An ultra-wideband strong-field terahertz radiation source generation device and method

Abstract

The application relates to an ultra-wideband strong-field terahertz radiation source generating device, belonging to the optical field, comprising a liquid container, a femtosecond laser amplifier system for emitting a femtosecond laser beam to the liquid container being arranged on one side of the liquid container, a laser window with a broadband antireflection film being arranged on a femtosecond laser beam incidence point on the liquid container, and a high-resistance silicon exit window for blocking and filtering supercontinuum white light and residual laser being arranged on a femtosecond laser beam exit point; a focusing lens is arranged on a femtosecond laser pulse light path in the liquid container, the focusing lens focuses the femtosecond laser beam into a focal point spark near the exit point; a first off-axis parabolic mirror is arranged on an exit light path outside the liquid container, a second off-axis parabolic mirror is arranged on a reflection light path of the first off-axis parabolic mirror, and a detector is arranged on a reflection light path of the second off-axis parabolic mirror. The application also relates to an ultra-wideband strong-field terahertz radiation source generating method, and the device and the method are simple in structure and convenient to adjust.

Description

Technical Field

[0001] This invention belongs to the field of optical technology and relates to an ultra-wideband strong field terahertz radiation source generation device and method. Background Technology

[0002] Terahertz waves are electromagnetic waves that lie between the infrared and microwave ranges, with frequencies between 0.1 and 10 THz (1 THz = 10 THz). 12 Terahertz waves (Hz) have short pulses, low photon energy, high coherence, good transmittance through non-metallic materials, and high spatiotemporal resolution, making them promising for applications in communications, astronomy, biology, chemistry, medicine, detection, and security. In particular, compared to X-rays, terahertz waves do not cause ionizing damage to matter, giving them a significant advantage in the biomedical field. Currently, the energy of miniaturized desktop ultra-wideband terahertz radiation sources is still relatively low, making it difficult to meet the needs of cutting-edge international research and applications in terahertz biomedical fields such as biological effects and tumor treatment.

[0003] Ultrashort pulse lasers, such as femtosecond lasers (1fs = 10^66 Hz), are -15 s) Laser pulses with timescales ranging from a few femtoseconds to hundreds of femtoseconds can generate extremely high peak power. High-energy femtosecond laser pulses interact with various target materials, such as solids, liquids, and gases, to generate laser plasmas or directly accelerate electrons or ions. These laser plasmas and the accelerated ultrashort pulsed electron beams can produce terahertz radiation under certain conditions. For example, the interaction of a large-scale plasma generated by an ultra-intense femtosecond laser obliquely incident on a solid target can produce ultra-intense broadband terahertz radiation through a linear mode conversion mechanism; the interaction of a femtosecond laser with a water thin film to generate liquid plasma can also radiate terahertz waves; and the interaction of a two-color femtosecond laser with a gas can generate ultra-wideband terahertz wave radiation.

[0004] Because the laser energy conversion efficiency of the aforementioned terahertz radiation sources is still relatively low, the terahertz radiation output is still not strong enough to meet the needs of the above applications. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an ultra-wideband strong field terahertz radiation source generating device and method, which generates an ultra-wideband strong field pulse terahertz radiation source by arranging optical elements in a horizontal plane, allowing a femtosecond laser pulse to be focused into a liquid by a focusing lens, and then using the interaction between the femtosecond laser and the liquid plasma.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] On one hand, the present invention provides an ultra-wideband strong-field terahertz radiation source generating device, comprising a liquid container, a femtosecond laser amplifier system for emitting a femtosecond laser beam into the liquid container on one side of the liquid container, a laser window with a broadband anti-reflection coating at the incident point of the femtosecond laser beam on the liquid container, and a high-resistivity silicon exit window at the exit point of the femtosecond laser beam; a focusing lens is provided in the femtosecond laser pulse optical path inside the liquid container to focus the femtosecond laser beam in the liquid near the exit point to generate a focal spark; a first off-axis parabolic mirror is provided in the exit optical path outside the liquid container, a second off-axis parabolic mirror is provided in the reflected optical path of the first off-axis parabolic mirror, and a detector is provided in the reflected optical path of the second off-axis parabolic mirror.

[0008] Furthermore, the liquid container is also equipped with a translation stage for adjusting the position of the focusing lens, which also facilitates the replacement of focusing lenses with different focal lengths.

[0009] Furthermore, it also includes a nitrogen hood to cover all optical paths and devices behind the high-resistivity silicon emission window, including a first off-axis parabolic mirror, a second off-axis parabolic mirror, and a detector.

[0010] Furthermore, an input pipe for pumping liquid into or out of the liquid container is provided at the opening of the liquid container.

[0011] Furthermore, the liquid in the liquid container is water, alcohol, acetone, or other liquids.

[0012] On the other hand, the present invention provides a method for generating an ultra-wideband strong-field terahertz radiation source, comprising the following steps:

[0013] S1: Pump liquid into the liquid container through the input pipe to cover the laser window, focusing lens, and high-resistivity silicon emission window coated with a broadband antireflective film;

[0014] S2: The femtosecond laser amplifier system emits a femtosecond laser beam, which is focused into the liquid after passing through the laser window and focusing lens, forming a focal spark that produces ultra-wideband terahertz radiation, supercontinuous white light, and other radiation.

[0015] S3: When ultra-wideband terahertz radiation, supercontinuous white light and residual laser pass through the high-resistivity silicon emission window, the supercontinuous white light and residual laser generated in the reaction of laser with liquid are blocked, and only the terahertz wave is emitted and reaches the first off-axis parabolic mirror.

[0016] S4: The first off-axis parabolic mirror collects terahertz waves and collimates them to form a terahertz beam, which is directed toward the second off-axis parabolic mirror;

[0017] S5: The second off-axis parabolic mirror focuses the terahertz beam and converges it onto the detector.

[0018] Furthermore, the position of the focusing lens can be precisely adjusted by the translation stage to optimize the position of the focal spark, making it as close as possible to the high-resistivity silicon emission window, but without allowing residual laser to damage the high-resistivity silicon emission window.

[0019] Furthermore, a nitrogen hood is used to cover the optical path, the first off-axis parabolic mirror, the second off-axis parabolic mirror, and the detector outside the high-resistivity silicon emission window, and nitrogen is introduced into the hood.

[0020] The beneficial effects of this invention are as follows: Instead of using femtosecond lasers to interact with solid or gas targets, this invention utilizes the interaction between femtosecond lasers and liquids such as water; it generates ultra-wideband terahertz radiation through the interaction of femtosecond lasers with liquid plasma. The device for generating the ultra-wideband strong-field terahertz radiation source in this invention has a simple structure and is easy to adjust. The generated ultra-wideband strong-field terahertz waves can be used in many fields such as nonlinear terahertz optics, research on the biological effects of terahertz waves, and potential terahertz wave tumor therapy.

[0021] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0023] Figure 1 This is a schematic diagram of the ultra-wideband strong field terahertz radiation source generating device described in this invention.

[0024] Figure reference numerals: 1. Femtosecond laser amplifier system; 2. Liquid container; 3. Laser window with broadband antireflection coating; 4. High-resistivity silicon emission window; 5. Focusing lens; 6. Translation stage; 7. Input pipe; 8. Liquid; 9. Focusing spark; 10. Off-axis parabolic mirror; 11. Terahertz beam; 12. Off-axis parabolic mirror; 13. Detector; 14. Nitrogen hood. Detailed Implementation

[0025] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0027] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0028] Please see Figure 1 The ultra-wideband strong field terahertz radiation source generating device consists of the following parts: femtosecond laser amplifier system 1, liquid container 2, laser window coated with broadband antireflection film 3, high-resistivity silicon emission window 4, focusing lens 5, translation stage for adjusting the position of focusing lens 6, pipe 7 for pumping in (or extracting) liquid 8 (such as water or other various liquids or liquid mixtures), focal spark 9, off-axis parabolic mirror 10, off-axis parabolic mirror 12, detector 13, and nitrogen hood 14.

[0029] First, a liquid, such as water (or alcohol, acetone, or other liquids, or mixtures of different types of liquids), is pumped into container 2 through input pipe 7. The femtosecond laser beam, after passing through laser window 3, is focused onto liquid 8 in container 2 by focusing lens 5 (convex lens) mounted on adjustable translation stage 6. Strong ultra-wideband terahertz radiation and other radiation are generated at the focal spark 9. When this radiation passes through the high-resistivity silicon window 4 at the right end of container 2, the supercontinuous white light (visible light) and residual laser light generated during the laser-liquid reaction are blocked and filtered, leaving only the terahertz wave. It passes through the high-resistivity silicon window 4 and reaches off-axis parabolic mirror 10 for collection and collimation in the vertical or horizontal direction, forming a terahertz beam 11. This beam is then converged to detector 13 by another off-axis parabolic mirror 12. The adjustable translation stage 6 optimizes the position of the focal spark 9 to maximize radiation output. A nitrogen hood 14 covers the space where terahertz radiation and propagation occur after silicon window 4, displacing air and reducing the absorption and attenuation of terahertz waves by water molecules in the air. The focal spark 9 described in this invention is a liquid plasma spark formed by focusing a femtosecond laser beam in a liquid. The incident window 3 with a broadband antireflection coating, which is installed at the incident end of the liquid container 2 and is designed for the femtosecond laser wavelength, can reduce the energy loss of the input laser.

[0030] Considering the strong absorption of terahertz waves by water in the liquid, the position of the focal spark 9 can be optimized by adjusting the translation stage 6, so that it is as close as possible to the high-resistivity silicon emission window 4 at the right end of the container 2, but not so much that the residual laser damages the silicon window 4. This minimizes the absorption and attenuation of the terahertz waves generated at the focal spark 9 by the liquid 7 in front of the focal spark 9, optimizes the terahertz radiation output energy, and collects as much terahertz radiation as possible in the far field, ultimately obtaining the strongest terahertz radiation source.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for generating an ultra-wideband strong-field terahertz radiation source, characterized in that: The system includes a liquid container, a femtosecond laser amplifier system that emits a femtosecond laser beam into the liquid container on one side, a laser window with a broadband antireflection coating at the incident point of the femtosecond laser beam on the liquid container, and a high-resistivity silicon exit window at the exit point of the femtosecond laser beam; a focusing lens is provided in the femtosecond laser pulse optical path inside the liquid container to focus the femtosecond laser beam in the liquid near the exit point to generate a focal spark; A first off-axis parabolic mirror is provided on the outgoing light path outside the liquid container, a second off-axis parabolic mirror is provided on the reflected light path of the first off-axis parabolic mirror, and a detector is provided on the reflected light path of the second off-axis parabolic mirror; the liquid inside the liquid container is water, alcohol, acetone, or a mixture of different types of liquids; the liquid container also includes a translation stage for adjusting the position of the focusing lens; it also includes a nitrogen hood for covering all optical paths and devices behind the high-resistivity silicon outgoing window, including the first off-axis parabolic mirror, the second off-axis parabolic mirror, and the detector; an input pipe for pumping or extracting liquid into or out of the liquid container is provided at the opening of the liquid container.

2. A method for generating an ultra-wideband strong-field terahertz radiation source, characterized in that: Based on the ultra-wideband strong-field terahertz radiation source generating device according to claim 1, the method includes the following steps: S1: Pump liquid into the liquid container through the input pipe to cover the laser window, focusing lens, and high-resistivity silicon emission window coated with a broadband antireflective film; S2: The femtosecond laser amplifier system emits a femtosecond laser beam, which is focused in the liquid after passing through the laser window and focusing lens, forming a focal spark that produces ultra-wideband terahertz radiation and supercontinuous white light. S3: When ultra-wideband terahertz radiation, supercontinuous white light and residual laser pass through the high-resistivity silicon emission window, the supercontinuous white light and residual laser generated in the reaction of laser with liquid are blocked and filtered, and only terahertz waves are emitted to reach the first off-axis parabolic mirror. S4: The first off-axis parabolic mirror collects terahertz waves and collimates them to form a terahertz beam, which then propagates to the second off-axis parabolic mirror. S5: The second off-axis parabolic mirror focuses the terahertz beam and directs it to the detector; The position of the focusing lens is adjusted by the translation stage to optimize the position of the focal spark, so that it is as close as possible to the high-resistivity silicon emission window, but without causing residual laser to damage the high-resistivity silicon emission window. A nitrogen hood is used to cover the optical path, the first off-axis parabolic mirror, the second off-axis parabolic mirror, and the detector outside the high-resistivity silicon emission window, and is filled with nitrogen to reduce the absorption loss of terahertz waves by water vapor in the air.

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