A broadband continuously tunable integrated optical waveguide delay line

Abstract

The application relates to the field of integrated optics and discloses a broadband continuously adjustable integrated optical waveguide delay line, which comprises a micro-ring structure and an N bit switch type optical delay line; wherein the micro-ring structure comprises an input straight waveguide, one adjustable coupler and one thermo-optic phase shifter; the N bit switch type optical delay line comprises an Nth optical switch, an N-1th optical switch, an N-2th optical switch, an Mth optical switch, an M-1th optical switch, an M-2th optical switch, an M-0th optical switch arranged in sequence, N delay line units arranged between the optical switches and an output straight waveguide. The broadband continuously adjustable integrated optical waveguide delay line provided by the application adopts the micro-ring structure and the N bit switch type optical delay line, realizes the performances of large optical bandwidth, low delay fluctuation, continuously adjustable delay and large delay adjustment range, solves the problems of the limitation of the bandwidth of a traditional phased array radar electric signal and beam deflection, simultaneously reduces the requirement of optical phased array radar for the stability of a working optical wavelength, and improves the beam scanning angle resolution.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of integrated optics, and particularly relates to a wideband continuous adjustable integrated optical waveguide delay line. BACKGROUND

[0002] An optical delay line is an important component in the fields of optical computing, optical communication and optical interconnection. According to the size of the device, it can be divided into an integrated optical delay line and a fiber delay line. Compared with the fiber delay line, the integrated waveguide optical delay line has the advantages of high precision, small loss, small area, stable performance and the like.

[0003] According to the delay step, the integrated optical delay line can be divided into a discrete integrated optical delay line and a continuous adjustable integrated optical delay line. The discrete integrated optical delay line mainly relies on adjusting the on-state and cross-state of an optical switch to select the length of the optical through waveguide. The advantage of this scheme is that the bandwidth is large, and there is almost no delay fluctuation near the working wavelength. However, it can only realize discrete delay adjustment, and when applied to an optical phased array antenna, the beam scanning angle resolution of the optical phased array antenna is easily limited by the delay step. Based on this, researchers designed a continuous adjustable integrated optical delay line using a micro-ring and the like. However, the micro-ring is easily limited by the delay bandwidth product, and a large delay adjustment range and a large bandwidth are often incompatible. Since the above delay lines cannot simultaneously realize the effects of a large bandwidth, continuous delay adjustment and a large delay adjustment range, there is an urgent need to design a wideband continuous adjustable integrated optical waveguide delay line with a large delay range. SUMMARY

[0004] The present application belongs to the field of integrated optics, and particularly relates to a wideband continuous adjustable integrated optical waveguide delay line. The integrated optical waveguide delay line has the advantages of a large optical bandwidth, low delay fluctuation, continuous delay adjustment and a large delay adjustment range. It not only solves the problems of the limitation of the bandwidth of a traditional phased array radar electrical signal and beam deflection, but also reduces the requirement of the optical phased array radar for the stability of the working optical wavelength and improves the beam scanning angle resolution.

[0005] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0006] A wideband continuous adjustable integrated optical waveguide delay line, comprising a micro-ring structure 11 and an N bit switch type optical delay line 12.

[0007] The micro-ring structure comprises an input straight waveguide, one adjustable coupler 111 and one thermo-optic phase shifter 112; wherein the input lower port of the adjustable coupler 111 is connected to the input straight waveguide, the output upper port is connected to one end of the thermo-optic phase shifter through a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, and the other end of the thermo-optic phase shifter is connected to the input upper port of the adjustable coupler through a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, forming a micro-ring structure;

[0008] The N-bit switch type optical delay line 12 comprises N+1 optical switches (Nth optical switch, N-1th optical switch, N-2th optical switch, …, 1st optical switch, 0th optical switch) arranged in sequence, N delay line units between the optical switches, and an output straight waveguide; the delay line unit comprises a reference delay line and a delay line; the input lower port of the Nth optical switch is connected to the output lower port of the adjustable coupler;

[0009] The output upper port of the nth optical switch is connected to the input lower port of the n-1th optical switch through a reference delay line formed by a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, and a straight waveguide; the output lower port of the nth optical switch is connected to the input upper port of the n-1th optical switch through a delay line formed by “straight waveguide / 180-degree circular arc waveguide / (straight waveguide / 180-degree circular arc waveguide)m / straight waveguide”, and m is a positive integer, n=1, 2, …, N;

[0010] By adjusting m, the delay time between the Nth optical switch and the N-1th optical switch, between the N-1th optical switch and the N-2th optical switch, …, between the 2nd optical switch and the 1st optical switch, and between the 1st optical switch and the 0th optical switch is 2 (N-1) Δτ, 2 (N-2) Δτ, …, 2Δτ, Δτ; wherein Δτ=n g ΔL / c, n g n is the group refractive index of the waveguide, c is the speed of light, and ΔL is the length difference of the delay line and the reference delay line between the 1st optical switch and the 0th optical switch;

[0011] By adjusting the coupling coefficient of the adjustable coupler, the delay time of the micro-ring structure changes in the range of 0-Δτ.

[0012] Further, when N is an odd number, the output upper port of the 0th optical switch is connected to the output straight waveguide through a straight waveguide, a 180-degree circular arc waveguide, and a straight waveguide; when N is an even number, the output upper port of the 0th optical switch is directly connected to the output straight waveguide.

[0013] Further, the optical switch is an MZI (Mach-Zehnder) optical switch.

[0014] Further, the adjustable coupler is a MZI (Mach-Zehnder) structure.

[0015] The application provides a broadband continuous adjustable integrated optical waveguide delay line, which realizes a wideband continuous delay adjustment function through a micro-ring structure 11, and an N bit switch type optical delay line 12 connected with the micro-ring, so that the delay adjustment range is increased. An MZI structure is used as an adjustable coupler at a coupling point of the micro-ring structure, and the delay of the micro-ring is adjusted by adjusting the coupling coefficient of the adjustable coupler. The equivalent coupling coefficient of the micro-ring depends on the phase difference between two arms of the MZI, and the phase difference between the two arms can be changed by tuning a phase shift arm, so that the optical power of the two output ports of the adjustable coupler is redistributed, the condition of the optical coupling into the micro-ring is changed, and the delay of the optical wave through the micro-ring is continuously adjusted. A thermo-optic phase shifter is arranged in the micro-ring structure, so that the working wavelength is stabilized at the anti-resonance of the micro-ring, and the performance of small delay jitter and large optical bandwidth is realized. For the N bit switch type optical delay line part, unlike the existing mode in which optical delay units with Δτ, 2Δτ, 4Δτ,..., 2 N-1 Δτ delay are sequentially arranged from the near input end, the application sequentially arranges optical delay units with 2 N-1 Δτ,..., 4Δτ, 2Δτ, Δτ delay from the near input end, so that when the delay amount changes from small to large, only the optical switch closest to the output port needs to be changed, and the previous stage switch is not affected. In the optical waveguide delay line of the application, the relative delay amount Δt1 of the micro-ring structure is 0-Δτ, and the relative delay amount Δt2 of the N bit switch type optical delay line is 0-(2 N -1)Δτ, so the relative delay amount Δt of the optical waveguide delay line is Δt1+Δt2, and therefore the optical waveguide delay line of the application can realize continuous adjustment of the delay range of 0-2 N Δτ.

[0016] Compared with the prior art, the application has the following beneficial effects:

[0017] The application provides a broadband continuous adjustable integrated optical waveguide delay line, which adopts a micro-ring structure and an N bit switch type optical delay line, realizes the performances of large optical bandwidth, low delay fluctuation, continuous delay adjustment, and large delay adjustment range, solves the problems of the limitation of the bandwidth of the traditional phased array radar electrical signal and the beam deflection, reduces the requirement of the optical phased array radar for the stability of the working optical wavelength, and improves the beam scanning angle resolution. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Fig. 1 is a structural schematic diagram of a broadband continuous adjustable integrated optical waveguide delay line provided by the application;

[0019] Figure 2 A structure schematic diagram of a broadband continuously adjustable integrated optical waveguide delay line provided by the embodiment is shown in the figure.

[0020] Figure 3 A structure schematic diagram of the MZI. DETAILED DESCRIPTION

[0021] The technical solutions of the present application are described in detail below with reference to the accompanying drawings and embodiments.

[0022] Embodiment

[0023] A broadband continuously adjustable integrated optical waveguide delay line provided by the embodiment is shown in the figure. Figure 2 N=2. It includes a micro-ring structure and a 2bit switch type optical delay line; the micro-ring structure includes an input straight waveguide, one adjustable coupler and one thermo-optic phase shifter; wherein the input lower port of the adjustable coupler is connected to the input straight waveguide, the output upper port is connected to one end of the thermo-optic phase shifter through a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, and the other end of the thermo-optic phase shifter is connected to the input upper port of the adjustable coupler through a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, and a straight waveguide, forming a micro-ring structure.

[0024] The 2bit switch type optical delay line includes a 2nd optical switch, a 1st optical switch, and a 0th optical switch arranged in sequence, two delay line units between the optical switches, and an output straight waveguide; the delay line unit includes a reference delay line and a delay line; the input lower port of the 2nd optical switch is connected to the output lower port of the adjustable coupler, the output upper port of the 2nd optical switch is connected to the input lower port of the 1st optical switch through a reference delay line formed by a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, and a straight waveguide, and the output lower port of the 2nd optical switch is connected to the input upper port of the 1st optical switch through a delay line formed by “straight waveguide / 180-degree circular arc waveguide / (straight waveguide / 180-degree circular arc waveguide)4 / straight waveguide”; the output upper port of the 1st optical switch is connected to the input lower port of the 0th optical switch through a reference delay line formed by a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, and a straight waveguide, the output lower port of the 1st optical switch is connected to the input upper port of the 0th optical switch through a delay line formed by “straight waveguide / 180-degree circular arc waveguide / (straight waveguide / 180-degree circular arc waveguide)2 / straight waveguide”, and the output upper port of the 0th optical switch is directly connected to the output straight waveguide.

[0025] Wherein, the delay time between the 2nd optical switch and the 1st optical switch is 2Δτ, and the delay time between the 1st optical switch and the 0th optical switch is Δτ; Δτ=n g ΔL / c, n gLet be the group refractive index of the waveguide, c be the speed of light, and ΔL be the length difference between the delay line and the reference delay line between the first and zeroth optical switches.

[0026] By adjusting the coupling coefficient of the adjustable coupler, the delay of the micro-ring structure can be varied within the range of 0 to Δτ.

[0027] This embodiment provides a broadband continuously adjustable integrated optical waveguide delay line. It achieves broadband continuously adjustable delay functionality through a micro-ring structure, and an N-bit switch-type optical delay line connected to the micro-ring increases the delay adjustment range. A 2×2 symmetrical MZI structure is used as an adjustable coupler at the coupling point of the micro-ring structure. The delay of the micro-ring is adjusted by regulating the coupling coefficient of the adjustable coupler. The equivalent coupling coefficient of the micro-ring depends on the phase difference between the two arms of the MZI. By tuning the phase-shifting arms, the phase difference between the two arms can be varied between 0 and π, thus achieving a redistribution of optical power at the two output ports of the adjustable coupler and changing the way light couples into the micro-ring. For light at the anti-resonance point of the micro-ring, its relative delay through the micro-ring changes from Δτ to 0, thereby achieving continuous delay adjustment. A thermo-optical phase shifter is set in the micro-ring structure to stabilize the operating wavelength at the anti-resonance point of the micro-ring, achieving performance with low delay jitter and large optical bandwidth. For the N-bit switch-type optical delay line section, the delay amount can be adjusted by switching the through state and cross state of the optical switch to select the length of the delay line through which light passes. The delay amount can be 0, Δτ, 2Δτ, or 3Δτ. In the embodiment, the relative delay amount Δt1 of the micro-ring structure is 0 to Δτ, and the relative delay amount Δt2 of the 2-bit switch-type optical delay line is 0 to 3Δτ, with a delay step of Δτ. Therefore, the optical waveguide delay line in this embodiment can achieve continuous adjustment of the delay range from 0 to 4Δτ.

[0028] Both the optical switch and the adjustable coupler adopt an MZI structure, such as... Figure 3 As shown, this is a 2×2 symmetrical MZI structure, including an S-bend waveguide, a multimode interferometer (MMI), interferometer arms, electrodes, and an air slot. Light enters from the upper input port. When no voltage is applied to the electrodes on the interferometer arms, the two beams interfere destructively at the upper output port, while the two beams interfere constructively at the lower output port, resulting in all light being output from the lower output port – this is the crossover state of the optical switch. When power is applied to the electrodes on the interferometer arms, a phase change in the π phase occurs through the thermo-optical effect. At the output, the two beams interfere constructively at the upper output port, while the two beams interfere destructively at the lower output port, resulting in all light being output from the upper output port – this is the straight-through state of the optical switch.

Claims

1. A wideband continuously tunable integrated optical waveguide delay line, characterized by, The micro-ring structure (11) and an N-bit switch type optical delay line (12) are included. The micro-ring structure includes an input straight waveguide, an adjustable coupler (111) and a thermo-optic phase shifter (112); wherein the input lower port of the adjustable coupler is connected to the input straight waveguide, the output upper port is connected to one end of the thermo-optic phase shifter through a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, and the other end of the thermo-optic phase shifter is connected to the input upper port of the adjustable coupler through a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide; The N-bit switch type optical delay line includes an Nth optical switch, an N-1th optical switch, an N-2th optical switch, …, a 1st optical switch, a 0th optical switch, a delay line unit between the optical switches, and an output straight waveguide; the delay line unit includes a reference delay line and a delay line; the input lower port of the Nth optical switch is connected to the output lower port of the adjustable coupler; The output upper port of the Nth optical switch is connected to the input lower port of the N-1th optical switch through a reference delay line formed by a straight waveguide, a 90-degree circular arc waveguide, a straight waveguide, a 90-degree circular arc waveguide, and a straight waveguide; the output lower port of the Nth optical switch is connected to the input upper port of the N-1th optical switch through a delay line formed by "straight waveguide / 180-degree circular arc waveguide / (straight waveguide / 180-degree circular arc waveguide)m / straight waveguide", m is a positive integer, and n=1, 2, …N; By adjusting m, the delay amount between the Nth optical switch and the N-1th optical switch, between the N-1th optical switch and the N-2th optical switch, between the 2th optical switch and the 1th optical switch, between the 1th optical switch and the 0th optical switch is 2 (N-1) Δτ, 2 (N-2) Δτ,..., 2Δτ, Δτ; wherein Δτ = n g ΔL / c, n g is the group refractive index of the waveguide, c is the speed of light, and ΔL is the length difference of the delay line and the reference delay line between the 1th optical switch and the 0th optical switch. By adjusting the coupling coefficient of the adjustable coupler, the delay of the micro-ring structure is changed in the range of 0-Δτ.

2. The wideband continuously tunable integrated optical waveguide delay line according to claim 1, characterized in that, When N is odd, the output upper port of the 0th optical switch is connected to the output straight waveguide through a straight waveguide, a 180-degree circular arc waveguide, and a straight waveguide; when N is even, the output upper port of the 0th optical switch is directly connected to the output straight waveguide.

3. The wideband continuously tunable integrated optical waveguide delay line according to claim 1, wherein, The optical switch and the adjustable coupler are in MZI structure.

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