Terahertz wide-spectrum radiation source device based on nonlinear crystal

Abstract

The utility model provides a terahertz wide-spectrum radiation source device based on a nonlinear crystal, which relates to the technical field of electromagnetic radiation and terahertz, and comprises a coupling prism, the bottom of the coupling prism is connected with a ridge-shaped waveguide, and the side surface of the ridge-shaped waveguide is coated with a buffer layer; the top of the ridge-shaped waveguide substrate is connected with a middle layer, and the top of the middle layer is connected with the bottom of the ridge-shaped waveguide. The terahertz wide-spectrum radiation source device has the beneficial effects that the ridge-shaped waveguide coupling prism forms the terahertz wide-spectrum radiation source device, the middle layer and the ridge-shaped waveguide substrate are arranged below the ridge-shaped waveguide, the coupling prism is attached to the ridge-shaped waveguide, the coupling prism is tightly attached to the buffer layer, pump light can be limited in the ridge-shaped waveguide to be transmitted, the operating distance of a nonlinear crystal is increased, and the effect of the nonlinear crystal is improved. And meanwhile, the loss of the terahertz waves in the transmission process is also reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of electromagnetic radiation and terahertz, and in particular to a terahertz wide-spectrum radiation source device based on nonlinear crystals. Background Art

[0002] Terahertz waves are electromagnetic waves with a frequency range of 100GHz to 10THz, and their corresponding wavelengths are 3mm to 30um. In the electromagnetic spectrum, the terahertz band is located at the transition band from microwaves to infrared light waves. Therefore, terahertz waves not only have the unique properties of this band, but also have some characteristics of both microwave and infrared light waves. This makes the research on terahertz technology integrate the methods and technologies of electronics and photonics, and belongs to the frontier cross-field research. Due to the rapid development of related technologies in the fields of lasers, semiconductors and microelectronics, terahertz wave generation and detection technology has made breakthrough progress, showing its unique properties and broad application prospects. Broadband terahertz radiation sources are the key to terahertz engineering applications and play an important role in terahertz spectral analysis.

[0003] Broadband terahertz waves can be obtained through nonlinear optical frequency conversion methods such as femtosecond laser rectification technology. Electro-optical crystals such as LiNbO3 and GaSe are used to generate broadband terahertz wave radiation in this way. Among them, LiNbO3 crystal not only has a high nonlinear coefficient, but has also been used as an ideal gain medium for terahertz radiation sources.

[0004] However, LiNbO3 crystals have a low damage value, and it is difficult for terahertz wave radiation sources based on LiNbO3 crystals to cover the entire terahertz band, which limits its practical application. In addition, the transmission loss of terahertz waves in nonlinear crystals is large, which reduces the conversion efficiency of terahertz waves. Utility Model Content

[0005] In view of the problems existing in the prior art, the utility model provides a terahertz wide-spectrum radiation source device based on nonlinear crystals, comprising:

[0006] A coupling prism, wherein a ridge waveguide is connected to the bottom of the coupling prism, and a buffer layer is attached to the side of the ridge waveguide;

[0007] A ridge waveguide substrate, the top of which is connected to an intermediate layer, and the top of which is connected to the bottom of the ridge waveguide.

[0008] Preferably, the coupling prism is a triangular prism, and a right-angled side of the triangular prism close to the vertex is connected to the ridge waveguide.

[0009] Preferably, the coupling prism is a semi-conical prism.

[0010] Preferably, the vertex angle of the triangular prism is 40°.

[0011] Preferably, the length of the ridge waveguide is equal to the length of the intermediate layer, and the width of the ridge waveguide is smaller than the width of the intermediate layer.

[0012] Preferably, the ridge waveguide is made of lithium niobate and is doped with magnesium oxide at a concentration of 5 mol %.

[0013] Preferably, the buffer layer is a polyethylene terephthalate film.

[0014] Preferably, the material of the intermediate layer is silicon oxide.

[0015] Preferably, the coupling prism is made of high-resistance silicon, and its resistivity is greater than 20 kΩ.

[0016] The above technical solution has the following advantages or beneficial effects: a terahertz broadband radiation source device is formed by a ridge waveguide coupling prism, an intermediate layer and a ridge waveguide substrate are arranged below the ridge waveguide, the coupling prism is attached to the ridge waveguide, and the coupling prism is tightly attached to the buffer layer, so that the pump light can be confined to the ridge waveguide for transmission, thereby increasing the effective distance of the nonlinear crystal and reducing the loss of the terahertz wave during the transmission process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural schematic diagram of a terahertz wide-spectrum radiation source device based on nonlinear crystals in a preferred embodiment of the utility model;

[0018] Figure 2 This is a schematic structural diagram of a terahertz wide-spectrum radiation source device based on nonlinear crystals in a preferred embodiment of the present utility model. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The present invention is not limited to the implementation mode, and other implementation modes may also fall within the scope of the present invention as long as they meet the purpose of the present invention.

[0020] In a preferred embodiment of the present invention, based on the above problems existing in the prior art, a terahertz wide-spectrum radiation source device based on nonlinear crystal is provided. Figure 1 As shown, including:

[0021] A coupling prism 1, wherein a ridge waveguide 2 is connected to the bottom of the coupling prism 1, and a buffer layer 3 is attached to the side of the ridge waveguide 2;

[0022] A ridge waveguide substrate 4 , the top of which is connected to an intermediate layer 5 , and the top of which is connected to the bottom of the ridge waveguide 2 .

[0023] In a preferred embodiment of the present invention, the coupling prism 1 is a triangular prism, a right-angled side of the triangular prism close to the vertex is connected to the ridge waveguide 2, and the vertex angle a of the triangular prism is 40°.

[0024] In a preferred embodiment of the present invention, the coupling prism 1 is a semi-conical prism.

[0025] Specifically, Figure 2 As shown, the coupling prism 1 can also be a semi-conical prism. The semi-conical prism can be regarded as a complete conical prism cut in half, and the resulting cut surface is connected to the ridge waveguide 2 below, achieving the same effect as the aforementioned triangular prism.

[0026] In a preferred embodiment of the present invention, the length of the ridge waveguide 2 is equal to the length of the intermediate layer, and the width of the ridge waveguide 2 is smaller than the width of the intermediate layer 5 .

[0027] Specifically, in this embodiment, the ridge waveguide substrate 4 is made of fused quartz, the cutting direction is y-cut, and the size is 10mm×5mm×5mm; the intermediate layer 5 is made of silicon oxide, the cutting direction is y-cut, and the size is 10mm×5mm×2um; the ridge waveguide 2 is lithium niobate doped with magnesium oxide at a concentration of 5mol%, which can enhance the limiting ability of the pump laser in the horizontal direction, the cutting direction is y-cut, and the size is 10mm×5um×5μm.

[0028] In a preferred embodiment of the present invention, the ridge waveguide 2 is made of lithium niobate and doped with magnesium oxide at a concentration of 5 mol %.

[0029] In a preferred embodiment of the present invention, the buffer layer 3 is a polyethylene terephthalate film.

[0030] In a preferred embodiment of the present invention, the material of the intermediate layer 5 is silicon oxide.

[0031] In a preferred embodiment of the present invention, the coupling prism 1 is made of high-resistance silicon, and its resistivity is greater than 20 kΩ.

[0032] Specifically, in this embodiment, the terahertz broadband radiation source device is composed of a ridge waveguide 2 and a coupling prism 1 on the ridge waveguide. An intermediate layer 5 made of SiO2 and a ridge waveguide substrate 4 are arranged below the ridge waveguide 2. The refractive index of the pump light in the ridge waveguide 2 is smaller than that of the terahertz wave. When the pump femtosecond laser pulse is incident on the ridge waveguide 2 (such as Figure 1As shown, the pump femtosecond laser has a wavelength of 1560nm, an average power of 50mW, and a pulse width of 60fs. It is emitted from point A and enters the ridge waveguide 2, then refracted in the coupling prism 1, and finally emitted to point B. After being focused by the coupling prism 1, the beam waist width is 8.3μm), which will generate Cherenkov radiation in the terahertz band; the terahertz wave generated by the Cherenkov phase matching of the prism coupling 1 is not limited by the wavelength of the pump light. In addition, when used in combination with a nonlinear waveguide crystal, the Cherenkov phase matching can efficiently generate high-power and broadband terahertz waves. Using the lithium niobate (LiNbO3) ridge waveguide 2 combined with the designed coupling lens 1, the terahertz wave intensity we generated is about three orders of magnitude stronger than that of the traditional photoconductive antenna, and at the same time can reduce the transmission loss of the terahertz wave in the nonlinear crystal.

[0033] The coupling prism 1 is attached to the ridge waveguide 2, and the coupling prism 1 is closely attached to the buffer layer 3 (PET film), so that the pump light can be limited to be transmitted in the ridge waveguide 1. Since the selected coupling prism 1 is high-resistance silicon with a resistivity greater than 20 kΩ, and the ridge waveguide 2 is lithium niobate doped with magnesium oxide at a concentration of 5 mol%, and the thickness of the ridge waveguide 2 is relatively thin (the size in this embodiment is 10 mm×5 um×5 μm), the lithium niobate absorbs less terahertz waves, which can enhance the horizontal limitation ability of the pump laser, thereby greatly reducing the transmission loss of the terahertz wave in the ridge waveguide, and making the action distance of the nonlinear crystal longer, so that the problem that the terahertz wave radiation source cannot cover the entire terahertz band can be solved to a great extent.

[0034] The terahertz radiation source device in this embodiment has a conversion efficiency of 0.13%, and a spectral range of 0.7-6.8 THz, which increases the spectral range and has the advantages of simple, reasonable, compact and efficient structure, and can be widely used in biomedicine, aerospace and other fields.

[0035] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. A terahertz broadband radiation source device based on nonlinear crystal, characterized in that: include: A coupling prism, wherein a ridge waveguide is connected to the bottom of the coupling prism, and a buffer layer is attached to the side of the ridge waveguide; A ridge waveguide substrate, the top of which is connected to an intermediate layer, and the top of which is connected to the bottom of the ridge waveguide.

2. The terahertz broadband radiation source device according to claim 1, characterized in that: The coupling prism is a triangular prism, and a right-angled side of the triangular prism close to the vertex is connected to the ridge waveguide.

3. The terahertz broadband radiation source device according to claim 1, characterized in that: The coupling prism is a semi-conical prism.

4. The terahertz broadband radiation source device according to claim 2, characterized in that: The vertex angle of the triangular prism is 40°.

5. The terahertz broadband radiation source device according to claim 1, characterized in that: The length of the ridge waveguide is equal to the length of the intermediate layer, and the width of the ridge waveguide is smaller than the width of the intermediate layer.

6. The terahertz broadband radiation source device according to claim 1, characterized in that: The buffer layer is a polyethylene terephthalate film.

7. The terahertz broadband radiation source device according to claim 1, characterized in that: The material of the middle layer is silicon oxide.

8. The terahertz broadband radiation source device according to claim 1, characterized in that: The coupling prism is made of high-resistance silicon, and its resistivity is greater than 20 kΩ.

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