A device and method for generating ultra-wideband strong field terahertz and infrared radiation sources

Abstract

The invention relates to an ultra-wideband strong field terahertz and infrared radiation source generating device, belonging to the field of optics, comprising a femtosecond laser amplifier system and a liquid container, wherein a laser window coated with a broadband anti-reflection film is arranged at the bottom of the liquid container, a broadband dielectric film reflector and a focusing lens are arranged outside the laser window, a femtosecond laser beam is emitted to the broadband dielectric film reflector, and after reflection, it is focused near a liquid surface in the liquid container to form a focal spark, and ultra-wideband terahertz, infrared radiation and supercontinuum white light are emitted from the sparking position to the outside of an opening, a first off-axis parabolic mirror for collecting and collimating the ultra-wideband terahertz and infrared radiation is arranged outside the opening, a gold-plated reflector dedicated to terahertz waves and infrared rays is arranged on the reflection light path of the first off-axis parabolic mirror, a high-resistance silicon wafer and a second off-axis parabolic mirror for blocking supercontinuum white light and residual laser are arranged on the reflection light path of the gold-plated reflector, and a detector is arranged on the reflection converging light path of the second off-axis parabolic mirror.

Description

Technical Field

[0001] The invention belongs to the field of optical technology and relates to an ultra-wideband strong-field terahertz and infrared radiation source generating device and method. Background Art

[0002] Terahertz waves refer to waves with a frequency of 0.1-10THz (1THz = 10 12 Hz), which is between infrared and microwave, and is at the intersection of electronics and photonics, and has special characteristics different from other electromagnetic spectra. Terahertz waves have short pulses, high coherence, high transmittance to non-metallic materials, high temporal and spatial resolution, and very small energy of terahertz photons, which will not cause ionization and damage to materials. Compared with X-rays, terahertz imaging technology and spectroscopy technology have more advantages, and have broad application prospects in many fields such as broadband communications, astronomy, medical imaging, non-destructive testing, and safety inspection. At present, ultra-wideband strong-field terahertz and infrared radiation sources are the premise and foundation for the most cutting-edge international research directions such as terahertz nonlinear optics, terahertz strong-field physics, interaction between terahertz waves and materials, terahertz biological effects, and tumor treatment.

[0003] Femtosecond (1fs=10 -15 s) Laser pulses are laser pulses with a time scale of several femtoseconds to hundreds of femtoseconds. Due to its ultra-short time characteristics, it can produce extremely high peak power. Femtosecond laser pulses with high pulse energy interact with atoms in gases, clusters, liquids, solids, etc., ionizing atoms to produce free electrons and ions to form plasmas. These laser plasmas can generate terahertz radiation under certain conditions and extend to the infrared band. For example, the interaction between two-color femtosecond lasers and gases can generate ultra-broadband terahertz waves and infrared radiation, the interaction between femtosecond lasers and water films to generate liquid plasma can also radiate terahertz waves, and the interaction between ultra-strong femtosecond lasers and solid film targets can generate ultra-strong broadband terahertz radiation through the transition radiation mechanism.

[0004] In addition to laser-plasma interaction, the strong nonlinear interaction between high-energy femtosecond laser and liquid molecules can also generate high-energy ultra-wideband strong-field terahertz waves and infrared radiation, with wavelengths ranging from a few microns to 3 mm and frequencies ranging from 0.1 to tens of THz or more. However, due to the strong absorption of terahertz and infrared radiation by water molecules in a large amount of liquid around the focus, the overall terahertz and infrared radiation output is not strong, making it difficult 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 and infrared radiation source generating device and method, which utilizes the interaction between the femtosecond laser and the liquid plasma and the nonlinear effect of the strong laser field on the liquid molecules after the femtosecond laser pulse is focused in the liquid through a focusing mirror to generate an ultra-wideband strong field pulse terahertz and infrared radiation source.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] On the one hand, the present invention provides an ultra-wideband strong-field terahertz and infrared radiation source generating device, comprising a femtosecond laser amplifier system and a liquid container with an opening on the top, wherein a laser window coated with a broadband anti-reflection film is provided at one end of the liquid container opposite to the opening, a broadband dielectric film reflector and a focusing lens are provided outside the laser window, the femtosecond laser amplifier system emits a femtosecond laser beam to the broadband dielectric film reflector, and focuses it near the liquid surface in the liquid container to form a focal spark, and ultra-wideband terahertz and infrared radiation and other radiation such as supercontinuum white light are emitted from the focal spark to the outside of the opening, a first off-axis parabolic mirror for collecting and collimating the ultra-wideband terahertz and far-infrared radiation and residual laser is provided outside the opening of the liquid container, a gold-plated reflector dedicated to terahertz waves and infrared rays is provided on the reflected light path of the first off-axis parabolic mirror, a high-resistance silicon wafer for blocking and filtering supercontinuum white light and residual laser and a second off-axis parabolic mirror are provided on the reflected light path of the gold-plated reflector, and a detector is provided on the reflected light path of the second off-axis parabolic mirror.

[0008] Furthermore, a liquid pipeline for pumping in and out liquid is provided at the opening of the liquid container.

[0009] Furthermore, a nitrogen hood is provided, which seals the liquid container, the broadband dielectric film reflector, the focusing lens, the laser window, the first off-axis parabolic mirror, the gold-plated reflector, the high-resistance silicon wafer, the second off-axis parabolic mirror, and the detector as a whole.

[0010] Furthermore, the liquid in the liquid container is water or other non-flammable liquid.

[0011] In another aspect, the present invention provides a method for generating an ultra-wideband strong field terahertz and infrared radiation source, comprising the following steps:

[0012] S1: pump liquid into the liquid container through the input pipe;

[0013] S2: The femtosecond laser amplifier system emits a femtosecond laser beam, which enters the liquid container through a broadband dielectric film reflector, a focusing lens, and a laser window coated with a broadband anti-reflection film, and is focused near the liquid surface to form a focal spark, generating ultra-broadband terahertz and infrared radiation and supercontinuum white light radiation;

[0014] S3: Ultra-broadband terahertz and far-infrared radiation and other radiation (including supercontinuum white light and residual laser) are emitted from the liquid focal spark to the outside of the container opening and reach the first off-axis parabolic mirror;

[0015] S4: The first off-axis parabolic mirror collects and collimates ultra-broadband terahertz and far-infrared radiation as well as other radiation, and propagates to the gold-coated reflector dedicated to terahertz waves and infrared rays;

[0016] S5: The gold-coated mirror reflects ultra-broadband terahertz and far-infrared radiation as well as other radiation, and the supercontinuum white light and residual laser light generated in the reaction are filtered out using a high-resistance silicon wafer;

[0017] S6: The remaining terahertz wave and infrared radiation beam pass through the high-resistance silicon wafer and reach the second off-axis parabolic mirror;

[0018] S7: The second off-axis parabolic mirror collects the terahertz wave and infrared radiation beam and converges them to the detector.

[0019] Furthermore, the liquid is pumped in and out through the input pipe to accurately adjust the liquid level, thereby reducing the absorption and attenuation of the terahertz waves and infrared rays generated by the focal spark by the liquid above the focal spark.

[0020] Furthermore, it also includes: using a nitrogen hood to cover the liquid container, the broadband dielectric film reflector, the focusing lens, the laser window, the first off-axis parabolic mirror, the gold-plated reflector, the high-resistance silicon wafer, the second off-axis parabolic mirror, and the detector, and filling it with nitrogen.

[0021] The beneficial effects of the present invention are:

[0022] 1. Femtosecond laser is focused in the liquid instead of interacting with solid target, gas target, cluster target or liquid film. It utilizes the interaction between femtosecond laser and liquid plasma and the strong nonlinear effect of the strong field of femtosecond laser on liquid molecules to produce ultra-wideband terahertz and infrared radiation, instead of only utilizing the interaction between femtosecond laser and solid target, gas target, cluster target or liquid film to generate laser plasma to generate terahertz radiation. Therefore, ultra-wideband terahertz and infrared radiation sources from terahertz to infrared bands can be obtained.

[0023] 2. The present invention adopts a three-dimensional spatial layout of optical elements that focuses the laser beam into the liquid in the vertical direction instead of focusing in the horizontal direction. The liquid can be pumped in or out through a pipeline to accurately adjust the liquid level, minimize the absorption and attenuation of the terahertz waves and infrared rays generated at the focus 8 by the liquid 7 above the focus, optimize the output energy of terahertz and infrared radiation, and collect as much terahertz and infrared radiation as possible in the far field. This method can avoid the situation in which the liquid length cannot be adjusted in the horizontal focusing method, making it difficult to optimize the radiation output, and the exit window is easily damaged by residual laser.

[0024] 3. The device for generating ultra-wideband strong field terahertz and infrared radiation sources in the present invention has a simple structure and is easy to adjust. The ultra-wideband strong field terahertz and infrared radiation sources generated can be used in many fields such as biomedical imaging, nonlinear terahertz optics, terahertz strong field physics, nonlinear interaction between terahertz and materials, research on terahertz wave biological effects, and possible terahertz wave tumor treatment.

[0025] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0027] Figure 1 This is a schematic diagram of the structure of the ultra-wideband strong field terahertz and infrared radiation source generating device of the present invention;

[0028] Figure numerals: femtosecond laser amplifier system 1, broadband dielectric film reflector 2, focusing lens 3, laser window 4, liquid container 5, input pipe 6, liquid 7, focal spark 8, first off-axis parabolic mirror 9, gold-coated reflector 10, high-resistance silicon wafer 11, terahertz wave and infrared radiation beam 12, second off-axis parabolic mirror 13, detector 14, nitrogen hood 15. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways 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 only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0030] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0031] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0032] See also Figure 1 The present invention provides an ultra-broadband strong field terahertz and infrared radiation source generating device, which is composed of the following parts: a femtosecond laser amplifier system 1, a broadband dielectric film reflector 2, a focusing lens 3, a liquid container 5 equipped with a laser window 4 coated with a broadband anti-reflection film, into which a liquid 7 (including water and other various non-flammable liquids and mixed liquids of different types of liquids) can be pumped (or drawn out) through a pipeline 6, a focal spark 8, a first off-axis parabolic mirror 9, a terahertz wave and infrared reflector 10, a high-resistance silicon chip 11, a second off-axis parabolic mirror 13, a detector 14, etc. The focal spark 8 is a liquid plasma spark generated by focusing a femtosecond laser beam in a liquid.

[0033] The terahertz wave and infrared radiation generation and collection process of the present invention is as follows: a femtosecond laser beam is reflected by a reflector 2 and then vertically upwardly focused by a focusing lens 3 and passes through a laser window 4 and then focused in pure water (or other non-flammable liquid) in a liquid container 5, and strong ultra-wideband terahertz and infrared radiation and other radiations can be generated at a focal spark 8, and these radiations are collected and collimated in the horizontal direction by a first off-axis parabolic mirror 9 above, and then reflected by a gold-plated reflector 10 dedicated to terahertz waves and infrared rays and then propagated downward, and a supercontinuum white light (visible light) and residual laser generated in the reaction between the laser and the liquid are filtered by a high-resistance silicon wafer 11, and only a terahertz wave and infrared radiation beam 12 are left to pass through the high-resistance silicon wafer and reach a second off-axis parabolic mirror 13, and after being focused by the second off-axis parabolic mirror 13, they converge in the horizontal direction to a detector 14 for detection.

[0034] The principle and characteristics of the present invention are as follows: the femtosecond laser is focused in the liquid instead of interacting with a solid target, a gas target, a cluster target, or a liquid film. The interaction between the femtosecond laser and the liquid plasma and the strong nonlinear effect of the strong field of the femtosecond laser on the liquid molecules are used to generate ultra-wideband terahertz and infrared radiation, rather than only using the interaction between the femtosecond laser and the solid target, a gas target, a cluster target, or a liquid film to generate laser plasma to generate terahertz radiation. Therefore, an ultra-wideband terahertz and infrared radiation source from the terahertz to infrared bands can be obtained.

[0035] Considering the properties of the liquid, the present invention adopts a three-dimensional spatial layout of optical elements that focuses the laser beam into the liquid in the vertical direction instead of focusing in the horizontal direction. The liquid 7 can be pumped in or out in small amounts through the input pipe 6 to achieve precise adjustment of the liquid level, minimize the absorption and attenuation of the terahertz waves and infrared rays generated by the focal spark 8 by the liquid 7 above the focal spark 8, optimize the output energy of the terahertz and infrared radiation, and collect as much terahertz and infrared radiation as possible in the far field. This method can avoid the situation in which the liquid length cannot be adjusted in the horizontal focusing method, making it difficult to optimize the radiation output, and the exit window is easily damaged by residual laser.

[0036] In the present invention, an incident laser window 4 coated with a broadband anti-reflection film for the wavelength of the femtosecond laser is installed at the bottom of the liquid container 5, which can reduce the energy loss of the input laser.

[0037] In the present invention, there is free space above the liquid container 5, and the terahertz and infrared radiation generated at the focal spark 8 together with the residual laser and the supercontinuum white light generated in the reaction can be directly collected by the first off-axis parabolic mirror 9 with a gold-plated protective film. The supercontinuum white light can be used to fine-tune all optical components after the focus, such as the first off-axis parabolic mirror 9, the gold-plated reflector 10 dedicated to terahertz waves and infrared rays, the second off-axis reflector 12, the detector 14, etc., which is convenient to adjust and simple and easy.

[0038] The generation, transmission and detection parts of the terahertz and infrared radiation generating device of the present invention are covered with a nitrogen cover 15 ( Figure 1 The dotted box) is covered and filled with nitrogen during the measurement process, and the water vapor generated by the laser focus spark 8 in the air is discharged out of the nitrogen cover as much as possible to minimize the attenuation effect of water vapor on terahertz and infrared radiation.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. An ultra-wideband strong field terahertz and infrared radiation source generating device, Features: The invention comprises a femtosecond laser amplifier system and a liquid container with an opening on the top, wherein a laser window coated with a broadband anti-reflection film is arranged at one end of the liquid container opposite to the opening, a broadband dielectric film reflector and a focusing lens are arranged outside the laser window, the femtosecond laser amplifier system emits a femtosecond laser beam to the broadband dielectric film reflector, which is focused near the liquid surface in the liquid container after reflection to form a focal spark, and ultra-broadband terahertz, infrared radiation and supercontinuum white light are emitted from the focal spark to the outside of the opening, a first off-axis parabolic mirror for collecting and collimating the ultra-broadband terahertz, infrared radiation, supercontinuum white light and residual laser is arranged outside the opening of the liquid container, a gold-plated reflector dedicated to terahertz waves and infrared rays is arranged on the reflected light path of the first off-axis parabolic mirror, a high-resistance silicon wafer for blocking and filtering supercontinuum white light and residual laser and a second off-axis parabolic mirror are arranged on the reflected light path of the gold-plated reflector, and a detector is arranged on the reflected light path of the second off-axis parabolic mirror.

2. The ultra-wideband strong field terahertz and infrared radiation source generating device according to claim 1, Features: The opening of the liquid container is provided with a liquid pipeline for pumping in and out the liquid.

3. The ultra-wideband strong field terahertz and infrared radiation source generating device according to claim 1, Features: A nitrogen hood is also provided, which seals the liquid container, the broadband dielectric film reflector, the focusing lens, the laser window, the first off-axis parabolic mirror, the gold-plated reflector high-resistance silicon wafer, the second off-axis parabolic mirror, and the detector as a whole.

4. The ultra-wideband strong field terahertz and infrared radiation source generating device according to claim 1, Features: The liquid in the liquid container is a non-flammable liquid.

5. A method for generating ultra-wideband strong-field terahertz and infrared radiation sources, Features: Based on the ultra-wideband strong field terahertz and infrared radiation source generating device according to any one of claims 1 to 4, the method comprises the following steps: S1: pump liquid into the liquid container through the input pipe; S2: The femtosecond laser amplifier system emits a femtosecond laser beam, which enters the liquid container through a broadband dielectric film reflector, a focusing lens, and a laser window coated with a broadband anti-reflection film, and is focused near the liquid surface in the liquid to form a focal spark, generating ultra-broadband terahertz, infrared radiation, and supercontinuum white light; S3: Ultra-broadband terahertz, far-infrared radiation and supercontinuum white light are emitted from the focal spark and reach the first off-axis parabolic mirror through the opening of the liquid container; S4: The first off-axis parabolic mirror collects and collimates ultra-broadband terahertz, infrared radiation, supercontinuum white light, and residual laser light, and propagates them to gold-coated mirrors dedicated to terahertz waves and infrared rays; S5: The gold-plated mirror reflects ultra-broadband terahertz, far-infrared radiation, supercontinuum white light and residual laser, and uses a high-resistance silicon wafer to block and filter out the supercontinuum white light and residual laser generated by the reaction between the laser and the liquid; S6: The remaining terahertz wave and infrared radiation beam pass through the high-resistance silicon wafer and reach the second off-axis parabolic mirror; S7: The second off-axis parabolic mirror collects the terahertz wave and infrared radiation beam and converges them to the detector.

6. The method for generating ultra-wideband strong field terahertz and infrared radiation sources according to claim 5, Features: The method for generating an ultra-wideband strong-field terahertz and infrared radiation source is characterized in that: the liquid level is accurately adjusted and optimized by pumping in and out of the liquid through an input pipe, thereby reducing the absorption attenuation of the terahertz waves and infrared rays generated by the focal spark by the liquid above the focal spark.

7. The method for generating ultra-wideband strong field terahertz and infrared radiation sources according to claim 5, Features: Also includes: A liquid container, a broadband dielectric film reflector, a focusing lens, a laser window, a first off-axis parabolic mirror, a gold-plated reflector high-resistance silicon wafer, a second off-axis parabolic mirror, and a detector are covered with a nitrogen hood and filled with nitrogen.

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