Optical switch based on reverse Fano coupling micro-ring
Technical Field
The invention belongs to the field of integrated photonic devices, and particularly relates to an optical switch based on a reverse Fano coupling micro-ring.
Background
With the development of the times, the demand for communication capacity is continuously increasing, and higher demands are also made on the performance of the optical control module in the optical network. The optical switch is an important basic component unit in the optical control module, and the performance of the optical switch can often directly affect the working performance of the whole optical module. The existing optical switch mainly has two structures, one is based on a Mach-Zehnder interferometer structure, and the other is based on a coupling micro-ring structure. An optical switch based on a mach-zehnder interferometer structure has an ultra-high bandwidth, but has a great limitation in practical application due to a large volume and the need for high power consumption to achieve a large phase shift. The switch based on the micro-ring structure has small volume, easy integration, low power consumption and narrower bandwidth. Researchers now propose to increase bandwidth by cascading multiple microrings, but at the same time increase device size and power consumption. There is a need to develop an optical switch device that can meet the requirements of small size, large bandwidth, low insertion loss, and low power consumption.
Disclosure of Invention
Aiming at the defects of the related art, the invention aims to provide an optical switch based on a reverse Fano coupling micro-ring, and aims to solve the problems of narrow bandwidth and high power consumption of the existing optical switch.
In order to achieve the above object, the present invention provides an optical switch based on a reverse Fano coupling micro-ring, comprising a first annular waveguide, a first straight waveguide, a second annular waveguide and a second straight waveguide; the first straight waveguide comprises a first input end and a first output end, and the second straight waveguide comprises a second input end and a second output end;
the first straight waveguide is positioned between the first annular waveguide and the second annular waveguide, and the first annular waveguide, the first straight waveguide and the second annular waveguide are coupled with each other in pairs;
the second straight waveguide and the first straight waveguide are positioned on two sides of the second annular waveguide, and the second straight waveguide is coupled with the second annular waveguide;
light enters the first straight waveguide from the first input end, one part of the light enters the first annular waveguide and the second annular waveguide through coupling, and the other part of the light is output from the first output end; light in the first annular waveguide and the second annular waveguide is also coupled with each other to enter the other annular waveguide from one annular waveguide; and the light in the second annular waveguide is coupled into the second straight waveguide and then output from the second output end.
Further, the spectral line output from the first output end or the second output end is an inverse Fano spectral line.
Further, when the widths of the first straight waveguide and the second straight waveguide are changed, left and right reverse Fano spectral lines are output.
Further, when the refractive index of the second annular waveguide changes, switching of the switch state is generated at both the first output end and the second output end.
Further, simultaneously changing the refractive index of the first annular waveguide and the second annular waveguide produces switching of the switch state at both the first output terminal and the second output terminal.
Further, the refractive index of the first and second annular waveguides may be changed by electro-optical, thermo-optical, all-optical, or acousto-optical effects.
Further, the first annular waveguide, the second annular waveguide, the first straight waveguide and the second straight waveguide are made of silicon on insulator, lithium niobate, silicon nitride, indium phosphide or gallium arsenide.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, two annular waveguides are directly coupled, and by utilizing the characteristics of steepness of reverse Fano spectral lines and wide bandwidth of Lorentz spectral lines, the output spectral lines have high extinction ratio, large bandwidth and steepness, and the transmittance can be changed rapidly, so that the bandwidth of the optical switch is large, the movement of resonance wavelength required by the switch is small, and the power consumption of the switch is low.
(2) The reverse Fano spectral line is realized based on the two coupled micro-rings, and when the direct coupling coefficients of the two annular waveguides are larger than 0 and the resonant wavelength of the first annular waveguide is slightly smaller than that of the second annular waveguide, a left reverse Fano spectral line appears; and when the direct coupling coefficients of the two annular waveguides are less than 0 and the resonant wavelength of the first annular waveguide is slightly longer than that of the second annular waveguide, a right reverse Fano spectral line appears.
(3) The optical switch is realized based on the coupling micro-ring, and the device has small volume, compact structure and convenient integration. And by changing the refractive index to slightly shift the resonance wavelength, the spectral line changes or shifts, on-state or off-state switching is realized, and the loss of the on-state operation is very low, namely the insertion loss is low when the on-state switching device is applied to a system.
Drawings
FIG. 1 is a schematic diagram of the structure of a coupling micro-ring of the present invention;
FIG. 2 is a left-reversed or right-reversed Fano spectrogram of the present invention by varying the width of the straight waveguide;
FIG. 3 is a diagram of an optical switch implemented by the present invention by changing the refractive index of a first annular waveguide;
FIG. 4 shows an optical switch implemented by the present invention by simultaneously changing the refractive indices of two annular waveguides;
fig. 5 is an eye diagram of the present invention for transmission in an optical switch using high speed signals.
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.
The technical scheme adopted by the invention is as follows:
as shown in fig. 1, the present invention includes a first annular waveguide 1, a second annular waveguide 2, a first straight waveguide 3, and a second straight waveguide 4. When light enters the first straight waveguide 3 from the first input end 7, a part of the light is coupled into the first annular waveguide 1 and the second annular waveguide 2 through the coupling region 5, and another part of the light is output from the first output end 8 through the coupling region 5. The light in the two ring waveguides 1 and 2 will also be directly coupled into each other into the other ring waveguide. Light in the second annular waveguide 2 enters the second straight waveguide 4 through the coupling region 6 and is output through the second output end 9.
And establishing a model based on a time coupling mode theory to analyze the light field of the structure. By 1/taue1、1/τe2、1/τe3Describing the coupling coefficients between a first annular waveguide and a first straight waveguide, a second annular waveguide and a first straight waveguide, and a second annular waveguide and a second straight waveguide, the direct coupling coefficient between the first annular waveguide and the second annular waveguide being expressed as mu; intrinsic loss 1/tau of the first annular waveguide and the second annular waveguideo1、1/τo2Denotes λ1And λ2The resonance wavelengths of the two annular waveguides.
Under steady state conditions, the transmission coefficients of the first output terminal 8 and the second output terminal 9 are respectively
Wherein, γ1=i(2πc/λ)-i(2πc/λ1)-1/τo1-1/τe1,γ2=i(2πc/λ)-i(2πc/λ2)-1/τo2-1/τe3-1/τe2。
In this embodiment, a silicon-on-insulator (SOI) based strip optical waveguide is selected, the waveguide thickness is 220nm, the lower cladding substrate material is 2 μm thick silica, and the upper cladding is 1 μm thick silica. And manufacturing a hot electrode above the two annular waveguides, and changing the power of the hot electrode to change the refractive index of the annular waveguides. The radiuses of the two annular waveguides are both 10 mu m, the distances between the annular waveguides and the straight waveguides are both 130nm, the waveguide widths of the first annular waveguide 1, the second annular waveguide 2, the first straight waveguide 3 and the second straight waveguide 4 are all 420nm, and the output spectral line is a left-reverse Fano. Obtaining intrinsic loss 1/tau of two annular waveguides by theoretical fittingo1、1/τo2Are respectively 1.3 multiplied by 1010rad/s and 3X 1010rad/s, coupling coefficient 1/τe1Is 1.6X 1011rad/s,1/τe2And 1/taue3Are all 2.2 × 1011rad/s, direct coupling coefficient mu of the two ring waveguides is 4.1 × 1011rad/s, resonant wavelength λ of the first annular waveguide11550.85nm, the resonance wavelength λ of the second annular waveguide2At 1551.65nm, the spectral lines at the first output end and the second output end both have a steep left-side variation and a gentle right-side variation, as shown in (a) (c) of fig. 2, the solid line is an experimental test curve, and the dotted line is a theoretical fitting curve. When the waveguide width of the first straight waveguide 3 and the second straight waveguide 4 is changed to 310nm, the output spectral line is right-reversed Fano. Two rings are obtained by theoretical fittingIntrinsic loss 1/tau of waveguideo1、1/τo2Are all 5 × 109rad/s, coupling coefficient 1/τe1Is 3.5 multiplied by 1011rad/s,1/τe2And 1/taue3Are all 4 × 1011rad/s, direct coupling coefficient μ of two ring waveguides-3.2 × 1011rad/s, resonant wavelength λ of the first annular waveguide11561.51nm, the resonance wavelength λ of the second annular waveguide2At 1560.38nm, the spectral lines at the first output end and the second output end both have gentle left-side variation and steep right-side variation, as shown in (b) (d) of fig. 2, the solid line is an experimental test curve, and the dotted line is a theoretical fitting curve. Therefore, two mirror symmetric left and right reverse Fano spectral lines can be obtained by changing the coupling state of the coupling region 5 by changing the width of the straight waveguide.
The resonant wavelength of the second annular waveguide 2 is kept unchanged, the refractive index of the first annular waveguide 1 is changed, the resonant wavelength is shifted, the shape of the reverse Fano spectral line of the output end is changed, the transmittance of the first output end and the transmittance of the second output end are changed, and the optical switch effect is achieved.
Or the refractive indexes of the two annular waveguides are changed simultaneously to shift the resonant wavelength of the two annular waveguides, so that the spectral lines at the output ends horizontally shift, the transmittances at the first output end and the second output end are changed, and the optical switch effect is achieved.
Specific embodiments of the optical switch device based on the right-reverse Fano coupling micro-ring are given below.
The spectral lines observed at the first output terminal and the second output terminal are right-inverted Fano spectral lines, respectively as shown in fig. 3 (a) (b), it can be seen that the 3dB bandwidth of the output spectral line of the first output terminal 8 is 280GHz, the steepness of the right-inverted Fano spectral line is 65dB/nm, the 3dB bandwidth of the transmission spectral line of the second output terminal 9 is 270GHz, and the steepness of the right-inverted Fano spectral line is 72 dB/nm. Keeping the resonant wavelength of the second annular waveguide 2 unchanged, increasing the power of the hot electrode above the first annular waveguide by 4.6mW, moving the resonant wavelength to the left by 1.25nm, changing the output spectral line of the first output end 8, as shown in (c) of FIG. 3, changing the transmittance of the dotted line corresponding to the wavelength from-28.5 dB to-0.2 dB, and realizing the change from the off state to the on state; the change in the transmission line of the second output terminal 9 is shown in (d) of fig. 3, and it can be seen that the transmittance of the dotted line for the wavelength changes from-1.2 dB to-25.7 dB, and the change from the on-state to the off-state is achieved. When the switch works in an on state, the insertion loss of the first output end 8 is 0.2dB, and the insertion loss of the second output end 9 is 1.2 dB.
Or the power of the hot electrode above the two annular waveguides is increased by 4.6mW simultaneously, so that the spectral line is horizontally moved and the shape is unchanged, as shown in FIG. 4, the 3dB bandwidth of the transmission spectral line is 250GHz, and the steepness of the right reverse Fano spectral line is 28 dB/nm. The change of the transmission line of the first output terminal 8 is shown in fig. 4 (a) (c), and it can be seen that the transmittance of the corresponding wavelength at the dotted line is changed from-10.7 dB to-0.7 dB, and the change from the off state to the on state is realized; the change in the transmission line of the second output terminal 9 is shown in fig. 4 (b) (d), and it can be seen that the transmittance at the dotted line for the corresponding wavelength changes from-0.65 dB to-22.1 dB, effecting a change from the on-to-off state. Fig. 5 shows the eye diagrams for high bandwidth transmission using 80Gbit/s, 160Gbit/s, 240Gbit/s, 320Gbit/s gaussian non-return-to-zero pseudo-random signal analog switches, with the left eye diagram for output from the second output terminal 9 and the right eye diagram for output from the first output terminal 8. It can be seen from the figure that the signal rate is very good up to the quality of the 240Gbit/s eye diagram, and that the signal quality starts to deteriorate significantly already at 320 Gbit/s. When the switch is operated in the on state, the insertion loss of the first output end 8 and the second output end 9 is 0.7dB and 0.65dB respectively.
The optical switch is realized by utilizing a coupling double-ring structure, and the optical switch is simple in structure and easy to integrate; the bandwidth of the optical switch can reach 250GHz by utilizing a reverse Fano spectral line; by utilizing the steep characteristic of the spectral line, the optical switch with low power consumption and low crosstalk is realized, and a solution is provided for the practical application of the reverse Fano in the field of optical switches.
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.