An on-chip optical waveguide phase deviation correction structure, MZI and preparation method

Abstract

The present invention discloses an on-chip optical waveguide phase deviation correction structure, in which optical glue is used to fill the refractive index correction area to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure; the present invention also provides a method for preparing the phase deviation correction structure, an on-chip MZI, and a method for preparing the on-chip MZI. The optical waveguide phase deviation caused by wafer non-uniformity and manufacturing deviation is corrected, that is, the optical waveguide phase deviation is corrected without increasing circuit complexity, introducing additional power consumption, and affecting the performance of other on-chip devices.

Description

Technical Field

[0001] The present invention relates to the technical field of optical chip waveguide phase deviation correction, and in particular to an on-chip optical waveguide phase deviation correction structure, MZI and a preparation method thereof. Background Art

[0002] During the preparation of optical chips, the non-uniformity of wafer thickness and the dimensional deviation caused by preparation will cause the effective refractive index of the optical waveguide structure to differ from the designed value, thereby causing the optical waveguide phase deviation and affecting the device performance.

[0003] In the prior art, the effective refractive index deviation is adjusted and corrected by adding a thermal resistor and an electrode near the optical waveguide and applying an external voltage to increase the temperature of the optical waveguide, or by performing P / N type doping on the optical waveguide to form a PN junction and applying an external voltage to change the carrier concentration in the PN junction region of the optical waveguide. The technical problems of the above two methods are that both methods will increase the circuit pins of the optoelectronic chip, thereby increasing the complexity of the optoelectronic chip control circuit, and because of active control, the device will introduce additional energy consumption when working, and the current generated by the thermal resistor and the PN junction will cause the device to generate heat, thereby affecting other devices on the chip. Summary of the invention

[0004] To solve the above technical problems, the present invention provides an on-chip optical waveguide phase deviation correction structure, MZI and preparation method. In order to have a basic understanding of some aspects of the disclosed embodiments, a simple summary is given below. This summary is not a general review, nor is it intended to identify key / important components or describe the scope of protection of these embodiments. Its only purpose is to present some concepts in a simple form as a preface to the detailed description that follows.

[0005] The present invention adopts the following technical solution:

[0006] The present invention provides an on-chip optical waveguide phase deviation correction structure, in which optical glue is used to fill the refractive index correction area to form the phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure, wherein the refractive index correction area is a recessed space formed by removing part of the upper cladding layer on the basis of the original optical waveguide structure.

[0007] Furthermore, the refractive index correction area is located above the original optical waveguide structure, or located above and to the side of the original optical waveguide structure.

[0008] The present invention also provides a method for preparing an on-chip optical waveguide phase deviation correction structure, comprising: removing part of the upper cladding layer on the basis of the original optical waveguide structure to form a refractive index correction zone; filling optical glue in the refractive index correction zone to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure.

[0009] Furthermore, the refractive index correction zone is a recessed space formed by removing a portion of the upper cladding layer above the original optical waveguide structure, or is a recessed space formed by removing a portion of the upper cladding layer above and to the side of the original optical waveguide structure.

[0010] The present invention also provides an on-chip MZI, comprising the phase deviation correction structure, and an effective refractive index correction amount Δn obtained by filling with optical glue. eff The length L' of the refractive index correction zone 1 Satisfy -Δn eff ·L' 1 =mΔλ; where

[0011] Δn eff =n' eff -n eff , n' eff The effective refractive index of the optical waveguide in the refractive index correction zone after replacing part of the original upper cladding with an optical adhesive with a refractive index of n, n eff is the effective refractive index of the originally designed MZI optical waveguide; m is the interference order;

[0012] Δλ is the wavelength offset, Δλ=λ'-λ, λ is the originally designed coherent enhancement wavelength, and λ' is the actually tested coherent enhancement wavelength.

[0013] The present invention also provides a method for preparing an on-chip MZI, comprising: removing part of the upper cladding and filling optical glue on the basis of the original optical waveguide structure of the phase shift arm to be corrected of the MZI to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure.

[0014] Furthermore, the process of removing part of the upper cladding layer and filling the optical glue includes:

[0015] The coherent enhancement wavelength λ' of the originally designed MZI is tested, and the wavelength shift Δλ=λ'-λ is calculated, where λ is the coherent enhancement wavelength of the original design;

[0016] Determine the optical glue with a suitable refractive index n according to the wavelength offset Δλ. If Δλ>0, the refractive index of the optical glue to be filled is lower than that of the original optical glue of the upper cladding. If Δλ<0, the refractive index of the optical glue to be filled is higher than that of the original optical glue of the upper cladding.

[0017] The effective refractive index n' of the optical waveguide in the refractive index correction zone after replacing part of the original upper cladding with an optical glue with a refractive index of n is obtained by simulation. eff , and the effective refractive index n of the original designed MZI optical waveguide eff , and calculate the effective refractive index correction Δn obtained by filling with optical glue eff =n' eff -n eff ;

[0018] According to -Δn eff ·L' 1 =mΔλ to solve for the length L' of the refractive index correction zone 1 , m is the interference order;

[0019] Part of the original upper cladding layer is removed at the phase shift arm of the prepared MZI to etch a length of L' 1 The refractive index correction area is filled with the determined optical glue with a suitable refractive index n and cured to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure.

[0020] Furthermore, before removing part of the upper cladding layer and filling the optical glue, the method further includes: designing the MZI and preparing it according to the initial design value to obtain the originally designed MZI, wherein the optical waveguide structure of the originally designed MZI is covered by the original upper cladding layer.

[0021] Furthermore, the process of removing part of the upper cladding layer and filling the optical glue includes:

[0022] Several MZIs with the same design parameters are manufactured on a wafer, wherein the MZIs with the same design parameters include: an MZI with an original design having a complete structure and an MZI to be modified, wherein the MZI to be modified removes part of the upper cladding layer on the basis of the complete structure to form a MZI with a length of L' 1 A reserved refractive index correction area;

[0023] Testing the coherent enhancement wavelength λ' of the originally designed MZI, and calculating the wavelength shift Δλ=λ'-λ, where λ is the coherent enhancement wavelength of the originally designed MZI;

[0024] According to -Δn eff ·L' 1 = mΔλ to solve for the effective refractive index correction Δn obtained by filling with optical glue eff , m is the interference order;

[0025] Simulate and calculate the effective refractive index correction Δn eff The refractive index n of the optical glue required to be filled in the reserved refractive index correction area;

[0026] The reserved refractive index correction area of ​​the MZI to be corrected is filled with an optical glue with a refractive index of n and cured to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure.

[0027] Further, one or more originally designed MZIs on the wafer are tested, and wavelength correction is performed on other MZIs to be corrected on the entire wafer based on the wavelength offset of the originally designed MZIs;

[0028] or,

[0029] One or more originally designed MZIs in a certain area on the wafer are tested, and wavelength correction is performed on other MZIs to be corrected in the area based on the wavelength offset of the originally designed MZIs in the area.

[0030] The beneficial effects brought by the present invention are as follows: the optical waveguide phase deviation caused by wafer non-uniformity and manufacturing deviation is corrected, that is, the optical waveguide phase deviation is corrected without increasing circuit complexity, introducing additional power consumption, and affecting the performance of other on-chip devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 is a schematic diagram of the original optical waveguide structure;

[0033] Figure 2 Schematic diagram of an optical waveguide structure with part of the upper cladding removed;

[0034] Figure 3 It is a schematic diagram of the optical waveguide structure after a part of the upper cladding layer is replaced by optical adhesive in the present invention;

[0035] Figure 4 is a schematic diagram of the upper cladding layer above the strip optical waveguide after being replaced;

[0036] Figure 5 It is a schematic diagram after the upper cladding layer above and on the side of the strip optical waveguide is replaced;

[0037] Figure 6 is a schematic diagram of the upper cladding layer above the ridge optical waveguide after being replaced;

[0038] Figure 7It is a schematic diagram after the upper cladding layer above and on the side of the ridge optical waveguide is replaced;

[0039] Figure 8 Schematic diagram of a modifiable array waveguide grating;

[0040] Fig. 9 Schematic diagram of a correctable optical phased array;

[0041] Fig.10 Schematic diagram of a modifiable micro-ring resonator;

[0042] Fig.11 is a schematic diagram of a correctable grating coupler;

[0043] Fig.12 Schematic diagram of an MZI capable of correcting wavelength shift;

[0044] Fig.13 is a schematic flow chart of an on-chip MZI preparation method in one embodiment;

[0045] Fig.14 This is a simulation diagram of the refractive index distribution of the optical waveguide structure of the first phase shift arm of the originally designed MZI;

[0046] Fig.15 This is a simulation diagram of the TE0 mode field distribution of the optical waveguide structure of the first phase shift arm of the originally designed MZI;

[0047] Fig.16 This is a simulation diagram of the refractive index distribution of the optical waveguide structure of the first phase shift arm of the modified MZI;

[0048] Fig.17 This is a simulation diagram of the TE0 mode field distribution of the optical waveguide structure of the first phase shift arm of the modified MZI;

[0049] Fig.18 MZI transmission spectrum before and after refractive index correction;

[0050] Fig.19 FIG. 4 is a flow chart of an on-chip MZI preparation method in another embodiment. DETAILED DESCRIPTION

[0051] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Figure 1 As shown, the original optical waveguide structure includes: a substrate 1, a buried oxide layer 2, a waveguide 3, and an upper cladding layer 4.

[0053] like Figure 3 As shown, the present invention provides an on-chip optical waveguide phase deviation correction structure, including: a refractive index correction area 5 and an optical glue 6 filled in the refractive index correction area 5, that is, the refractive index correction area 5 is filled with the optical glue 6 to form a phase deviation correction structure, and the phase deviation correction structure changes the refractive index of the outer layer material of the original optical waveguide structure. The refractive index correction area 5 is a concave space formed by removing part of the upper cladding layer on the basis of the original optical waveguide structure, such as Figure 2 shown.

[0054] The refractive index of the optical glue 6 used in the phase deviation correction structure is slightly larger or smaller than the upper cladding of the original optical waveguide, and plays a role in correcting the effective refractive index of the optical waveguide without significantly affecting the mode field distribution of the optical waveguide propagation mode.

[0055] The phase deviation correction structure provided by the present invention can be applied to the correction of the phase deviation of the optical waveguide on any optical chip, for example, Fig.12 As shown in, the wavelength correction applied to the Mach-Zehnder interferometer; Figure 8 As shown, the phase correction of the arrayed waveguide 8 in the arrayed waveguide grating is applied; Fig. 9 As shown in, it is applied to waveguide phase correction in phased array radar; Fig.10 As shown, it is applied to the phase correction of microring or microdisk resonators; Fig.11 As shown, cladding refractive index modification applied to a grating coupler.

[0056] like Figure 4-5 As shown, the refractive index correction area 5 is located above the original optical waveguide structure, or as shown in Figure 6-7 As shown, it is located above and to the side of the original optical waveguide structure to facilitate more precise correction.

[0057] The present invention also provides a method for preparing an on-chip optical waveguide phase deviation correction structure, comprising: removing a portion of the upper cladding layer on the basis of the original optical waveguide structure to form a refractive index correction region 5, such as Figure 2 In the refractive index correction area 5 is filled with optical glue 6 to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure, such as Figure 3 shown.

[0058] The refractive index correction area 5 is a concave space formed by removing part of the upper cladding layer above the original optical waveguide structure. Figure 4-5 or a concave space formed by removing part of the upper cladding layer above and on the side of the original optical waveguide structure, such as Figure 6-7 shown.

[0059] Since the refractive index of the filled optical glue 6 is different from the refractive index of the original upper cladding, the phase deviation can be corrected by changing the effective refractive index of the waveguide structure in the refractive index correction zone 5. When correcting, an optical glue with a suitable refractive index can be selected for filling and the length of the refractive index correction zone 5 can be controlled during preparation. This can achieve correction of the optical waveguide phase deviation caused by wafer non-uniformity and manufacturing deviation, and can correct the optical waveguide phase deviation without increasing circuit complexity, introducing additional power consumption, or affecting the performance of other on-chip devices.

[0060] like Fig.12 As shown, the present invention also provides an on-chip MZI, including the phase deviation correction structure. Specifically, the phase deviation correction structure can be selectively manufactured on one or two phase shift arms of the MZI to correct the MZI interference wavelength deviation caused by design deviation and various process deviations.

[0061] The phase deviation correction structure removes part of the upper cladding layer on the basis of the original optical waveguide structure, and uses an optical glue with a specific refractive index to fill the removed upper cladding layer, so that the refractive index of the outer material of the optical waveguide structure changes. The refractive index of the optical glue is slightly larger or slightly smaller than that of the upper cladding layer of the original optical waveguide structure, which plays a role in correcting the effective refractive index of the optical waveguide structure without significantly affecting the mode field distribution of the propagation mode of the optical waveguide structure.

[0062] like Fig.12 As shown, the input light first passes through the beam splitter 7 (the beam splitter 7 can be 1X2 or 2X2 beam splitting) and then is divided into two paths, one of which passes through the first phase shift arm 9 and the other passes through the second phase shift arm 10. After that, the two beams of light interfere at the beam combiner 11 (the beam combiner 11 can be 2X1 beam combiner or 2X2 beam combiner) and are output from the output port of the beam combiner 11. The optical waveguides of the first phase shift arm 9 and the second phase shift arm 10 can have the same cross-sectional size and length or different cross-sectional sizes and lengths according to their application requirements. Fig.12 In the figure, the first phase shift arm 9 and the second phase shift arm 10 have the same optical waveguide cross section and material, but different optical waveguide lengths, and the phase deviation correction structure is prepared only on the first phase shift arm for illustration:

[0063] When the optical path difference of the two lights is an integer multiple of the wavelength, the two lights are coherently enhanced, that is, the light intensity of the output MZI is the strongest; when the optical path difference of the two lights is an odd multiple of half the wavelength, the two lights are coherently canceled, that is, the light intensity of the output MZI is the weakest. The wavelength point of coherent enhancement follows formula 1:

[0064] Formula 1: mλ=n eff1 ·L 1 -n eff2 ·L 2 ;

[0065] Where m is the coherence order, λ is the wavelength of coherence enhancement, and n eff1 is the effective refractive index of the first phase shift arm, n eff2 is the effective refractive index of the second phase shift arm, L 1 is the length of the first phase shift arm, L 2 is the length of the second phase shift arm.

[0066] When the thickness or width deviation causes the coherence wavelength to shift, Equation 2 is satisfied:

[0067] Formula 2: m(λ+Δλ)=(n eff1 +Δn eff1 )·L 1 -(n eff2 +Δn eff2 )·L 2 ;

[0068] Among them, Δn eff1 , Δn eff2 are the effective refractive index changes of the first phase shift arm and the second phase shift arm caused by the manufacturing deviation, and Δλ is the coherent enhancement wavelength offset caused by the manufacturing deviation.

[0069] When the phase deviation correction structure of the present invention is used to correct the first phase shift arm 9 of the MZI with coherent wavelength shift, Formula 3 is satisfied:

[0070] Formula 3: m(λ+Δλ-Δλ)=(n eff1 +Δn eff1 )·L 1 +Δn eff ·L 1 '-(n eff2 +Δn eff2 )·L 2 ;

[0071] Among them, fully corrected to the design value, Δn eff is the effective refractive index correction of the optical waveguide structure in the refractive index correction zone, L 1 ' is the length of the refractive index correction zone.

[0072] Combining formula 1, formula 2, and formula 3, we can get formula 4:

[0073] Formula 4: -Δn eff ·L' 1 =mΔλ=Δn eff1 ·L 1 -Δn eff2 ·L 2 .

[0074] Therefore, when the diffraction order m of the originally designed MZI and the coherent wavelength offset Δλ of the manufactured MZI are known, the effective refractive index correction Δn obtained by filling with optical glue can be obtained. eff and the length L' of the refractive index correction zone 1 The effective refractive index correction value Δn obtained by filling the phase deviation correction structure of the on-chip MZI with optical glue eff and the length L' of the refractive index correction zone 1 Satisfy the following formula:

[0075] -Δn eff ·L′ 1 =mΔλ;

[0076] Among them, Δn eff =n' eff -n eff , n' eff The effective refractive index correction amount of the optical waveguide in the refractive index correction zone after replacing part of the original upper cladding layer with an optical adhesive with a refractive index of n, n eff is the effective refractive index of the originally designed MZI optical waveguide; m is the interference order; Δλ is the wavelength offset, Δλ=λ'-λ, λ is the originally designed coherence enhancement wavelength, and λ' is the actually tested coherence enhancement wavelength.

[0077] Specifically, due to the effective refractive index correction Δn eff It is related to the cross-sectional correction area of ​​the optical waveguide and the refractive index n of the optical glue used. Therefore, an optical glue with a specific refractive index n can be selected in advance, and n' can be obtained through simulation calculation. eff and n eff , we can get Δn eff =n' eff -n eff , and then the length L' of the refractive index correction zone is obtained by formula 4 1 After obtaining the length value, the upper cladding of the MZI optical waveguide phase shift arm on the chip is etched and removed according to the length value to form a refractive index correction zone, the depth of which can be changed according to the wavelength offset to be corrected. Finally, the optical glue with a refractive index of n is filled and then cured to complete the wavelength correction. In this case, the length of the refractive index correction zone is L' 1 , is based on the corrected effective refractive index correction Δn eff , interference order m and wavelength shift Δλ.

[0078] In addition to the above method, part of the upper cladding of the on-chip MZI optical waveguide phase shift arm can be etched and removed in advance to form a refractive index correction zone, and the length value L' of the refractive index correction zone is recorded. 1 , and then the effective refractive index correction Δn is obtained by formula 4eff Due to the refractive index n of the optical adhesive used, the effective refractive index correction amount Δn can be adjusted as needed. eff The effective refractive index correction Δn is calculated based on the optical waveguide structure. eff The refractive index n of the matching optical glue can be obtained, and then the optical glue that meets the refractive index n is filled in the refractive index correction area and cured to complete the wavelength correction. In this case, the required effective refractive index correction amount Δn eff , is based on the refractive index correction zone length L' 1 , interference order m and wavelength shift Δλ.

[0079] The on-chip MZI of the present invention uses an optical glue with a specific refractive index to fill and solidify the refractive index correction area to form an on-chip MZI that can correct the interference wavelength offset. The refractive index of the optical glue used needs to be slightly larger or smaller than the upper cladding of the original optical waveguide structure, and it plays a role in correcting the effective refractive index of the optical waveguide structure without significantly affecting the mode field distribution of the optical waveguide propagation mode.

[0080] The present invention also provides a method for preparing an on-chip MZI, comprising: removing part of the upper cladding and filling optical glue on the basis of the original optical waveguide structure of the phase shift arm to be corrected of the MZI to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure.

[0081] The phase deviation correction structure realizes wavelength correction. The present invention can selectively manufacture the phase deviation correction structure on one or two phase shift arms of the MZI to correct the MZI interference wavelength deviation caused by design deviation and various process deviations.

[0082] Specifically, the first wavelength correction method is as follows: Figure 12-13 As shown, this method is suitable for small batches and for scenarios with high requirements for the accuracy of the MZI coherent wavelength. First, step 101 is performed, and then step 102 is performed. The following is an example of performing wavelength correction on the first phase shift arm 9 to illustrate:

[0083] 101: Design MZI according to formula 1, where L 1 >L 2 , determine the coherence enhancement wavelength λ, the coherence order m, and the effective refractive index n of the first phase shift arm 9 eff1 , the effective refractive index n of the second phase shift arm 10 eff2 , the length L of the first phase shift arm 9 1 , the length L of the second phase shift arm 10 2 .

[0084] 102: Prepare the initial MZI according to the design value. The initial MZI includes the original upper cladding. That is, prepare the beam splitter, beam combiner, phase shift arm, and upper cladding that constitute the MZI according to the initial design value. The MZI prepared in this step is called the original designed MZI. At this time, the optical waveguide in the refractive index correction area is still covered by the original upper cladding. Its structure is as follows: Figure 1 shown.

[0085] In the first wavelength correction method, the process of removing part of the upper cladding and filling with optical glue includes:

[0086] 103: Use an optical communication test system to test the coherent enhancement wavelength λ' of the prepared initial MZI, that is, the originally designed MZI, and calculate the wavelength offset Δλ=λ'-λ; λ is the originally designed coherent enhancement wavelength, which is a known value; at this time, Δλ represents the offset of the MZI coherent enhancement wavelength.

[0087] 104: Determine an optical adhesive with a suitable refractive index n according to the wavelength offset Δλ. If Δλ>0, the refractive index of the optical adhesive to be filled is lower than that of the original optical adhesive of the upper cladding layer, that is, the effective refractive index correction Δn is used. eff If Δλ is negative, an optical adhesive with a refractive index slightly lower than that of the original upper cladding should be selected. If Δλ<0, the refractive index of the optical adhesive to be filled is higher than that of the original upper cladding, that is, the effective refractive index correction Δn eff is positive, an optical adhesive with a refractive index slightly higher than that of the original upper cladding should be selected.

[0088] 105: Use optical waveguide simulation software to simulate to obtain the effective refractive index n' of the optical waveguide in the refractive index correction area after replacing part of the original upper cladding layer with an optical glue with a refractive index of n eff , and the effective refractive index n of the original designed MZI optical waveguide eff , and calculate the effective refractive index correction Δn obtained by filling with optical glue eff =n' eff -n eff .

[0089] 106: According to formula 4: -Δn eff ·L' 1 =mΔλ to solve for the length L' of the refractive index correction zone 1 , m is the interference order, i.e. the coherence order of MZI;

[0090] 107: Remove part of the original upper cladding layer at the first phase shift arm 9 of the prepared original design MZI to etch a length of L' 1 The refractive index correction zone, at this time, the optical waveguide structure of the refractive index correction zone is as follows Figure 2 As shown, the etching depth is equal to the depth of the optical glue replacement part of the simulation structure, and the length is L' 1; Fill the determined optical glue with a suitable refractive index n in the refractive index correction area and solidify it to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure, such as Figure 3 shown.

[0091] The first wavelength correction method is described below with specific parameters:

[0092] Device design stage:

[0093] The core layer is silicon nitride, and the upper cladding layer is silicon dioxide. The thickness of the core layer silicon nitride is 300nm and the width is 1000nm. Now we design an MZI with a coherent enhancement wavelength λ of 1300nm, a mode of TE0, and a free spectrum range FSR of 40nm. Through simulation design, the length L of the first phase shift arm 9 is obtained. 1 =121.568um, the length L of the second phase shift arm 10 2 = 100um. As mentioned above, the silicon nitride optical waveguides of the phase shift arms are 300nm thick and 1000nm wide, and the effective refractive index at the wavelength of 1300nm is n eff1 =n eff2 =1.6274, interference order m = 27, so it satisfies formula 1: mλ = n eff1 ·L 1 -n eff2 ·L 2 .

[0094] Device fabrication phase:

[0095] During manufacturing, the thickness of the silicon nitride material is 310 nm (increased by 10 nm compared to the design value), and the width of the first phase shift arm 9 and the second phase shift arm 10 is 990 nm (reduced by 10 nm compared to the design value). The actual manufacturing width and thickness errors here are assumed values ​​and may be different in the actual manufacturing process.

[0096] Device testing phase:

[0097] The parameters with width and thickness deviation after fabrication are brought into the optical waveguide simulation software to obtain the effective refractive index n of the first phase shift arm 9 and the second phase shift arm 10 of the initial MZI. eff1 +Δn eff1 =n eff2 +Δn eff2 =1.6336, the length of the first phase shift arm is L 1 , the length of the second phase shift arm L 2 And the interference order m remains unchanged, according to formula 2: m(λ+Δλ)=(n eff1 +Δn eff1 )·L 1 -(neff2 +Δn eff2 )·L 2 , and we get Δλ=4.9nm.

[0098] The calculation in this step is only to demonstrate the influence of manufacturing errors on the coherent enhancement wavelength. During the implementation of the solution of the present invention, the wavelength offset Δλ is obtained through optical communication system testing.

[0099] Calculate the length of the refractive index correction zone:

[0100] Since Δλ=4.9nm>0, the effective refractive index correction Δn eff is negative, so an optical glue with a refractive index slightly lower than that of the silica cladding (refractive index 1.45) should be used to replace part of the upper cladding. The refractive index of the optical glue used here is 1.40. The original upper cladding position is as follows: Figure 4 The refractive index distribution of the optical waveguide of the first phase shift arm 9 of the original MZI and the modified MZI is brought into the optical waveguide simulation software: Figure 14-15 FIG. 1 is a simulation diagram of the optical waveguide refractive index distribution and TE0 mode field distribution of the first phase shift arm 9 of the originally designed MZI; Figure 16-17 The figure shows the refractive index distribution of the optical waveguide of the first phase shift arm 9 of the modified MZI and the simulation diagram of the TE0 mode field distribution. The effective refractive index correction is calculated to be Δn eff =-0.0072. The wavelength shift Δλ = 4.9nm, the interference order m = 27, Δn eff =-0.0072Substitute into formula 4: -Δn eff ·L' 1 =mΔλ, and the length of the refractive index correction zone L' is calculated 1 =18.375um.

[0101] Device modification phase:

[0102] An optical glue with a refractive index of 1.40 is used to make a phase shift arm 9 of the original MZI with a length of L'. 1 =18.375um refractive index correction zone, the refractive index correction zone length L' 1 =18.375um and effective refractive index correction Δn eff =-0.0072 These two parameters are put into formula 3: mλ+Δλ-Δλ=n eff1 +Δn eff1 ·L 1 +Δn eff ·L 1 '-(n eff2 +Δn eff2 )·L 2, the corrected coherent enhancement wavelength is calculated to be 1300.04nm, which basically coincides with the coherent enhancement wavelength in the design stage.

[0103] The effect of the first wavelength correction method:

[0104] Use optical simulation software to bring in the refractive index distribution of the original optical waveguide structure and the modified optical waveguide structure, such as Figure 14-17 As shown, the effective refractive index of the original TE0 mode of the optical waveguide structure is 1.6274, and the effective refractive index of the TE0 mode of the corrected optical waveguide structure is 1.6202. The effective refractive index correction amount Δn eff It is -0.0072.

[0105] like Fig.18 As shown, the continuous line is the transmission spectrum when the waveguide size of the MZI phase shift arm is the design value, and its coherent enhancement wavelength point is 1300nm; the dotted line is the transmission spectrum of the originally designed MZI when the waveguide size deviates, and its coherent enhancement wavelength point is 1304.9nm, which is +4.9nm offset compared to the design value; the dotted line is the MZI transmission spectrum after the refractive index is corrected according to the method of the present invention, and its coherent enhancement wavelength point is about 1300.04nm, which is only 0.04nm offset compared to the design value, which is basically consistent with the design value.

[0106] Specifically, the second wavelength correction method is as follows: Fig.12 and Fig.19 As shown, it is suitable for mass production scenarios. First, step 201 is performed, and then step 202 is performed. The following is an example of wavelength correction of the first phase shift arm 9:

[0107] 201: Design MZI according to formula 1, where L 1 >L 2 , determine the coherence enhancement wavelength λ, the coherence order m, and the effective refractive index n of the first phase shift arm 9 eff1 , the effective refractive index n of the second phase shift arm 10 eff2 , the length L of the first phase shift arm 9 1 , the length L of the second phase shift arm 10 2 .

[0108] 202: Produce an initial MZI and an MZI to be corrected according to the design values, that is, produce several MZIs with the same design parameters on the wafer, wherein the MZIs with the same design parameters include: an MZI with an original design having a complete structure and an MZI to be corrected. In this example, the MZI with the original design is only used to test and calibrate the wavelength offset on the wafer or a certain area of ​​the wafer, and the coherent wavelength will not be corrected.

[0109] The MZI with a complete original design structure refers to the complete manufacture of the beam splitter, beam combiner, phase shift arm and upper cladding structure. The phase shift arm optical waveguide structure is as follows: Figure 1 shown.

[0110] The MZI to be modified is to remove part of the upper cladding layer on the basis of the complete structure to form a length of L' 1 The reserved refractive index correction area is formed by manufacturing a beam splitter, a beam combiner, a phase shift arm and an upper cladding structure, and removing part of the upper cladding above the first phase shift arm optical waveguide. The optical waveguide structure is as follows: Figure 2 As shown, at this time L' 1 The first phase shift arm optical waveguide region where part of the upper cladding is removed is a reserved refractive index correction region, and the length of the refractive index correction region is L' 1 Should be as long as possible, but not longer than L 1 , and cannot cover other optical waveguide devices and electronic devices other than the first phase shift arm 9.

[0111] In the second wavelength correction method, the process of removing part of the upper cladding and filling with optical glue includes:

[0112] 203: Using an optical communication test system, testing the coherent enhancement wavelength λ' of the initial MZI, that is, the originally designed MZI, and calculating the wavelength offset Δλ=λ'-λ, where λ is the originally designed coherent enhancement wavelength and is a known value; at this time, Δλ represents the offset of the MZI coherent enhancement wavelength.

[0113] 204: According to -Δn eff ·L' 1 = mΔλ to solve for the effective refractive index correction Δn obtained by filling with optical glue eff , m is the interference order.

[0114] 205: Use optical waveguide simulation software to simulate and calculate the effective refractive index correction Δn eff The refractive index n of the optical glue required to be filled in the reserved refractive index correction area.

[0115] 206: Filling and curing the reserved refractive index correction area of ​​the MZI to be corrected with an optical glue having a refractive index of n to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure.

[0116] Among them, one or more originally designed MZIs on the wafer are tested, and the wavelength of other MZIs to be corrected on the entire wafer is corrected based on the wavelength offset of the originally designed MZI; or, one or more originally designed MZIs in a certain area on the wafer (such as an exposure unit, where the width and thickness deviation of the optical waveguide will not be very large) are tested, and the wavelength of other MZIs to be corrected in the area is corrected based on the wavelength offset of the originally designed MZI in the area.

[0117] The difference between the first wavelength correction method and the second wavelength correction method is:

[0118] The first wavelength correction method is to manufacture, test, and correct the refractive index for the same MZI. After the MZI is manufactured and tested, an additional step is required to remove the upper cladding layer to form a refractive index correction zone. The advantage is that the refractive index n of the optical glue is determined first, and then the length L' of the refractive index correction zone is calculated. 1 , which can make the wavelength correction more accurate.

[0119] The second wavelength correction method is to make two types of MZI from the beginning: the original design MZI and the MZI to be corrected. The original design MZI has the original upper cladding layer, which is only used to measure the wavelength deviation. The MZI to be corrected has part of the upper cladding removed and can be directly used for optical glue filling. It is necessary to first determine the length of the refractive index correction zone L' 1 , and then calculate the refractive index n of the required optical glue. The advantage is that the steps are relatively simple, and there is no need to add a process step of removing the upper cladding layer after the MZI is completed and tested, and it can be processed in batches with the wafer or a certain area on the wafer as a unit.

[0120] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing an on-chip MZI, characterized in that: Used to prepare an on-chip MZI, including an on-chip optical waveguide phase deviation correction structure, in which an optical glue is used to fill a refractive index correction area to form the phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure, wherein the refractive index correction area is a concave space formed by removing part of the upper cladding layer on the basis of the original optical waveguide structure; the refractive index correction area is located above the original optical waveguide structure, or located above and to the side of the original optical waveguide structure; and the effective refractive index correction amount Δn obtained by filling with the optical glue eff The length L of the refractive index correction zone ′ 1 satisfies -Δn eff ·L ′ 1 = mΔλ; where Δn eff =n ′ eff -n eff , n ′ eff The effective refractive index of the optical waveguide in the refractive index correction zone after replacing part of the original upper cladding with an optical adhesive with a refractive index of n, n eff is the effective refractive index of the originally designed MZI optical waveguide; m is the interference order; Δλ is the wavelength offset, Δλ=λ ′ -λ, λ is the originally designed coherent enhancement wavelength, λ ′ The coherence enhancement wavelength for actual testing; The preparation method comprises: removing part of the upper cladding layer and filling optical glue on the basis of the original optical waveguide structure of the phase shift arm to be corrected of the MZI, so as to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure; The process of removing part of the upper cladding layer and filling the optical glue comprises: The coherent enhancement wavelength λ of the original designed MZI was tested and prepared. ′ , and calculate the wavelength shift Δλ=λ ′ -λ, λ is the originally designed coherent enhancement wavelength; Determine the optical glue with a suitable refractive index n according to the wavelength offset Δλ. If Δλ>0, the refractive index of the optical glue to be filled is lower than that of the original optical glue of the upper cladding. If Δλ<0, the refractive index of the optical glue to be filled is higher than that of the original optical glue of the upper cladding. The effective refractive index n of the optical waveguide in the refractive index correction zone after replacing part of the original upper cladding layer with an optical glue with a refractive index of n is obtained by simulation. ′ eff , and the effective refractive index n of the original designed MZI optical waveguide eff , and calculate the effective refractive index correction Δn obtained by filling with optical glue eff =n ′ eff -n eff ; According to -Δn eff ·L ′ 1=mΔλ to solve for the length L of the refractive index correction zone ′ 1, m is the interference order; Part of the original upper cladding layer is removed from the phase shift arm of the originally designed MZI to etch a length of L ′ 1, fill the refractive index correction area with the determined optical glue having a suitable refractive index n, and solidify it to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure.

2. The method for preparing an on-chip MZI according to claim 1, characterized in that: Before removing part of the upper cladding layer and filling the optical glue, the method further includes: designing the MZI and preparing it according to the initial design value to obtain the originally designed MZI, wherein the optical waveguide structure of the originally designed MZI is covered by the original upper cladding layer.

3. The method for preparing an on-chip MZI according to claim 2, characterized in that: The process of removing part of the upper cladding layer and filling the optical glue comprises: A plurality of MZIs with the same design parameters are manufactured on a wafer, wherein the MZIs with the same design parameters include: an MZI with an original design having a complete structure and an MZI to be modified, wherein the MZI to be modified removes part of the upper cladding layer on the basis of the complete structure to form a MZI with a length of L. ′ 1 reserved refractive index correction area; The coherent enhancement wavelength λ of the original designed MZI produced by testing ′ , and calculate the wavelength shift Δλ=λ ′ -λ, λ is the originally designed coherent enhancement wavelength; According to -Δn eff ·L ′ 1 = mΔλ to solve for the effective refractive index correction Δn obtained by filling with optical glue eff , m is the interference order; Simulate and calculate the effective refractive index correction Δn eff The refractive index n of the optical glue required to be filled in the reserved refractive index correction area; The reserved refractive index correction area of ​​the MZI to be corrected is filled with an optical glue having a refractive index of n and cured to form a phase deviation correction structure that changes the refractive index of the outer layer material of the original optical waveguide structure.

4. The method for preparing an on-chip MZI according to claim 3, characterized in that: Testing one or more originally designed MZIs on the wafer, and performing wavelength correction on other MZIs to be corrected on the entire wafer based on the wavelength offset of the originally designed MZIs; or, One or more originally designed MZIs in a certain area on the wafer are tested, and wavelength correction is performed on other MZIs to be corrected in the area based on the wavelength offset of the originally designed MZIs in the area.

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