An optical detection device

Abstract

The present application provides an optical detection device, comprising: a first optical coupler, which outputs a first optical signal and a second optical signal according to an input optical signal, a ratio of an intensity of the first optical signal to an intensity of the input optical signal being k, 0 < k < 1; an optical transmitter, which transmits the first optical signal; an optical receiver, which receives a return optical signal based on reflection or scattering of the first optical signal; a second optical coupler, which outputs a third optical signal and a fourth optical signal according to the second optical signal and the return optical signal; and a detector, which generates a detection signal (S) based on the third optical signal and the fourth optical signal. Thus, the detection efficiency can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric detection, and in particular to an optical detection device. BACKGROUND

[0002] Label-free optical biosensors offer the possibility to detect many small size analytes such as nanoparticles, microparticles.

[0003] One application using label-free detection is the description of viruses that are essential for disease prevention and diagnosis. The size characteristics of a single virus can be used for identification. Another example of application is flow cytometry, which can be used for various applications such as molecular biology, cancer biology, etc. It is a tool for detecting moving cells or particles suspended in a physiological solution.

[0004] The biosensor system using label-free detection chips can optimize the product cost and stability. Figure 1 is a schematic diagram of the detection of the existing label-free optical biosensor. As shown in Figure 1 Label-free optical biosensors can directly detect scattered light, transmitted light, or back-reflected light of fluorescent light. The detection efficiency (a) is the product of the efficiency of the excitation end coupler and the efficiency of the collection end coupler. The excitation light signal is directed to the cell or particle. The receiver collects the reflected light from the cell or particle.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of clearly and completely describing the technical solutions of the present application, and for the understanding of those skilled in the art. The above technical solutions cannot be considered as known to those skilled in the art only because they are described in the background section of the present application. SUMMARY

[0006] In the prior art, due to the propagation loss of the waveguide, the returned light (e.g., reflected light / scattered light) collected by the receiver is very weak in intensity when reaching the photoelectric sensor. Even if the light is focused by using optical focusing components (e.g., focusing grating couplers, lenses, etc.) to excite the scattering phenomenon, the power of the collected light is still very low due to the small scattering coefficient. Therefore, the detection efficiency a is usually a small number, which is about 10 -6 , while the noise (e.g., shot noise) can be much larger, resulting in a low signal-to-noise ratio of the detection signal.

[0007] To solve the above problems, the embodiment of the present application provides an optical detection device, in which input light is split, a part of which is mixed with return light for coherent detection, so as to amplify the return light, thereby improving the signal-to-noise ratio of the detection signal, and realizing the detection of weak signals.

[0008] According to an aspect of the embodiment of the present application, an optical detection device is provided, which comprises:

[0009] a first optical coupler, which outputs a first optical signal (I1k) and a second optical signal (I1(1-k)) according to an input optical signal (I1), the ratio of the intensity of the first optical signal (I1k) to the intensity of the input optical signal (I1) being k, 0<k<1;

[0010] an optical transmitter, which transmits the first optical signal;

[0011] an optical receiver, which receives a return optical signal (I1kα) based on the reflection or scattering of the first optical signal;

[0012] a second optical coupler, which outputs a third optical signal and a fourth optical signal according to the second optical signal (I1(1-k)) and the return optical signal (I1kα); and

[0013] a detector, which generates a detection signal (S) based on the third optical signal and the fourth optical signal.

[0014] According to another aspect of the embodiment of the present application, the detector comprises:

[0015] a first photodiode, which generates a first electrical signal according to the third optical signal;

[0016] a second photodiode, which generates a second electrical signal according to the fourth optical signal, the second photodiode and the first photodiode being connected in series; and

[0017] a calculation unit, which calculates the difference between the first electrical signal and the second electrical signal, and generates the detection signal (S) according to the difference.

[0018] According to another aspect of the embodiment of the present application, the optical transmitter and the optical receiver both have a grating structure.

[0019] According to another aspect of the embodiment of the present application, the first optical coupler has at least one input end and at least two output ends,

[0020] the at least one input end is input with the input optical signal (I1),

[0021] The optical transmitter and the optical receiver are arranged side by side in a direction parallel to a transmission direction of the first optical signal (I1k).

[0022] According to another aspect of embodiments of the present application, the first optical coupler has at least one input end and at least two output ends,

[0023] The at least one input end is inputted with the input optical signal (I1),

[0024] The optical transmitter and the optical receiver are arranged side by side in a direction perpendicular to a transmission direction of the first optical signal (I1k).

[0025] According to another aspect of embodiments of the present application, the value of k is 0.5.

[0026] According to another aspect of embodiments of the present application, the optical transmitter and the optical receiver are the same grating,

[0027] The first optical coupler has at least two input ends and at least two output ends,

[0028] One of the two output ends is used to output the first optical signal (I1k) and receive the return optical signal (I1kα), and the other of the two output ends outputs the second optical signal (I1(1-k)),

[0029] One of the two input ends is inputted with the input optical signal (I1), and the other of the two input ends is connected with one input end of the second optical coupler.

[0030] According to another aspect of embodiments of the present application, the value of k is 1 / 3.

[0031] According to another aspect of embodiments of the present application, the optical detection device further comprises a surface plasmon-based Bragg grating, the surface plasmon-based Bragg grating comprising:

[0032] a substrate;

[0033] a metal layer on one surface of the substrate, the metal layer having a hole; and

[0034] a metal grating structure on another surface of the substrate, the metal grating structure being formed around the hole,

[0035] wherein the another surface of the substrate faces the optical transmitter.

[0036] According to another aspect of embodiments of the present application, there is provided a surface plasmon-based Bragg grating, the surface plasmon-based Bragg grating comprising:

[0037] a substrate;

[0038] a metal layer on a surface of the substrate, the metal layer having an aperture; and

[0039] a metal grating structure on another surface of the substrate, the metal grating structure being formed around the aperture.

[0040] According to another aspect of embodiments of the present application, wherein the metal layer and the metal grating structure use the same metal material or different metal materials.

[0041] According to another aspect of embodiments of the present application, wherein the metal layer and the metal grating structure use gold (Au) as the metal material.

[0042] According to another aspect of embodiments of the present application, wherein a boundary of the metal grating structure is aligned with a boundary of the aperture.

[0043] According to another aspect of embodiments of the present application, wherein a diameter of the aperture is less than 1 micrometer.

[0044] According to another aspect of embodiments of the present application, there is provided yet another optical detection device, the optical detection device comprising:

[0045] a light emitting unit emitting a light signal and focusing the emitted light signal in an aperture of a surface plasmon-based Bragg grating;

[0046] a surface plasmon-based Bragg grating, a metal grating structure of the surface plasmon-based Bragg grating being arranged towards the light emitting unit;

[0047] a light receiving unit receiving light scattered from the aperture of the surface plasmon-based Bragg grating; and

[0048] a detector generating a detection signal (S) based on the light signal received by the light receiving unit.

[0049] According to another aspect of embodiments of the present application, wherein the light emitting unit comprises an out-of-plane focusing grating.

[0050] The present application has the beneficial effect that in the optical detection device, after the input light is split, a part of the input light is used as a reference signal to perform a mixing coherent detection with the return light, thereby amplifying the return light, and thus the signal-to-noise ratio of the detection signal can be improved, thereby realizing the detection of a weak signal.

[0051] The particular implementations of the application described herein can best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

[0052] Features described and / or illustrated with respect to one implementation can be used in one or more other implementations in the same or similar manner, in combination with or in place of the features of the other implementations.

[0053] It should be emphasized that the term "comprises / comprising" when used in this specification is taken to mean the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. BRIEF DESCRIPTION OF DRAWINGS

[0054] The accompanying drawings are included to provide a further understanding of embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. It is to be understood that other embodiments can be taken without departing from the spirit of the application, and that the drawings are, therefore, to be regarded as illustrative rather than restrictive.

[0055] Figure 1 is a schematic illustration of detection by a prior art label-free optical biosensor;

[0056] Figure 2 (a) of is a schematic illustration of the optical detection device;

[0057] Figure 2 (b) of is a further schematic illustration of the optical detection device;

[0058] Figure 2 (c) of is a further schematic illustration of the optical detection device;

[0059] Figure 3 is a schematic illustration of a surface plasmon based Bragg grating of Example 2;

[0060] Figure 4 is a schematic illustration of a coherence detector of Example 3. DETAILED DESCRIPTION

[0061] The foregoing and other features of the present application will become apparent to those skilled in the art upon consideration of the following description of the application taken in conjunction with the accompanying drawings. In the drawings, specific embodiments of the application are disclosed in detail. As will be apparent, however, the application is not limited to the embodiments described, but instead includes all modifications, variations, and equivalents that fall within the scope of the appended claims.

[0062] Embodiment 1

[0063] Embodiment 1 of the present application provides an optical detection device.

[0064] Figure 2 (a) is a schematic diagram of the optical detection device. As shown in (a) of FIG. 1, the optical detection device 200 includes a first optical coupler 10, a light emitter 20, a light receiver 30, a second optical coupler 40, and a detector 50. Figure 2 (a) of FIG. 1, the optical detection device 200 includes a first optical coupler 10, a light emitter 20, a light receiver 30, a second optical coupler 40, and a detector 50.

[0065] In this embodiment, the first optical coupler 10 outputs a first light signal and a second light signal according to an input light signal (e.g., intensity I1). The ratio of the intensity of the first light signal to the intensity of the input light signal (I1) is k, 0 < k < 1, i.e., the intensity of the first light signal is I1k, and the intensity of the second light signal is I1(1-k). The first optical coupler 10 is, for example, a 1X2 coupler, such as a 1X2 multi-mode interference (MMI) coupler; or the first optical coupler 10 can also be a 2X2 coupler, such as a 2X2 multi-mode interference (MMI) coupler.

[0066] The light emitter 20 can emit the first light signal. For example, the light emitter 20 can be a grating that can focus and emit the first light signal to a region to be detected. For example, the grating can be a planar external focusing grating or the like that can focus the first light signal out of the plane in which the grating is located.

[0067] The light receiver 30 receives a return light signal based on the reflection or scattering of the first light signal. The intensity of the return light signal is represented as I1kα, where α represents the detection efficiency.

[0068] The second optical coupler 40 outputs a third optical signal and a fourth optical signal according to the second optical signal and the return optical signal. For example, the second optical coupler 40 can mix the input second optical signal and the return optical signal based on a self-image principle, and divide the mixed signal into the third optical signal and the fourth optical signal for output. In one embodiment, the second optical coupler 40 can be a 2X2 coupler, such as a directional coupler or a 2X2 multimode interference (MMI) coupler. The second optical signal can be input to one input end of the second optical coupler 40 as a reference signal, and the return optical signal can be input to another input end of the second optical coupler 40.

[0069] The detector 50 generates a detection signal (S) based on the third optical signal and the fourth optical signal.

[0070] In the optical detection device, after the input light is split, a part of the input light is used as a reference signal to mix with the return light for coherent detection, so that the return light is amplified, thereby improving the signal-to-noise ratio of the detection signal, and achieving weak signal detection.

[0071] For example, in (a) of FIG. 1, Figure 2 the detection signal S generated by the detector 50 is proportional to As a result, the detection signal S is proportional to Since the detection efficiency α is 10 -6 orders of magnitude, is 10 -3 orders of magnitude, compared with the detection signal S proportional to α in the prior art, the detection signal S of the embodiment is proportional to which can improve the intensity of the detection signal S by times.

[0072] As shown in (a) of FIG. 1, Figure 2 the detector 50 can include a first photodiode 51, a second photodiode 52, and a calculation unit (not shown).

[0073] The first photodiode 51 generates a first electrical signal according to the third optical signal, and the second photodiode 52 generates a second electrical signal according to the fourth optical signal. The second photodiode 52 and the first photodiode 51 are connected in series.

[0074] The calculation unit calculates the difference between the first electrical signal and the second electrical signal, and generates the detection signal S according to the difference.

[0075] In detector 50, the use of a first photodiode 51 and a second photodiode 52 enables balanced photo-detection. The calculation unit 53 calculates the difference between the first and second electrical signals, which can eliminate DC components and other defects in the first and second electrical signals, thereby improving detection accuracy.

[0076] like Figure 2 As shown in (a), both the light emitter 20 and the light receiver 30 have grating structures.

[0077] The first optical coupler 10 has at least one input terminal and at least two output terminals, wherein the at least one input terminal is input with an input optical signal (e.g., intensity I1), and the two output terminals output a first optical signal and a second optical signal, respectively. An optical transmitter 20 and an optical receiver 30 are arranged side-by-side in a direction parallel to the transmission direction D1 of the first optical signal.

[0078] Figure 2 (b) is another schematic diagram of the optical detection device. Figure 2 The optical detection device 200a shown in (b) and Figure 2 The difference between the optical detection device 200 shown in (a) is that, in the optical detection device 200a, the light emitter 20 and the light receiver 30 are arranged side by side in a direction D2 perpendicular to the transmission direction D1 of the first optical signal. Furthermore, the similarities between the optical detection device 200a and the optical detection device 200 will not be described further.

[0079] exist Figure 2 In (a) and (b), the light emitter 20 and the light receiver 30 can be placed as close to each other as possible in order to optimize detection efficiency.

[0080] exist Figure 2 In (a) and (b), the value of k can be 0.5, which allows the detection signal S to be maximized.

[0081] Figure 2 (c) is another schematic diagram of the optical detection device. Figure 3 In the optical detection device 200b shown in (c), the light emitter 20 and the light receiver 30 are the same grating, that is, the same grating performs the functions of both the light emitter 20 and the light receiver 30. This allows the light emitter 20 and the light receiver 30 to achieve the optimal distance from the object being detected, thus resulting in higher detection efficiency.

[0082] In the optical detection device 200b, the first optical coupler 10 has at least two input ends and at least two output ends, for example, the first optical coupler 10 is a 2X2 coupler. In the first optical coupler 10, one of the two output ends is used to output the first optical signal and receive the return optical signal, i.e., the output end is connected with the optical grating as the optical transmitter 20 and the optical receiver 30 through the optical waveguide. In the first optical coupler 10, the other of the two output ends outputs the second optical signal (I1(1-k)), one of the two input ends is input with the input optical signal I1, and the other of the two input ends is connected with one input end of the second optical coupler 40.

[0083] In the optical detection device 200b, the detection signal S generated by the detector 50 is proportional to For example, the value of k can be 1 / 3, thereby enabling the detection signal S to be maximized.

[0084] According to the embodiment 1 of the present application, after the input light is split, a part of the input light is used as the reference signal and mixed with the return light for coherent detection, thereby amplifying the return light, and thus the signal-to-noise ratio of the detection signal can be improved, and thus the detection of the weak signal can be realized.

[0085] Embodiment 2

[0086] The embodiment 2 provides a surface plasmon-based Bragg grating.

[0087] Figure 3 Fig. 1 is a schematic diagram of a surface plasmon-based Bragg grating. As shown in Fig. 1, the surface plasmon-based Bragg grating 300 includes a substrate 301, a metal layer 302, and a metal grating structure 303. Figure 3

[0088] In the embodiment, the metal layer 302 and the metal grating structure 303 use the same metal material or different metal materials. For example, the metal layer 302 and the metal grating structure 303 use gold (Au) as the metal material.

[0089] In addition, the substrate 301 can be a metal material, for example, the same or different metal material as the metal layer 302 and the metal grating structure 303. In addition, the substrate 301 can also be a non-metal material.

[0090] In addition, the substrate 301 can be a metal material, for example, the same or different metal material as the metal layer 302 and the metal grating structure 303. In addition, the substrate 301 can also be a non-metal material.

[0091] ​In the present embodiment, when light is focused in the hole 3021, the metal interface will generate a strong plasmonic field, thereby generating strong excitation light in the hole 3021, thereby increasing the scattering coefficient of light within the hole 3021, and in turn, the detection efficiency (a) of the object to be detected (e.g., cells or microparticles, etc.) located within the hole 3021 can be directly improved.

[0092] The metal grating structure 303 can be disposed on the light-receiving side of the substrate 301, and the metal grating structure 303 can be a metal Bragg grating, i.e., the metal grating structure 303 satisfies the Bragg condition, thereby forming a resonant cavity of the Bragg grating, and thereby, more light of a predetermined wavelength can be coupled into the hole 3021.

[0093] In the present embodiment, the boundary of the metal grating structure 303 is aligned with the boundary of the hole 3021. For example, the first grating around the hole 3021 can be aligned with the boundary of the hole 3021, thereby maximizing the coupling efficiency when coupling light into the hole 3021. As a result, the intensity of light within the hole 3021 can be, for example, 30 times the intensity under normal circumstances, thereby making the scattering coefficient β reach 100 times that under normal circumstances. In the present embodiment, the surface plasmon-based Bragg grating 300 is applied to an optical detection device. For example, Figure 4 The optical detection device 3 shown can include a light emitting unit 31, a surface plasmon-based Bragg grating 300, a light receiving unit 32, and a detector 33.

[0094] The light emitting unit 31 can emit a light signal and focus the emitted light signal in the hole 3021 of the surface plasmon-based Bragg grating 300, and the light emitting unit 31 can include, for example, an out-of-plane focusing grating. The metal grating structure 303 of the surface plasmon-based Bragg grating 300 is disposed toward the light emitting unit 31; the light receiving unit 32 receives light scattered from the hole 3021 of the surface plasmon-based Bragg grating 300; and the detector 33 generates a detection signal S based on the light signal received by the light receiving unit 32.

[0095] In addition, the surface plasmon-based Bragg grating 300 of Embodiment 2 can also be applied to the optical detection device 200, 200a, 200b of Embodiment 1, for example, the object to be detected is disposed within the hole 3021 of the surface plasmon-based Bragg grating 300, and the light emitter 20 of Embodiment 1 focuses the first light signal into the hole 3021, thereby detecting the object to be detected.

[0096] According to Embodiment 2, the scattering coefficient of the light in the hole 3021 can be increased by exciting the plasmonic field, so as to improve the single-particle detection efficiency.

[0097] Embodiment 3

[0098] Embodiment 3 provides a coherent detector.

[0099] Figure 4 is a schematic diagram of the coherent detector of Embodiment 3. As shown in ​ , the coherent detector 400 can include a coherent mixer 401, a balanced detector 402, and an extraction unit 403.

[0100] The coherent mixer 401 mixes the light signal corresponding to the reference light signal and the detection signal S, and outputs the mixed light signal at four output ends, for example, the coherent mixer 401 can be a 2X4 90° hybrid or a 4X4 MMI. Among them, the reference light signal can be A r is the amplitude, w r is the frequency. The light signal corresponding to the detection signal S can be A s (t) is the amplitude, w s is the frequency, is the phase information. The output signals of the coherent mixer 401 are E s +E LO , E s +j·E LO , E s -E LO , E s +j·E LO .

[0101] The balanced detector 402 balances the light signals output at the four output ends of the coherent mixer 401 respectively to obtain the in-phase component and the quadrature component of the light signal corresponding to the detection signal, for example, the in-phase component I is proportional to , and the quadrature component Q is proportional to .

[0102] The extraction unit 403 calculates the amplitude information and / or the phase information of the light signal corresponding to the detection signal according to the in-phase component I and the quadrature component Q. For example, in the case of w s =w r , A S (t) can be calculated by calculating I2+Q2, and the phase information can be obtained by calculating the ratio of I and Q.

[0103] The phase information and the amplitude information in the optical signal can be separated by the coherent detector of embodiment 3, so that the information about the size and the position of the detected object can be obtained more accurately.

[0104] The coherent detector 400 of embodiment 3 can be applied to the optical detection apparatus 200, 200a, 200b of embodiment 1. For example, the second optical coupler 40 and the detector 50 in the optical detection apparatus 200, 200a, 200b of embodiment 1 can be replaced by the coherent detector 400, i.e., the return optical signal of embodiment 1 can be input into the coherent detector 400 as Es in embodiment 3, and the second optical signal of embodiment 1 can be input into the coherent detector 400 as Er in embodiment 3.

[0105] The coherent detector 400 of embodiment 3 can also be applied to the optical detection apparatus 3 of embodiment 2, for example, the detector 33 in the optical detection apparatus 3 of embodiment 2 is replaced by the coherent detector 400 of embodiment 3.

[0106] The application has been described in detail with reference to specific embodiments, but it should be clear to those skilled in the art that these descriptions are exemplary and not limiting to the scope of protection of the application. Those skilled in the art can make various modifications and changes to the application according to the spirit and principles of the application, and these modifications and changes are also within the scope of the application.

Claims

1. An optical detection device, characterized in that The optical detection device comprises: a first optical coupler, which outputs a first optical signal I1k and a second optical signal I1(1-k) according to an input optical signal I1, the intensity ratio of the first optical signal I1k to the input optical signal I1 being k, 0<k<1; an optical transmitter connected with the first optical coupler, which transmits the first optical signal to a region to be detected; an optical receiver, which receives a return optical signal I1kα based on reflection or scattering of the first optical signal; a second optical coupler, which outputs a third optical signal and a fourth optical signal according to the second optical signal I1(1-k) and the return optical signal I1kα; and a detector, which generates a detection signal S based on the third optical signal and the fourth optical signal.

2. The optical detection device according to claim 1, wherein the detector comprises: a first photodiode, which generates a first electrical signal according to the third optical signal; a second photodiode, which generates a second electrical signal according to the fourth optical signal, the second photodiode and the first photodiode being connected in series; and a calculation unit, which calculates a difference between the first electrical signal and the second electrical signal, and generates the detection signal S according to the difference.

3. The optical detection device according to claim 1, wherein the optical transmitter and the optical receiver both have a grating structure.

4. The optical detection device according to claim 1, wherein the first optical coupler has at least one input end and at least two output ends, the at least one input end is input with the input optical signal I1, the optical transmitter and the optical receiver are arranged side by side in a direction parallel to the transmission direction of the first optical signal I1k.

5. The optical detection device according to claim 1, wherein the first optical coupler has at least one input end and at least two output ends, the at least one input end is input with the input optical signal I1, the optical transmitter and the optical receiver are arranged side by side in a direction perpendicular to the transmission direction of the first optical signal I1k.

6. The optical detection device according to claim 4 or 5, wherein the value of k is 0.

5.

7. The optical detection device according to claim 1, wherein the optical transmitter and the optical receiver are the same grating, the first optical coupler has at least two input ends and at least two output ends, one of the two output ends is used to output the first optical signal I1k and receive the return optical signal I1kα, and the other of the two output ends outputs the second optical signal I1(1-k), one of the two input ends is input with the input optical signal I1, and the other of the two input ends is connected with one input end of the second optical coupler.

8. The optical detection device according to claim 7, wherein the value of k is 1 / 3.

9. The optical detection device according to claim 1, wherein The optical detection device further comprises a surface plasmon polariton based Bragg grating, the surface plasmon polariton based Bragg grating comprising: a substrate; a metal layer on a surface of the substrate, the metal layer having an aperture; and a metal grating structure on another surface of the substrate, the metal grating structure being formed around the aperture, wherein the another surface of the substrate faces the light emitter.

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