CN102255225B - Independent chirp parameter regulating system for realizing two-tone laser field - Google Patents

Abstract

The invention relates to an independent adjustment system for realizing the chirp parameters of the two-color laser field. A beam splitter is inserted at the entrance of the pulse compressor of the femtosecond laser to split the energy-amplified light in the femtosecond laser into two The first beam of light enters a set of pulse compressor and hollow fiber stretching and compression system, and the other beam of light enters another set of pulse compressor and hollow fiber stretching and compression system after passing through the plane mirror B, and then passes through the mirror delay system , frequency doubling crystal, the two beams of light are combined into one beam through a beam combining plate, and after passing through a reversible plane mirror, they are respectively connected with a high-order harmonic generation and detection device and a spectral phase interferometer to form a two-color laser The chirp parameter of the field independently tunes the system. The invention can perform separate pulse compression on the energy-amplified light in the femtosecond amplifier to obtain two laser light sources whose chirp can be adjusted independently; the structure is simple and easy to operate.

Description

A Chirp Parameter Independent Adjustment System for Two-color Laser Field

technical field

The invention relates to a system for independently adjusting chirp parameters for realizing a two-color laser field. It can be used in a two-color laser field or a period-level two-color laser field to realize independent adjustment of the chirp parameters of the two light sources.

Background technique

In the existing two-color laser field system, after the pulse compressor of the femtosecond laser amplifier, the light source is divided into two beams, and one beam is frequency-multiplied and then combined with the other beam to form a two-color field. Since the parameters of intensity, wavelength, polarization, and time-delay coincidence of the two beams of light can be adjusted separately, this dual-color field method is widely used in the process of generating ultraviolet precision spectra with high-order harmonics. However, this method uses the light source output by the same pulse compressor, and the amount of chirp contained in the light is the same. Once the pulse compressor is adjusted, the chirp content of the two separated beams will change. Therefore, the chirp parameters cannot be adjusted independently in the existing two-color field or period-level two-color field. However, in the process of generating ultraviolet precision spectra by high-order harmonic method, the chirp content of the light source is a very important parameter, which directly affects the spectral form of the final ultraviolet precision spectrum and the attosecond pulse obtained after Fourier transform. time domain width. Therefore, we need a two-color laser field system whose chirp parameters can be accurately and independently tuned.

Contents of the invention

The invention discloses a system for independently adjusting the chirp parameters of a two-color laser field, and aims to overcome the disadvantage that the prior art cannot realize the independent adjustment of the chirp parameters of two beams of light sources while using the two-color laser field to generate ultraviolet spectra. The present invention separates the light sources from the source of the chirp adjustment—before the pulse compressor, and recombines the beams after passing through the pulse compressor and subsequent adjustment. It can not only maintain the multi-parameter regulation function of the original two-color laser field on the ultraviolet spectrum, but also It can effectively realize the independent adjustment of the chirp parameters of the two-color light source, laying the foundation for the multi-dimensional adjustment of the ultraviolet precision spectrum in the later stage and the acquisition of a single attosecond pulse with the transformation limit.

A system for independently adjusting chirp parameters of a two-color laser field. A beam splitter is inserted at the entrance of the pulse compressor of the femtosecond laser to split the energy-amplified light in the femtosecond laser into two beams, wherein The first beam of light enters a set of pulse compressor, hollow fiber stretching and compression system, and the other beam passes through the plane mirror B and then enters another set of pulse compressor, hollow fiber stretching and compression system, and then passes through the mirror delay system, multiplier After the frequency crystal, the two beams of light are combined into one beam through a beam combining plate, and after passing through the reversible plane mirror, they are respectively connected with the high-order harmonic generation and detection device and the spectral phase interferometer to form the two-color laser field. Chirp parameter independent adjustment system, the two beams can realize independent adjustment of these parameters such as chirp, intensity, wavelength, polarization, and delay coincidence on their respective optical paths.

In the femtosecond laser, the light after the energy amplification is realized through the regenerative amplification cavity, and the pulse width is compressed in the pulse compressor. The pulse compressor consists of a grating, a right-angle mirror delay system and a flat mirror A. After the incident light is broadened by the dispersion of the grating, it is divided into many lights with different wavelengths. After passing through the right-angle mirror and the plane mirror fixed on the delay system, the light of these different wavelengths travels different optical paths when returning to the grating. The system changes the distance between the right-angle mirror and the grating by adjusting the delay system to adjust the optical path difference between different wavelengths, thereby realizing the adjustment of the pulse width of the final output light source. For the narrowest pulse width that can be realized, it is called the zero-chirp state at this time, and the state where the pulse width is greater than the narrowest pulse width is called the chirp state, and the pulse width information contained in the corresponding pulse is called chirp amount of chirp. In this way, we can adjust the chirp parameters of the output light source as long as the distance between the rectangular mirror and the grating is properly changed during the actual operation.

The hollow fiber stretching and compression system is a relatively mature device used to compress the pulse width of femtosecond light source, and the narrowest femtosecond pulse can be obtained in the order of period. This system mainly consists of a hollow fiber system and several pairs of chirped mirrors. The hollow fiber is filled with an inert gas, and the femtosecond laser has a strong nonlinear interaction with the inert gas in the fiber, and the spectrum is broadened, and then the pulse width is compressed by a chirped mirror. The system can adjust the finally obtained pulse width according to actual needs. Our two-color laser field chirp adjustment system is applicable to light sources with various pulse widths. And the narrower the pulse width of light, the more obvious the effect of adjusting its chirp content on the ultraviolet precision spectrum.

The beam combiner is used to realize the collinear transmission of two beams of two-color light sources. The beam combiner lens can select the anti-reflection coating and reflective film corresponding to the wavelength of the light source according to the actual situation, so as to achieve the lowest energy loss of the two beams of light source. In addition, for the special case of period-level femtosecond light source beam combining, we cannot ignore the influence of the lens on the pulse width of the two light sources. At this time, we can also use an independent chirp adjustment system to perform chirp pre-compensation on the two light sources separately, so that the energy of the entire system can not be affected, and the pulse width of each light source can be guaranteed.

Advantage and positive effect of the present invention:

1. Two pulse compressors are used to separately pulse compress the energy-amplified light in the femtosecond amplifier, so that two laser light sources with independently adjustable chirp can be obtained;

2. The present invention is simple in structure, easy to operate, and the adjustment result is stable. In actual operation, as long as the distance between the rectangular mirror and the grating is properly changed, the chirp parameters of the output light source can be adjusted independently. It does not affect the chirp adjustment of another optical path, and can also appropriately change the chirp amount according to the subsequent actual optical path (such as the acquisition of periodic light sources and the introduction of polarizers) to ensure the accurate pulse width of each light source;

3. The two-color laser field chirp adjustment system is applicable to light sources with various pulse widths. When the final output pulse width is not required to be narrower than the pulse width of the laser itself, the hollow fiber stretching and compression system can be omitted, so that The system is more concise and easy to tune;

4. When this method is applied to the process of high-order harmonic generation, in addition to the effective generation of ultraviolet precision spectra, it can also perform precise and real-time control of the chirp content and spectral form of the generated ultraviolet precision spectra.

Description of drawings

FIG. 1 is a schematic structural diagram of a system for independently adjusting chirp parameters of a two-color laser field according to Embodiment 1 of the present invention.

1. The optical pulse after the energy amplification is realized by the regenerative amplification cavity in the femtosecond laser, 2. Plane mirror A, 3. Grating, 4. Right-angle mirror delay system, 5. Pulse compressor, 6. Plane mirror B , 7. Adjustable attenuation plate, 8. Hollow fiber stretching and compression system, 9. High-order harmonic generation and detection device, 10. Beam splitter, 11. Polarizer, 12. Mirror delay system, 13. Frequency multiplication Crystal, 14. Beam combiner, 15. Reversible plane mirror, 16. Spectral phase interferometer.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

A chirp parameter independent adjustment system for realizing a two-color laser field, the structure is shown in Figure 1, a beam splitter 10 is inserted at the entrance of the pulse compressor 5 of the femtosecond laser, and the regenerative amplification cavity in the femtosecond laser is realized The energy-amplified light is divided into two beams, the first beam of light directly enters a set of pulse compressor 5 and hollow fiber stretching and compression system 8, and the other beam of light enters another set of pulse compressor 5 and hollow fiber after passing through the plane reflector B. Optical fiber widening and compression system 8, and then after mirror delay system 12 and frequency doubling crystal 13, the two beams of light are combined into one beam through a beam combining plate 14, and after the reversible plane mirror 15, they are respectively combined with high-order Harmonic generation is connected with the optical path of the detection device 9 and the spectral phase interferometer 16 to form an independent adjustment system for the chirp parameters of the two-color laser field. The two beams can realize chirp, intensity, wavelength, polarization, and time delay on their respective optical paths Overlap independent adjustments of these parameters.

The following embodiment: the central wavelength of the laser output light is 800nm, and the pulse width is 40fs. Taking the frequency-doubled light of the 800nm light source obtained by the BBO frequency-doubling crystal 13 as an example, the specific process of independently adjusting the chirp parameters of the two-color laser field is as follows: by femtosecond In the laser, the optical pulse 1 after the energy amplified by the regenerative amplification cavity enters the pulse compressor 5, and the adjustment of the pulse chirp amount is realized by adjusting the relative distance between the grating 3 and the delay system 4 of the right-angle mirror. The chirp-adjustable laser pulse is adjusted in intensity by the adjustable attenuation sheet 7, and then converged into the hollow fiber stretching and compression system 8 to obtain a chirped femtosecond laser with tunable pulse width (pulse width range: 40-4fs) . At this time, another completely identical chirped femtosecond laser that can be tuned independently is connected in parallel at the 1:1 beam splitter 10 and the beam combiner 14 . An adjustable attenuation film 7 is also added in this way to facilitate the continuous adjustment of laser intensity; a BBO frequency doubling crystal 13 is added to obtain a 400nm light source, and its polarization state is changed through a polarizer 11 . Placing the polarizing plate 11 before the hollow fiber stretching and compressing system 8 can avoid the energy loss of the periodic light source by the polarizing plate 11 in the case of the periodic light source. The beam combiner 14 combines the light sources of 800 nm and 400 nm into a two-color laser field propagating collinearly, and the time overlap of the two is adjusted by the mirror delay system 12 . The combined light sources enter the high-order harmonic generation and detection device 9 to realize the effective generation and multi-dimensional regulation of ultraviolet precision spectra. The parameters for regulation include: the respective intensity, pulse width, and chirp of the two beams of 800nm and 400nm amount and relative polarization. In addition, the chirp information contained in the collinearly propagating two-color laser field can be reflected to the spectral phase interferometer 16 through the reversible plane mirror 15, and continuously measured and determined.

Claims (1)

1. parameter independent regulation system that warbles that realizes the two-color laser field; It is characterized in that: a beam splitting chip is inserted in the pulse shortener porch at femto-second laser; With realizing that through the regenerative amplification chamber light after energy amplifies is divided into two bundles in the femto-second laser; Wherein the first bundle light gets into a cover pulse shortener, hollow optical fiber chirped system, gets into another set of pulse shortener, hollow optical fiber chirped system behind another Shu Guangjing plane mirror B, passes through speculum delayed time system, frequency-doubling crystal again; Two-beam closes the bundle sheet through one and is combined into a branch of light; Behind turnover plane mirror, be connected with sniffer, spectrum position interference measuring instrument with the high order harmonic component generation respectively, constitute the parameter independent regulation system that warbles of two-color laser field.

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