CN110006874B

CN110006874B - Coaxial femtosecond time correlation coherent anti-stokes Raman scattering test system

Info

Publication number: CN110006874B
Application number: CN201910322121.0A
Authority: CN
Inventors: 王英惠; 王文岩
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2019-04-21
Filing date: 2019-04-21
Publication date: 2021-07-30
Anticipated expiration: 2039-04-21
Also published as: CN110006874A

Abstract

The invention relates to a coaxial femtosecond time correlation coherent anti-Stokes Raman scattering test system, belonging to the field of ultrafast femtosecond lasers. The device mainly comprises a femtosecond pulse laser generator, an optical parametric oscillator, a reflector, a beam splitter, a dichroic mirror, a circular ring light generating device, a sample cell, a photomultiplier signal receiving device and a computer. The invention has the advantages of novel structure, reducing the number of reflectors originally used for adjusting the angle between laser pulses from 6 to 2, adjusting the angle between the femtosecond laser pulses by changing the diameter of the circular ring of the annular femtosecond laser pulses, optimizing the time-dependent coherent anti-Stokes Raman scattering technology which originally needs 6 femtosecond laser pulses to adjust the freedom degree into 3 adjustment freedom degrees only by adjusting the diameters of the circular rings of the 2 reflectors and the annular femtosecond laser pulses, and greatly improving the stability, the adjustment usability and the repeatability of the system.

Description

Coaxial femtosecond time correlation coherent anti-stokes Raman scattering test system

Technical Field

The invention belongs to the field of ultrafast femtosecond lasers, and particularly relates to a coaxial femtosecond time-dependent coherent anti-Stokes Raman scattering light testing system which has good stability and adjustable usability and is realized by a beam of annular femtosecond laser pulse with adjustable wavelength and a beam of femtosecond laser pulse with fixed wavelength.

Background

The time-dependent coherent anti-stokes raman scattering technique is a typical nonlinear laser technique. The time-dependent coherent anti-Stokes Raman scattering technology has various evolution forms by changing the characteristics of the laser pulse, and can detect various information on a ground state or an excited state of a sample. The development of picosecond laser technology in the middle of the sixties of the twentieth century, the emergence of a subpicosecond-level impact mode-locked dye laser in the seventies of the twentieth century, and the successful development of a commercial self-mode-locked Qiyun gem laser with simple operation in the early nineties lead the femtosecond laser technology to be rapidly developed in different application fields. In which, by using the time-dependent coherent anti-stokes raman scattering technique of femtosecond laser multi-pulse pumping, many important results such as structural change or energy conversion of substances can be obtained, and people can use the technique to research substances and luminescence processes with luminescence characteristics, flame temperature detection of fuel, identification of intermediate products, and the like.

For the realization of the time-dependent coherent anti-stokes raman scattering technology, three femtosecond laser pulses are required to be utilized, wherein the wavelengths of two femtosecond laser pulses are the same, the wavelength of the other femtosecond laser pulse is different from that of the aforementioned femtosecond laser pulse, the three femtosecond laser pulses are required to be converged on the same point of a detected sample, and the relative angles between the three femtosecond laser pulses when the three femtosecond laser pulses are incident on the sample are required to meet a specific formula. The direction of the three beams of femtosecond laser pulses needs to be accurately adjusted, in order to meet the experimental condition that the emergent angle and the position of each beam of laser pulse of the three beams of femtosecond laser pulses can be adjusted, 2 reflectors need to be arranged for each beam of femtosecond laser pulse to adjust the angle, and 6 reflectors are needed in total. This greatly increases the difficulty and complexity of the experimental operation, and the repeatability of the experiment is also poor. (Wang Ying. ultrafast spectrum study of two typical organic conjugated polymers coherent vibration process [ D ]. Harbin Industrial university, 2009.)

Disclosure of Invention

The invention provides a coaxial femtosecond time correlation coherent anti-Stokes Raman scattering test system, which aims to solve the problems that the difficulty and complexity of experimental operation are greatly increased and the repeatability of experiments is poor due to the complex structure at present.

The technical scheme adopted by the invention is as follows: after a beam of femtosecond pulse laser generated by the femtosecond pulse laser generator passes through the first reflecting mirror and the beam splitter, dividing the femtosecond pulse laser into two beams of femtosecond pulse laser I and femtosecond pulse laser II with the same wavelength, wherein the second femtosecond pulse laser enters the optical parametric oscillator, the wavelength of the third femtosecond pulse laser emitted from the optical parametric oscillator is changed, the adjustment of the wavelength of the third femtosecond pulse laser in a certain range is realized, the third femtosecond pulse laser generated by the optical parametric oscillator passes through the annular light generating device to form a beam of annular femtosecond pulse laser, the annular femtosecond pulse laser and the femtosecond pulse laser I reflected by the second reflecting mirror are combined at the dichroic mirror to obtain a beam of coaxial mixed femtosecond pulse laser, wherein the femtosecond pulse laser I is positioned in the middle of the annular femtosecond pulse laser; the coaxial mixed femtosecond pulse laser is converged at a sample positioned in the middle of the sample cell after passing through the convex lens I, at the moment, the coaxial mixed femtosecond pulse laser interacts with the sample in the middle of the sample cell to generate a signal pulse laser with a wavelength different from that of the coaxial mixed femtosecond pulse laser converged on the sample cell, so that the pulse laser penetrating through the sample cell comprises femtosecond pulse lasers with three wavelengths, annular femtosecond pulse lasers and signal pulse lasers, the signal pulse lasers with the three wavelengths are retained after passing through the third reflector and the optical filter, the signal pulse lasers pass through the three converging beams of the convex lens and are received by the photomultiplier receiving device and recorded on a computer connected with the photomultiplier receiving device.

The dichroic mirror reflects the annular femtosecond pulse laser and transmits the femtosecond pulse laser I;

the annular light generating device consists of a concave lens and a convex lens of a femtosecond pulse laser beam expanding part and a 0-2 pi spiral phase plate of an annular light generating part.

The invention has the advantages of novel structure, reducing the number of reflectors originally used for adjusting the angles among laser pulses from 6 to 2, and adjusting the angles among the femtosecond laser pulses by changing the diameter of the circular ring of the circular femtosecond laser pulses.

Drawings

Fig. 1 is a schematic diagram of the present invention.

Detailed Description

After a beam of femtosecond pulse laser 3 generated by the femtosecond pulse laser generator 1 passes through the first reflecting mirror 2 and the beam splitter 6, the femtosecond pulse laser 3 is divided into two beams of a femtosecond pulse laser I9 and a femtosecond pulse laser II 5 with the same wavelength, wherein the second femtosecond pulse laser 5 enters the optical parametric oscillator 4, the wavelength of the third femtosecond pulse laser 7 emitted from the optical parametric oscillator 4 can be changed, the adjustment of the wavelength of the third femtosecond pulse laser 7 in a certain range is realized, the third femtosecond pulse laser 7 generated by the optical parametric oscillator 4 passes through the annular light generating device 8 to form a beam of annular femtosecond pulse laser 12, the annular femtosecond pulse laser 12 and the femtosecond pulse laser I9 reflected by the second reflecting mirror 10 are combined at the dichroic mirror 11 to obtain a coaxial mixed femtosecond pulse laser, wherein the femtosecond pulse laser I9 is positioned in the middle of the annular femtosecond pulse laser 12; the coaxial mixed femtosecond pulse laser passes through the convex lens I13 and is converged at a sample positioned in the middle of the sample cell 14, at the moment, the coaxial mixed femtosecond pulse laser interacts with the sample in the middle of the sample cell 14 to generate a signal pulse laser 15 with a wavelength different from that of the coaxial mixed femtosecond pulse laser converged on the sample, so that the pulse laser penetrating through the sample comprises a femtosecond pulse laser 9 with three wavelengths, a ring-shaped femtosecond pulse laser 12 and the signal pulse laser 15, the signal pulse laser 15 is reserved after the pulse laser with the three wavelengths passes through a reflector III 17 and an optical filter 18, the signal pulse laser 15 is condensed through a convex lens III 19 and is received by a photomultiplier receiving device 20, and the condensed beam is recorded on a computer 21 connected with the photomultiplier receiving device 20. The computer can record the information such as the intensity and wavelength of the signal pulse laser 15 under different experimental conditions, for example, after the sample is excited by the femtosecond laser pulse and passes through different delay times, and can draw a corresponding chart to analyze the experimental result.

The dichroic mirror 11 reflects the annular femtosecond pulse laser 12 and transmits the femtosecond pulse laser I9;

the annular light generating device 8 is composed of a concave lens 801 of a femtosecond pulse laser beam expanding part, a convex lens 802 and a 0-2 pi spiral phase plate 803 of an annular light generating part.

The whole system is placed on a unified optical platform, the femtosecond pulse laser generator 1 is positioned at the right lower part of the whole system, the optical parametric oscillator 4 is positioned at the left side of the femtosecond pulse laser generator 1, the annular light generating device 8 is positioned at the left side of the optical parametric oscillator 4, and the sample cell 14 is positioned above the femtosecond pulse laser generator 1, the optical parametric oscillator 4 and the annular light generating device 8.

Claims

1. A coaxial femtosecond time correlation coherent anti-Stokes Raman scattering test system is characterized in that: a beam of femtosecond pulse laser generated by the femtosecond pulse laser generator passes through the first reflecting mirror and the beam splitter, dividing the femtosecond pulse laser into two beams of femtosecond pulse laser I and femtosecond pulse laser II with the same wavelength, wherein the second femtosecond pulse laser enters the optical parametric oscillator, the wavelength of the third femtosecond pulse laser emitted from the optical parametric oscillator is changed, the adjustment of the wavelength of the third femtosecond pulse laser in a certain range is realized, the third femtosecond pulse laser generated by the optical parametric oscillator passes through the annular light generating device to form a beam of annular femtosecond pulse laser, the ring-shaped femtosecond pulse laser and the femtosecond pulse laser I reflected by the second reflecting mirror are combined at the dichroic mirror to obtain a beam of coaxial mixed femtosecond pulse laser, wherein the femtosecond pulse laser I is positioned in the middle of the ring-shaped femtosecond pulse laser; the coaxial mixed femtosecond pulse laser passes through the convex lens I and is converged at a sample positioned in the middle of the sample cell, at the moment, the coaxial mixed femtosecond pulse laser interacts with the sample in the middle of the sample cell to generate a signal pulse laser with a wavelength different from that of the coaxial mixed femtosecond pulse laser converged on the sample cell, so that the pulse laser penetrating through the sample cell comprises three pulse lasers with different wavelengths, namely femtosecond pulse laser, annular femtosecond pulse laser and signal pulse laser, the signal pulse laser is reserved after the three pulse lasers with different wavelengths pass through the reflector III and the optical filter, the signal pulse laser passes through the convex lens III beam, is received by the photomultiplier receiving device and is recorded on a computer connected with the photomultiplier receiving device;

2. A coaxial femtosecond time dependent coherent anti-stokes raman scattering test system according to claim 1, wherein: the dichroic mirror reflects the ring-shaped femtosecond pulse laser and transmits the femtosecond pulse laser I.