CN105092032B - Transient state high resolution spectrometer based on F-P etalons - Google Patents

Abstract

The invention is a kind of transient state high resolution spectral measuring apparatus, is related to high resolution spectral measuring field and transient state spectral measurement field.The high resolution spectral measuring apparatus realizes the high-resolution measurement to single impulse transient spectrum using the angle light splitting and the technology by concatenating multiple F P etalons of etalon itself.The invention can be applied to the high-resolution spectras fields of measurement such as Brillouin scattering, Zeemen effect, spintronics.

Description

Transient High Resolution Spectrometer Based on F-P Etalon

technical field

The invention relates to a transient high-resolution spectrometer designed based on an etalon-connected multi-pass technology, which is mainly used in the field of high-resolution spectrum measurement such as Brillouin scattering.

Background technique

Spectral analysis has always been one of the most basic analytical and testing methods in various disciplines such as physics, chemistry, biology, and materials, and ultra-high resolution spectroscopy is the most cutting-edge technology in this field.

Among the existing spectral analysis technologies, one is the scanning interferometer that mainly realizes high-resolution spectrum through FP interferometer, such as the scanning FP interferometer developed by Burleigh Company, and the serial 3+3 Brillouin developed by JRS Scientific Instruments. Scattering spectrometers, which can now achieve resolution Resolution conditions for sharpness>90 and contrast>10000. Because of its 3+3 serial multi-pass system, it greatly improves the contrast of the spectrum. Although the scanning spectrometer can achieve a scanning accuracy of <10MHz, it cannot achieve real-time measurement and cannot measure pulse signals (1-100ns); in addition, the wavelength meter, as a high-resolution spectral measurement instrument, has also been recognized at home and abroad. widely used. The wavelength meter can generally obtain a resolution of 10MHz. However, the general time response is relatively "slow" (above microseconds), and it is still impossible to perform transient measurements, and the wavelength meter often only gives a wavelength and cannot give a spectrum. When there is When there are multiple modes or the laser has mode hopping, the wavelength meter cannot meet the measurement requirements.

Another type of spectrometer can measure the single-pulse transient spectrum, which can be applied to the study of spin dynamic waves, including the study of transient effects such as carrier modulation and nonlinear effects, and it can also be applied to oceans modulated by lasers LiDAR systems, most stochastic laser systems and nanolaser systems operating under pulsed laser pumping conditions. Among them, for lidar, a system that works in a complex environment, the inability to measure in real time means that the work efficiency is greatly reduced, and the scanning has too high a stability requirement, and even causes the instrument to lose its on-site measurement capability. Therefore, a spectrometer that can realize real-time measurement and ultra-fine spectral measurement at the same time can play a huge role in similar fields.

In 2007, French scientists published an article on Nature Photonics, proposing a very compact Fourier transform Brillouin scattering spectrometer structure. This kind of spectrometer detects the evanescent wave of the optical waveguide, and then obtains the spectrum through Fourier transform. In principle, it can realize transient measurement, but its biggest problem is that the sensitivity is relatively low and the signal-to-noise ratio is very high; at the same time, its spectral resolution Only to the order of hundreds of MHz, which limits its application range. In addition, the fiber optic spectrometer developed rapidly in recent years can realize the measurement of dynamic spectrum and transient spectrum, but limited by CCD or other photosensitive array components, its spectral resolution is low, and it cannot meet the needs of high-resolution spectral measurement. occasions.

Contents of the invention

Aiming at the defect that the high-resolution spectrum and transient spectrum measurement in the prior art cannot be achieved at the same time, the technical problem to be solved by the present invention is to provide a method that can obtain a high resolution and greatly improve the sensitivity, and can measure a single Spectrometer for Pulse Transient Spectroscopy.

In order to solve the above-mentioned technical problem, a kind of high-resolution spectrometer provided by the present invention is characterized in that it comprises a beam converter, a polarizing prism, a 1/2 wave plate, a beam splitting system, and three reflectors in sequence from the signal incident end. Ring series, in which a polarizing prism, a 1/2 wave plate and three mirrors connected in series form a ring cavity system. The final signal is reflected back into a polarizing prism, a telephoto fixed-focus lens with f ≥ 0.8m, and a CCD (CCD can be ICCD or EMCCD, according to actual needs). The light beam converter includes a lens, a diaphragm, a lens and a cylindrical lens sequentially from the signal input end. The spectroscopic system is composed of one or more etalons. The multiple etalons refer to two or more etalons. The free spectral range of the multiple etalons must satisfy the integer proportional relationship. For example, we can connect a fixed cavity length etalon and a variable cavity length etalon in series. The signal transmitted through the cylindrical mirror passes through the fixed-cavity-length etalon and the variable optical-cavity-length etalon in sequence, and the positions of the two are interchangeable.

The solution of the present invention to solve the technical problem is: the incident signal first passes through the collimation system in the beam converter to become parallel light, and then becomes a cylindrical wave after passing through the cylindrical lens, and the cylindrical wave is incident on the polarizing prism, wherein the p component passes through the After the 1/2 wave plate, it becomes the s component, and then enters the spectroscopic system composed of fixed cavity length etalon + variable optical cavity length etalon, and the split light passes through the ring cavity system clockwise and is reflected by the polarizing prism again Entering the 1/2 wave plate, at this time, the s component passes through the 1/2 wave plate and becomes the p component again, and passes through the ring cavity system clockwise again. Finally, it passes through the polarizing prism and reaches the focusing element. Through the focusing of the focusing element, the light of different wavelengths will form a separated point spectrum on the rear focal plane of the lens. Finally, the CCD is used to image the signal on the rear focal plane of the lens to complete the spectrum. The measurement of ; while the initial s component is reflected by any optical surface and exits the system counterclockwise through the ring cavity system.

The technical advantages of the present invention are as follows: Utilize the transient high-resolution spectrometer provided by the present invention, owing to have used the spectrometer that cylindrical lens and Fabry-Perot etalon form, the outgoing signal only has spatial frequency in x direction, and y direction still has spatial frequency. Maintaining the characteristics of the plane wave, this spectrometer makes the energy of the signal scattered on the circular ring concentrate on two points in each order spectrum of the original equal-tilt interference fringe, which enhances the signal strength and signal-to-noise ratio, and significantly improves the The strength of the signal and the data transmission speed of the receiving system improve the detection sensitivity of the system for weak signals; and because the space angle spectroscopy of the etalon is used instead of the cavity length scanning spectroscopy of the scanning interferometer, it can meet the requirements of most transient spectra. At the same time, the series connection multi-pass technology of the etalon has been developed, so if the thickness of the two etalons is an integer multiple, the order of the thick etalon is m times that of the thin etalon, and the final position of the main maximum determined by the thin etalon; meanwhile, the width of the main maximum is determined by the thick etalon. Finally, the tandem etalon system achieves a large free spectral range (FSR) and a narrow spectral line width while maintaining its transient signal splitting ability. In the same way, multi-pass technology is actually equivalent to the series connection of two identical etalons, and the FSR does not change significantly, but the spectral line width will be further compressed.

Therefore, the optical path configuration scheme of the fixed cavity length etalon + variable optical cavity length etalon in the spectroscopic system can be adjusted to the multiple relationship between the thickness of the two etalons, which is used when the resolution requirement is not very high, but the free spectrum requirement is relatively wide ; It can also be adjusted to the equal thickness of the two etalons for the measurement of fine spectra in a small free spectral range.

Description of drawings

Accompanying drawing 1 is the structural diagram and light path diagram of the whole system

Accompanying drawing 2 is the schematic diagram of beam conversion system.

1-lens 1; 2-stop; 3-lens 2; 4-cylindrical lens

Detailed ways

The embodiments of the present invention are described in further detail below in conjunction with the accompanying drawings, but the present embodiments do not limit other inventions, and all similar structures and similar changes of the present invention should be included in the scope of protection of the present invention.

As shown in Figure 1, the example of the present invention provides a spectrometer device that utilizes one or more F-P etalon serial connection multi-pass technology to simultaneously measure high-resolution spectrum and transient spectrum. It includes a beam converter system composed of lens 1 (1), diaphragm (2), lens 2 (3), cylindrical lens, polarizing prism, 1/2 wave plate and three mirrors connected in series in a ring. Ring cavity system, a spectroscopic system composed of a fixed cavity length etalon and a variable optical cavity length etalon, focusing lens and CCD. Among them, the refractive index of the etalon is n=1.4607, the reflectivity R=0.99, the fixed cavity length and thickness h>23.2mm; the focal length of the focusing lens is f≥lm, the CCD pixel l=16μm, and the number of CCD pixels: 1024×1024. The incident light first passes through the beam converter system shown in Figure 2, and the specific process is as follows: the lens 1 (1) focuses the incident light into a point light source and casts it on the pinhole diaphragm. Wherein the diaphragm is on the focal plane of lens 1(1) and lens 2(3). After the light passes through the spatial filtering of the diaphragm, it is diverged by the lens 2 (3) to obtain parallel light. The light passes through a custom-made cylindrical lens (4), changing from a spherical wave to a cylindrical wave, which only has spatial frequency in the x direction, and maintains the plane wave characteristic in the y direction.

The cylindrical wave is incident on the polarizing prism, and the P component passes through the ring cavity twice clockwise, and finally reaches the focusing element and the area array detector such as ICCD to complete the final measurement of the spectrum. This is the so-called multi-pass technology. In this process, the p component passes through the spectroscopic system and mirror group twice. The spectroscopic system includes a fixed cavity length F-P etalon and a variable optical cavity length F-P etalon. This is the so-called cascaded etalon system. When the thickness of the fixed cavity length F-P etalon is different from that of the variable optical cavity length, a large free spectral range (FSR) and narrow spectral line width can be achieved; when the thickness of the two etalons is the same, the FSR is the same as a single There is no change in time, but the spectral line width is further compressed, so the use of multiple etalons in series can achieve the spectroscopic requirements of high-resolution spectra, and the cavity length and variable optical cavity length F-P etalon can be adjusted according to requirements. Replace the fixed cavity length F-P etalon to meet different measurement needs. After the cylindrical wave is incident on the polarizing prism, another component, namely the s component, will be reflected by any optical surface and exit through the ring cavity system counterclockwise.

After the light splitting is completed, the light enters the group of three reflectors arranged in the form shown in FIG. 1 . The mirror 1 is placed at an angle of 135° to the +x-axis direction, and the light propagates through the mirror 1 from the +x direction to the -y-axis direction. The reflector 2 is placed at an angle of 45° to the +x direction, and the light propagates through the reflector 2 from the -y direction to the -x direction. Through the reflection of the mirror 3 parallel to the mirror 1, the light propagation direction changes from the -x direction to the +y direction. All the light rays reflected by the reflector 3 are required to be perpendicularly incident on the polarizing prism opposite to the reflector 3 .

The light reaches the telephoto fixed-focus lens, enters the focus of the lens, and the parallel light converges and projects on the area array optical photosensitive element to complete the measurement of the spectrum. Optical photosensitive elements are photosensitive elements such as ICCD and EMCCD, which can be selected according to actual needs.

Claims (4)

1. the transient state high-resolution light-splitting method based on F-P etalons, it is characterised in that：It is concatenated by multiple F-P etalons Mode improves the resolution ratio and Free Spectral Range of spectrometer, and Real-Time Optical is realized in the space light splitting ability using F-P etalons The requirement of high-resolution, wide Free Spectral Range can be realized while spectrum detection again；Incoming signal first passes around beam converter In colimated light system become directional light, then by becoming cylindrical wave after cylindrical lens, cylindrical wave is incident on devating prism, wherein P-component becomes s components after 1/2 wave plate, subsequently enters the beam splitting system being made of concatenation etalon, and the light after light splitting is suitable Hour hands can be reflected into 1/2 wave plate by devating prism again after annular chamber system, and at this moment s components are again heavy after 1/2 wave plate Newly become p-component, again clockwise through annular chamber system, concentrating element is reached finally through devating prism, by focusing member The focusing of part makes the light of different wave length that will form the dotted spectrum of separation on the back focal plane of lens, finally uses CCD in lens Back focal plane signal is imaged, complete transient state high-resolution spectra real-time measurement；And initial s components are by arbitrary optics table After the reflection of face system is projected through annular chamber system counterclockwise.

2. the transient state high resolution spectrometer based on F-P etalons, it is characterised in that：By light incident side, light beam is respectively included Converter, devating prism, 1/2 wave plate, beam splitting system, annular chamber system, concentrating element and planar array detector；

Incident light is converted to cylindrical wave by beam converter by spherical wave, then by devating prism, wherein p-component is through 1/2 wave Piece enters beam splitting system, and the light after light splitting can be reached by devating prism after the circle of annular chamber system two focus member clockwise Part makes the light projection of different wave length on planar array detector, completes the measurement of spectrum by the focusing of concentrating element；S component quilts After reflection system is projected through loop system counterclockwise；The beam splitting system include multiple FP etalons, each etalon from It is integral multiple relation by spectral region, multiple etalons refer to two or more etalons；The optical beam transformation The light beam conversion element of device is two lens, diaphragm and cylindrical lens composition；The annular chamber system is gone here and there in a ring by three Plane mirror, devating prism and the 1/2 wave plate composition connect.

3. the transient state high resolution spectrometer based on F-P etalons according to right 2, it is characterised in that：Using by one Determine the long etalon of chamber to concatenate with a long etalon of variable optical chamber.

4. the transient state high resolution spectrometer based on F-P etalons according to right 2, it is characterised in that：Concentrating element is f The focal length fix-focus lens of >=0.8m, planar array detector are ICCD or EMCCD, and pixel dimension is more than or equal to 16 μm, and pixel number is more than It is equal to：1024×1024.