CN102494767B - Device for generating orthogonal polarized double-color laser field - Google Patents

Abstract

A device for generating an orthogonally polarized two-color laser field, which includes a femtosecond laser. A beam splitter is placed at the exit of the femtosecond laser. The light is divided into two beams by the beam splitter. Enter the first focusing lens, another beam of light passes through the 1/2 wave plate and the frequency doubling crystal in turn, and then exits. The first plane reflector is installed on the exit light path, and the second focus lens is installed on the exit light path of the first plane reflector. , the light is focused by the second focusing lens and then enters the second plane reflector, the light is reflected by the second plane reflector and then enters the gas box, and the gas box is connected with the high-order harmonic generation and detection device. The device can freely adjust the angle of the two combined beams and keep the spatial position of the laser focus and the gas medium unchanged. It can not only filter long electron trajectories in time, but also retain short electron trajectories in space. Thus, short electron trajectories can be obtained to the greatest extent.

Description

A device for generating orthogonally polarized two-color laser fields

technical field

The invention relates to the technical field of laser generating devices, in particular to a device for generating orthogonally polarized two-color laser fields that can be optimally controlled synchronously in time and space.

Background technique

In recent years, high-order harmonics have gradually become a frontier research topic in the field of strong field physics in the world due to its wide application prospects. Due to the unique advantage that the radiation spectrum presents a platform area and the harmonics in the platform area have a regular distribution of equal frequency intervals, high-order harmonics are widely used in research to obtain attosecond pulses. Through the acquisition of attosecond pulses, humans can measure various atoms, The movement process of the inner electrons in the molecular medium, detecting the dynamics of the bound state and the continuous state electrons under a strong field; high-order harmonics can also generate optical frequency combs of different periods under the condition that the carrier phase is locked. And the visible light band is extended to the ultraviolet and extreme ultraviolet bands, so that ultra-high resolution spectral detection can be realized.

The generation process of higher harmonics is mainly produced by the combined action of long electron trajectories and short electron trajectories. At present, when studying the high-order harmonic spectrum, the focus is on the role of isolated short electron trajectories. In order to effectively suppress the generation of high-order harmonic long Experimental methods are adopted in space and space respectively.

In general, for the selective control of short electron trajectories, it is mainly controlled by using either of the two-color laser field with orthogonal polarization or the laser focus located in front of the gas medium. Although these two methods can collect short electron trajectories to a large extent, there is still the influence of long electron trajectories, which still has a great impact on the effective acquisition of precise single attosecond pulses and the improvement of their energy conversion efficiency.

In addition, most of the existing two-color laser fields adopt the method of fixing the angle between the two laser beams. If the angle needs to be adjusted during the work process, the optical path of the two beams will be changed, which requires not only accurate calculation, but also the adjustment of the experimental device It is very cumbersome, and the spatial position of the laser focus cannot be kept unchanged while changing the angle between the two beams.

Contents of the invention

The purpose of the present invention is to provide a device for generating an orthogonally polarized two-color laser field, which can freely adjust the angle of the combined beam of the two beams, and keep the spatial position of the laser focus and the interaction of the gas medium unchanged, not only from the time It can filter long electron trajectories and reserve short electron trajectories in space, so that short electron trajectories can be obtained to the greatest extent.

Technical solutions

In order to solve the above-mentioned technical problems, the present invention designs a generation device of an orthogonally polarized two-color laser field, which includes a femtosecond laser, a beam splitter is placed at the exit of the femtosecond laser, and the light emitted by the femtosecond laser is divided into two beams by the beam splitter , one beam of light enters the plane reflector delay device and then enters the first focusing lens. A first flat mirror is installed on the outgoing light path, and a second focusing lens is installed on the outgoing optical path of the first flat reflecting mirror. After entering the gas box, the gas box is connected with the high-order harmonic generation and detection device, which is characterized in that:

The second flat reflector is installed on the combined motor, the combined motor includes a first motor and a second motor, the first motor is installed on the second motor, the first motor can move along the horizontal direction together with the second motor, and the second motor can move horizontally together with the second motor. The plane reflecting mirror is mounted on the first motor and can rotate around the first motor shaft together with the first motor.

The first plane reflector is a dichroic mirror.

The second plane reflector is a dichroic mirror.

A third plane reflector is installed on the optical path between the plane reflector delay device and the first focusing lens, and the light is emitted from the plane reflector delay device and then reflected by the third plane reflector and then injected into the first focusing lens. lens.

A fourth plane reflector and a fifth plane reflector are sequentially installed on the optical path between the first plane reflector and the second focusing lens, and the light passes through the fourth plane reflector and the fifth plane reflector after being emitted from the first plane reflector. After being reflected by the plane mirror, it enters the second focusing lens.

The third plane reflector is a plane reflector.

Both the fourth plane reflector and the fifth plane reflector are dichroic mirrors

The frequency doubling crystal is BBO crystal, LBO crystal or KTP crystal.

The first, second, third, fourth and fifth plane mirrors are high reflection plane mirrors.

Beneficial effect

The invention is simple and simple, easy to operate, and can freely adjust the included angle of the two beams of light. It is only necessary to adjust the moving position of the second motor and the rotation angle of the first motor appropriately to change the angle of combined beams, and to ensure that the optical paths of the two beams are equal by changing the reflection delay system of the plane mirror, while the laser focus and the gas medium The spatial interaction position between them remains unchanged, and the selection control of long and short electron trajectories in the process of high-order harmonic generation can be realized simultaneously in time and space, effectively removing the influence of long electron trajectories, and only retaining the advantages of short electron trajectories. It is conducive to the generation of phase-stable high-order harmonics and the acquisition of a single attosecond pulse, and the time-space synchronously optimized two-color laser field adjustment system is applicable to light sources of various pulse widths and wavelengths, saving costs.

Description of drawings

Accompanying drawing 1 is the structure diagram of the embodiment of the present invention.

Among them, 1. Femtosecond laser, 2. 1:1 beam splitter, 3. Plane mirror delay device, 4. The third high-reflection plane mirror, 5. The first focusing lens, 6. 1/2 wave plate, 7 , BBO frequency doubling crystal, 8, the first high-inversion plane mirror, 9, the fourth high-inversion plane mirror, 10, the fifth high-inversion plane mirror, 11, the second focusing lens 12, combined motor, 12a, the first motor, 12b, the first Two motors, 13, the second high inverse plane mirror, 14, the gas box, 15, the high-order harmonic generation and detection device.

Detailed ways

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

As shown in Figure 1, taking the central wavelength of the output light of the femtosecond laser as 800nm and the pulse width as 40fs, and taking the frequency doubled light of 400nm obtained by the BBO frequency doubling crystal 7 as an example, a beam splitter 2 is placed at the exit of the femtosecond laser 1 , the light emitted by the femtosecond laser 1 is divided into two beams by the beam splitter 2, and one beam enters the plane reflector delay device 3, and the light is emitted from the plane reflector delay device 3 and then reflected by the third high-reflection plane with a specification of HR800nm After being reflected by the mirror 4, it enters the first focusing lens 5, and the light enters the gas box 14 after being focused by the first focusing lens 5; another beam of light source passes through a BBO frequency doubling crystal 7 to produce a 400nm light source, due to the characteristics of the BBO crystal, this The polarization state of the 400nm light source and the incident 800nm light source are orthogonal to each other. If other crystals are used for the frequency doubling crystal 7 or the polarization state of the 400nm outgoing light source needs to be adjusted, the 1/2 wave plate 6 is used to rotate the polarization state of the incident light. At this time, the output light source of the BBO frequency doubling crystal 7 includes two light sources of 800nm and 400nm, and the output light path of the BBO frequency doubling crystal 7 is sequentially equipped with the first high-reflective plane mirror 8 and the fourth high-reflective plane mirror with the same specifications of HR400nm/AR800nm 9 and the fifth high-reflection flat mirror 10, after light is emitted from the first high-reflective flat mirror 8, it is reflected by the fourth high-reflective flat mirror 9 and the fifth high-reflective flat mirror 10, and then the 800nm light source is transmitted, and the reflected 400nm light source enters the second focusing lens 11 After the light is focused by the second focusing lens 11, it enters the second high-reflection flat mirror 13 of HR400nm/AR800nm, and the second high-reflection flat mirror 13 is installed on the combined motor 12. The combined motor 12 includes a first motor 12a, a first The motor 12a is installed on the second motor 12b, the first motor 12a can move along the horizontal direction together with the second motor 12b, and the second high inverse plane mirror 13 is installed on the first motor 12a and can wind around the first motor together with the first motor 12a The 12a axis rotates; the light enters the gas box 14 after being reflected by the second high-inversion plane mirror 13, and the gas box 14 is connected with the high-order harmonic generation and detection device 15, and the focus of the second 400nm light source and the first 800nm light source is in the gas Convergence in the box 14 becomes a two-color laser field with orthogonal polarization. Since the 400nm light source does not generate high-order harmonics, it only plays the role of polarization perturbation in the entire generation process, and is used to select short electron trajectories in time, so in When adjusting the angle between the two light sources, a small amount of error between the 400nm focus and the beam-combining point is acceptable, and no additional adjustment is required. Finally, the high-order harmonics generated by the two-color light source enter the high-order Harmonic generation and detection device 15 collects and detects signals.

The invention is simple and easy to operate, and can freely adjust the angle between the two beams of light. It only needs to properly adjust the moving position of the second motor and the rotation angle of the first motor to realize the change of the angle of the combined beam, and by changing the plane mirror The reflective delay system ensures that the optical paths of the two beams are equal, and at the same time the spatial interaction position between the laser focus and the gas medium remains unchanged, and can simultaneously realize the selection control of the long and short electron trajectories in the process of high-order harmonic generation in terms of time and space. Effectively remove the influence of long electron trajectories and only retain the advantages of short electron trajectories, which is conducive to the generation of phase-stable high-order harmonics and the acquisition of a single attosecond pulse, and the two-color laser field adjustment system that can be optimized synchronously in time and space It is applicable to light sources with various pulse widths and wavelengths, which saves costs.

The technology to be protected in the present invention is not limited to the technical features mentioned in this embodiment, and any technical solution inspired by the present invention falls within the protection scope of the present invention.

Claims (7)

1. the generation device of a cross polarization two-color laser field, it comprises femto-second laser, the femto-second laser exit is placed with beam splitting chip, femto-second laser penetrates light and is divided into two bundles by beam splitting chip, a branch of light is injected first condenser lens after entering the plane mirror time-delay mechanism, light enters gas box after first condenser lens focuses on, another Shu Guang is successively through outgoing behind 1/2 wave plate and the frequency-doubling crystal, first plane mirror is housed on the emitting light path, second condenser lens is housed on the emitting light path of first plane mirror, light is injected second plane mirror after second condenser lens focuses on, light is gone into the gas box through the second plane reflection mirror reflection is laggard, the gas box produces with higher hamonic wave and is connected with sniffer, it is characterized in that:

Described second plane mirror is installed on the composition motor, composition motor comprises first motor and second motor, first motor is installed on second motor, first motor can move with second motor along continuous straight runs together, and second plane mirror is contained on first motor and can rotates around first motor shaft together with first motor;

Described first plane mirror is selected dichroic mirror for use;

Described second plane mirror is selected dichroic mirror for use.

2. the generation device of a kind of cross polarization two-color laser as claimed in claim 1 field, it is characterized in that: on the light path between described plane mirror time-delay mechanism and first condenser lens the 3rd plane mirror is installed, light penetrates by injecting first condenser lens again after the 3rd plane reflection mirror reflection from the plane mirror time-delay mechanism.

3. the generation device of a kind of cross polarization two-color laser as claimed in claim 2 field, it is characterized in that: on the light path between described first plane mirror and second condenser lens Siping City's face catoptron and the 5th plane mirror are housed successively, light penetrates by Siping City's face catoptron and the 5th plane reflection mirror reflection are laggard from first plane mirror goes into second condenser lens.

4. the generation device of a kind of cross polarization two-color laser as claimed in claim 2 field, it is characterized in that: described the 3rd plane mirror is plane mirror.

5. the generation device of a kind of cross polarization two-color laser as claimed in claim 3 field, it is characterized in that: described Siping City face catoptron and the 5th plane mirror are all selected dichroic mirror for use.

6. the generation device of a kind of cross polarization two-color laser as claimed in claim 1 field, it is characterized in that: described frequency-doubling crystal is bbo crystal or lbo crystal or ktp crystal.

7. as the generation device of claim 3 or 5 described a kind of cross polarization two-color laser fields, it is characterized in that: described first, second, third and fourth is high antiplane mirror with five plane mirrors.

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