Optical waveguide delay line

Abstract

The invention discloses an optical waveguide delay line, which comprises a structure in which delay units and optical switch units are alternately arranged between an input channel and an output channel, and a phase change material is distributed on the delay units along the length direction of a waveguide; or a single micro-ring structure or a multi-micro-ring cascade structure comprising a phase shifter and a tunable coupler, wherein the phase change material is distributed on the single micro-ring structure or the multi-micro-ring cascade structure; or the phase change material comprises a Bragg grating structure, and the phase change material is distributed at intervals in the waveguide length direction to form a Bragg grating; the phase change material can be embedded into the waveguide and can also be flatly laid on the surface of the waveguide; the electrode is located over the phase change material and used for changing the phase state of the phase change material. The optical waveguide delay line has zero static power consumption, is compact in structure, and can realize non-volatile tuning; the introduction of the phase change material enables the integrated optical waveguide structure to be greatly reduced. The delay time can be tuned by tuning the physical length or the resonant wavelength or the reflection wavelength through which the optical signal passes.

Description

Technical Field

[0001] The invention relates to an integrated optical waveguide device, in particular 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. The tunability of traditional optical waveguide devices usually utilizes weak tuning mechanisms, which provide small refractive index changes and require larger sizes to accumulate the required phase changes, which will lead to larger device sizes and higher power consumption, limiting the scalability of tunable delay lines. Even after optimizing power consumption, the maintenance of the tunable delay state requires continuous input of voltage to the tuning unit. When a large number of tuning units work at the same time, thermal crosstalk will inevitably occur, which will affect the performance of the device. Maintaining the high performance of the device also requires more complex tuning mechanisms. These factors in terms of power consumption and size limit the expansion and wide application of optical waveguide devices. Summary of the invention

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

[0004] The purpose of the present invention is achieved through the following technical solutions: An optical waveguide delay line comprises 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; The delay unit is a pair of waveguides of unequal lengths, and the waveguide type is a strip waveguide or a ridge waveguide; Along the length direction of the waveguide, a phase change material is 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-shaped or ridge-shaped waveguide of the long waveguide in the unequal-length waveguide pair.

[0005] Furthermore, 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.

[0006] Furthermore, along the length direction of the waveguide, the phase change material embedded or laid in the strip-shaped or ridge-shaped waveguide is a segmented structure arranged at intervals.

[0007] Furthermore, along the length direction of the waveguide, there are also multiple electrodes located on the long waveguide or the short waveguide, corresponding one-to-one to the segmented structure of the phase change material.

[0008] Furthermore, 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.

[0009] An optical waveguide delay line, wherein the optical waveguide delay line is a cascade structure of N microring resonators, where N is a positive integer; N identical microrings are independently coupled to a common waveguide, or N identical microrings are cascaded by coupling resonant optical waveguides; Each of the microrings includes a tunable phase shifter; The waveguide type of the optical waveguide delay line is a strip waveguide or a ridge waveguide; A phase change material is embedded in the strip or ridge waveguide of the tunable phase shifter, or a layer of phase change material is laid on the upper surface of the strip or ridge waveguide of the tunable phase shifter.

[0010] Furthermore, along the length direction of the waveguide, the phase change material embedded or laid in the strip or ridge waveguide of the tunable phase shifter is a segmented structure arranged at intervals.

[0011] An optical waveguide delay line, wherein the optical waveguide delay line is a cascade structure of N Bragg gratings; N Bragg gratings are cascaded uniform Bragg gratings with different periods. or, The N Bragg gratings are chirped Bragg gratings; The waveguide type is strip or ridge waveguide; Along the length direction of the strip or ridge waveguide, the phase change material is uniformly embedded in the strip or ridge waveguide, or laid on the surface of the strip or ridge waveguide.

[0012] Furthermore, the phase change material is selected from any one of Sb2S3, Sb2Se3, GST, GSST and VO2.

[0013] Furthermore, the optical waveguide delay line is spiral-shaped as a whole.

[0014] The beneficial effects of the present invention are as follows: (1) The optical waveguide delay line of the present invention can reduce the length of the interference arm 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 waveguide pairs of unequal lengths, and at the same time, the long waveguide in the delay unit composed of each waveguide pair can achieve at least three delay times, which can achieve continuous tunability when the device size is reduced, and at the same time, the delay line maintains a large delay bandwidth.

[0015] (2) For a delay line composed of a series of microrings, 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 achieves zero static power consumption. This structure can realize the function of a continuously tunable delay line. For a delay line composed of a Bragg grating, the continuously tunable function can be achieved by selectively controlling the phase of the phase change material.

[0016] (3) The optical waveguide delay line of the present invention avoids thermal crosstalk caused by a large number of switches and tunable units working simultaneously, 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

[0017] Figure 1 Schematic diagram of an optical waveguide delay line comprising two optical switch units and a delay unit consisting of a pair of unequal length waveguides with phase change material.

[0018] Figure 2 for Figure 1 Schematic diagram of an optical waveguide delay line in which the phase change material is a segmented structure.

[0019] Figure 3 Schematic diagram of an optical waveguide delay line formed by alternately connecting N+1 optical switches and delay units consisting of N unequal-length waveguide pairs with phase change materials.

[0020] Figure 4 For Figure 3 Schematic diagram of a delay line in which a complete phase change material is replaced with a segmented phase change material.

[0021] Figure 5 Schematic diagram of an optical waveguide delay line with a micro-ring structure consisting of a tunable coupler and a phase shifter with phase change material.

[0022] Figure 6 For the general Figure 5 Schematic diagram of a phase change material of a phase shifter being replaced with a phase change material having a segmented structure.

[0023] Figure 7 Schematic diagram of an optical waveguide delay line with a side-coupled integrated spatial sequence resonator formed by independently coupling six identical microrings into a common waveguide.

[0024] Figure 8 Schematic diagram of an optical waveguide delay line of a microring resonator cascade structure formed by cascading six identical microrings through coupled resonant optical waveguides.

[0025] Fig. 9 Schematic diagram of a Bragg grating delay line based on Sb2Se3 phase change material, in which the phase change material is laid on the upper surface of the core layer.

[0026] Fig.10 The figure is a schematic diagram of a cross section of a phase shifter with phase change material or a cross section of one arm of a switch unit, in which the phase change material is embedded in a ridge waveguide.

[0027] 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, 5-3 is a core layer, 5-4 is a phase change material, 5-5 is an upper cladding, and 5-6 is an electrode. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more clear. 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.

[0029] In the optical waveguide delay line of the present invention, the phase change material is respectively located in the waveguide of the delay unit, the phase shifter and the Bragg grating to form a hybrid waveguide. By changing the voltage applied by the electrode above the phase change material, 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. The phase change material is heated by applying voltage to change the phase state of the phase change material. After the phase state change is completed, the applied voltage can be removed, and the phase state of the phase change material remains unchanged. Corresponding to the switch unit array, the transmission direction of the optical path remains unchanged, and corresponding to the tunable phase shifter, the phase remains unchanged. These states are maintained without continuous voltage application, and the static power consumption is zero. The phase change material can be designed as a phase change material with a segmented structure. On the one hand, it prevents backflow in the amorphous phase state, and on the other hand, the phase state of each segmented phase change material can be controlled separately. Then, the optical switch unit can realize the function of a tunable coupler, and the phase shifter can realize the function of continuously tunable phase. This can then realize a reconfigurable, scalable, and continuously tunable delay line function.

[0030] In addition, due to the large difference in effective refractive index of phase change materials in different phases, a shorter length can achieve a larger phase change. Relative to the interference arm length of an ordinary optical switch, the interference arm can be reduced by 3-4 orders of magnitude, reducing the overall size of the device and the dynamic power consumption of changing the device state. More importantly, the static power consumption of the optical waveguide delay line is zero, which reduces the power consumption of the device. The introduction of phase change materials reduces the size of the device and reduces the power consumption of the device, avoiding 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 compact device structure, and can be widely used in optical communications, optical interconnection, optical buffers, optical neural networks, etc.

[0031] Figure 1 The optical waveguide delay line includes two optical switch units 1 located between an input channel and an output channel and a delay unit 2 consisting of a pair of unequal length waveguides with phase change material, such as Figure 1 As 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 of 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 the optical signal enters the long waveguide in the delay unit, the phase change material on the long waveguide is in the amorphous state, which 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, the continuous delay time t1~t2 can be achieved, and the function of wide bandwidth can be maintained, so that a delay unit can achieve a wide bandwidth continuously tunable delay time and a reference delay time. Compared with the discrete tunable delay line of the ordinary structure, the device structure is not only greatly reduced, but also the structure can realize a continuously tunable delay line while being reduced. By analogy, the N-bit wide bandwidth delay line structure can realize the function of a wide bandwidth large continuously tunable delay range delay line.

[0032] After the function is realized, the voltage applied to the electrode can be removed, and the state of the switch unit remains unchanged, avoiding thermal crosstalk caused by a large number of switches working at the same time.

[0033] In order to couple with commercial fiber arrays, 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.

[0034] Figure 2 is Figure 1 On the basis of the above, the phase change material distributed in the long waveguide of the unequal length waveguide pair of the delay unit 2 is changed into a segmented structure with intervals to avoid the backflow of the phase change material. At the same time, the electrode film located on the upper cladding of the waveguide is also changed into a plurality of electrodes with intervals, which correspond to the phase change material of the segmented structure one by one, so that the electrodes control the phase change material after a single segment respectively, and each delay unit can realize the continuous tuning of the delay time. The delay line has the performance of wide bandwidth delay, compact structure and low power consumption. Similarly, the static power consumption is zero.

[0035] In addition, a phase change material can 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 a 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 and heating the phase change material with a length of micrometers, the phase state of the phase change material can be changed, thereby changing the transmission direction of the optical signal and entering 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 thermal crosstalk caused by a large number of switches working at the same time.

[0036] Figure 3 It is an optical waveguide delay line composed of N delay units 2 and N+1 optical switch units 1 in cascade, and the optical switch units 1 and delay units 2 are arranged alternately. The optical switch unit 1 in the figure is a directional coupler structure, and the delay unit 2 is an unequal length waveguide pair structure, and the waveguide material is a lithium niobate film. The phase change material is an Sb2Se3 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+1th delay unit is twice the length of the long waveguide in the unequal length waveguide pair of the i-th delay unit. That is, Figure 6 As shown, the length of the long waveguide of the unequal length waveguide pair of the first delay unit is , the length of the long waveguide of the unequal length waveguide pair of the second delay unit is 2 , until the long waveguide length of the unequal length waveguide pair of the Nth delay unit is .

[0037] Figure 4 is Figure 3 On the basis of this, the phase change materials embedded in the ridge waveguide are replaced with phase change materials with a segmented structure.

[0038] Figure 5The invention relates to a delay line composed of a tunable coupler 3 with a phase change material and a phase shifter 4 with a phase change material. The delay line is a micro-ring structure, the tunable coupler is a directional coupler structure or a Mach-Zehnder interferometer, the phase change material is located in the phase shifter 4, the upper cladding is covered on the phase change material, and the upper cladding is covered with an electrode film. There is an electrode film on the tunable coupler waveguide, and the function of a continuously tunable coupler can be realized by tuning the voltage applied to the electrode film. The tunable coupler has a small interference arm size and low dynamic power consumption. Since the phase change material is non-volatile, the static power consumption is zero. In addition, the phase state of the phase shifter can be tuned to achieve phase tuning, and its static power consumption is zero. By tuning the tunable coupler, the power coupling ratio of the micro-ring is tuned, and the phase shifter on the micro-ring is tuned, a high-performance filter and a continuously tunable delay line function are realized. In order to couple with a commercial optical fiber array, the input channel spacing of the delay line of this embodiment is 250 μm, and the output channel spacing is also 250 μm. The device has compact structure, low power consumption, reconfigurability and scalable functions.

[0039] Figure 6 For Figure 5 On the basis of the above, the phase change material on the tunable phase shifter 4 is changed into a segmented phase change material set at intervals, and the electrodes on the waveguide of the tunable phase shifter are also changed into multiple electrodes, corresponding to the segmented phase change materials one by one, and each segment of the phase change material is controlled by the corresponding electrode. The delay line has the performance of compact structure, zero static power consumption and low dynamic power consumption.

[0040] Figure 7 and Figure 8 It is a cascade structure of 6 microrings. Figure 7 For side-coupled integrated spatial sequence resonators, six identical microrings are independently coupled to a common waveguide, wherein Sb2Se3 phase change materials 5-4 are embedded in the strip or ridge waveguide of each microring; Figure 8 To couple the resonant optical waveguides, six identical microrings are cascaded by coupling the resonant optical waveguides, and Sb2Se3 phase change material is embedded in the strip or ridge waveguide of each microring, and Sb2Se3 phase change material can also be laid flat in each microring strip or ridge waveguide.

[0041] Fig. 9This is a schematic diagram of a Bragg grating delay line based on Sb2Se3 phase change material, in which the optical waveguide 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. There are also multiple electrodes 5-6 located above the upper cladding 5-5, which correspond one to one to each segment of the segmented phase change material.

[0042] Fig.10 The cross section of the optical waveguide 5 of all tunable units of the optical waveguide delay line, wherein the phase change material 5-4 shown in the figure is embedded in the core layer 5-3 of the ridge waveguide. The electrode 5-6 can be a metal electrode, more preferably a graphene electrode. The upper cladding layer 5-5 is used to protect the phase change material 5-4 on the one hand, and to separate the electrode 5-6 from the core layer 5-3 on the other hand, so as to reduce the absorption of the optical signal by the electrode 5-6.

[0043] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, 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 comprises 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; The delay unit is a pair of waveguides of unequal lengths, and the waveguide type is a strip waveguide or a ridge waveguide; Along the length direction of the waveguide, a phase change material is 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-shaped or ridge-shaped waveguide of the long waveguide in the unequal-length waveguide pair.

2. The optical waveguide delay line according to claim 1, characterized in that: 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.

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

4. The optical waveguide delay line according to claim 3, characterized in that: Along the length direction of the waveguide, there are also multiple electrodes located on the long waveguide or the short waveguide, corresponding one-to-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. An optical waveguide delay line, characterized in that: The optical waveguide delay line is a cascade structure of N microring resonators, where N is a positive integer; N identical microrings are independently coupled to a common waveguide, or N identical microrings are cascaded by coupling resonant optical waveguides; Each of the microrings includes a tunable phase shifter; The waveguide type of the optical waveguide delay line is a strip waveguide or a ridge waveguide; A phase change material is embedded in the strip or ridge waveguide of the tunable phase shifter, or a layer of phase change material is laid on the upper surface of the strip or ridge waveguide of the tunable phase shifter.

7. The optical waveguide delay line according to claim 6, characterized in that: Along the length direction of the waveguide, the phase change material embedded or laid in the strip or ridge waveguide of the tunable phase shifter is a segmented structure arranged at intervals.

8. An optical waveguide delay line, characterized in that: The optical waveguide delay line is a cascade structure of N Bragg gratings; N Bragg gratings are cascaded uniform Bragg gratings with different periods. or, The N Bragg gratings are chirped Bragg gratings; The waveguide type is strip or ridge waveguide; Along the length direction of the strip or ridge waveguide, the phase change material is uniformly embedded in the strip or ridge waveguide, or laid on the surface of the strip or ridge waveguide.

9. The optical waveguide delay line according to claim 1, 6 or 8, characterized in that: The phase change material is selected from any one of Sb2S3, Sb2Se3, GST, GSST and VO2.

10. The optical waveguide delay line according to claim 1 or 8, characterized in that: The optical waveguide delay line is in a spiral shape as a whole.

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