CN115826143A - Electrostatic comb driven integrated waveguide MEMS optical switch based on adiabatic coupler - Google Patents
Electrostatic comb driven integrated waveguide MEMS optical switch based on adiabatic coupler Download PDFInfo
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Abstract
The invention discloses an electrostatic comb driven integrated waveguide MEMS optical switch based on an adiabatic coupler. The waveguide type adiabatic coupler comprises a substrate, a mechanical driving structure and an adiabatic coupler, wherein the adiabatic coupler comprises a fixed tapered waveguide and a movable tapered waveguide which are arranged in parallel, the movable tapered waveguide is connected with the mechanical driving structure, the two waveguide structures are the same, the lengths are the same, but the width gradual change directions are opposite, and the two waveguide structures are arranged in a centrosymmetric mode. The invention realizes the effect of optical path switching by driving the separated heat insulation coupler by the electrostatic comb, and has the remarkable advantages of large bandwidth range, low insertion loss, low crosstalk, high extinction ratio, simple manufacturing process, low processing cost, low power consumption, strong expandability and the like.
Description
Technical Field
The invention belongs to an optical switch in the field of integrated optoelectronic devices, and particularly relates to an integrated waveguide MEMS optical switch and an array thereof, wherein the distance between two conical waveguides in a heat-insulating coupler is adjusted through electrostatic comb driving, so that optical path adjustment is realized.
Background
In recent years, the scale of a data center network is rapidly enlarged, and with the mature application of new technologies such as 5G, internet of things, cloud computing, artificial intelligence and the like, the network data traffic is rapidly increased, which puts new demands on the data center network, and a data center with higher performance is urgently needed to support the rapid development of digital economy with the above technologies as key contents. Under the background, the optical interconnection technology rapidly rises by virtue of the advantages that the traditional electrical interconnection is difficult to resist, such as large bandwidth, low power consumption and the like, so that a solution is provided for improving the performance of the data center, and the optical interconnection is the key technology of the large-scale data center at present.
With the development of the optical interconnection network, the scale of the optical interconnection network is continuously enlarged, and the complexity is increased, so how to realize the flexible reconfiguration of the optical interconnection network becomes a new problem. A large-scale nxn optical switch array is a key device for realizing flexible reconfiguration of an optical interconnection network, and has been one of research focuses, and various optical switch structures based on different platforms are proposed in succession, such as an optical switch based on a micro-mechanical system (MEMS), an integrated waveguide optical switch based on a mach-zehnder interferometer (MZI), and the like.
Among numerous optical switch structures, MEMS-based optical switches have attracted much attention due to their low loss, fast speed, good reliability, and high scalability, and large-scale MEMS-based optical switch arrays have been applied to data center networks. MEMS-based optical switches are further classified into free-space switches and integrated waveguide optical switches. For a free space optical switch, an optical signal is transmitted and switched in a free space from an optical fiber input switch and then received by an output optical fiber, and most of the optical switches in the data center network are free space optical switches at present. The MEMS-based free space switch has good expandability, and can realize hundreds of port numbers under the premise of ensuring low insertion loss and low crosstalk at present, but the switch of the switch has longer switching time, generally on the level of several milliseconds and dozens of milliseconds, and limits the reconstruction speed of a large-scale data center. In the integrated waveguide optical switch, an optical signal is transmitted in an integrated waveguide after being input into a chip from an input optical fiber, and the switching of an optical path is realized through a waveguide structure and a mechanical structure which are integrated together. In recent years, there has been great progress in MEMS-based integrated waveguide optical switches that enable fast switching times on the order of sub-microsecond, low insertion loss, low crosstalk, and large port count. The integrated waveguide optical switch based on the MEMS is expected to break through the restrictive factors of the existing optical switch array, and is applied to a large-scale optical interconnection network.
Disclosure of Invention
In view of the above background, an object of the present invention is to provide an integrated waveguide MEMS optical switch driven by a stationary electrostatic comb and based on an adiabatic coupler, and an nxn array, where the switch applies a driving voltage to the stationary electrostatic comb to generate an attractive force between the stationary electrostatic comb and a grounded movable electrostatic comb, so as to drive the movable electrostatic comb to generate a motion, and further drives a movable tapered waveguide in the adiabatic coupler to move through a transmission rod, so as to change a distance between the movable tapered waveguide and the stationary tapered waveguide, thereby achieving an optical path switching effect.
The technical scheme adopted by the invention is as follows:
the invention comprises at least one switch unit, each switch unit comprises a substrate, a mechanical driving structure and an adiabatic coupler, the mechanical driving structure and the adiabatic coupler are arranged on the substrate, the adiabatic coupler mainly comprises a fixed conical waveguide and a movable conical waveguide, the fixed conical waveguide is kept fixed, the fixed conical waveguide and the movable conical waveguide are arranged in parallel along a moving direction vertical to the mechanical driving structure, two ends of the fixed conical waveguide are connected with bent waveguides, two ends of the movable conical waveguide are connected with the mechanical driving structure through a pair of multimode interference crossed waveguide structures, and the movable conical waveguide is driven by the mechanical driving structure to move close to or far away from the fixed conical waveguide.
Each end of two ends of the movable tapered waveguide is sequentially connected with a first bent waveguide in a shape of a Chinese character 'hui', a cross-shaped multimode interference crossed waveguide and a second bent waveguide in a shape of a Chinese character 'hui', the cross-shaped multimode interference crossed waveguide is composed of a longer waveguide and a shorter waveguide, the longer waveguide is composed of a pair of symmetrical mode evolution tapered waveguides and a long multimode wide waveguide, the wide ends of the pair of mode evolution tapered waveguides are respectively connected with two ends of the long multimode wide waveguide, and the narrow ends of the pair of mode evolution tapered waveguides are respectively connected with the two bent waveguides in the shape of the Chinese character 'hui'; the shorter one is a short multi-mode-width waveguide, one end of the short multi-mode-width waveguide is connected with the mechanical driving structure, and the other end of the short multi-mode-width waveguide is not connected; the longer one of the cross-shaped multimode interference cross waveguides is used for transmission of optical signals and the shorter one is used for mechanical fixation.
The fixed conical waveguide and the movable conical waveguide are of the same structure and are both conical waveguides with gradually changed widths, the fixed conical waveguide and the movable conical waveguide are the same in length but opposite in width gradually changing direction, the width of an input end of the fixed conical waveguide is the same as that of an output end of the movable conical waveguide, the width of an output end of the fixed conical waveguide is the same as that of an input end of the movable conical waveguide, and the size of a gap between the fixed conical waveguide and the movable conical waveguide is always kept unchanged.
The mechanical driving structure comprises an electrostatic comb driver consisting of a fixed electrostatic comb and a movable electrostatic comb, a T-shaped transmission structure and three groups of fixed islands and spring structures;
the T-shaped transmission structure is arranged in a suspended mode on the substrate, the top rod part of the T-shaped transmission structure is parallel to the movable conical waveguide, the bottom rod part of the T-shaped transmission structure is perpendicular to the movable conical waveguide, a first group of fixed islands and spring structures, a second group of fixed islands and spring structures and a third group of fixed islands and spring structures are sequentially arranged on the bottom rod part of the T-shaped transmission structure from one end close to the movable conical waveguide along the length direction, and the first group of fixed islands and spring structures, the second group of fixed islands and spring structures and the third group of fixed islands and spring structures are all connected with the T-shaped transmission structure;
electrostatic comb drivers are arranged on two sides of the T-shaped transmission structure between the second group of fixed islands and the spring structure and between the third group of fixed islands and the spring structure, each electrostatic comb driver comprises a pair of fixed electrostatic combs and a pair of movable electrostatic combs, the fixed electrostatic combs are fixed on the substrate, and the pair of fixed electrostatic combs are symmetrically distributed on two sides of the length direction of the bottom rod part of the T-shaped transmission structure and are not connected with the bottom rod part of the T-shaped transmission structure; the movable electrostatic combs are suspended on the substrate, the pair of movable electrostatic combs are symmetrically distributed on two sides of the length direction of the bottom rod part of the T-shaped transmission structure, and one end of each movable electrostatic comb close to the bottom rod part of the T-shaped transmission structure is fixedly connected with the side edge of the bottom rod part; the comb teeth of the fixed electrostatic comb and the movable electrostatic comb are distributed in an opposite and staggered penetrating manner.
The first group of fixed island and spring structures mainly comprise a fixed island and a pair of half-folded springs, the fixed island is fixed on the substrate, two ends of the fixed island are connected with one end, close to the movable conical waveguide, of the bottom rod part of the T-shaped transmission structure through the half-folded springs, and the half-folded springs are suspended on the substrate.
The semi-folding spring is of a suspended structure and comprises a spring handle and two beams which are connected to two ends of the spring handle and vertical to the length direction of the spring handle, wherein the two beams extend towards the same side far away from the spring handle and are respectively connected with the fixed island and the T-shaped transmission structure.
The second group of fixed islands and the spring structures have the same structure as the third group of fixed islands and spring structures and are respectively composed of four fixed islands and a pair of folding springs; the fixed island is fixed in the basement, uses two fixed islands as a set of in four fixed islands, and a set of fixed island arranges same one side at T shape transmission structure bottom bar portion, and two sets of fixed islands are arranged respectively in the both sides of T shape transmission structure bottom bar portion, and two fixed islands with one side are connected through a folding spring and T shape transmission structure bottom bar portion side, and the folding spring is unsettled and is arranged in the basement.
Folding spring be unsettled structure, including the spring handle, connect at the spring handle both ends and with two stub beams of spring handle length direction vertically and connect in the spring handle middle part and constitute with two long roof beams of spring handle length direction vertically, the one end of two stub beams is connected to the both ends of spring handle respectively, the other end that the spring handle was kept away from to two stub beams links to each other with two fixed islands that are located T shape transmission structure sill bar portion homonymy respectively, the one end of two long roof beams is connected to two places at the spring handle middle part respectively, the other end that the spring handle was kept away from to two long roof beams links to each other with two places that are located T shape transmission structure sill bar portion homonymy respectively.
The pair of fixed electrostatic combs are connected with an external circuit, and the regulation and control of the optical switch are realized by applying or removing voltage to the pair of fixed electrostatic combs.
The fixed electrostatic comb is connected with an external circuit, and potential difference is generated between voltage applied by the external circuit and the movable electrostatic comb, so that attraction is generated between the fixed electrostatic comb and the movable electrostatic comb, the movable electrostatic comb generates motion close to the fixed electrostatic comb, the whole T-shaped transmission structure is driven to generate displacement vertical to the length direction of the fixed conical waveguide through connection between the movable electrostatic comb and the bottom rod part of the T-shaped transmission structure, the movable conical waveguide is further driven to generate displacement vertical to the length direction of the fixed conical waveguide through connection between the top edge of the T-shaped transmission structure and the multimode interference crossed waveguide, and meanwhile, three groups of spring structures connected with the T-shaped transmission structure all generate certain elastic deformation. The displacement of the movable conical waveguide can be controlled by adjusting the voltage applied by an external circuit, namely the distance between the fixed conical waveguide and the movable conical waveguide is regulated and controlled, so that the function of switching the optical propagation path of the integrated waveguide MEMS optical switch is realized.
The fixed conical waveguide, the movable conical waveguide, the T-shaped transmission structure, the three groups of fixed islands, the spring structure and the electrostatic comb driver are made of the same material and have the same thickness, and the whole switch unit structure or the NxN array can be manufactured by adopting single-chip integration processing.
The fixed conical waveguide, the movable conical waveguide, the T-shaped transmission structure, the semi-folding spring, the folding spring and the movable electrostatic comb are all suspended structures and released through corrosion of the buried layer.
The fixed island and the fixed piece are both connected with the substrate through the buried layer, and the rest parts are arranged in a suspended manner.
The N multiplied by N optical switch array at least comprises four integrated waveguide MEMS optical switch units, adjacent switch units are connected with waveguides in a Cross mode through single-mode waveguides, and the connection mode among the switch units can adopt topological structures such as but not limited to Benes, cross-Bar and the like.
The invention is characterized in that the adiabatic coupler composed of a movable tapered waveguide 3 and a fixed tapered waveguide 2 is used in the optical switch, the principle is adiabatic evolution of a mode, compared with coupling structures based on an interference principle, such as a directional coupler, a microbend directional coupler and the like, the coupling structure has the principle advantages of large process tolerance, realization of ultra-large bandwidth and ultra-low loss, and the effect advantages of larger process tolerance, larger bandwidth and lower loss can be brought by the arrangement of the adiabatic coupler in the optical switch.
The invention has the beneficial effects that:
(1) The invention has the advantages of single material, simple structure and low manufacturing cost;
(2) The switch unit has low insertion loss, low crosstalk and high extinction ratio in a large wavelength range and a large processing tolerance range;
(3) The driving mode adopted by the switch unit is a capacitive structure, and the energy consumption of the switch unit is extremely low;
(4) The switch unit is provided with two input ports and two output ports, and the 2 multiplied by 2 switch unit can be cascaded into a large-scale optical switch array by adopting various topological structures and has strong expansibility.
In a word, the invention realizes the effect of optical path switching by driving the separated adiabatic coupler by the electrostatic comb, and has the remarkable advantages of large bandwidth range, low insertion loss, low crosstalk, high extinction ratio, simple manufacturing process, low processing cost, low power consumption, strong expandability and the like.
Drawings
FIG. 1 is a top view of the structure of the present invention in an initial state (OFF);
FIG. 2 isbase:Sub>A cross-sectional view A-A' of FIG. 1;
FIG. 3 is a cross-sectional view B-B' of FIG. 1;
FIG. 4 is a top view of the structure of the present invention after application of a voltage (ON);
FIG. 5 is a schematic illustration of a fixed tapered waveguide and a moving tapered waveguide;
FIG. 6 is a schematic diagram of an NxN integrated waveguide MEMS optical switch structure based on a Benes topology;
FIG. 7 is a diagram showing the optical field transmission of the adiabatic coupler section of the present invention in the OFF and ON states, (a) showing the optical field transmission of the adiabatic coupler in the OFF state, and (b) showing the optical field transmission of the adiabatic coupler in the ON state.
In the figure: 1. the device comprises a first group of fixed islands and spring structures, 2, fixed conical waveguides, 3, movable conical waveguides, 4, a T-shaped transmission structure, 5, a second group of fixed islands and spring structures, 6, a fixed electrostatic comb, 7, a movable electrostatic comb, 8, a third group of fixed islands and spring structures, 9, a buried layer, 10 and a substrate.
Detailed Description
The invention is further illustrated with reference to the following figures and examples, which should not be construed as limiting the scope of the invention.
As shown in fig. 1 and 4, the present invention mainly includes at least one switching unit, each of which includes a substrate 10, and a mechanical driving structure and an adiabatic coupler disposed on the substrate, wherein the adiabatic coupler mainly includes a fixed tapered waveguide 2 and a movable tapered waveguide 3, the fixed tapered waveguide 2 is kept fixed, the fixed tapered waveguide 2 and the movable tapered waveguide 3 are both arranged in parallel along a moving direction perpendicular to the mechanical driving structure, both ends of the fixed tapered waveguide 2 are connected with S-shaped bent waveguides, and the bent waveguides at both ends serve as input/output ends of the switching unit. The fixed tapered waveguide 2 is supported and fixed by the curved waveguides at the two ends so that the fixed tapered waveguide 2 is fixed. Two ends of the movable conical waveguide 3 are connected with a T-shaped transmission structure 4 of a mechanical driving structure through a pair of multimode interference crossed waveguide structures, and the mechanical driving structure drives the movable conical waveguide 3 to move close to or far away from the fixed conical waveguide 2.
The fixed tapered waveguide and the movable tapered waveguide both comprise a set of curved waveguides, and one part of the curved waveguides is a width-graded waveguide, the width of which is graded from the end width of the tapered waveguide to the width of a single-mode waveguide. Both the fixed tapered waveguide 2 and the movable tapered waveguide 3 increase the structural flexibility by providing curved waveguides.
Each end of the two ends of the movable tapered waveguide 3 is sequentially connected with a first bent waveguide in a shape of a Chinese character 'hui', a cross-shaped multimode interference crossed waveguide and a second bent waveguide in a shape of a Chinese character 'hui', the cross-shaped multimode interference crossed waveguide is composed of a longer waveguide and a shorter waveguide, the longer waveguide is composed of a pair of symmetrical mode evolution tapered waveguides and a long multimode wide waveguide, the wide ends of the pair of mode evolution tapered waveguides are respectively connected with the two ends of the long multimode wide waveguide, and the narrow ends of the pair of mode evolution tapered waveguides are respectively connected with the two bent waveguides in a shape of a Chinese character 'hui'; the shorter one is a short multi-mode-width waveguide, one end of the short multi-mode-width waveguide is connected with the T-shaped transmission structure 4 of the mechanical driving structure, and the other end of the short multi-mode-width waveguide is not connected; the longer one of the cross-shaped multimode interference cross waveguides is used for transmission of optical signals and the shorter one is used for mechanical fixation. And the second curved waveguide is used as the input/output end of the switch unit at the other end of the unconnected multi-mode interference cross waveguide.
The multimode interference crossed waveguide comprises a pair of adiabatic tapered waveguides and a pair of orthogonal multimode wide waveguides, two ends of the multimode wide waveguides perpendicular to the length direction of the fixed tapered waveguide are respectively connected with one adiabatic tapered waveguide, so that the mode in the multimode waveguide and the mode in the single-mode waveguide are subjected to adiabatic evolution mutually, the multimode wide waveguides parallel to the length direction of the fixed tapered waveguide are not used for transmitting signals, one end of each multimode wide waveguide is connected with the T-shaped transmission structure, and the other end of each multimode wide waveguide is not connected.
When the movable conical waveguide and the return bends connected with the two ends of the movable conical waveguide are close to the fixed conical waveguide under the driving of the MEMS driving device, the movable conical waveguide and the fixed conical waveguide form an adiabatic coupler, the outer ends of the fixed conical waveguide and the movable conical waveguide are connected with single mode waveguides, optical signals are input and output through the single mode waveguides, and adjacent switch units in the N x N array are also connected with each other through the single mode waveguides.
The adjacent switch units are connected with each other through the bent waveguides of the switch units, and the bent waveguides are used as input and output waveguides of the switch units.
As shown in fig. 5, the fixed tapered waveguide 2 and the movable tapered waveguide 3 have the same structure, and are both a tapered waveguide with gradually changing width, the fixed tapered waveguide 2 and the movable tapered waveguide 3 have the same length but opposite width-changing directions along the waveguide direction, the input end width of the fixed tapered waveguide 2 is the same as the output end width of the movable tapered waveguide 3, the output end width of the fixed tapered waveguide 2 is the same as the input end width of the movable tapered waveguide 3, and the gap between the fixed tapered waveguide 2 and the movable tapered waveguide 3 is always constant, so that the fixed tapered waveguide 2 and the movable tapered waveguide 3 are finally arranged in central symmetry.
The mechanical driving structure comprises an electrostatic comb driver consisting of a fixed electrostatic comb 6 and a movable electrostatic comb 7, a T-shaped transmission structure 4 and three groups of fixed island and spring structures 1, 5 and 8; the set of fixed islands and spring structures closest to the movable tapered waveguide is the first set, and the two sets of fixed islands and spring structures further from the movable tapered waveguide are the second and third sets, respectively. The T-shaped transmission structure is uniformly distributed with openings so as to facilitate the entry of chemical agents for corroding the buried layer. The three groups of fixed islands and the springs are distributed along the length direction of the bottom rod part of the T-shaped transmission structure.
The T-shaped transmission structure 4 is arranged in a suspended mode on the substrate 10, the top rod part of the T-shaped transmission structure 4 is parallel to the movable conical waveguide 3, the bottom rod part of the T-shaped transmission structure 4 is perpendicular to the movable conical waveguide 3, the bottom rod part of the T-shaped transmission structure 4 is sequentially provided with a first group of fixed islands and spring structures 1, a second group of fixed islands and spring structures 5 and a third group of fixed islands and spring structures 8 along the length direction from one end close to the movable conical waveguide 3, and the first group of fixed islands and spring structures 1, the second group of fixed islands and spring structures 5 and the third group of fixed islands and spring structures 8 are all connected with the T-shaped transmission structure 4; the T-shaped transmission structure 4 is connected with a movable electrostatic comb 7.
Electrostatic comb drivers are arranged on two sides of the T-shaped transmission structure 4 between the second group of fixed islands and the spring structure 5 and between the third group of fixed islands and the spring structure 8, each electrostatic comb driver comprises a pair of fixed electrostatic combs 6 and a pair of movable electrostatic combs 7, the fixed electrostatic combs 6 are fixed on a substrate 10, the pair of fixed electrostatic combs 6 are symmetrically distributed on two sides of the length direction of a bottom rod part of the T-shaped transmission structure 4 and are not connected with the bottom rod part of the T-shaped transmission structure 4, the fixed electrostatic combs are fixed on the substrate 10 and are positioned at positions close to the second group of fixed islands and the spring structure 5, and buried layers 9 are arranged below the fixed electrostatic combs; the movable electrostatic combs 7 are suspended on the substrate 10 and are of a suspended structure, the pair of movable electrostatic combs 7 are symmetrically distributed on two sides of the length direction of the bottom rod part of the T-shaped transmission structure 4 and are positioned at positions close to the third group of fixed islands and the spring structure 8, one end of each pair of movable electrostatic combs 7 close to the bottom rod part of the T-shaped transmission structure 4 is fixedly connected with the side edge of the bottom rod part, and the other end of each pair of movable electrostatic combs 7 far away from the bottom rod part of the T-shaped transmission structure 4 is not connected; the comb teeth of the fixed electrostatic comb 6 and the movable electrostatic comb 7 on the two sides of the bottom rod part of the T-shaped transmission structure 4 in the length direction are distributed in an opposite and staggered penetrating manner.
The fixed islands are all rectangular structures, as shown in fig. 2 and 3, the fixed islands and the fixed electrostatic combs 6 are connected with the substrate 10 through the buried layer 9, and the rest parts are not connected with the substrate 10.
The first group of fixed islands and spring structures 1 mainly comprise a fixed island and a pair of semi-folding springs, the fixed island is connected and fixed on a substrate 10 through a buried layer 9, the fixed island is fixed on the substrate 10, two ends of the fixed island are connected with one end, close to the movable conical waveguide 3, of the bottom rod part of the T-shaped transmission structure 4 through the semi-folding springs, and the semi-folding springs are suspended on the substrate 10.
The half-folded spring in the first group of fixed island spring structure 1 is a suspended structure and comprises a spring handle and two beams which are connected to two ends of the spring handle and vertical to the length direction of the spring handle, wherein the two beams extend towards the same side far away from the spring handle and are respectively connected with the fixed island and the T-shaped transmission structure 4.
The second group of fixed islands and spring structures 5 and the third group of fixed islands and spring structures 8 have the same structures and are respectively composed of four fixed islands and a pair of folding springs; the fixed islands are connected and fixed on the substrate 10 through the buried layer 9, the fixed islands are fixed on the substrate 10, two fixed islands are taken as one group in the four fixed islands, one group of fixed islands are arranged on the same side of the bottom rod part of the T-shaped transmission structure 4, two groups of fixed islands are respectively arranged on two sides of the bottom rod part of the T-shaped transmission structure 4, two fixed islands on the same side under one group of fixed islands are connected with the side part of the bottom rod part of the T-shaped transmission structure 4 through a folding spring, and the folding spring is suspended in the air in the substrate 10.
The folding springs in the second group of fixed island and spring structure 5 and the third group of fixed island and spring structure 8 are of a suspended structure, and comprise spring handles, two short beams which are connected to two ends of each spring handle and are perpendicular to the length direction of the spring handles, and two long beams which are connected to the middle of each spring handle and are perpendicular to the length direction of the spring handles, one ends of the two short beams are respectively connected to two ends of each spring handle, the other ends of the two short beams, which are far away from the spring handles, are respectively connected with two fixed islands which are positioned on the same side of the length direction of the bottom rod part of the T-shaped transmission structure 4, one ends of the two long beams are respectively connected to two positions in the middle of each spring handle, and the other ends of the two long beams, which are far away from the spring handles, are respectively connected with two positions which are positioned on the same side of the length direction of the bottom rod part of the T-shaped transmission structure 4.
The pair of fixed electrostatic combs 6 is connected with an external circuit, the regulation and control of the optical switch are realized by applying or removing voltage to the pair of fixed electrostatic combs 6, and the top layer structure and the silicon substrate 10 except the fixed electrostatic combs 6 are grounded.
A pair of fixed electrostatic combs 6 applies voltage to generate attraction force or repulsion force to drive the movable electrostatic combs 7 to move towards the direction close to or away from the fixed electrostatic combs 6, and further drive the T-shaped transmission structure 4 to drive the movable conical waveguide 3 to move towards the direction close to or away from the fixed conical waveguide 2 under the elastic control of the three groups of fixed islands and the spring structures 1, 5 and 8, so that the coupling connection/contact connection between the movable conical waveguide 3 and the fixed conical waveguide 2 is controlled, and the regulation and control of the optical switch are realized.
The implementation working process of the invention is as follows:
when an external circuit applies voltage to a pair of fixed electrostatic combs 6, the fixed electrostatic combs 6 generate attraction force to the movable electrostatic combs 7 to drive the movable electrostatic combs 7 to move towards the fixed electrostatic combs 6, the part of the movable electrostatic combs 7 connected with the bottom rod part of the T-shaped transmission structure 4 drives the whole T-shaped transmission structure 4 to displace in the direction vertical to the length direction of the movable conical waveguide 3, the part of the movable conical waveguide 3 connected with the top edge of the T-shaped transmission structure 4 drives the movable conical waveguide 3 to displace, and the movement close to the fixed conical waveguide 2 and the T-shaped transmission structure 4 causes the half-folded springs in the first group of fixed island and spring structures 1 and the folded springs in the second and third groups of fixed island and spring structures 5 and 8 connected with the fixed conical waveguide to elastically deform.
The distance between the movable tapered waveguide 3 and the fixed tapered waveguide 2 can be controlled by regulating the voltage applied to the pair of fixed electrostatic combs 6, and the regulation of the light propagation path is realized when the movable tapered waveguide and the fixed tapered waveguide are close to each other to a certain extent.
The electrostatic comb drivers 6, 7 in the embodiment are placed between the second set of fixed islands and spring structures 5 and the third set of fixed islands and spring structures 8, and the two sets of fixed islands and spring structures 5, 8 are beneficial to increasing the stability of the electrostatic comb drivers 6, 7 in the working process.
As shown in fig. 1, when the integrated waveguide MEMS optical switch in the embodiment is in a natural state, i.e., an OFF state without a voltage applied, the distance between the movable tapered waveguide 3 and the fixed tapered waveguide 2 is large, and the optical signals between the tapered waveguides 2 and 3 are not coupled. In this state, there is a large distance between the comb teeth of the stationary electrostatic comb 6 and the moving electrostatic comb 7 in the length direction of the bottom bar portion of the T-shaped transmission structure, and the distance is greater than the distance between the movable tapered waveguide 3 and the stationary tapered waveguide 2 in the natural state, so as to avoid collision between the comb teeth of the electrostatic combs 6 and 7 when the two tapered waveguides are close to each other, i.e., in the ON state shown in fig. 4.
As shown in fig. 4, when the integrated waveguide MEMS optical switch in the embodiment is in an ON state with a certain bias applied, the movable tapered waveguide 3 is close to the fixed tapered waveguide 2, a small gap is kept between the two tapered waveguides, and at this time, the two tapered waveguides form a directional adiabatic coupler, and an optical signal can undergo adiabatic evolution, thereby implementing path switching of the optical signal.
In the process of switching the integrated waveguide MEMS optical switch from a natural OFF state to an ON state, the fixed electrostatic comb 6 keeps a voltage-applied state all the time, and the voltage is adjusted to stabilize the movable tapered waveguide 3 at a certain distance from the fixed tapered waveguide 2. When the integrated waveguide MEMS optical switch in the embodiment needs to be switched from the ON state to the OFF state, the bias applied to the fixed electrostatic comb 6 is simply removed.
The fixed tapered waveguide 2 and the movable tapered waveguide 3 in the embodiment are portions for optical transmission, the fixed tapered waveguide 2 has connected single-mode bent waveguides at both ends, and the movable tapered waveguide 3 has connected single-mode bent waveguides and multimode interference cross waveguides at both ends. The buried layers below the fixed conical waveguide 2 and the movable conical waveguide 3 are both hollowed, the fixed conical waveguide 2 and the movable conical waveguide 3 are both of a suspended waveguide structure, the fixed conical waveguide 2 is kept still, the movable conical waveguide 3 can be close to the fixed conical waveguide 2 to form an adiabatic directional coupler, and the lengths of the fixed conical waveguide 2 and the movable conical waveguide 3 and a gap between the fixed conical waveguide 2 and the movable conical waveguide 3 support an optical signal to complete adiabatic evolution in the fixed conical waveguide and the movable conical waveguide.
In one embodiment, the top structures of the adiabatic coupler and the electrostatic comb driver are made of the same material and are in the same plane regardless of whether the buried layer is hollowed. For the whole switch structure, except that the fixed island and the fixed electrostatic comb 6 are supported by a buried layer, other structures are all suspension structures, and all the suspension structures except the fixed tapered waveguide 2 can move.
In specific implementation, the top layer structures of the heat-insulating coupler and the electrostatic comb driver are made of the same material, and monolithic integrated processing and manufacturing can be achieved. The integrated waveguide MEMS optical switch of the embodiment has a 2 × 2 port structure, can be connected in an N × N switch array in different topologies, and can increase the scale of the N × N array by increasing the number of switch units.
Fig. 6 is a schematic diagram of a 4 × 4 switch array cascaded by adopting a Benes topology structure, the 4 × 4 switch array includes six switch units, where the switch unit 1 and the switch unit 2 are first stages, the switch unit 3 and the switch unit 4 are second stages, the switch unit 5 and the switch unit 6 are third stages, and the switch units of different stages are connected to each other through a straight waveguide or a cross waveguide. Two output ports of the switch unit 1 at the first stage are respectively connected with one input port of the switch unit 3 and one input port of the switch unit 4 at the second stage, two output ports of the switch unit 2 at the first stage are respectively connected with the other input ports of the switch unit 3 and the switch unit 4 at the second stage, and the connection between the switch unit at the second stage and the switch unit at the third stage is the same as that.
The operation of the integrated waveguide MEMS optical switch of the present invention is described as follows:
fig. 1 is the OFF state of the switch when no bias is applied to the stationary electrostatic comb 6, and a large gap is maintained between the stationary electrostatic comb 6 and the moving electrostatic comb 7, and between the stationary tapered waveguide 2 and the movable tapered waveguide 3. At this time, for the signal inputted from the lower side of the fixed tapered waveguide 2, since the movable tapered waveguide 3 is far away, the signal is outputted from the upper side of the fixed tapered waveguide 2 without being affected, and similarly, the optical signal inputted from the lower side of the movable tapered waveguide 3 is outputted from the upper side of the movable tapered waveguide 3 without being affected.
A certain voltage is applied to the fixed electrostatic comb 6, induced charges are generated on the movable electrostatic comb 7, an electrostatic attraction force is generated between the fixed electrostatic comb 6 and the movable electrostatic comb 7, the movable electrostatic comb 7 moves close to the fixed electrostatic comb 6 under the action of the electrostatic attraction force, the T-shaped transmission structure 4 moves along the direction vertical to the length direction of the movable conical waveguide 3, and one end of a spring in the three groups of fixed islands and the spring structure is pulled to deform. When the elastic force generated by deformation is balanced with the electrostatic force between the electrostatic comb teeth, the whole mechanical structure reaches a balanced state.
As the applied voltage increases, the larger the electrostatic force generated between the stationary electrostatic comb 6 and the moving electrostatic comb 7, the larger the displacement generated when the mechanical structure reaches the equilibrium state, and the larger the moving distance of the movable tapered waveguide 3, and the closer to the movable tapered waveguide 2.
When the gap between the movable tapered waveguide 3 and the fixed tapered waveguide 2 is reduced to a certain extent, the movable tapered waveguide 3 and the fixed tapered waveguide 2 form an adiabatic directional coupler, which is the ON state of the switch.
Fig. 4 illustrates the ON state of the switch, when the fixed tapered waveguide 2 and the movable tapered waveguide 3 form an adiabatic directional coupler, and when the optical signal input from below the fixed tapered waveguide 2 is adiabatically evolved into the movable tapered waveguide 3 and output from above the movable tapered waveguide 3 due to the close distance of the movable tapered waveguide 3. If the OFF state of the switch is required to be recovered, only the voltage applied to the fixed electrostatic comb 6 needs to be removed, the mechanical structure is not stressed in balance after the electrostatic force is lost, and the switch is recovered to the initial OFF state under the action of the elastic force generated by the deformation of the spring, so that the state switching of the switch is completed, and the adjustment of the light transmission path is realized.
The integrated waveguide MEMS optical switch described in this embodiment has two input ports and two output ports, and is a 2 × 2 optical switch, which is more scalable than a 1 × 2 optical switch having one input port and two output ports. The 1 x 2 optical switch generally adopts a Cross-bar topology to form the light required by the N x N arrayThe number of switch units is up to N 2 However, the 2 × 2 silicon-based MEMS optical switch can also adopt Benes topology, as shown in fig. 7, only N (log) is needed to form an N × N switch array 2 N-0.5) optical switch units. In addition to Benes topologies, other topologies may be used for the switch array of the switch cells of the present invention.
The following describes specific embodiments of the present invention:
silicon On Insulator (SOI) is selected as an implementation platform, the top layer is made of silicon with the thickness of 220nm, the buried layer is made of silicon dioxide with the thickness of 2um, and the substrate is made of silicon. The wavelength range considered is 1500nm to 1600nm, with TE polarized optical signals. The widths of the two ends of the fixed conical waveguide are respectively 400nm and 300nm, the widths of the two ends of the movable conical waveguide are respectively 300nm and 400nm, and the widths of the two ends of the movable conical waveguide are the same and are 120um. The distance between the fixed tapered waveguide and the movable tapered waveguide in the OFF state is 1um
The optical performance of the device is simulated and verified by a three-dimensional finite difference time domain method (3D-FDTD), and almost all incident optical fields propagate along the fixed conical waveguide in the OFF state, as shown in FIG. 7 (a). The low loss and high extinction ratio can be realized on the wave band of 1500nm to 1600nm, the loss is less than 0.04dB, and the crosstalk is lower than-30 dB. And (3) applying voltage to the fixed electrostatic comb, pushing the movable tapered waveguide to move towards the fixed tapered waveguide by the movable electrostatic comb through the T-shaped transmission structure, and enabling the switch to enter an ON state when the gap between the movable tapered waveguide and the fixed tapered waveguide is 100nm, wherein the incident light field almost adiabatically evolves into the movable tapered waveguide, as shown in fig. 7 (b). When the switch is in an OFF state, low loss and high extinction ratio can be realized on a wave band from 1500nm to 1600nm, the loss is less than 0.03dB, and the crosstalk is lower than-25 dB. Therefore, the integrated waveguide MEMS optical switch provided by the invention can achieve the effects of super-large bandwidth, ultralow loss, high extinction ratio, ultralow energy consumption and the like.
The above-described embodiments are intended to illustrate rather than to limit the invention, and any modifications and variations of the present invention are within the spirit of the invention and the scope of the appended claims.
Claims (9)
1. An electrostatic comb driven adiabatic coupler based integrated waveguide MEMS optical switch, characterized by:
the double-mode-interference-type adiabatic coupler comprises at least one switch unit, wherein each switch unit comprises a substrate (10), a mechanical driving structure and an adiabatic coupler, the mechanical driving structure and the adiabatic coupler are arranged on the substrate, the adiabatic coupler mainly comprises a fixed tapered waveguide (2) and a movable tapered waveguide (3), the fixed tapered waveguide (2) is kept fixed, the fixed tapered waveguide (2) and the movable tapered waveguide (3) are arranged in parallel along the moving direction perpendicular to the mechanical driving structure, both ends of the fixed tapered waveguide (2) are connected with bent waveguides, both ends of the movable tapered waveguide (3) are connected with the mechanical driving structure through a pair of multimode interference cross waveguide structures, and the mechanical driving structure drives the movable tapered waveguide (3) to move close to or far away from the fixed tapered waveguide (2).
2. An electrostatic comb driven adiabatic coupler based integrated waveguide MEMS optical switch as defined by claim 1, wherein:
each end of two ends of the movable tapered waveguide (3) is sequentially connected with a first bent waveguide in a shape of a Chinese character 'hui', a cross-shaped multimode interference crossed waveguide and a second bent waveguide in a shape of a Chinese character 'hui', the cross-shaped multimode interference crossed waveguide is composed of a longer waveguide and a shorter waveguide, the longer waveguide is composed of a pair of symmetrical mode evolution tapered waveguides and a long multimode wide waveguide, the wide ends of the pair of mode evolution tapered waveguides are respectively connected with two ends of the long multimode wide waveguide, and the narrow ends of the pair of mode evolution tapered waveguides are respectively connected with the two bent waveguides in a shape of a Chinese character 'hui'; the shorter one is a short multi-mode width waveguide, and one end of the short multi-mode width waveguide is connected with the mechanical driving structure.
3. The electrostatic comb driven adiabatic coupler based integrated waveguide MEMS optical switch of claim 1, wherein:
the fixed conical waveguide (2) and the movable conical waveguide (3) are identical in structure and are both conical waveguides with gradually changed widths, the fixed conical waveguide (2) and the movable conical waveguide (3) are identical in length but opposite in width gradually changing direction, the width of an input end of the fixed conical waveguide (2) is identical to that of an output end of the movable conical waveguide (3), the width of an output end of the fixed conical waveguide (2) is identical to that of an input end of the movable conical waveguide (3), and the size of a gap between the fixed conical waveguide (2) and the movable conical waveguide (3) is always kept unchanged.
4. The electrostatic comb driven adiabatic coupler based integrated waveguide MEMS optical switch of claim 1, wherein:
the mechanical driving structure comprises an electrostatic comb driver consisting of a fixed electrostatic comb (6) and a movable electrostatic comb (7), a T-shaped transmission structure (4) and three groups of fixed island and spring structures (1, 5 and 8);
the T-shaped transmission structure (4) is suspended in the substrate (10) and arranged, the top rod part of the T-shaped transmission structure (4) is parallel to the movable conical waveguide (3), the bottom rod part of the T-shaped transmission structure (4) is vertical to the movable conical waveguide (3), the bottom rod part of the T-shaped transmission structure (4) is sequentially provided with a first group of fixed islands and spring structures (1), a second group of fixed islands and spring structures (5) and a third group of fixed islands and spring structures (8) along the length direction from one end close to the movable conical waveguide (3), and the first group of fixed islands and spring structures (1), the second group of fixed islands and spring structures (5), the third group of fixed islands and spring structures (8) are all connected with the T-shaped transmission structure (4);
electrostatic comb drivers are arranged on two sides of a T-shaped transmission structure (4) between the second group of fixed islands and the spring structure (5) and between the third group of fixed islands and the spring structure (8), each electrostatic comb driver comprises a pair of fixed electrostatic combs (6) and a pair of movable electrostatic combs (7), each fixed electrostatic comb (6) is fixed on a substrate (10), and the pair of fixed electrostatic combs (6) are symmetrically distributed on two sides of the length direction of a bottom rod part of the T-shaped transmission structure (4) and are not connected with the bottom rod part of the T-shaped transmission structure (4); the movable electrostatic combs (7) are suspended on the substrate (10) and are symmetrically distributed on two sides of the length direction of the bottom rod part of the T-shaped transmission structure (4), and one end of each movable electrostatic comb (7) close to the bottom rod part of the T-shaped transmission structure (4) is fixedly connected with the side edge of the bottom rod part; the comb teeth of the fixed electrostatic comb (6) and the movable electrostatic comb (7) are distributed in an opposite and staggered penetrating way.
5. The electrostatic comb driven adiabatic coupler based integrated waveguide MEMS optical switch of claim 4, wherein:
the first group of fixed island and spring structures (1) mainly comprise a fixed island and a pair of half-folded springs, the fixed island is fixed on a substrate (10), two ends of the fixed island are connected with one end, close to the movable conical waveguide (3), of the bottom rod part of the T-shaped transmission structure (4) through the half-folded springs, and the half-folded springs are suspended on the substrate (10) to be arranged.
6. The electrostatic comb driven adiabatic coupler based integrated waveguide MEMS optical switch of claim 5, wherein:
the semi-folding spring is of a suspended structure and comprises a spring handle and two beams which are connected to two ends of the spring handle and vertical to the length direction of the spring handle, wherein the two beams extend towards the same side far away from the spring handle and are respectively connected with the fixed island and the T-shaped transmission structure (4).
7. The electrostatic comb driven adiabatic coupler based integrated waveguide MEMS optical switch of claim 4, wherein:
the second group of fixed islands and the spring structures (5) have the same structure as the third group of fixed islands and the spring structures (8) and are respectively composed of four fixed islands and a pair of folding springs; the fixed islands are fixed on the substrate (10), two fixed islands are taken as one group in the four fixed islands, one group of fixed islands are arranged on the same side of the bottom rod part of the T-shaped transmission structure (4), two groups of fixed islands are respectively arranged on two sides of the bottom rod part of the T-shaped transmission structure (4), the two fixed islands on the same side are connected with the side part of the bottom rod part of the T-shaped transmission structure (4) through a folding spring, and the folding spring is suspended in the substrate (10) to be arranged.
8. The electrostatic comb driven adiabatic coupler based integrated waveguide MEMS optical switch of claim 7, wherein:
folding spring be unsettled structure, including the spring handle, connect at the spring handle both ends and with two stub beams of spring handle length direction vertically and connect in the spring handle middle part and constitute with two long roof beams of spring handle length direction vertically, the one end of two stub beams is connected to the both ends of spring handle respectively, the other end that the spring handle was kept away from to two stub beams links to each other with two fixed islands that are located T shape transmission structure (4) sill bar portion homonymy respectively, the one end of two long roof beams is connected to two places at spring handle middle part respectively, the other end that the spring handle was kept away from to two long roof beams links to each other with two places that are located T shape transmission structure (4) sill bar portion homonymy respectively.
9. The electrostatic comb driven adiabatic coupler based integrated waveguide MEMS optical switch of claim 4, wherein:
the pair of fixed electrostatic combs (6) is connected with an external circuit, and the light switch is regulated and controlled by applying or removing voltage to the pair of fixed electrostatic combs (6).
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211240812.4A CN115826143A (en) | 2022-10-11 | 2022-10-11 | Electrostatic comb driven integrated waveguide MEMS optical switch based on adiabatic coupler |
| PCT/CN2023/118315 WO2024078237A1 (en) | 2022-10-11 | 2023-09-12 | Electrostatic-comb-driven integrated waveguide mems optical switch based on adiabatic coupler |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211240812.4A CN115826143A (en) | 2022-10-11 | 2022-10-11 | Electrostatic comb driven integrated waveguide MEMS optical switch based on adiabatic coupler |
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|---|---|
| CN (1) | CN115826143A (en) |
| WO (1) | WO2024078237A1 (en) |
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