CN115061237A - Reconfigurable power splitter based on phase change material and power splitting ratio adjusting method - Google Patents
Reconfigurable power splitter based on phase change material and power splitting ratio adjusting method Download PDFInfo
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
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- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12133—Functions
- G02B2006/12154—Power divider
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Abstract
The invention discloses a reconfigurable power splitter based on a phase-change material and a power splitting ratio adjusting method, belonging to the field of photonic devices, wherein the reconfigurable power splitter comprises: a substrate; the two arms of the Y-branch waveguide are used as output waveguides of the reconfigurable power splitter; and phase change material sequences deposited on the upper surfaces of the two arms of the Y-branch waveguide; the period of each phase change material unit in the phase change material sequence meets the sub-wavelength condition, and the state of each phase change material unit is independently adjustable; the state of a phase change material cell includes crystalline and amorphous states. The adjusting method comprises the following steps: and adjusting the state of the phase change material units in the phase change material sequence on the upper surfaces of the two arms of the Y-branch waveguide to adjust the equivalent refractive indexes of the two arms of the Y-branch waveguide until the light output by the two arms of the Y-branch waveguide reaches a preset power branching ratio. The invention can improve the bandwidth characteristic of the power branch ratio under the condition of ensuring that the power branch ratio of the power splitter is flexibly adjustable.
Description
Technical Field
The invention belongs to the field of photonic devices, and particularly relates to a reconfigurable power splitter based on a phase change material and a power splitting ratio adjusting method.
Background
Over the past decades, integrated technologies based on electrical interconnects have evolved at a high rate, but as the feature size of integrated technologies gradually approaches their physical limits, the world has entered the so-called "post-molar era". In order to meet the high-speed increasing information transmission and processing requirements, the on-chip optical interconnection technology becomes a powerful competitive scheme for further breaking through the bottleneck due to the characteristics of high speed, low loss, interference resistance and the like.
On-chip optical interconnects consist of a series of functionally distinct photonic device connections, with optical power splitters being one of the most basic and most commonly used photonic devices. At present, various power dividers with different power splitting ratios have been reported, but most of them are static devices, that is, a single power divider can only realize a certain power splitting ratio, which limits the functional flexibility of the optical network.
In the utility model patent of the publication number CN 201903668U, the name is "novel adjustable integrated optical power divider", disclose a novel adjustable integrated optical power divider, it includes Y branch waveguide and coupling area, set up the recess parallel with the arm as additional waveguide in two arms of Y branch, inject the material of different refracting indexes into in additional waveguide and can make coupling area equivalent refractive index change, through selecting the distance and the refracting index parameter between additional waveguide and the branch coupling interval, can make the power branch ratio of Y branch waveguide output change. However, in this scheme, once the power divider is manufactured, the distance between the additional waveguide and the branch coupling region is not adjustable, and the material filled in the additional waveguide is also not replaceable, so that the power divider with a specific structure can only realize one power branch ratio, and the power branch ratio is still not adjustable without changing the structure of the power divider.
Most of the reported reconfigurable power splitters are waveguide devices regulated and controlled based on a thermo-optic effect or an electro-optic effect, such as MMI and MZI, wherein the MZI scheme is most representative, and the continuous regulation of the power ratio can be realized by changing the phase shift amount on one phase shift arm through thermal regulation, but because the coupler and the phase shift arm in the MZI have wavelength correlation, the bandwidths of the methods are difficult to reach more than 100nm, and the bandwidth performance is poor. In addition, the schemes based on the electric heating regulation require continuous energy injection, and the power consumption is high.
Disclosure of Invention
Aiming at the defects and improvement requirements of the prior art, the invention provides a reconfigurable power splitter based on a phase-change material and a power splitting ratio adjusting method, and aims to improve the bandwidth characteristic of the power splitting ratio under the condition of ensuring that the power splitting ratio of the power splitter is flexible and adjustable.
The power splitter with flexibly adjustable power splitting ratio is provided under the condition of unchanging structure, thereby improving the flexibility and integration degree of the on-chip optical network.
To achieve the above object, according to one aspect of the present invention, there is provided a reconfigurable power splitter based on a phase change material, including:
a substrate;
the Y-branch waveguide is deposited on the substrate, and two arms of the Y-branch waveguide are used as output waveguides of the reconfigurable power splitter;
and phase change material sequences deposited on the upper surfaces of the two arms of the Y-branch waveguide; the period of each phase change material unit in the phase change material sequence meets the sub-wavelength condition, and the state of each phase change material unit is independently adjustable; the state of a phase change material cell includes crystalline and amorphous states.
Further, the reconfigurable power splitter provided by the present invention further includes: an upper cladding layer overlying the Y-branch waveguide and the phase change material sequence.
Further, the state of the phase change material cell also includes intermediate states between the crystalline and amorphous states.
Further, the phase change material is a chalcogenide phase change material; preferably Sb 2 Se 3 Or GSST.
According to another aspect of the present invention, there is provided a power splitting ratio adjusting method of the reconfigurable power splitter based on the phase change material, including:
and adjusting the state of the phase change material units in the phase change material sequence on the upper surfaces of the two arms of the Y-branch waveguide to adjust the equivalent refractive indexes of the two arms of the Y-branch waveguide until the light output by the two arms of the Y-branch waveguide reaches a preset power branching ratio.
Further, the state of the phase change material cell is adjusted by joule heating generated by a far field focused laser pulse or an electrical pulse.
Further, when the state of the phase change material cell is adjusted by focusing the laser pulse in the far field, the method for adjusting the state of the phase change material cell includes:
dividing each n phase change cells on each arm into a cell group; n is a positive integer;
focusing a first laser pulse on a unit group to switch the phase-change material in the unit group from an amorphous state to a crystalline state;
focusing a second laser pulse on the unit group to switch the phase-change material in the unit group from a crystalline state to an amorphous state;
in the two laser pulses, the first laser pulse has lower power and larger pulse width;
when the state of the phase change material unit is adjusted by joule heat generated by the electric pulse, the manner of adjusting the state of the phase change material unit includes:
injecting a first electric pulse into the electrode above the unit group to switch the phase-change material in the unit group from an amorphous state to a crystalline state;
injecting a second electric pulse into the electrode above the unit group to switch the phase-change material in the unit group from a crystalline state to an amorphous state;
of the two electrical pulses, the first electrical pulse has a lower voltage and a larger pulse width.
Further, when the state of the phase change material unit is adjusted by focusing the laser pulse in the far field, the method for adjusting the state of the phase change material unit further includes:
focusing a unit group by using a third laser pulse to switch the phase-change material in the unit group from an amorphous state to an intermediate state; the power of the third laser pulse is the same as that of the laser pulse, and the pulse width of the third laser pulse is between the first laser pulse and the second laser pulse;
when the state of the phase change material unit is adjusted by joule heat generated by the electric pulse, the method of adjusting the state of the phase change material unit further includes:
injecting a third electric pulse into the electrode above the unit group to switch the phase-change material in the unit group from an amorphous state to an intermediate state; the third electrical pulse has the same pulse width as the second electrical pulse and a voltage intermediate the first and second electrical pulses.
Further, according to the target power branching ratio, one arm with lower output power in the Y-branch waveguide is used as a passive arm, and the other arm is used as an active arm; in the process of adjusting the states of the phase change material units in the phase change material sequence on the upper surfaces of the two arms of the Y-branch waveguide, the states of the phase change material units on the driven arm are kept unchanged.
Furthermore, the state of each phase change material unit on the passive arm is in an amorphous state.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) the invention provides a power splitter, which comprises a Y branch and a sub-wavelength phase change material sequence deposited in the centers of the upper surfaces of two arms of the Y branch, wherein a phase change material unit can be switched between different states; because the phase-change materials have different refractive indexes in different states, the control of the equivalent refractive indexes of the two arms of the Y branch is realized by controlling the state combination of each unit in the phase-change material sequence, and then different power branch ratios can be realized under the condition that the structure of the power splitter is not changed by influencing the mode evolution process, so that the flexibility and the integration level of the on-chip optical network can be improved. Because the Y-branch waveguide realizes power branching based on mode evolution, and the wavelength correlation of the mode evolution is low, the power branching device provided by the invention has good bandwidth performance; experiments show that the power branching ratio of the power splitter provided by the invention is not obviously changed within the range of 200nm, and the power splitter is obviously superior to the existing reconfigurable optical power splitter represented by an MZI structure.
(2) The invention realizes the adjustment of the power branching ratio by regulating and controlling the state of the phase change material unit, and the power branching device can keep the current power branching ratio without continuous energy injection after the unit state setting is finished because the phase change material has non-volatility, thereby effectively reducing the power consumption.
(3) The reconfigurable power splitter provided by the invention can realize different power splitting ratios by using the same structure by only preparing the sub-wavelength phase change material sequence on the Y branch, has simple structure, and has the length of the whole device far smaller than that of other power splitters based on the Y branch because the refractive index of the phase change material is greatly changed in different states.
Drawings
Fig. 1 is a top view of a reconfigurable power splitter based on a phase change material according to an embodiment of the present invention;
fig. 2 is a front view of a reconfigurable power splitter based on phase change material according to an embodiment of the present invention;
FIG. 3 is a transmission spectrum simulation result under several different power splitting ratios provided by an embodiment of the present invention;
the same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
1-a substrate;
a 2-Y branched waveguide; 21-input waveguide, 22-branching region, 23-output waveguide;
3-a sequence of phase change materials;
4-upper cladding.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
In order to solve the problems that the conventional optical power splitter is limited in power splitting ratio and low in bandwidth and needs continuous energy injection to maintain a working state, and high power consumption is caused, the invention provides a reconfigurable power splitter based on a phase change material and a power splitting ratio adjusting method, and the overall thought is as follows: the sub-wavelength phase change material sequences are deposited on the two arms of the Y branch, the equivalent refractive indexes of the two arms of the Y branch are controlled by changing the state combination of the phase change material sequences by utilizing the refractive index difference between different states of the phase change material, and therefore reconfigurable multiple power branch ratios are achieved under the condition that the structure is not changed.
The reconfigurable optical power splitter based On the phase change material provided by the invention can be applied to On-chip optical network construction On various material platforms such as SOI (Silicon-On-Insulator), plc (planar light wave circuit) and the like, and for convenience of description, the SOI platform is taken as an example in the following embodiments for explanation without loss of generality.
The following are examples.
Example 1:
a reconfigurable power splitter based on phase change material, as shown in fig. 1 and 2, comprising: the phase change waveguide comprises a substrate 1, a Y-branch waveguide 2 deposited on the substrate 1, phase change material sequences 3 deposited on the upper surfaces of two arms of the Y-branch waveguide 2, and an upper cladding layer 4 covering the Y-branch waveguide 2 and the phase change material sequences 3.
Optionally, in this embodiment, the substrate 1 is made of silicon dioxide (SiO) 2 )。
Referring to fig. 1, the Y-branch waveguide 2 includes an input waveguide 21, a branch region 22 in which the waveguide pitch is gradually enlarged, and two output waveguides 23; optionally, in this embodiment, the waveguide layer material is silicon (Si) and has a thickness of 220 nm; the input waveguide 21 is 1.2um wide and the waveguide spacing of the branching region 22 is increased uniformly from 0 to 200nm and then connected to the output waveguide 23 500nm wide by two segments of arc-shaped waveguides. It should be noted that the description of the material and structural parameters of the Y-branch waveguide 2 is only an alternative embodiment and should not be construed as the only limitation of the present invention.
In order to avoid reflection and large scattering loss, in this embodiment, the period of each phase change material unit in the phase change material sequence is less than half of the optical wavelength in the waveguide material, that is, the phase change material unitThe period Λ of the element satisfies Λ<λ/2n eff Wherein λ represents a wavelength, n eff Representing the effective refractive index. Optionally, in this embodiment, the period of the phase change material unit is set to 200nm, and the duty ratio is 50%.
In this embodiment, the states of the phase change material units are independently adjustable; the states of a phase change material cell include crystalline and amorphous states, and intermediate states between the crystalline and amorphous states. Because the refractive indexes of the phase-change materials in different states are different, the control of the equivalent refractive index difference of the two arms of the Y-branch waveguide can be realized by controlling the state combination of each phase-change material unit in the phase-change material sequence under the condition of unchanged structure, so that the mode evolution process of the Y-branch waveguide can be influenced, the distribution of optical power between the two arms is changed, and different power branching ratios are finally realized. Because the Y-branch waveguide implements power branching based on the principle of mode evolution, and its wavelength dependency is superior, the power splitter provided by this embodiment has good bandwidth performance, see fig. 3, where "up" and "down" correspond to the upper arm and the lower arm of the Y-branch waveguide, respectively; as can be seen from the results shown in fig. 3, the reconfigurable power splitter provided in this embodiment has a high transmittance in the range of 1450 to 1650nm when the states of the phase change material sequences are different in the two arms of the Y-branch waveguide, and thus the power splitting ratio of the reconfigurable power splitter provided in this embodiment does not change significantly in the range of 200nm, and has good bandwidth characteristics.
Optionally, in this embodiment, the phase change material is Sb2Se3 (antimony selenide), and is deposited on the silicon waveguide by thermal evaporation, and the thickness is 40 nm; it should be noted that the descriptions of the material and the structural parameters of the phase change material unit are only optional embodiments, and should not be construed as the only limitation to the present invention; other phase change materials at least having two states of different refractive indexes, such as chalcogenide phase change materials such as GST and GSST, may also be used to achieve the same function, and the corresponding deposition process may also be selected according to actual needs.
In this embodiment, the upper cladding layer functions toPreventing the phase change material from being oxidized or the components from being evaporated during phase change; optionally, in this embodiment, the upper cladding material is specifically SiO 2 (silica), deposited on the top layer by means of PECVD with a thickness of 2um, it should be noted that the upper cladding consists of pure SiO 2 The composition is an alternative embodiment and should not be construed as the only limitation on the invention.
The reconfigurable power splitter based on the phase change material provided by this embodiment may set the state of each phase change material unit in the phase change material sequence by using a focused optical pulse or an electrical heating manner.
The corresponding principle of the way of focusing the light pulse is as follows: the transformation of a phase change material from an amorphous state to a crystalline state (crystallization) is performed by heating the material above the crystallization temperature for a period of time, while the transformation from a crystalline state to an amorphous state (amorphization) is performed by heating the material above the melting temperature and rapidly decreasing the temperature; because the melting temperature is higher than the crystallization temperature, crystallization is realized by low-power large-pulse-width light pulses, and amorphization is realized by high-power narrow-pulse-width light pulses.
The basic principle of the method using electric heating is as follows: the electrode generates Joule heat under the external voltage, and the phase-change material reaches the temperature required by phase change by controlling the voltage and the pulse width of the external electric pulse. It will be readily appreciated that, in order to apply the electrical pulses, after the deposition of the sequence of phase change materials, a transparent electrode is deposited, followed by an upper cladding layer, the transparent electrode material being ITO (indium tin oxide), IWO (tungsten doped indium oxide) or the like.
Generally, the reconfigurable power divider is constructed by combining the characteristics of large refractive index variation and non-volatility of the phase change material in different states with the good wide spectrum characteristic of Y branch, so that the wide-spectrum optical branch ratio tuning is realized on a single device, and the problem of high power consumption caused by the fact that a conventional electric-regulation-based thermal-regulation structure needs continuous power injection to keep a working state is solved. The reconfigurable optical power splitter provided by the embodiment can improve the flexibility of the on-chip optical interconnection network, the integration level and the power consumption, and has a wide application prospect.
Example 2:
the present embodiment is based on the reconfigurable power splitter based on the phase change material provided in embodiment 1.
The power branch ratio adjusting method provided by the embodiment includes: adjusting the state of phase change material units in the phase change material sequence 3 on the upper surfaces of the two arms of the Y-branch waveguide 2 to adjust the equivalent refractive indexes of the two arms of the Y-branch waveguide 2 until the light output by the two arms of the Y-branch waveguide 2 reaches a preset power branching ratio;
considering that in the reconfigurable power splitter based on the phase change material, the period of the phase change material unit is in the sub-wavelength order, the unit size is small, and if a single phase change material unit is taken as a unit for adjustment, the requirement on the focal spot diameter of the laser pulse is high in order not to influence the states of other surrounding phase change material units; in order to reduce the requirement on the laser pulse, in this embodiment, the multiple phase change material units on each arm are divided into one unit group, and the phase change material units in each unit group are uniformly adjusted by using the unit group as an adjustment unit; the number of cells in a cell group can be correspondingly determined according to the focal spot diameter of the selected laser pulse, so that the state of the phase change material cell in an adjacent cell group is not influenced when the state of the phase change material cell in one cell group is adjusted. It is easy to understand that, in the case of laser pulses meeting the respective requirements, the individual cells can also be adjusted directly as adjustment objects, which corresponds to the division of the individual cells into a group of cells.
Optionally, in this embodiment, the state of the phase change material unit is adjusted by focusing a laser pulse in a far field, and the specific adjustment manner includes:
focusing a first laser pulse on a unit group to switch the phase-change material in the unit group from an amorphous state to a crystalline state;
focusing a second laser pulse on the unit group to switch the phase-change material in the unit group from a crystalline state to an amorphous state;
focusing a third laser pulse on the unit group to switch the phase-change material in the unit group from an amorphous state to an intermediate state;
in the two laser pulses, the first laser pulse has lower power and larger pulse width; the power of the third laser pulse is the same as that of the laser pulse, and the pulse width of the third laser pulse is between the first laser pulse and the second laser pulse;
through the above steps, the state of the phase change material unit may be set to a crystalline state, an amorphous state, or an intermediate state.
In order to further simplify the adjustment process of the power branching ratio, in this embodiment, two arms of the Y-branched waveguide are divided into an active arm and a passive arm, specifically, one arm with lower output power in the Y-branched waveguide is used as the passive arm and the other arm is used as the active arm according to the target power branching ratio, so as to ensure a larger power branching ratio adjustment range; after the states of the phase change material units on the driven arm are preset, the states of the phase change material units on the driven arm are maintained unchanged in the adjusting process; considering that the phase change material itself absorbs light, the light loss in the amorphous state is smaller, and therefore, in this embodiment, the state of each phase change material unit is maintained in the amorphous state during the adjustment of the power splitting ratio.
Different power branch ratios are realized by controlling the state combination of the phase change material units on the driving arm. According to simulation results, the embodiment can realize a plurality of different power branch ratios from 1:1 to 1: 0. Part of simulation results are as follows: when all the phase change material units on the driving arm are in a crystalline state, 97.5% of power is output from the driving arm, and 1% of power is output from the driven arm; when 1/3 cells on the driving arm are in an amorphous state and 2/3 cells are in a crystalline state, 79.2% of power is output from the driving arm, and 9.4% of power is output from the driven arm; when 2/3 cells on the driving arm are in an amorphous state and 1/3 cells are in a crystalline state, 62.9% of power is output from the driving arm, and 25.9% of power is output from the driven arm; when all the units on the active arm are on, 49.7% of power is output from the active arm, and 49.7% of power is output from the passive arm.
It should be noted that, in some other embodiments, in order to achieve a greater power splitting ratio, the states of the phase change materials in the two arms may also be adjusted, and for the adjustment manner of each arm, reference may be made to the adjustment manner of the active arm in this embodiment.
Example 3:
a power splitting ratio adjusting method, which is similar to embodiment 2, except that the present embodiment adjusts the state of the phase change material unit by joule heat generated by the electrical pulse, specifically comprising:
injecting electrodes above the unit group by using a first electric pulse to switch the phase-change material in the electrodes from an amorphous state to a crystalline state;
injecting a second electric pulse into the electrode above the unit group to switch the phase-change material in the unit group from a crystalline state to an amorphous state;
injecting a third electric pulse into the electrode above the unit group to switch the phase-change material in the unit group from an amorphous state to an intermediate state;
of the two electrical pulses, the first electrical pulse has a lower voltage and a larger pulse width; the third electrical pulse has the same pulse width as the second electrical pulse and has a voltage between the first electrical pulse and the second electrical pulse.
In this embodiment, the implementation of the remaining steps can refer to the description in the above embodiment 2, and will not be repeated here.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A reconfigurable power splitter based on phase change materials, comprising:
a substrate;
the two arms of the Y-branch waveguide are used as output waveguides of the reconfigurable power splitter;
and a sequence of phase change materials deposited on the upper surfaces of the two arms of the Y-branch waveguide; the period of each phase change material unit in the phase change material sequence meets the sub-wavelength condition, and the state of each phase change material unit is independently adjustable; the states of the phase change material cell include crystalline and amorphous states.
2. The reconfigurable phase change material-based power splitter of claim 1, further comprising: an upper cladding overlying the Y-branch waveguide and the phase change material sequence.
3. The reconfigurable phase change material-based power splitter of claim 2, wherein the states of the phase change material cell further comprise intermediate states between crystalline and amorphous states.
4. The reconfigurable power splitter based on phase change materials according to any one of claims 1 to 3, wherein the phase change material is a chalcogenide phase change material.
5. The method for adjusting the power splitting ratio of the reconfigurable power splitter based on the phase change material according to any one of claims 1 to 4, comprising:
and adjusting the states of phase change material units in the phase change material sequences on the upper surfaces of the two arms of the Y-branch waveguide so as to adjust the equivalent refractive indexes of the two arms of the Y-branch waveguide until the light output by the two arms of the Y-branch waveguide reaches a preset power branching ratio.
6. The power split ratio adjustment method of claim 5, wherein the state of the phase change material cell is adjusted by joule heating generated by a far-field focused laser pulse or an electric pulse.
7. The power splitting ratio adjustment method of claim 6, wherein adjusting the state of the phase change material cell by far field focused laser pulses comprises:
dividing each n phase change units on each arm into a unit group; n is a positive integer;
focusing a first laser pulse on a unit group to switch the phase-change material in the unit group from an amorphous state to a crystalline state;
focusing a second laser pulse on the unit group to switch the phase-change material in the unit group from a crystalline state to an amorphous state;
in the two laser pulses, the power of the first laser pulse is lower, and the pulse width is larger;
when the state of the phase change material unit is adjusted by joule heat generated by the electric pulse, the manner of adjusting the state of the phase change material unit includes:
injecting a first electric pulse into the electrode above the unit group to switch the phase-change material in the unit group from an amorphous state to a crystalline state;
injecting a second electric pulse into the electrode above the unit group to switch the phase-change material in the unit group from a crystalline state to an amorphous state;
of the two electrical pulses, the first electrical pulse has a lower voltage and a larger pulse width.
8. The power splitting ratio adjustment method of claim 7, wherein adjusting the state of the phase change material cell by far field focused laser pulses further comprises:
focusing a third laser pulse on the unit group to switch the phase-change material in the unit group from an amorphous state to an intermediate state; the power of the third laser pulse is the same as that of the laser pulse, and the pulse width of the third laser pulse is between that of the first laser pulse and that of the second laser pulse;
when the state of the phase change material unit is adjusted by joule heat generated by the electric pulse, the method of adjusting the state of the phase change material unit further includes:
injecting a third electric pulse into the electrode above the unit group to switch the phase-change material in the unit group from an amorphous state to an intermediate state; the third electrical pulse has the same pulse width as the second electrical pulse and a voltage between the first electrical pulse and the second electrical pulse.
9. The power splitting ratio adjusting method according to any one of claims 5 to 8, wherein one arm of the Y-branch waveguide having a lower output power is used as a passive arm and the other arm is used as an active arm according to a target power splitting ratio; in the process of adjusting the states of the phase change material units in the phase change material sequence on the upper surfaces of the two arms of the Y-branch waveguide, the states of the phase change material units on the driven arm are kept unchanged.
10. The power splitting ratio adjusting method according to claim 9, wherein the state of each phase change material unit on the driven arm is amorphous.
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