay lines. Even after optimizing the power consumption, maintaining the tunable delay state requires continuously inputting voltage to the tuning unit. When a large number of tuning units work simultaneously, thermal crosstalk will inevitably occur, thereby affecting the performance of the device. Maintaining high device performance also requires a more complex tuning mechanism. These factors in terms of power consumption and size limit the expansion and wide application of optical waveguide devices. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides an optical waveguide delay line, which has a compact structure, non-volatility, and zero static power consumption.

[0004] The object of the present invention is achieved by the following technical solutions:

[0005] An optical waveguide delay line includes N delay units and N + 1 optical switch units located between an input channel and an output channel; the delay units and the optical switch units are arranged alternately;

[0006] The delay unit is a pair of unequal-length waveguide pairs, and the waveguide type is strip or ridge waveguide;

[0007] Along the waveguide length direction, a phase change material is embedded in the strip or ridge waveguide of the long waveguide of the unequal-length waveguide pair,

[0008] Or,

[0009] A layer of phase change material is laid on the upper surface of the strip or ridge waveguide of the long waveguide in the unequal-length waveguide pair.

[0010] Further, a phase change material is embedded in the strip or ridge waveguide of the short waveguide of the unequal-length waveguide pair, or a layer of phase change material is laid on the surface of the strip or ridge waveguide of the short waveguide of the unequal-length waveguide pair.

[0011] Further, along the waveguide length direction, the phase change material embedded or laid in the strip or ridge waveguide is a segmented structure arranged at intervals.

[0012] Further, along the waveguide length direction, there are also multiple electrodes located on the long waveguide or short waveguide, corresponding one-to-one to the segmented structure of the phase change material.

[0013] Further, along the direction from the input waveguide to the output waveguide, the length of the long waveguide in the unequal-length waveguide pair of the (i + 1)-th delay unit is twice the length of the long waveguide in the unequal-length waveguide pair of the i-th delay unit.

[0014] An optical waveguide delay line, the optical waveguide delay line is a cascaded structure of N micro-ring resonators, where N is a positive integer;

[0015] The N identical micro-rings are independently coupled to a common waveguide, or the N identical micro-rings are cascaded by means of a coupled resonant optical waveguide;

[0016] Each of the micro-rings includes a tunable phase shifter;

[0017] The waveguide type of the optical waveguide delay line is a strip waveguide or a ridge waveguide;

[0018] The phase change material is embedded in the strip waveguide or ridge waveguide of the tunable phase shifter, or a layer of phase change material is laid on the upper surface of the strip waveguide or ridge waveguide of the tunable phase shifter.

[0019] Further, along the waveguide length direction, the phase change material embedded or laid in the strip waveguide or ridge waveguide of the tunable phase shifter is a segmented structure arranged at intervals.

[0020] An optical waveguide delay line, the optical waveguide delay line is a cascaded structure of N Bragg gratings;

[0021] The N Bragg gratings are cascaded by uniform Bragg gratings with different periods,

[0022] Or,

[0023] The N Bragg gratings are chirped Bragg gratings;

[0024] The waveguide type is a strip waveguide or a ridge waveguide;

[0025] Along the length direction of the strip waveguide or ridge waveguide, the phase change material is uniformly embedded in the strip waveguide or ridge waveguide, or laid on the surface of the strip waveguide or ridge waveguide.

[0026] Further, the phase change material is selected from any one of Sb2S3, Sb2Se3, GST, GSST, and VO2.

[0027] Further, the optical waveguide delay line is integrally spiral.

[0028] The beneficial effects of the present invention are as follows:

[0029] (1) The optical waveguide delay line of the present invention can reduce the lengths of the interferometric arms in the phase shifter or switch unit in the delay unit by nearly 3-4 orders of magnitude, and the static power consumption is zero; the phase change material further reduces the size of the unequal-length waveguide pairs, and at the same time, the long waveguide in each delay unit composed of waveguide pairs can achieve at least three delay times, enabling continuous tunability while reducing the device size, and the delay line maintains a large delay bandwidth.

[0030] (2) For the delay line composed of a series of micro-rings, the phase change material is located in the tunable phase shifter. The phase change material not only makes the device structure more compact but also enables zero static power consumption, and this structure can achieve the function of a continuously tunable delay line. For the delay line composed of Bragg gratings, continuous tunability can be achieved by selectively controlling the phase of the phase change material.

[0031] (3) The optical waveguide delay line of the present invention avoids the thermal crosstalk caused by the simultaneous operation of a large number of switches and tunable units, which affects the performance of the delay line; the optical waveguide delay line of the present invention achieves low dynamic power consumption and zero static power consumption while maintaining high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of an optical waveguide delay line with a delay unit composed of two optical switch units and an unequal-length waveguide pair with a phase change material.

[0033] Figure 2 is Figure 1 Schematic diagram of an optical waveguide delay line in which the phase change material in is a segmented structure.

[0034] Figure 3 Schematic diagram of an optical waveguide delay line formed by alternately connecting N + 1 optical switches and N unequal-length waveguide pairs with a phase change material.

[0035] Figure 4 is in Figure 3 Schematic diagram of a delay line in which a complete phase change material is replaced with a segmented structure on the basis of.

[0036] Figure 5 Schematic diagram of an optical waveguide delay line with a micro-ring structure formed by connecting a tunable coupler and a phase shifter with a phase change material.

[0037] Figure 6 is to Figure 5 Schematic diagram of replacing the phase change material of the phase shifter in with a segmented structure.

[0038] Figure 7 Schematic diagram of an optical waveguide delay line of a side-coupled integrated spatial sequence resonator formed by independently coupling 6 identical micro-rings to a common waveguide.

[0039] Figure 8 Schematic diagram of an optical waveguide delay line of a micro-ring resonator cascade structure formed by cascading 6 identical micro-rings through coupled-resonator optical waveguides.

[0040] Figure 9 Schematic diagram of a Bragg grating delay line based on Sb2Se3 phase change material, where the phase change material is laid on the upper surface of the core layer.

[0041] Figure 10 Schematic cross-sectional view of a cross-section of a phase shifter with a phase change material or one arm of a switching unit, where the phase change material is embedded in a ridge waveguide in the figure.

[0042] Among them, 1 is an optical switch unit, 2 is a delay unit, 3 is a tunable coupler, 4 is a tunable phase shifter, 5 is an optical waveguide, 5-1 is a silicon substrate, 5-2 is a lower cladding layer, 5-3 is a core layer, 5-4 is a phase change material, 5-5 is an upper cladding layer, and 5-6 is an electrode. Detailed implementation manners

[0043] The present invention will be described in detail below according to the accompanying drawings and preferred embodiments. The purpose and effects of the present invention will become clearer. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] In the optical waveguide delay line of the present invention, the phase change materials are respectively located in the waveguides of the delay unit, the phase shifter, and the Bragg grating to form a hybrid waveguide. By changing the voltage applied to the electrodes above the phase change materials, the delay unit and the phase shifter are tuned, thereby realizing the functions of optical path switching, phase change, and signal caching. The phase change material has three phase states: crystalline phase, amorphous phase, and partial crystalline phase. These phase states are stable and reversible. By applying a voltage to heat the phase change material, the phase state of the phase change material is changed. After the phase change is completed, the applied voltage can be removed, and the phase state of the phase change material remains unchanged. Corresponding to the switching unit array, the transmission direction of the optical path remains unchanged. Corresponding to the tunable phase shifter, the phase remains unchanged. The maintenance of these states is carried out without continuously applying voltage, and the static power consumption is zero. The phase change material can be designed as a segmented phase change material. On the one hand, it prevents backflow in the amorphous phase state. On the other hand, it can control the phase states of the phase change materials in each segment respectively. Furthermore, the optical switch unit can realize the function of a tunable coupler, and the phase shifter can realize the function of continuously tunable phase. Furthermore, the functions of a reconfigurable, scalable, and continuously tunable delay line can be realized.

[0045] In addition, due to the large effective refractive index difference of the phase change material in different phases, a large phase transformation can be achieved with a relatively short length. Compared with the interference arm length of a conventional optical switch, the interference arm can be reduced by 3-4 orders of magnitude, reducing the overall size of the device and also resulting in a lower dynamic power consumption for changing the device state. More importantly, the static power consumption of the optical waveguide delay line is zero, reducing the power consumption of the device. The introduction of the phase change material reduces the device size and power consumption, avoiding the thermal crosstalk caused by the simultaneous operation of multiple tunable units. The optical waveguide delay line of the present invention has the characteristics of non-volatility, zero static power consumption, low dynamic power consumption, and a compact device structure, and can be widely applied in optical communication, optical interconnection, optical buffers, optical neural networks, etc.

[0046] Figure 1 An optical waveguide delay line includes two optical switch units 1 located between an input channel and an output channel and a delay unit 2 composed of an unequal-length waveguide pair with a phase change material. As Figure 1 shown, the delay unit 2 and the two optical switch units 1 are arranged alternately, and the phase change material is distributed in the long waveguide of the unequal-length waveguide pair in the delay unit 2. When the phase change material in the delay unit 2 is in the crystalline state and the amorphous state, it can correspond to two different delay times: when an optical signal enters the long waveguide in the delay unit, when the phase change material on the long waveguide is in the amorphous state, it is a time delay t1. By changing the voltage applied to the electrode on the long waveguide, the phase state in the delay unit is changed to achieve another time delay t2. By continuously changing the ratio of the crystalline state and the amorphous state in the delay unit, a continuous delay time t1~t2 can be achieved, and the function of maintaining a wide bandwidth can be realized. Furthermore, a single delay unit can achieve a wide bandwidth continuously tunable delay time and a reference delay time. Compared with a discrete tunable delay line with a conventional structure, the device structure is not only greatly reduced, but also a continuously tunable delay line can be realized while the structure is reduced. By analogy, an N-bit wide bandwidth delay line structure can realize the function of a wide bandwidth large continuously tunable delay range delay line.

[0047] After the function is realized, the voltage applied to the electrode can be removed, and the state of the switch unit remains unchanged, avoiding the thermal crosstalk caused by the simultaneous operation of a large number of switches.

[0048] In order to couple with a commercial fiber array, the input channel spacing of the delay line is 127 μm or 250 μm, and the output channel spacing is also 127 μm or 250 μm.

[0049] Figure 2 is in Figure 1On the basis of [the original structure], the unequal-length waveguide pair in the delay unit 2 has the phase change material distributed in the long waveguide changed to a segmented structure with intervals, avoiding the backflow of the phase change material. At the same time, the electrode film on the upper cladding of the waveguide is also changed to multiple electrodes with intervals, corresponding one by one to the phase change material of the segmented structure, so that the phase change material after segmentation can be controlled by the electrodes respectively. Each delay unit can achieve a continuously tunable delay time, and this delay line has the performance of wide bandwidth, compact structure and low power consumption. Similarly, the static power consumption is zero.

[0050] In addition, phase change material can also be embedded in the waveguide of the optical switch unit or a layer of phase change material can be laid on the upper surface of the waveguide. The optical switch unit can be of Mach-Zehnder interferometer structure, and the phase change material is located on the interference arm, which can reduce the length of the interference arm by 3-4 orders of magnitude. By applying a voltage to the electrode on one of the interference arms of the switch unit to heat the phase change material with a micron-scale length, the phase state of the phase change material can be changed, and then the transmission direction of the optical signal can be changed to enter different delay channels. After this state is completed, the voltage on the optical switch unit can be removed, and the state of the optical switch unit remains unchanged, avoiding the thermal crosstalk caused when a large number of switches work simultaneously.

[0051] Figure 3 It is an optical waveguide delay line composed of N delay units 2 and N + 1 optical switch units 1 cascaded, and the optical switch units 1 and the delay units 2 are arranged alternately. The optical switch unit 1 in this figure is of directional coupler structure, the delay unit 2 is of unequal-length waveguide pair structure, and the waveguide material is lithium niobate thin film. The phase change material is Sb2Se3 thin film, which is embedded in the ridge waveguide of the long waveguide of the unequal-length waveguide pair of each delay unit. Along the direction from the input waveguide to the output waveguide, the length of the long waveguide in the unequal-length waveguide pair of the (i + 1)-th delay unit is twice the length of the long waveguide in the unequal-length waveguide pair of the i-th delay unit. That is, as Figure 6 shown, the length of the long waveguide in the unequal-length waveguide pair of the first delay unit is , the length of the long waveguide in the unequal-length waveguide pair of the second delay unit is 2 , and so on until the length of the long waveguide in the unequal-length waveguide pair of the N-th delay unit is .

[0052] Figure 4 is on the basis of Figure 3 , and all the phase change materials embedded in the ridge waveguide are replaced with phase change materials of segmented structure.

[0053] Figure 5A delay line formed by connecting a tunable coupler 3 with phase change material and a phase shifter 4 with phase change material. The delay line has a micro-ring structure. The tunable coupler is of a directional coupler structure or a Mach-Zehnder interferometer. The phase change material is located in the phase shifter 4. An upper cladding covers the phase change material, and an electrode film covers the upper cladding. There is an electrode film on the waveguide of the tunable coupler. By tuning the voltage applied to the electrode film, the function of a continuously tunable coupler can be achieved. Since the interference arm of the tunable coupler has a small size, the required dynamic power consumption is low. Because the phase change material is non-volatile, the static power consumption is zero. In addition, by tuning the phase state of the phase shifter, the tuning of the phase can be realized, and its static power consumption is zero. By tuning the tunable coupler, and then tuning the power coupling ratio of the micro-ring, and tuning the phase shifter on the micro-ring, the functions of a high-performance filter and a continuously tunable delay line can be achieved. In order to couple with a commercial fiber array, the input channel spacing of the delay line in this embodiment is 250 μm, and the output channel spacing is also 250 μm. This device has the functions of being structurally compact, low-power, reconfigurable, and scalable.

[0054] Figure 6 Based on Figure 5 On this basis, the phase change material on the tunable phase shifter 4 is changed to segmented phase change materials arranged at intervals. The electrodes on the waveguide of the tunable phase shifter also become multiple, corresponding one by one to the segmented phase change materials, and each segment of the phase change material is controlled by the corresponding electrode. This delay line has the properties of being structurally compact, zero static power consumption, and low dynamic power consumption.

[0055] Figure 7 and Figure 8 is a structure with 6 micro-rings cascaded. Figure 7 is a side-coupled integrated spatial sequence resonator. By independently coupling 6 identical micro-rings to a common waveguide, where the Sb2Se3 phase change material 5-4 is embedded in the strip or ridge waveguide of each micro-ring; Figure 8 is a coupled-resonator optical waveguide. The 6 identical micro-rings are cascaded in the way of a coupled-resonator optical waveguide. The Sb2Se3 phase change material is embedded in the strip or ridge waveguide of each micro-ring, or the Sb2Se3 phase change material can also be tiled in the strip or ridge waveguide of each micro-ring.

[0056] Figure 9It is a schematic diagram of a Bragg grating delay line based on Sb2Se3 phase change material. In this diagram, the optical waveguide generally includes a silicon substrate 5-1, a lower cladding 5-2 located on the silicon substrate 5-1, a core layer 5-3 located on the lower cladding 5-2, a phase change material 5-4 laid on the upper surface of the core layer 5-3, an upper cladding 5-5 located on the core layer 5-3, and an electrode 5-6 located on the upper cladding 5-5. The Sb2Se3 phase change material 5-4 is a segmented structure arranged at intervals. The electrodes 5-6 located above the upper cladding 5-5 are also multiple, corresponding to each segment of the segmented phase change material one by one.

[0057] Figure 10 It is a cross-section of the optical waveguide 5 of all tunable units of the optical waveguide delay line. Among them, the phase change material 5-4 demonstrated in this diagram is embedded in the core layer 5-3 of the ridge waveguide. The electrode 5-6 can be a metal electrode, and more preferably a graphene electrode. On the one hand, the upper cladding 5-5 is used to protect the phase change material 5-4, and on the other hand, it is used to separate the electrode 5-6 from the core layer 5-3, reducing the absorption of the optical signal by the electrode 5-6.

[0058] Those of ordinary skill in the art can understand that the above are only preferred examples of the invention and are not used to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing examples or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. An optical waveguide delay line, characterized in that, It includes N delay units and N+1 optical switch units located between the input channel and the output channel; the delay units and the optical switch units are arranged alternately; The delay unit is a pair of unequal-length waveguide pairs, the waveguide type is strip or ridge waveguide, and the waveguide is provided with electrodes for controlling phase change materials; Along the waveguide length direction, phase change materials are embedded in the strip or ridge waveguide of the long waveguide of the unequal-length waveguide pair, Or, A layer of phase change material is laid on the upper surface of the strip or ridge waveguide of the long waveguide in the unequal-length waveguide pair.

2. The optical waveguide delay line according to claim 1, wherein Phase change materials are embedded in the strip or ridge waveguide of the short waveguide of the unequal-length waveguide pair, or a layer of phase change material is laid on the surface of the strip or ridge waveguide of the short waveguide of the unequal-length waveguide pair.

3. The optical waveguide delay line according to claim 1 or 2, characterized in that, Along the waveguide length direction, the phase change materials embedded or laid in the strip or ridge waveguide are of a segmented structure arranged at intervals.

4. The optical waveguide delay line according to claim 3, characterized in that, Along the waveguide length direction, there are also multiple electrodes located on the long waveguide or the short waveguide, corresponding one by one to the segmented structure of the phase change material.

5. The optical waveguide delay line according to claim 1 or 4, characterized in that, Along the direction from the input waveguide to the output waveguide, the length of the long waveguide in the unequal-length waveguide pair of the (i+1)-th delay unit is twice the length of the long waveguide in the unequal-length waveguide pair of the i-th delay unit.

6. The optical waveguide delay line according to claim 1, wherein, The phase change material is selected from any one of Sb2S3, Sb2Se3, GST, GSST, and VO2.

7. The optical waveguide delay line according to claim 1, characterized in that, The optical waveguide delay line is in a spiral shape as a whole.

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