CN102928397A - Optical system of holographic needlepoint enhanced Raman spectrometer - Google Patents

Abstract

The invention discloses an optical system of a holographic needle-tip enhanced Raman spectrometer, relating to a Raman spectrometer. It is equipped with a laser, a beam splitting prism group, an edge filter, a high NA value lens, a sample stage and a Raman signal collection lens. The beam splitting prism group is used to split a laser beam emitted by the laser into two parallel beams Excitation light beam, the beam splitting prism group is provided with a cubic prism and a triangular prism, the edge filter is arranged in front of the beam splitting prism group, and two beams of laser light are incident on the Raman signal acquisition lens at an angle of 45°; the high NA value lens The two excitation beams reflected by the edge filter are converged at a focal point at the end of the needle tip; the Raman signal collection lens is used to transmit the collected Raman signal to a spectrometer and a detector for light separation and detection. The system is simple and easy to operate. In practical applications, two modes, upright and inverted, can be designed for different detection objects.

Description

Optical system of holographic tip-enhanced Raman spectrometer

technical field

The invention relates to a Raman spectrometer, in particular to an optical system of a holographic needle-tip enhanced Raman spectrometer.

Background technique

Regardless of conventional Raman spectroscopy or surface-enhanced Raman spectroscopy, the spatial resolution cannot break through the optical diffraction limit, so there are great limitations on the research objects.

In recent years, it has been discovered that the use of "tip-enhanced Raman spectroscopy" can achieve a spatial resolution of tens of nanometers to several nanometers that breaks through the optical diffraction limit and a single-molecule detection sensitivity. Under normal pressure and air conditions, tip-enhanced Raman spectroscopy (hereinafter referred to as TERS) is currently the only surface and interface optical characterization technique that can provide information on the chemical composition of samples at the scale of a few nanometers to tens of nanometers. Therefore, regardless of industrial applications or basic scientific research, there is a great demand for "tip-enhanced Raman spectroscopy instruments". The development, development and application of TERS instruments are currently research hotspots in the field of Raman spectroscopy. The optical system is the most important and important part of TERS.

The basic working principle of TERS is as follows: the gold or silver needle tip is approached to the substrate by using scanning probe microscopy technology. Under the irradiation of laser with suitable wavelength and polarization, the end of the needle tip generates an enhanced electromagnetic field due to the surface plasmon resonance effect, so it is located under the needle tip. The Raman signal of the sample is enhanced. TERS has high sensitivity and spatial resolution, and can simultaneously obtain the morphology and chemical information of the sample surface. It only needs to use milliwatt-level laser power, so it has been widely valued.

At present, some well-known companies in the world, such as NTMDT, Renishaw and Nanonics, have launched commercial TERS instruments. The independent intellectual property rights of TERS instruments have also been applied for, such as US patent US2002/0154301, patent US2010/0245816; Chinese patent CN101082585A and Chinese patent 201110354369.9 that the applicant has obtained.

A common feature of the above TERS instruments is that their optical systems are basically based on confocal microscopy techniques. This makes the operation of the instrument difficult and expensive. The high-level research work published internationally so far is basically obtained on the instruments developed by the laboratory itself, and few high-level research results have been obtained on the commercial TERS instrument.

Contents of the invention

The purpose of the present invention is to provide a holographic needle-tip enhanced Raman spectrometer optical system.

The present invention is provided with:

A laser, the laser is used to excite the Raman signal of the sample as a system excitation light source;

A beam-splitting prism group, the beam-splitting prism group is used to divide a laser beam emitted by the laser into two parallel-running excitation beams, the beam-splitting prism group is provided with a cubic prism and a triangular prism, and the beam-splitting prism group is located at in front of the laser;

An edge filter, the edge filter is used to reflect two beams of excitation beams running in parallel composed of a beam splitting prism, and filter the reflected excitation and sample light, Rayleigh scattering and other noises on the Raman collection optical path, the edge The filter is set in front of the splitter prism group, and the two laser beams are incident on the Raman signal collection lens at an angle of 45°;

A high NA value lens, the high NA value lens is used to converge the two excitation beams reflected by the edge filter to a focal point at the end of the needle tip;

A sample object stage, the sample object stage is used to place the sample to be tested;

A Raman signal collection lens, the Raman signal collection lens is used to transport the collected Raman signal to a spectrometer and a detector for light separation and detection.

The laser can be an LD laser or a gas laser.

The edge filter can be a long-pass filter or a notch filter.

The present invention has the following outstanding advantages:

1. The outgoing laser beam is divided into two beams running in parallel by the prism group, and the two beams are converged by a high numerical aperture lens. Obviously, this is a new type of holographic recording system. The system is simple and easy to operate. In practical applications, two modes, upright and inverted, can be designed for different detection objects.

2. The double-beam excitation avoids the reflection of the Gaussian center of the excitation light by the needle-tip support (such as the cantilever beam of the AFM needle-tip) when the needle tip is coupled with the spot, which greatly improves the excitation efficiency of the laser and reduces the background noise caused by this reflection , thus effectively improving Raman spectrum collection and signal processing.

3. The compact optical system is conducive to the miniaturization and practicality of the TERS instrument. The above characteristics make the present invention have unique advantages and innovations compared with patents US2002/0154301, US2010/0245816 and CN101082585A.

4. The present invention is different from the products reported so far. The present invention adopts a double-beam focusing system, so it is called a holographic TERS optical system. Compared with the TERS instrument system that has been reported so far, it is convenient and easy to use, and can be used in actual production and research.

Description of drawings

Fig. 1 is a schematic structural view of the upright optical system of the present invention.

FIG. 2 is a schematic structural view of the inverted optical system of the present invention.

In Figures 1 and 2, each mark is: 1 is a laser, 2 is a cube prism, 3 is a triangular prism, 4 is an edge filter, 5 is a high NA value lens, 6 is a needle tip, 7 is a sample stage, 8 Is the Raman signal collection lens, 9 is the Raman spectroscopic system, and 10 is the enlarged view of the focused light at the end of the needle tip.

Detailed ways

Referring to Figures 1 and 2, Figure 1 shows a schematic structural view of an upright optical system of the present invention, and Figure 2 shows a schematic structural view of an inverted optical system of the present invention.

Embodiments of the present invention are provided with:

A laser 1, the laser 1 is used to excite the Raman signal of the sample as a system excitation light source;

A beam-splitting prism group, the beam-splitting prism group is used to divide a laser beam emitted by the laser into two parallel-running excitation beams, the beam-splitting prism group is provided with a cubic prism 2 and a triangular prism 3, and the beam-splitting prism group Set in front of the laser 1;

An edge filter 4, the edge filter 4 is used to reflect two beams of parallel running excitation light beams formed by a beam splitting prism, and filter out reflected excitation and sample light, Rayleigh scattering and other noises on the Raman collection optical path, so The edge filter 4 is arranged in front of the beam splitting prism group, and the two beams of laser light are incident on the Raman signal collection lens 8 at an angle of 45°;

A high NA value lens 5, the high NA value lens 5 is used to converge the two excitation beams reflected by the edge filter 4 to a focus point at the end of the needle tip 6;

A sample stage 7, the sample stage 7 is used to place the sample to be tested;

A Raman signal collection lens 8, the Raman signal collection lens 8 is used to transmit the collected Raman signal to a Raman spectroscopic system 9 (including a spectrometer and a detector) for spectroscopic and detection.

The laser 1 can be an LD laser or a gas laser or the like.

The edge filter 4 can be a long-pass filter or a notch filter.

In Fig. 1, the upright structure is adopted, that is, the sample to be tested is opaque, the needle tip 6 is inserted from the angle between the two beams, and the beam will focus on the end of the needle tip 6 .

In FIG. 2 , an inverted structure is adopted, that is, the sample to be tested is a transparent body, and the end of the needle tip 6 is located at the focal point of the double beams.

Claims (3)

1. holographic Tip-Enhanced Raman Spectroscopy instrument optical system is characterized in that being provided with:

A laser instrument, described laser instrument is used for the Raman signal of excited sample, as system's excitation source;

An Amici prism group, the beam of laser bundle that described Amici prism group is used for laser instrument is sent is divided into the excitation beam that two bundles run parallel, and described Amici prism group is provided with block prism and triangular prism, and described Amici prism is mounted on laser instrument the place ahead;

An edge filter sheet, the excitation beam that two bundles that described edge filter sheet forms for the reflection beam splitting prism run parallel, and on the Raman collection light path the exciting and the noises such as sample light, Rayleigh scattering of filtering reflection, described edge filter sheet is located at Amici prism group the place ahead, two bundle laser is incident in Raman signal with 45° angle gathers lens;

High NA value lens, described high NA value lens are used for two bundle excitation beams of edge filter sheet reflection are converged at a tip end focus point;

A sample stage, described sample stage are used for placing testing sample;

A Raman signal gathers lens, and the Raman signal that described Raman signal collection lens are used for gathering is transported to spectrometer and detecting device carries out light splitting and detection.

2. holographic Tip-Enhanced Raman Spectroscopy instrument optical system as claimed in claim 1 is characterized in that described laser instrument adopts LD laser instrument or gas laser.

3. holographic Tip-Enhanced Raman Spectroscopy instrument optical system as claimed in claim 1 is characterized in that described edge filter sheet adopts long pass filter sheet or notch filter sheet.

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