All-fiber common-path illumination and collection system and method

Abstract

The invention discloses an all-fiber common-path illumination and collection system and method. The near-field optical imaging system comprises an optical fiber probe, a laser, a polarization controller, a detector, an optical fiber and an optical fiber light splitting structure, laser emitted by the laser device is coupled into the optical fiber and is transmitted to the tip of the optical fiber probe through the optical fiber light splitting structure to perform near-field illumination on a sample; and the excited near-field optical signal enters the optical fiber probe, returns to the optical fiber light splitting structure along the original path, and is further transmitted to the detector to obtain the near-field optical signal. According to the invention, high signal-to-noise ratio measurement of transparent and non-transparent samples by using the optical fiber probe can be realized, and a complex optical path system of the near-field optical microscope is simplified, so that the near-field optical microscope can be applied to a shear force type atomic force microscope and a scanning tunneling microscope to realize multi-modal information measurement of morphology information, optical information and the like.

Description

Technical Field

[0001] The present invention belongs to the field of near-field optical imaging, and relates to an all-fiber common light path illumination and collection system and method for near-field optical detection. Background Art

[0002] Microscopes provide convenience for the study of the microscopic world. However, with the development of science, the optical diffraction limit will limit the maximum resolution of optical microscopes. Therefore, breaking through the optical diffraction limit has become the main direction of the development of the new generation of microscopes. The invention of a series of nano-scale high-resolution measurement equipment such as scanning probe microscopes and scanning electron microscopes has brought observation into the nano field. However, these non-optical measurement methods have the disadvantage of damaging the sample, and of course they cannot obtain optical super-resolution images, so near-field optical microscopes came into being.

[0003] Near-field optical microscopes can detect in the optical near-field of the sample, and are not limited by the optical diffraction limit, thus achieving nanometer-level measurement resolution. According to the different near-field illumination and near-field signal collection methods, commonly used near-field optical microscopes are divided into transmission near-field optical microscopes and scattering near-field optical microscopes. Transmission near-field optical microscopes mainly use fiber optic probes to perform near-field illumination, and then use an objective lens to collect the transmitted near-field optical information from the back of the sample, or perform far-field illumination on the back of the sample, and use a fiber optic probe to collect near-field optical signals in the near field. The above two transmission near-field optical microscope systems will generate large background noise due to the existence of far-field illumination or far-field collection processes, which affects the measurement quality. Secondly, since it is necessary to build the illumination and collection optical path systems on the upper and lower sides of the sample respectively, the overall near-field optical microscope system is relatively large and complex, and can only measure transparent samples, which greatly limits the scope of application. The scattering near-field optical microscope is mainly built based on scanning probe microscopes such as atomic force microscope and scanning tunneling microscope. The laser is emitted from the far field to illuminate the measurement point of the scanning probe, and the near-field optical signal is stimulated to the far field and then collected directly through the objective lens on the same side of the sample or through the reflection focusing optical path. The illumination and collection processes are completed in the far field. Therefore, there is a lot of background noise interference in the illumination and collection processes. Therefore, it is often necessary to use a phase-locked amplifier to filter the collected signal in order to obtain a clearer near-field optical measurement image. The illumination and collection optical paths are very complicated and the signal noise is extremely large. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide an all-fiber common optical path illumination and collection system. The present invention can not only realize high signal-to-noise ratio measurement of transparent and non-transparent samples using optical fiber probes, but also simplify the complex optical path system of near-field optical microscopes, so that it can be applied to shear force atomic force microscopes and scanning tunneling microscopes to realize multimodal information measurement such as morphological information and optical information.

[0005] The technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an all-fiber common light path illumination and collection system, comprising: Fiber-optic probes for near-field illumination and collection of near-field optical signals; Laser, used for emitting laser light; A polarization controller, used for adjusting the polarization state of the laser entering the optical fiber probe to a radial polarization mode; a detector, used for detecting the near-field optical signal transmitted back; Optical fiber, used for transmitting the laser and near-field optical signals; An optical fiber splitting structure, used to connect an optical fiber probe, a laser and a detector via the optical fiber; The laser emits laser light and couples it into the optical fiber. Through the optical fiber splitter structure, the laser light propagates to the tip of the optical fiber probe to perform near-field illumination on the sample. The excited near-field optical signal enters the optical fiber probe and returns along the original path to the optical fiber splitter structure, and then is transmitted to the detector to obtain a near-field optical signal.

[0006] As a further improvement of the present invention, the optical fiber probe is a tapered optical fiber with a metal film on the outside.

[0007] As a further improvement of the present invention, the optical fiber probe is an aperture optical fiber probe, a metal film-coated surface plasmon optical fiber probe, or a carbon nanotube / metal nanowire composite optical fiber probe.

[0008] As a further improvement of the present invention, a small hole is provided at the conical bottom of the aperture-type optical fiber probe; The metal film outer wall of the metal film-coated surface plasmon optical fiber probe has surface plasmons excited and propagated, and focused at the tip; The conical bottom of the carbon nanotube / metal nanowire composite optical fiber probe is provided with carbon nanotubes / metal nanowires, and surface plasmons are excited and propagated on the outer wall of the metal film and the carbon nanotubes / metal nanowires and are focused at the tip.

[0009] As a further improvement of the present invention, the optical fiber splitting structure is a wavelength division multiplexer or a circulator.

[0010] As a further improvement of the present invention, the wavelength division multiplexer is connected to one or more detectors at the same time, and the multiple detectors are arranged in parallel.

[0011] As a further improvement of the present invention, the laser, fiber probe and detector are respectively connected to the three ports of the fiber splitting structure by fiber fusion splicing, fiber connector coupling or flange; a polarization controller is arranged at the connecting fiber between the fiber probe and the fiber splitting structure.

[0012] As a further improvement of the present invention, the detector is a photomultiplier tube (PMT) or a Raman spectrometer.

[0013] As a further improvement of the present invention, the excited near-field optical signal enters the optical fiber probe and returns to the optical fiber splitting structure along the original path, and the illumination and collection optical paths share the same optical fiber probe.

[0014] In a second aspect, the present invention provides a working method of an all-fiber common light path lighting and collection system, based on the all-fiber common light path lighting and collection system, comprising the following steps: The laser couples the laser into the fiber optic optical path system; The laser emits laser light and couples it into the optical fiber. Through the optical fiber splitting structure, the laser light propagates to the tip of the optical fiber probe to perform near-field illumination on the sample. A fiber-optic probe scans the sample; The fiber-optic probe collects near-field optical signals in the near field; The excited near-field optical signal enters the optical fiber probe and returns along the original path to the optical fiber splitting structure, and is then transmitted to the detector to obtain the near-field optical signal.

[0015] Compared with the prior art, the present invention has the following advantages: In the system of the present invention, after the laser light emitted by the laser is distributed by the light splitting structure, the laser light propagates to the tip of the optical fiber probe. The tip of the optical fiber probe performs near-field illumination on the sample, and the laser excites the sample surface to generate a near-field optical signal. The excited near-field optical signal returns to the optical fiber light splitting structure along the original path of the optical fiber probe. The light splitting structure distributes the light path again and transmits the signal to the detector for further processing. The near-field optical signal received by the detector is converted and amplified, and then sent to a computer or a signal processing system for analysis. Through analysis and processing, useful information such as the morphological image and optical properties of the sample can be obtained. The entire system adopts all-fiber connection, which has the advantages of compact structure, high stability, and strong anti-interference ability. As the transmission medium of the optical signal, the optical fiber can effectively reduce signal attenuation and noise interference, and improve the detection sensitivity and resolution of the system. The illumination and collection optical paths share the same optical fiber probe, which simplifies the system structure and improves the optical path transmission efficiency. At the same time, the common optical path design also helps to reduce the difficulty and error of optical path adjustment and improve the stability and reliability of the system. The polarization state of the laser is adjusted to a radial polarization mode through a polarization controller, which enhances the excitation and collection efficiency of the near-field optical signal. This design helps to improve the detection sensitivity and resolution of the system and is applicable to a wider range of detection needs. It can not only be used for near-field optical imaging and morphology measurement of micro-nanostructure surfaces, but also for research and application in fields such as optical fiber waveguides. By replacing different components such as optical fiber probes and detectors, the system can flexibly adapt to different detection task requirements. The method of the present invention has the advantages of high signal-to-noise ratio, compactness, convenience, low cost, and wide sample applicability, and is suitable for high signal-to-noise ratio near-field optical measurement of samples with various optical properties. The present invention can be combined with scanning probe microscope systems such as atomic force microscope systems and scanning tunneling microscope systems to measure multimodal information such as morphological information and optical information. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below with reference to the accompanying drawings, in which: Figure 1 The present invention is an all-fiber common light path illumination and collection system and a working method that uses a circulator as a fiber optic splitting element according to a first embodiment of the present invention.

[0017] Figure 2 The present invention is an all-fiber common optical path illumination and collection system and a working method that use a wavelength division multiplexer as a fiber optical splitting element according to a second example of the present invention.

[0018] Figure 3 , Figure 4 , Figure 5 for Figure 1 , Figure 2 Three examples of enlarged details of the circle dotted area.

[0019] Figure 3This is a detailed diagram of an example of connecting an aperture-type optical fiber probe according to the present invention.

[0020] Figure 4 Detailed diagram of an example of connecting a plasmon optical fiber probe coated with a metal film surface according to the present invention.

[0021] Figure 5 This is a detailed diagram of an example of connecting a carbon nanotube / metal nanowire composite nano-optical fiber probe according to the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] Terminology explanation: Wavelength Division Multiplexer (WDM) and Ring (usually refers to the ring structure in the network topology) play different roles in the fiber optic communication system, but they can be used in conjunction with each other to optimize network performance and reliability.

[0024] Wavelength division multiplexer (WDM) is a network transmission technology that can use a single optical fiber to transmit multiple channels at the same time. It multiplexes optical signals of different wavelengths into a single optical fiber to achieve the purpose of transmitting a large number of high-bandwidth signals on a single optical fiber. The main advantages of wavelength division multiplexer include improving bandwidth utilization, increasing transmission capacity, and flexibly supporting multiple signal formats and rates.

[0025] Ring Topology is a network topology in which all nodes (such as wavelength division multiplexers, optical line terminals, optical network units, etc.) are connected into a closed ring through unidirectional or bidirectional fiber links. In this structure, data can be transmitted in either direction along the ring or forwarded through each node on the ring.

[0026] In optical fiber communication systems, WDM and rings can be used in combination to build an efficient and reliable network architecture. For example, in a metropolitan area network or backbone network, a ring topology can be used to connect multiple WDM nodes, each of which has the ability to multiplex and demultiplex. In this way, not only can optical signals of multiple wavelengths be transmitted on a single optical fiber, but also high reliability and redundancy can be provided through the ring structure. When a node or link fails, the network can automatically switch to a backup path to ensure continuous data transmission.

[0027] The present invention belongs to the field of near-field optical imaging, morphology measurement and optical fiber waveguide of micro-nanostructure surface, and relates to an all-fiber common optical path illumination and collection system for near-field optical detection, such as Figures 1 to 5 As shown, it includes a fiber probe, a fiber splitting structure, a laser 10 and a detector 40, and each device is connected by an optical fiber.

[0028] The laser 10, the optical fiber probe, and the detector 40 are respectively connected to the three ports 1, 2, and 3 of the optical fiber splitting structure by means of optical fiber fusion splicing, optical fiber connector coupling, etc. A polarization controller 30 is arranged at the connecting optical fiber between the optical fiber probe and the optical fiber splitting structure. The laser 10 emits a laser that is coupled into the optical fiber. Through the optical fiber splitting structure, the laser is transmitted to the tip of the optical fiber probe to perform near-field illumination on the sample. The excited near-field optical signal enters the optical fiber probe and returns to the optical fiber splitting structure along the original path, and then is transmitted to the detector 40 to obtain a near-field optical signal.

[0029] The optical fiber probe is used for near-field illumination and collecting near-field optical signals. The laser 10 is used to emit laser light. The optical fiber splitting structure is used to connect the optical fiber probe, the laser 10 and the detector 40. The polarization controller 30 is used to adjust the polarization state of the laser entering the optical fiber probe to a radial polarization mode. The detector 40 is used to detect the near-field optical signal optical fiber transmitted back by the optical fiber, and is used to transmit the laser and near-field optical signals.

[0030] The all-fiber common optical path illumination and collection system designed by the present invention has significant application value in the fields of near-field optical imaging, morphology measurement and optical fiber waveguide of micro-nanostructure surfaces. The system realizes efficient excitation, transmission and detection of near-field optical signals through ingenious optical fiber connection and structural design. Its detailed principles and features are as follows: Fiber optic probe: As the core component of the system, the fiber optic probe is responsible for near-field illumination and collection of near-field optical signals. Its tip design can be close to the sample surface to achieve nanoscale optical detection.

[0031] Fiber splitter structure: This structure plays the role of connecting and distributing the optical path, guiding the laser light emitted by the laser 10 to the tip of the optical fiber probe, and transmitting the near-field optical signal returned from the probe to the detector 40. The fiber splitter structure has multiple ports, which are respectively connected to the laser 10, the optical fiber probe and the detector 40 to ensure the precise control and efficient transmission of the optical path.

[0032] Laser 10: As a light source, laser 10 emits a high-quality laser beam, providing a stable light source guarantee for near-field optical detection. The selection of laser 10 needs to be optimized according to specific detection requirements (such as wavelength, power, etc.).

[0033] Detector 40: Responsible for receiving the near-field optical signal transmitted back by the optical fiber and converting it into a processable electrical signal or digital signal. The performance of detector 40 directly affects the detection sensitivity and resolution of the system.

[0034] Polarization controller 30: It is arranged at the connecting optical fiber between the optical fiber probe and the optical fiber splitting structure, and is used to adjust the polarization state of the laser entering the optical fiber probe to a radial polarization mode. This polarization state helps to enhance the excitation and collection efficiency of near-field optical signals.

[0035] Working principle: The laser emitted by the laser 10 enters the optical fiber splitting structure through optical fiber fusion or optical fiber connector coupling, and after being distributed by the splitting structure, the laser propagates to the tip of the optical fiber probe. The tip of the optical fiber probe performs near-field illumination on the sample, and the laser excites the surface of the sample to generate near-field optical signals. These signals contain rich information such as the morphology, structure, and optical properties of the sample. The excited near-field optical signal returns to the optical fiber splitting structure along the original path of the optical fiber probe. The splitting structure distributes the light path again and transmits the signal to the detector 40 for further processing. The near-field optical signal received by the detector 40 is converted and amplified, and then sent to a computer or signal processing system for analysis. Through analysis and processing, useful information such as the morphological image and optical properties of the sample can be obtained.

[0036] The entire system adopts all-fiber connection, which has the advantages of compact structure, high stability and strong anti-interference ability. As the transmission medium of optical signals, optical fiber can effectively reduce signal attenuation and noise interference, and improve the detection sensitivity and resolution of the system. The illumination and collection optical paths share the same optical fiber probe, which simplifies the system structure and improves the optical path transmission efficiency. At the same time, the common optical path design also helps to reduce the difficulty and error of optical path adjustment and improve the stability and reliability of the system. The polarization state of the laser is adjusted to a radial polarization mode through the polarization controller 30, which enhances the excitation and collection efficiency of the near-field optical signal. This design helps to improve the detection sensitivity and resolution of the system and is suitable for a wider range of detection needs. It can not only be used for near-field optical imaging and morphology measurement of micro-nanostructure surfaces, but also can be used for research and application in fields such as optical fiber waveguides. By replacing different optical fiber probes and detectors 40 and other components, the system can flexibly adapt to different detection task requirements.

[0037] As a preferred embodiment, the present invention provides multiple groups of embodiments, for example, the optical fiber probe includes an aperture optical fiber probe, a metal film 52 surface plasmon 53 optical fiber probe, and a carbon nanotube or metal nanowire composite nano optical fiber probe and other optical fiber probes for near-field optical detection.

[0038] The optical fiber probes in the multiple groups of embodiments provided by the present invention, including aperture optical fiber probes, metal film 52 surface plasmon 53 optical fiber probes, and carbon nanotube or metal nanowire composite nano optical fiber probes, all have significant advantages and are suitable for near-field optical detection.

[0039] The advantages of aperture fiber probes are: through structural parameter optimization, aperture fiber probes can adjust the internal signal transmission mode, achieve EOT effect, and greatly improve light transmittance and resolution. This design enables the probe to have excellent performance in a specific band (such as 500nm to 1000nm). Aperture fiber probes can adjust the aperture size and shape according to specific needs to adapt to different detection tasks.

[0040] Advantages of metal-coated 52 surface plasmon 53 fiber probes: Surface plasmon 53 functionalized fiber probes combine metal nano-functional units with compact fiber probes, and can be integrated and constructed on the fiber end face to support localized surface plasmon 53 modes. This structure can produce a near-field "hotspot" effect under any incident angle and polarization state light excitation, greatly enhancing the interaction between light and matter. Due to the existence of the surface plasmon 53 effect, metal-coated 52 fiber probes can detect weak signals with high specificity and can distinguish different types of molecules or particles.

[0041] Advantages of carbon nanotube or metal nanowire composite nanofiber probes: Carbon nanotubes have extremely high tensile strength, elastic modulus and electrical conductivity, while maintaining good flexibility and stability. These excellent physical properties enable the carbon nanotube composite fiber probe 54 to maintain good working conditions even in extreme environments. Metal nanowires have similar conductivity and optical properties and are suitable for specific detection tasks. The addition of carbon nanotubes or metal nanowires can further enhance the detection capabilities of fiber probes, such as improving sensitivity, resolution and signal stability. At the same time, they can also be used as sensing elements to achieve specific identification of specific substances.

[0042] Therefore, different types of optical fiber probes can be selected and combined according to actual needs to meet different detection tasks. For example, aperture optical fiber probes are suitable for occasions requiring high resolution and high light transmittance; metal-coated optical fiber probes 52 are suitable for occasions requiring high sensitivity and specificity; and carbon nanotube or metal nanowire composite optical fiber probes 54 are suitable for occasions requiring operation in extreme environments.

[0043] The optical fiber probes in the multiple groups of embodiments provided by the present invention each have their own characteristics and significant advantages, and provide powerful tool support for near-field optical detection.

[0044] The optical fiber splitting structure includes a circulator 20, a wavelength division multiplexer 22, etc. The detector 40 includes a photomultiplier tube (PMT) or a Raman spectrometer, etc., which can be selected according to different needs.

[0045] The first specific combination scheme is an all-fiber reflective near-field illumination and collection system for near-field optical detection, including: Aperture fiber optic probes for near-field illumination and collection of near-field optical signals.

[0046] The circulator 20 is used to connect the optical fiber probe, the laser 10 and the detector 40, to isolate the interference of the laser light emitted by the laser 10 on the near-field signal light received by the detector 40, and to isolate the damage caused by the near-field signal light returning from the needle tip to the laser 10.

[0047] The laser 10 is used to emit laser light.

[0048] The polarization controller 30 is used to adjust the polarization state of the laser light entering the optical fiber probe to a radial polarization mode.

[0049] The detector 40 is used to detect the near-field optical signal transmitted back by the optical fiber.

[0050] The optical fiber is used to transmit the laser and near-field optical signals.

[0051] The second specific combination scheme is an all-fiber reflective near-field illumination and collection system for near-field optical detection, including: The metal-coated film 52 surface plasmon 53 optical fiber probe is used for near-field illumination and collection of near-field optical signals.

[0052] The circulator 20 is used to connect the optical fiber probe, the laser 10 and the detector 40, to isolate the interference of the laser light emitted by the laser 10 on the near-field signal light received by the detector 40, and to isolate the damage caused by the near-field signal light returning from the needle tip to the laser 10.

[0053] The laser 10 is used to emit laser light.

[0054] The polarization controller 30 is used to adjust the polarization state of the laser light entering the optical fiber probe to a radial polarization mode.

[0055] The detector 40 is used to detect the near-field optical signal transmitted back by the optical fiber.

[0056] The optical fiber is used to transmit the laser and near-field optical signals.

[0057] The third specific combination scheme is an all-fiber reflective near-field illumination and collection system for near-field optical detection, including: The carbon nanotube / metal nanowire composite optical fiber probe 54 is used for near-field illumination and collection of near-field optical signals.

[0058] The circulator 20 is used to connect the optical fiber probe, the laser 10 and the detector 40, to isolate the interference of the laser light emitted by the laser 10 on the near-field signal light received by the detector 40, and to isolate the damage caused by the near-field signal light returning from the needle tip to the laser 10.

[0059] The laser 10 is used to emit laser light.

[0060] The polarization controller 30 is used to adjust the polarization state of the laser light entering the optical fiber probe to a radial polarization mode.

[0061] The detector 40 is used to detect the near-field optical signal transmitted back by the optical fiber.

[0062] The optical fiber is used to transmit the laser and near-field optical signals.

[0063] The fourth specific combination scheme, an all-fiber reflective near-field illumination and collection system for near-field optical detection, includes: Aperture fiber optic probes for near-field illumination and collection of near-field optical signals.

[0064] The wavelength division multiplexer 22 is used to connect the optical fiber probe, the laser 10, and one or more detectors 40 at the same time. The laser 10 is used to emit laser light.

[0065] The polarization controller 30 is used to adjust the polarization state of the laser light entering the optical fiber probe to a radial polarization mode.

[0066] The detector 40 is used to detect the near-field optical signal transmitted back by the optical fiber.

[0067] The optical fiber is used to transmit the laser and near-field optical signals.

[0068] A fifth specific combination scheme, an all-fiber reflective near-field illumination and collection system for near-field optical detection, comprising: The metal-coated film 52 surface plasmon 53 optical fiber probe is used for near-field illumination and collection of near-field optical signals.

[0069] The wavelength division multiplexer 22 is used to connect the optical fiber probe, the laser 10, and one or more detectors 40 at the same time. The laser 10 is used to emit laser light.

[0070] The polarization controller 30 is used to adjust the polarization state of the laser light entering the optical fiber probe to a radial polarization mode.

[0071] The detector 40 is used to detect the near-field optical signal transmitted back by the optical fiber.

[0072] The optical fiber is used to transmit the laser and near-field optical signals.

[0073] The sixth specific combination scheme is an all-fiber reflective near-field illumination and collection system for near-field optical detection, comprising: The carbon nanotube / metal nanowire composite optical fiber probe 54 is used for near-field illumination and collection of near-field optical signals.

[0074] The wavelength division multiplexer 22 is used to connect the optical fiber probe, the laser 10, and one or more detectors 40 at the same time. The laser 10 is used to emit laser light.

[0075] The polarization controller 30 is used to adjust the polarization state of the laser light entering the optical fiber probe to a radial polarization mode.

[0076] The detector 40 is used to detect the near-field optical signal transmitted back by the optical fiber.

[0077] The optical fiber is used to transmit the laser and near-field optical signals.

[0078] The present invention provides a method for operating an all-fiber reflective near-field illumination and collection system for near-field optical detection, comprising the following steps: Coupling step: coupling the laser into the fiber optic optical system; Illumination step: The fiber optic probe illuminates the sample in the near field; Scanning step: the fiber probe scans the sample; Collection step: The fiber probe collects near-field optical signals in the near field; Detection step: The detector 40 detects the collected near-field optical signal.

[0079] The optical fiber probe is connected to the circulator 20 by optical fiber fusion or flange. The optical fiber probe is connected to the wavelength division multiplexer 22 by optical fiber fusion or flange. The detector 40 includes a photomultiplier tube (PMT), a Raman spectrometer, a CMOS, and a CCD camera.

[0080] The present invention is described in detail below with reference to specific embodiments and accompanying drawings: The first example is an all-fiber common optical path illumination and collection system and working method for near-field optical detection using a circulator 20 as an optical fiber splitting structure. Figure 1 Schematic diagram of the optical path of the first implementation example.

[0081] The laser is emitted by a single-frequency laser 10, enters the circulator 20 from port 1, and is emitted from port 202 of the circulator. Before the laser enters the fiber probe, the polarization state of the laser in the fiber is converted into radial polarization, i.e., TM0 mode, by a polarization controller 30. Under the incidence of TM0 mode light, the probe performs near-field illumination on the sample.

[0082] Figure 3 This is a schematic diagram of the illumination / collection of the aperture-type fiber optic probe connected in the present invention. The incident light passes through the nanoscale hole at the tip of the probe to perform near-field illumination on the sample.

[0083] After being excited, the near-field optical signal is collected through a small hole and returns upward along the same path.

[0084] Figure 4 Schematic diagram of illumination / collection of optical fiber probe with metal-coated film 52 and surface plasmon 53 connected in the present invention. TM0 mode incident light propagates toward the probe cone tip, excites surface plasmon 53 on the outer surface of metal film 52 at a specific diameter, and surface plasmon 53 propagates toward the tip and finally forms a nanoscale focused light field at the tip to illuminate the sample.

[0085] According to the principle of reversible optical path, the excited near-field optical signal part propagates upward along the outer surface of the metal film 52 in the form of surface plasmons 53, is converted into light propagating in the optical fiber at a specific diameter, and returns upward along the original path.

[0086] Figure 5 The schematic diagram of the illumination / collection of the carbon nanotube / metal nanowire composite nanofiber probe connected by the present invention. The TM0 mode incident light propagates toward the probe cone tip, excites the surface plasmon 53 on the outer surface of the metal film 52 at a specific diameter, and the surface plasmon 53 propagates toward the tip and couples to the carbon nanotube / metal nanowire at the tip of the probe, and finally forms a nanoscale focused light field at the tip of the carbon nanotube / metal nanowire to illuminate the sample.

[0087] Figures 3 to 5 The three types of fiber optic probes are described as follows: The optical fiber probe is a tapered optical fiber 51 with a metal film 52 on the outside. The optical fiber probe is an aperture optical fiber probe, a metal film 52 coated surface plasmon 53 optical fiber probe or a carbon nanotube / metal nanowire composite optical fiber probe 54.

[0088] The first type is that a small hole is provided at the conical bottom of the aperture type optical fiber probe; The second type is that the outer wall of the metal film 52 of the metal-coated surface plasmon 53 optical fiber probe has surface plasmons excited and propagated and focused at the tip; The third type is that the conical bottom of the carbon nanotube / metal nanowire composite optical fiber probe 54 is provided with carbon nanotubes / metal nanowires, and surface plasmons are excited and propagated on the outer wall of the metal film 52 and the carbon nanotubes / metal nanowires and are focused at the tip.

[0089] According to the reversible principle of optical path, the excited near-field optical signal part propagates upward along the carbon nanotube / metal nanowire in the form of surface plasmon 53, propagates to a specific diameter outside the metal film 52, is converted into propagating light in the optical fiber, and returns upward along the original path.

[0090] The near-field optical signal collected by the optical fiber probe enters the circulator 20 through port 2 and is emitted through port 3 to enter the detector 40. The detector 40 is a photomultiplier tube (PMT) or a Raman spectrometer, etc., which can obtain light intensity information, frequency information, etc.

[0091] In the first example, the circulator 20 is selected as the optical fiber splitting structure for the all-fiber common optical path illumination and collection system of near-field optical detection. While achieving the high signal-to-noise ratio measurement of near-field illumination / collection, the interference of the laser emitted by the laser 10 on the near-field signal light received by the detector 40 can be effectively isolated, and the measurement with a higher signal-to-noise ratio can be achieved. At the same time, the near-field signal light returning from the needle tip can be effectively isolated from returning to the laser 10 to damage the laser 10.

[0092] The second example is an all-fiber common optical path illumination and collection system and working method for near-field optical detection using a wavelength division multiplexer 22 as an optical fiber splitting structure. Figure 2 FIG. 1 is a schematic diagram of the optical path of the first embodiment. The laser is emitted by a single-frequency laser 10 and passes through a wavelength division multiplexer 22. Before the laser enters the optical fiber probe, the polarization state of the laser in the optical fiber is converted into radial polarization, i.e., TM0 mode, by a polarization controller 30. Under the incidence of TM0 mode light, the probe performs near-field illumination on the sample.

[0093] The principles of probe illumination and collection details are exactly the same as the three probes in the first example. See the detailed diagram for details. Figure 3 , Figure 4 , Figure 5 .

[0094] The near-field signal light collected from the probe is divided into multiple paths through the wavelength division multiplexer 22 , one path returns along the incident optical fiber path of the laser 10 , and the remaining multiple paths can be connected to multiple detectors 40 .

[0095] The detector 40 can be a photomultiplier tube (PMT) or a Raman spectrometer to obtain light intensity information, frequency information, etc.

[0096] In the second example, a wavelength division multiplexer 22 is selected as the all-fiber common optical path illumination and collection system for near-field optical detection. Although the obtained near-field optical signal-to-noise ratio is not as good as the signal-to-noise ratio obtained by using the circulator 20 as the spectroscopic element in the first example, the wavelength division multiplexer 22 is selected at a lower cost and can connect multiple detectors 40 at one time, thereby obtaining multiple information such as the light intensity information and frequency information of the near-field signal.

[0097] The present invention utilizes the principle of reversible optical path and uses an optical fiber probe to simultaneously perform near-field illumination and signal collection on the sample, so that both the illumination and collection processes are completed in the near field, greatly reducing the background noise generated by far-field light and greatly improving the signal-to-noise ratio of near-field optical signal detection. Using an optical fiber probe to simultaneously perform illumination and signal collection, and the entire optical path system is connected by optical fiber optical paths, greatly reducing the complexity of the near-field optical measurement system. Compared with the traditional optical fiber probe applied to the transmission near-field optical microscope, the present invention can simultaneously meet the measurement of transparent and non-transparent samples, greatly improving its application range.

[0098] The optical fiber probe tips used in the present invention are covered by a conductive metal film 52, so they can be used as scanning tunneling microscope probes. The present invention combined with a scanning tunneling microscope system can simultaneously obtain high-resolution morphological information, light intensity information, and spectrum information of the sample.

[0099] Although the present invention has been described through preferred embodiments, the present invention is not limited to the embodiments described herein but includes various changes and modifications that may be made without departing from the scope of the present invention.

[0100] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An all-fiber common light path lighting and collection system, characterized in that: include: Fiber-optic probes for near-field illumination and collection of near-field optical signals; Laser, used for emitting laser light; A polarization controller, used for adjusting the polarization state of the laser entering the optical fiber probe to a radial polarization mode; a detector, used for detecting the near-field optical signal transmitted back; Optical fiber, used for transmitting the laser and near-field optical signals; An optical fiber splitting structure, used to connect an optical fiber probe, a laser and a detector via the optical fiber; The laser emits laser light which is coupled into the optical fiber. Through the optical fiber splitting structure, the laser light is transmitted to the tip of the optical fiber probe to perform near-field illumination on the sample. The excited near-field optical signal enters the optical fiber probe and returns to the optical fiber splitting structure along the original path, and then is transmitted to the detector to obtain the near-field optical signal.

2. The all-fiber common light path lighting and collection system according to claim 1, characterized in that: The optical fiber probe is a tapered optical fiber with a metal film on the outside.

3. The all-fiber common light path lighting and collection system according to claim 2, characterized in that: The optical fiber probe is an aperture optical fiber probe, a metal film-coated surface plasmon optical fiber probe, or a carbon nanotube / metal nanowire composite optical fiber probe.

4. The all-fiber common light path lighting and collection system according to claim 3, characterized in that: A small hole is provided at the conical bottom of the aperture type optical fiber probe; The metal film outer wall of the metal film-coated surface plasmon optical fiber probe has surface plasmons excited and propagated, and focused at the tip; The conical bottom of the carbon nanotube / metal nanowire composite optical fiber probe is provided with carbon nanotubes / metal nanowires, and surface plasmons are excited and propagated on the outer wall of the metal film and the carbon nanotubes / metal nanowires and are focused at the tip.

5. The all-fiber common light path lighting and collection system according to any one of claims 1 to 4, characterized in that: The optical fiber splitting structure is a wavelength division multiplexer or a circulator.

6. The all-fiber common light path lighting and collection system according to claim 5, characterized in that: The wavelength division multiplexer is connected to one or more detectors at the same time, and multiple detectors are arranged in parallel.

7. The all-fiber common light path lighting and collection system according to claim 1, characterized in that: The laser, optical fiber probe and detector are respectively connected to the three ports of the optical fiber splitting structure by optical fiber fusion, optical fiber joint coupling or flange; a polarization controller is arranged at the connecting optical fiber between the optical fiber probe and the optical fiber splitting structure.

8. The all-fiber common light path lighting and collection system according to claim 1, characterized in that: The detector is a photomultiplier tube or a Raman spectrometer.

9. The all-fiber common light path lighting and collection system according to claim 1, characterized in that: The excited near-field optical signal enters the optical fiber probe and returns to the optical fiber splitting structure along the original path. The illumination and collection optical paths share the same optical fiber probe.

10. A working method of an all-fiber common light path lighting and collection system, based on the all-fiber common light path lighting and collection system according to any one of claims 1 to 9, characterized in that: The steps include: The laser couples the laser into the fiber optic optical path system; The laser emits laser light and couples it into the optical fiber. Through the optical fiber splitting structure, the laser light propagates to the tip of the optical fiber probe to perform near-field illumination on the sample. A fiber-optic probe scans the sample; The fiber-optic probe collects near-field optical signals in the near field; The excited near-field optical signal enters the optical fiber probe and returns along the original path to the optical fiber splitting structure, and is then transmitted to the detector to obtain the near-field optical signal.

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