Cosine grating micro-ring resonant cavity sensor and testing method thereof

Abstract

The invention relates to a cosine grating micro-ring resonant cavity sensor which is connected with an input light source, a first detector and a second detector and comprises an upper channel waveguide and a lower channel waveguide, and a sensing ring is connected between the upper channel waveguide and the lower channel waveguide in an end face coupling mode. The sensing ring is provided with a cosine grating structure. Compared with a common upload and download type micro-ring resonant cavity, the cosine type grating micro-ring resonant cavity sensor has the advantages that the cosine type grating is additionally arranged, so that the influence of the external environment temperature is greatly reduced, and the sensing sensitivity of the sensor is greatly improved; the detection modes are flexible and diverse, a tunable laser can be used as an input light source, an optical power meter can be used as a detector, a broadband light source can also be used as the input light source, and a spectrograph can be used as the detector; the structure design is also flexible and diverse, different actual requirements can be met by adjusting the height, the width and the periodicity of the cosine grating, and the practicability of the sensor is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of biosensor detection, and in particular to a cosine grating micro-ring resonant cavity sensor and a testing method thereof. Background Art

[0002] With the rapid development of modern science and technology, the demand for high-precision detection of tiny physical and chemical quantities is growing. Traditional sensors are gradually unable to meet these requirements in terms of sensitivity, resolution, and integration. Microring resonant cavity sensors have emerged as a new type of optical sensor. Optical sensing technology has been widely used in the field of biosensing due to its advantages such as non-contact, high sensitivity, and strong anti-electromagnetic interference. The microring resonant cavity is based on the principle of optical resonance and uses the propagation characteristics of light in micro-nanoscale structures to detect physical or chemical quantities. Microring resonant cavity sensors have been widely used due to their compact size, high integration, low power consumption, and high sensitivity.

[0003] Since the resonant wavelength of the microring resonator is very sensitive to the change of the refractive index of the waveguide surface, the microring resonator is easily affected by the external temperature, which seriously limits the sensing performance of the microring resonant cavity sensor. Therefore, the temperature sensitivity of the microring resonant cavity sensor should be controlled low enough to reduce the influence of the external temperature. At the same time, the quality factor, extinction ratio and sensing sensitivity of the spectral resonance peak are also factors that need to be considered.

[0004] In view of the above technical problems, an improved technical solution is proposed. Summary of the invention

[0005] In order to achieve the purpose of the present invention, the technical solution adopted by the present invention is: a cosine-type grating micro-ring resonant cavity sensor, connected to an input light source, a first detector and a second detector, including: an upper channel waveguide and a lower channel waveguide, wherein a sensing ring is connected between the upper channel waveguide and the lower channel waveguide by end face coupling; the sensing ring is provided with a cosine-type grating structure.

[0006] Preferably, the left end of the upper channel waveguide is connected to an input light source, and the right end of the upper channel waveguide is connected to a first detector; The left end of the lower channel waveguide is a coupling output end and is connected to a second detector.

[0007] Preferably, an upper cladding layer and a lower cladding layer are further provided, wherein the upper cladding layer is an aqueous solution and the lower cladding layer is silicon dioxide.

[0008] Preferably, the upper channel waveguide and the lower channel waveguide are straight waveguides, the sensing ring is an annular waveguide, and the annular waveguide includes: a rectangular waveguide and a cosine waveguide.

[0009] Preferably, the input light source includes: a tunable laser or a broadband light source; the first detector and the second detector include: an optical power meter or a spectrometer.

[0010] Preferably, the polarization mode used for sensing is the TE fundamental mode.

[0011] Preferably, a testing method for a cosine-type grating microring resonant cavity sensor comprises: The input light of the light source enters the cosine type grating micro-ring resonant cavity sensor in the form of optical coupling; The light interacts with the test agent and is output to the first detector and the second detector; When the cosine grating micro-ring resonant cavity sensor is undergoing a sensing test, the resonant peak of the output spectrum will shift, and the sensing sensitivity can be determined by observing the shift.

[0012] Preferably, the sensing sensitivity includes: the sensitivity S1 when the sensor is affected by the refractive index change of the upper cladding; The calculation formula of S1 is expressed as:

[0013] Wherein, Δnc represents the refractive index change of the upper cladding layer; Δλ represents the resonant wavelength change.

[0014] Preferably, the detection limit is also an important performance parameter when performing a sensor test. The detection limit refers to the minimum refractive index change that can be detected during the sensor test, and is represented by DL:

[0015] Among them, σ is the standard deviation of the acquired signal change; 3σ is the minimum measurable signal sensed by the device, which represents the offset randomness of the light source output wavelength and the wavelength error of the detector during actual testing; S is the sensitivity of the sensor.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Compared with the common up-down-down microring resonant cavity, the present invention adds a new structure of cosine grating. The cosine grating microring resonant cavity sensor greatly reduces the influence of the external environment temperature and greatly improves the sensing sensitivity of the sensor.

[0017] 2. Its detection methods are flexible and diverse. It can use a tunable laser as the input light source and an optical power meter as the detector, or a broadband light source as the input light source and a spectrometer as the detector.

[0018] 3. Its structural design is also flexible and diverse. It can meet different practical needs by adjusting the height, width and periodicity of the cosine grating, thereby improving the practicality of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a cosine-type grating micro-ring resonant cavity sensor of the present invention; Figure 2 A comparison diagram of the temperature sensitivity of the present invention and a conventional up-down-down type micro-ring resonant cavity; Figure 3 A comparison diagram of the sensing sensitivity of the present invention and a conventional up-down-down type micro-ring resonant cavity; Figure 4 It is a schematic diagram of the temperature sensitivity and sensor sensitivity detected by the coupling output end of the present invention.

[0020] In the figure: 1. input light source; 2. first detector; 3. second detector; 4. cosine grating micro-ring resonant cavity sensor; 41. upper channel waveguide; 42. lower channel waveguide; 43. sensing ring. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not 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.

[0022] Example: like Figures 1 to 4 As shown, the present invention provides a technical solution: a cosine-type grating microring resonant cavity sensor, connected with an input light source 1, a first detector 2 and a second detector 3, including: an upper channel waveguide 41 and a lower channel waveguide 42, the left end of the upper channel waveguide 41 is connected with the input light source 1, and the input light source 1 can use a tunable laser or a broadband light source.

[0023] The upper channel waveguide 41 and the lower channel waveguide 42 are straight waveguides, and the sensing ring 43 is an annular waveguide. The annular waveguide is composed of a rectangular waveguide and a cosine waveguide. The shape of the cosine waveguide is directly constructed by a cosine function. In this embodiment, its width is 0.28 μm, its height is 0.32 μm, and the number is 82.

[0024] The right end of the upper channel waveguide 41 is connected to the first detector 2, and the left end of the lower channel waveguide 42 is a coupling output end and is connected to the second detector 3. The first detector 2 and the second detector 3 can use an optical power meter or a spectrometer.

[0025] A sensing ring 43 is connected between the upper channel waveguide 41 and the lower channel waveguide 42 by end face coupling, and the sensing ring 43 is provided with a cosine grating structure.

[0026] The cosine grating micro-ring resonant cavity sensor is also provided with an upper cladding and a lower cladding, wherein the upper cladding is an aqueous solution and the lower cladding is silicon dioxide. And the polarization mode used for sensing by the cosine grating micro-ring resonant cavity sensor 4 is the TE fundamental mode.

[0027] During the sensing test, the testing method of the cosine grating micro-ring resonant cavity sensor includes: The input light of the input light source 1 enters the cosine type grating micro-ring resonant cavity sensor 4 in the form of optical coupling; After the light interacts with the test agent, it is output to the first detector 2 and the second detector 3; When the cosine grating micro-ring resonant cavity sensor 4 is subjected to a sensing test, reagents with different refractive indices are used as the upper cladding of the sensing ring 43, causing the resonance peak of the output spectrum corresponding to the right through output end of the upper channel waveguide 41 to shift. The sensing sensitivity can be determined by observing the shift.

[0028] Among them, the sensing sensitivity includes: the sensitivity S1 when the sensor is affected by the refractive index change of the upper cladding; The calculation formula of S1 is expressed as:

[0029] Among them, Δnc represents the refractive index change of the upper cladding, which will cause the effective refractive index of the waveguide to change, and the effective refractive index is directly related to the size of the resonant wavelength λ; Δλ represents the change in the resonant wavelength.

[0030] The effective refractive index is represented by neff. After being affected by the sensing factor nc, neff produces an effective refractive index difference Δneff before and after, that is, S n =Δneff / Δnc, S n is the sensitivity of the effective refractive index change, which is only related to the waveguide structure; According to the resonance equation of the microring resonator: L∙neff = m∙λ, where L represents the circumference of the microring resonator, m represents the resonance order, and neff is the average effective refractive index of the ring waveguide in the microring resonator. Under the condition that L and m remain unchanged, Δneff is proportional to the change in the resonance wavelength Δλ, that is, Δλ / Δneff can be regarded as a constant within a certain wavelength range at this time, indicating the working nature of waveguide sensing. The change in the effective refractive index will directly affect the change in the resonance wavelength, and the change in the effective refractive index will be affected by external factors. The direct impact of external factors on the resonance wavelength is the sensitivity mentioned in this embodiment, so S1=Δneff / Δnc×(Δλ / Δneff)=Δλ / Δnc.

[0031] Among them, when the sensor is designed to monitor the temperature of the waveguide structure, the temperature sensitivity is improved by changing the temperature of the waveguide structure; The sensitivity S2 of the sensor when it is affected by the temperature change of the waveguide structure;

[0032] Where ΔT represents the change in temperature of the waveguide structure, and Δλ represents the change in the resonant wavelength.

[0033] The effective refractive index is represented by neff. After being affected by the sensing factor T, neff produces an effective refractive index difference Δneff before and after, that is, Sw=Δneff / ΔT. Sw is the waveguide sensitivity and is only related to the waveguide structure.

[0034] According to the resonance equation of the microring resonator: L∙neff = m∙λ, where L represents the circumference of the microring resonator, m represents the resonance order, and neff is the average effective refractive index of the ring waveguide in the microring resonator. Under the condition that L and m remain unchanged, Δneff is proportional to the change in the resonance wavelength Δλ, that is, Δλ / Δneff, so S2=Δneff / ΔT×(Δλ / Δneff)=Δλ / ΔT.

[0035] The detection limit is also an important performance parameter when performing sensor testing. The detection limit refers to the minimum refractive index change that can be detected during the sensor test, expressed as DL:

[0036] Among them, σ is the standard deviation of the acquired signal change; 3σ is the minimum measurable signal sensed by the device, which represents the offset randomness of the light source output wavelength and the wavelength error of the detector during actual testing; S is the sensitivity of the sensor.

[0037] Among them, the sensor is mainly used to detect the change of external refractive index. It is necessary to eliminate the temperature influence, so the temperature sensitivity is 0. Then the minimum refractive index change is mainly aimed at the Δnc change actually used for testing to determine the minimum change of nc that can be detected.

[0038] In this embodiment, the waveguide width of the upper channel waveguide 41 and the lower channel waveguide 42 is 0.41 μm, the radius of the micro-ring is set to 4 μm, and the waveguide width is 0.43 μm. Figure 2 As shown in the left figure, with the change of the external environment temperature, the resonance peak shift of the output spectrum corresponding to the right through output end of the upper channel waveguide 41 of the cosine grating micro-ring resonant cavity sensor 4 is not large, and its temperature sensitivity is 20pm / °C.

[0039] like Figure 2As shown in the figure on the right, as the ambient temperature changes, the resonance peak shift of the output spectrum corresponding to the common up-down-down microring resonant cavity sensor is large, and its temperature sensitivity is as high as 78pm / ℃. It can be seen that the cosine grating structure can reduce the influence of the external temperature on the sensing effect.

[0040] like Figure 3 As shown, when reagents with different refractive indices are used as the upper cladding of the sensor ring 43, no matter what structure it has, the resonance peak of the output spectrum corresponding to the right direct output end of the upper channel waveguide 41 will shift to the right as the refractive index of the reagent to be tested increases. However, it is obvious that the resonance peak corresponding to the right direct output end of the upper channel waveguide 41 of the cosine-type grating microring resonant cavity sensor 4 has a larger offset, and its sensing sensitivity is as high as 405nm / RIU, while the sensing sensitivity of the ordinary upper and lower type microring resonant cavity sensor is only 136nm / RIU.

[0041] It can be seen that the cosine grating structure greatly improves the sensing sensitivity of the sensor. Based on this, if biomolecules are modified on the sensing waveguide, biomolecule sensing can be further realized.

[0042] like Figure 4 As shown, the resonance peak of the output spectrum corresponding to the left coupling output end of the lower channel waveguide 42 of the cosine-type grating micro-ring resonant cavity sensor 4 is observed by the second detector 3 .

[0043] By comparison Figure 2 and Figure 3 It is found that the resonance peak of the output spectrum corresponding to the through output end is easier to observe than that of the coupled output end. Therefore, when performing a sensing test, the first detector 2 is generally used to observe the resonance peak of the output spectrum.

[0044] The embodiments of the present invention disclose preferred embodiments, but are not limited thereto. A person skilled in the art can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. However, as long as they do not deviate from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A cosine grating micro-ring resonant cavity sensor, connected to an input light source, a first detector and a second detector, characterized in that: include: An upper channel waveguide and a lower channel waveguide are provided, wherein a sensing ring is connected between the upper channel waveguide and the lower channel waveguide by end face coupling; and the sensing ring is provided with a cosine grating structure.

2. The cosine type grating micro-ring resonant cavity sensor according to claim 1, characterized in that: The left end of the upper channel waveguide is connected to an input light source, and the right end of the upper channel waveguide is connected to a first detector; The left end of the lower channel waveguide is a coupling output end and is connected to a second detector.

3. The cosine type grating micro-ring resonant cavity sensor according to claim 1, characterized in that: An upper cladding layer and a lower cladding layer are also provided. The upper cladding layer is an aqueous solution, and the lower cladding layer is silicon dioxide.

4. The cosine type grating micro-ring resonant cavity sensor according to claim 1, characterized in that: The upper channel waveguide and the lower channel waveguide are straight waveguides, the sensing ring is an annular waveguide, and the annular waveguide includes: a rectangular waveguide and a cosine waveguide.

5. The cosine type grating micro-ring resonant cavity sensor according to claim 1, characterized in that: The input light source includes: a tunable laser or a broadband light source; the first detector and the second detector include: an optical power meter or a spectrometer.

6. The cosine type grating micro-ring resonant cavity sensor according to claim 1, characterized in that: The polarization mode used for sensing is the TE fundamental mode.

7. A method for testing the cosine grating micro-ring resonant cavity sensor according to claims 1 to 6, characterized in that: include: The input light of the light source enters the cosine type grating micro-ring resonant cavity sensor in the form of optical coupling; The light interacts with the test agent and is output to the first detector and the second detector; When the cosine grating micro-ring resonant cavity sensor is undergoing a sensing test, the resonant peak of the output spectrum will shift, and the sensing sensitivity can be determined by observing the shift.

8. The method for testing a cosine-type grating micro-ring resonant cavity sensor according to claim 7, characterized in that: The sensing sensitivity includes: the sensitivity S1 when the sensor is affected by the refractive index change of the upper cladding; The calculation formula of S1 is expressed as: Wherein, Δnc represents the refractive index change of the upper cladding layer; Δλ represents the resonant wavelength change.

9. The method for testing a cosine-type grating micro-ring resonant cavity sensor according to claim 8, characterized in that: The detection limit is also an important performance parameter when performing sensor testing. The detection limit refers to the minimum refractive index change that can be detected during the sensor test, expressed as DL: Among them, σ is the standard deviation of the acquired signal change; 3σ is the minimum measurable signal sensed by the device, which represents the randomness of the offset of the light source output wavelength and the wavelength error of the detector during actual testing; S is the sensitivity of the sensor.

Images