Vortex light amplification device for realizing high space contrast based on annular pumping

Abstract

The invention relates to a vortex light amplification device for realizing high space contrast based on annular pumping, which comprises a pumping light source, an annular light beam generation lens, a signal light source, a vortex light beam generation lens, a dichroic mirror and a nonlinear crystal, and is characterized in that the pumping light source generates common pumping light, and the common pumping light is converted into an annular pumping light beam through the annular light beam generation lens; the signal light source generates seed light, and the seed light is converted into vortex seed light through the vortex light beam generation lens. After being combined through the dichroic mirror, the two beams of light are collinearly emitted into the nonlinear crystal, and optical parametric amplification of the vortex light is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of ultrafast laser light field regulation, and in particular to a vortex light amplification device based on ring pumping to achieve high spatial contrast. Background Art

[0002] A vortex beam is a new type of structured beam with a spiral phase or wavefront. During the transmission process, the beam advances in a spiral manner, and the photons carry orbital angular momentum. Since vortex beams have a unique light field structure, they have important application value in many fields. In the field of optical communications, the use of vortex light will greatly broaden the channel flux and achieve large-capacity information transmission; in the field of detection, the rotational Doppler effect of vortex beams can be used to measure the rotation speed of rotating bodies; when a vortex beam acts on an object (such as a particle), the orbital angular momentum carried by the beam can be transferred to the particle to control the particle to rotate or translate. This feature can be used to develop optical tweezers and optical wrenches, etc.; at the same time, vortex light also has broad application prospects in optical processing, astronomical detection, quantum information processing and other fields.

[0003] However, in order to achieve the maximum benefit of these applications, the vortex beam needs to have a high spatial contrast, that is, the light intensity should be highly concentrated on the spiral line. When observed from the beam propagation direction, the annular edge area should be clear and the light intensity distribution in the center area should be as weak as possible, so as to approach the ideal vortex beam shape. However, the center area of ​​the traditionally generated vortex light often has some residual light intensity, which leads to the amplification of the residual light intensity in the center area during the optical parametric amplification process using traditional Gaussian pump light, which ultimately leads to a low contrast between the light intensity of the annular edge area and the center area of ​​the obtained vortex beam. Summary of the invention

[0004] In view of the above-mentioned problems existing in the prior art, the present invention provides a vortex light amplifying device based on annular pumping to achieve high spatial contrast. Therefore, this patent invents an optical parametric amplification of a vortex light beam based on annular pumping light. By applying an annular beam generating lens, an annular pumping light that matches the vortex light beam intensity distribution in space is obtained, and the annular pumping light is used to amplify the vortex signal light, thereby effectively avoiding the amplification of the residual light intensity in the central area of ​​the vortex light and only amplifying the annular edge area of ​​the vortex light, thereby finally achieving vortex light amplification with high spatial contrast.

[0005] The technical solution of the present invention is as follows:

[0006] A vortex light amplifying device based on annular pumping to achieve high spatial contrast, characterized in that it comprises a pump light source, an annular light beam generating lens, a signal light source, a vortex light beam generating lens, a dichroic mirror, and a nonlinear crystal;

[0007] The pump light source is used to generate pump light for the annular pump to achieve high spatial contrast vortex optical parametric amplification;

[0008] The pump light source is transformed into a pump light having an annular light field after passing through the annular light beam generating lens, so as to spatially match the vortex signal light generated after passing through the vortex light beam generating lens;

[0009] The signal light source is a seed light that generates a vortex light beam;

[0010] The vortex signal light generated after the vortex beam generating lens and the annular pump light generated after the annular beam generating lens are collinearly incident into the nonlinear crystal using a dichroic mirror, and after optical parameter amplification, a vortex signal light with high spatial contrast is obtained.

[0011] The dichroic mirror is a beam combining mirror, which is used to combine the pump light and the signal light into a collinear beam, and then transmit them together to the nonlinear crystal to perform optical parametric amplification on the vortex signal light;

[0012] The nonlinear crystal has a nonlinear effect and can be used as a crystal medium in which annular pump light and vortex signal light are subjected to optical parametric amplification.

[0013] Furthermore, the vortex signal light generated by the signal light source through the vortex beam generating lens and the annular pump light generated by the pump light source through the annular beam generating lens need to be incident on the nonlinear crystal on the same line, and the two beams of light overlap in the time domain; the angle of the nonlinear crystal is adjusted to meet the phase matching condition, and the idle light and pump light after passing through the nonlinear crystal can be filtered out by a dichroic mirror.

[0014] Furthermore, the light-transmitting area of ​​the lens is changed to make the lens light-transmitting in the edge area and opaque in the center area. Therefore, when an ordinary light beam passes through the lens, it can be shaped into a special light beam with a ring-shaped light intensity distribution.

[0015] The time-space coincidence of the annular pump vortex light is characterized by: accurately adjusting the annular pump light and the vortex signal light generated after being shaped by the annular beam generating lens so that the two light beams completely coincide in space, that is, the annular area of ​​the annular pump light just matches the annular area of ​​the vortex light; and by accurately controlling the time delay of the annular pump light, the annular pump light can also completely coincide with the vortex signal light in time, that is, they are simultaneously incident on the nonlinear crystal for optical parametric amplification.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The present invention can effectively solve the problem that the residual light intensity in the central area will be amplified during the optical parametric amplification of vortex light by conventional pump light, resulting in low spatial contrast of the amplified vortex light beam.

[0018] 2. The present invention uses an annular beam generating lens to generate annular pump light, thereby achieving vortex light amplification with high spatial contrast.

[0019] 3. The annular beam generating lens is used to shape the pump light into an annular light field distribution that can match the vortex beam, so that the annular light field area where the vortex beam should be amplified can be specifically amplified during the optical parametric amplification process, without amplifying the area where there should be no light intensity distribution at the central singularity of the vortex beam, thereby achieving a vortex beam with higher contrast between the amplified annular light field and the central singularity light field.

[0020] 4. The present invention has the advantages of simple optical path structure, easy implementation, low cost and significant effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the optical path of the vortex light amplification device for realizing high spatial contrast by annular pumping of the present invention.

[0022] Figure 2 Schematic diagram of the process of generating annular pump light using an annular beam generating lens.

[0023] Figure 3 Schematic diagram of the process of optical parametric amplification of vortex seed light driven by ring pump light to obtain high-contrast vortex light.

[0024] Figure 4 Schematic diagram of the light intensity and contrast at different light field positions of the amplified vortex light. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] As shown in the figure, the present invention is a vortex light amplification device based on annular pumping to achieve high spatial contrast, including a pump light source 1, an annular light beam generating lens 2, a signal light source 3, a vortex light beam generating lens 4, a dichroic mirror 5, and a nonlinear crystal 6.

[0027] The pump light source 1 generates a beam of ordinary pump light for optical parametric amplification, and can use a high-power, short-pulse laser, such as a Nd:YAG laser, and is finely adjusted to achieve synchronization with the signal light source.

[0028] After the ordinary pump light passes through the annular beam generating lens 2, the light field distribution of the beam changes to an edge annular distribution, and a beam of annular pump light beam is obtained; by optimizing the parameters of the annular beam generating lens 2, a more uniform annular light intensity distribution can be achieved, thereby improving the amplification efficiency. The annular pump light beam is transmitted to the dichroic mirror 5 through the reflector;

[0029] The signal light source 3 generates a seed light beam. In this embodiment, a femtosecond seed light output by a Ti:sapphire laser is used, and the energy is amplified by an optical parametric pulse amplifier. To ensure the stability and quality of the seed light, the laser can be finely adjusted and calibrated.

[0030] After the seed light passes through the vortex beam generating lens 4, a vortex seed light is obtained. The vortex beam generating lens 4 can use optical elements such as a spiral phase plate. By adjusting its parameters, the topological charge and light intensity distribution of the vortex light can be changed.

[0031] The vortex seed light and the obtained annular pump light are transmitted together to the dichroic mirror 5 for beam combining. After beam combining, the vortex signal light generated by the signal light source through the vortex beam generating lens and the annular pump light generated by the pump light source after the annular beam generating lens need to be incident on the nonlinear crystal 6 in a colinear manner, and the two beams of light are overlapped in the time domain, and then the angle of the nonlinear crystal is adjusted to meet the phase matching condition, and finally the annular pump is obtained to achieve vortex light amplification with high spatial contrast. The design of the dichroic mirror needs to consider the wavelength, incident angle and reflection / transmission efficiency of the two beams of light. By optimizing the parameters of the dichroic mirror, efficient beam combining and precise alignment of the two beams of light can be achieved. The selection of the nonlinear crystal needs to consider its light transmission range, nonlinear coefficient and phase matching condition. By adjusting the cutting angle and length of the crystal, the optical parametric amplification requirements of different wavelengths and energies can be met.

[0032] Embodiment:

[0033] In the process of seed light generation, the femtosecond seed light output by the Ti:sapphire laser is amplified by a 4-micron optical parametric pulse amplifier to output a high-energy femtosecond seed light with a single pulse energy of 100 microjoules and a central wavelength of 4 microns. The femtosecond seed light output from the optical parametric pulse amplifier is stretched into a chirped seed light after passing through a mid-infrared laser pulse stretcher, and the corresponding pulse width is about 70 picoseconds. The stretched chirped seed light is transformed into a beam of vortex seed light after passing through a vortex beam generating lens (such as a spiral phase plate).

[0034] In the process of generating pump light, the Nd:YAG laser uses Ti:sapphire laser injection as seed light to control the synchronization of pulses emitted by the two lasers in the time domain. The Nd:YAG laser outputs picosecond pump light with 200 mJ energy, a central wavelength of 1064 nm, a pulse width of 70 picoseconds, and a repetition frequency of 20 Hz. The picosecond pump light passes through an annular beam generating lens to generate a pump light with an annular intensity distribution.

[0035] A dichroic mirror is used to make the obtained vortex seed light and annular pump light overlap in space, and jointly incident on a 10mm thick KTA crystal. The relative time delay of the seed light and the pump light is adjusted to ensure that they can be fully coupled in time and space. In addition, it is necessary to ensure that the cutting angle of the nonlinear crystal can accurately meet the phase matching conditions required in the optical parametric amplification process. After the annular pump light and the vortex seed light are precisely overlapped in time and space, they are jointly incident on the nonlinear mid-infrared crystal. Due to the nonlinear effect of the crystal, part of the energy of the pump light is transferred to the vortex seed light in the form of optical parameters to amplify its intensity, and the other part is converted into a beam of idle light. Since the pump light with annular intensity is used in the amplification process, it can better meet the parametric amplification of the vortex seed light whose intensity distribution is already annular, and since there is almost no energy distribution in the central area of ​​the pump light, any residual light in the center of the vortex seed light will not be amplified, so that the contrast between the light intensity of the annular edge and the central area of ​​the vortex light can be greatly improved, and high-contrast vortex light parametric amplification can be achieved.

[0036] Figure 2 Schematic diagram of the generation process of annular pump light, that is, a beam of pump light 7 with a traditional light field is transformed into a beam of annular pump light 8 through an annular beam generating lens 2. Figure 3 This is a schematic diagram of the amplification process of the vortex seed light driven by the ring pump light. The generated ring pump light 8 and vortex seed light 9 are adjusted to coincide in time and space by the dichroic mirror 5 and then incident on the nonlinear crystal 6 for optical parametric amplification to obtain high-contrast vortex light 10, thus realizing high-contrast vortex light amplification. Figure 4 This is a schematic diagram of the light intensity at different light field positions of the amplified vortex light. The contrast between the edge light field intensity and the center light intensity is greater than 40dB.

[0037] The present invention realizes vortex light amplification with high spatial contrast by introducing an annular pump beam and vortex seed light and combining nonlinear crystals to realize optical parametric amplification. The device has the advantages of simple structure, convenient operation, high amplification efficiency, etc., and is of great significance for promoting the development of optical information processing, optical communication, laser processing and other fields.

Claims

1. A vortex light amplification device based on ring pumping to achieve high spatial contrast, characterized in that: include: A pump light source, used to generate pump light; An annular beam generating lens, used for converting the pump light into an annular pump beam having an edge annular light field distribution; A signal light source, used for generating a vortex signal light as a seed light; A vortex beam generating lens, used for converting the seed light into a vortex signal light having a spiral phase structure; A dichroic mirror, used for combining the annular pump beam and the vortex signal photosynthesize beam; The nonlinear crystal is used for optical parametric amplification of the combined incident annular pump light beam and vortex signal light to obtain vortex light with high spatial contrast.

2. The vortex light amplification device based on annular pumping to achieve high spatial contrast according to claim 1, characterized in that: The high spatial contrast is greater than 40 dB.

3. The vortex light amplification device based on annular pumping to achieve high spatial contrast according to claim 1, characterized in that: The annular pump light beam is spatially matched with the vortex signal light.

4. The vortex light amplification device based on annular pumping to achieve high spatial contrast according to claim 1, characterized in that: By adjusting the annular beam generating lens and the vortex beam generating lens, it is ensured that the two beams completely overlap in spatial position and are synchronously incident on the nonlinear crystal 6 in time for optical parametric amplification.

5. The vortex light amplification device based on annular pumping to achieve high spatial contrast according to claim 1, characterized in that: The nonlinear crystal has a nonlinear effect.

6. The vortex light amplification device based on annular pumping to achieve high spatial contrast according to claim 5, characterized in that: The angle of the nonlinear crystal is adjusted to meet a phase matching condition.

7. The vortex light amplification device based on annular pumping to achieve high spatial contrast according to claim 1, characterized in that: The annular light beam generating lens has the characteristics of being light-transmissive in the edge area and light-impermeable in the center area, and is used to shape the circular light beam into a light beam with a light intensity distribution in an annular shape.

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