A highly efficient spin terahertz emitter

Abstract

The present invention discloses a high-efficiency spin terahertz emitter, comprising a substrate, one side of which is sequentially stacked with a one-dimensional periodic photonic crystal, a silicon dioxide intercalation layer, and a spin terahertz source; the one-dimensional periodic photonic crystal is composed of a plurality of one-dimensional photonic crystal primitives, each of which includes a silicon nitride layer and a silicon dioxide layer. The present invention achieves the excitation of Tamm plasmons at the interface through the interaction between the one-dimensional periodic photonic crystal and the spin terahertz source, thereby achieving efficient absorption of femtosecond lasers. Theoretically, the femtosecond laser absorption rate can reach 100%, thereby improving the emission efficiency of the spin terahertz. In addition, due to the introduction of the one-dimensional periodic photonic crystal, there is no femtosecond laser passing through the high-efficiency spin terahertz emitter, eliminating the need for components such as ceramic wafers and silicon wafers, and reducing the volume and complexity of the system.

Description

Technical Field

[0001] The present invention relates to the field of terahertz technology, and in particular to a high-efficiency spin terahertz emitter. Background Art

[0002] The terahertz (THz) frequency band, located between infrared and microwaves, represents a transitional frequency band between macroscopic electronics and microscopic photonics. It possesses numerous advantages, including broadband, low energy, high transparency, and uniqueness. It holds significant scientific value and broad application prospects in fields such as nondestructive testing, satellite communications, medical diagnostics, and satellite communications. Spin THz sources, due to their unique THz generation mechanism, offer advantages such as low cost and high efficiency, making them a key development direction for future THz technology.

[0003] The intensity of the terahertz radiation generated by a spin terahertz emitter is closely related to its absorption rate of femtosecond laser light. However, existing spin terahertz emitters are mostly nanometer thick, with a femtosecond laser absorption rate of around 40%, resulting in a relatively weak terahertz radiation. Furthermore, in addition to the femtosecond laser light absorbed by the spin terahertz emitter, a significant portion of the femtosecond laser light still passes through the emitter. To eliminate the impact of this transmitted light on subsequent equipment in the optical path, traditional methods often use ceramic or silicon wafers to block this transmitted light, resulting in a complex and bulky system. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a high-efficiency spin terahertz emitter.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A high-efficiency spin terahertz emitter comprises a quartz substrate, with a one-dimensional periodic photonic crystal, a silicon dioxide intercalation layer, and a spin terahertz source stacked sequentially on one side of the quartz substrate. The one-dimensional periodic photonic crystal is composed of multiple one-dimensional photonic crystal primitives, each of which includes a silicon nitride layer and a silicon dioxide layer, both of which are formed by phase deposition. Preferably, the silicon dioxide layer has a thickness of 131.2 nm, and the silicon nitride layer has a thickness of 92.24 nm. The number of one-dimensional photonic crystal primitives is 10-15.

[0007] Furthermore, the silicon dioxide intercalation layer has a thickness of 55 nm and can be prepared on the one-dimensional photonic crystal element by vapor deposition.

[0008] Furthermore, the spin terahertz source includes a magnetic layer and a non-magnetic layer, which form a heterostructure and are grown on a silicon dioxide intercalation layer via magnetron sputtering. Furthermore, the magnetic layer is a cobalt layer, and the non-magnetic layer is a platinum layer; the cobalt and platinum layers have the same thickness, preferably 4 nm.

[0009] Compared with the prior art, the beneficial technical effects of the present invention are:

[0010] This invention utilizes the interaction between a one-dimensional periodic photonic crystal and a spin terahertz source to excite Tamm plasmons at their interface, thereby achieving efficient absorption of femtosecond laser light. Theoretically, this absorption rate can reach 100%, thereby improving the emission efficiency of the spin terahertz. Furthermore, the introduction of the one-dimensional periodic photonic crystal eliminates the need for femtosecond laser light to pass through the high-efficiency spin terahertz emitter, eliminating the need for ceramic and silicon wafers and reducing the system's size and complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The overall structure diagram of the spin terahertz high-efficiency emitter provided for the invention;

[0012] Figure 2 This is the field intensity distribution diagram of femtosecond laser inside the spin terahertz high-efficiency emitter;

[0013] Figure 3 is the relationship between the absorptivity of the emitter to femtosecond laser and the wavelength of the femtosecond laser;

[0014] Figure 4 is the reflectivity / transmittance curve of a one-dimensional periodic photonic crystal at different wavelengths;

[0015] Figure 5 The terahertz time domain signal generated by the experimentally measured spin terahertz high-efficiency emitter.

[0016] In the figure: 101 quartz substrate; 102 one-dimensional periodic photonic crystal; 102-1 one-dimensional photonic crystal element; 103 silicon dioxide intercalation layer; 104 spin terahertz source. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to the embodiments and drawings so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0018] refer to Figure 1A high-efficiency spin terahertz emitter includes a quartz substrate 101, on one side of which are stacked a one-dimensional periodic photonic crystal 102, a silicon dioxide intercalation layer 103, and a spin terahertz source 104; the one-dimensional periodic photonic crystal 102 is composed of a plurality of one-dimensional photonic crystal units 102-1 stacked together, and the one-dimensional photonic crystal unit 102-1 includes a silicon nitride layer and a silicon dioxide layer. Figure 1 In the embodiment, the silicon dioxide layer is close to the quartz substrate. It should be noted that the silicon nitride layer can also be designed to be close to the quartz substrate, which can also achieve the purpose of the present invention.

[0019] Preferably, the number of the one-dimensional photonic crystal elements is 10-15.

[0020] Preferably, the spin terahertz source 104 includes a magnetic layer and a non-magnetic layer, forming a heterogeneous structure; the magnetic layer is a cobalt layer, and the non-magnetic layer is a platinum layer; the cobalt layer and the platinum layer have the same thickness. It should be noted that the structure of the spin terahertz source is conventional in the art, wherein: in addition to cobalt, the magnetic layer material can also be selected from other magnetic metals; in addition to platinum, the non-magnetic layer material can also be selected from other non-magnetic metals, all of which can achieve the objectives of the present invention. Those skilled in the art may make appropriate modifications based on actual conditions, and all such modifications fall within the scope of protection of the present invention.

[0021] The working principle of the present invention is described below with reference to the accompanying drawings. The present invention is based on the Tamm plasmon at the interface between metal and one-dimensional periodic photonic crystal. Tamm plasmon is a new type of resonant mode of surface plasmons that exists at the interface between one-dimensional periodic photonic crystal and metal. When light enters the one-dimensional periodic photonic crystal from the metal side, it will be excited when the following relationship is met:

[0022] r m ·r BG exp(2iδ)≈1

[0023] where r m Represents the reflection coefficient of light irradiated on the metal film, r BG represents the reflection coefficient of light irradiated by a one-dimensional periodic photonic crystal, and δ represents the phase delay of light propagating from the metal interface to the one-dimensional periodic photonic crystal interface, which is closely related to the thickness of the intercalation layer between the metal interface and the one-dimensional periodic photonic crystal. The electric field intensity of the excited Tamm plasmon is strongest at the interface between the metal and the one-dimensional periodic photonic crystal.

[0024] like Figure 2As shown, in one embodiment, a femtosecond laser with a central wavelength of 780 nm is incident on the high-efficiency spin terahertz emitter from the air layer on the left. Tamm plasmons are excited in the intermediate intercalation layer (silicon dioxide intercalation layer 103) between the spin terahertz source 104 and the one-dimensional periodic photonic crystal 102. The optical field intensity here is the strongest, thereby increasing the interaction between the femtosecond laser and the spin terahertz source 104. The intensity of the generated spin terahertz is closely related to the optical field intensity acting on the spin terahertz source 104. Therefore, enhanced spin terahertz emission is achieved under Tamm plasmon enhancement. In this example, the refractive indices of silicon dioxide and silicon nitride are 1.486 and 2.114, respectively, and their thicknesses are 131.2 nm and 92.24 nm, respectively. The silicon dioxide intercalation layer is 55 nm thick. The cobalt and platinum thin films are of equal thickness, 4 nm, and the number of periods N of the one-dimensional photonic crystal unit is 10. Figure 3 Figure 2 is the relationship between the light energy absorption rate of the emitter and the wavelength. It can be seen that the light absorption rate of the emitter in the 780nm band is greater than 95%, which is much higher than the 40% absorption efficiency of traditional spin terahertz emitters.

[0025] Figure 4 The following is a graph showing the reflectivity / transmittance of a one-dimensional periodic photonic crystal at different wavelengths. It can be seen that the one-dimensional periodic photonic crystal has a higher reflectivity in the 700nm-800nm ​​band, which is far away from the terahertz band. Therefore, it has little effect on terahertz transmission. The enhanced terahertz wave generated by the spin terahertz source will be emitted unimpeded through the one-dimensional periodic photonic crystal, while the femtosecond laser in this band will be blocked. Therefore, there is no femtosecond laser passing through the one-dimensional periodic photonic crystal, eliminating the use of ceramic wafers, silicon wafers, etc., and reducing the volume and complexity of the system.

[0026] Figure 5 The figure shows the terahertz time domain signal generated by the experimentally measured spin terahertz emitter. The dotted line 1 is the signal generated by an ordinary spin terahertz emitter without a one-dimensional periodic photonic crystal, and the solid line 2 is the terahertz signal generated by a spin terahertz high-efficiency emitter containing a one-dimensional periodic photonic crystal. It can be seen that the terahertz signal generated by the spin terahertz high-efficiency emitter with a one-dimensional periodic photonic crystal is enhanced, and the terahertz signal intensity it generates is more than twice that of the ordinary spin terahertz emitter.

[0027] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. It is intended that all variations within the meaning and range of equivalents of the claims be embraced herein, and any reference signs in the claims should not be construed as limiting the claims to which they relate.

[0028] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A high-efficiency spin terahertz emitter, characterized by: The invention comprises a substrate, on one side of which a one-dimensional periodic photonic crystal, a silicon dioxide intercalation layer and a spin terahertz source are sequentially stacked; the one-dimensional periodic photonic crystal is composed of a plurality of one-dimensional photonic crystal primitives stacked together, and the one-dimensional photonic crystal primitives include a silicon nitride layer and a silicon dioxide layer; The spin terahertz source includes a magnetic layer and a non-magnetic layer, and the magnetic layer and the non-magnetic layer form a heterostructure; the material of the magnetic layer is a metal with magnetism; the material of the non-magnetic layer is a non-magnetic metal.

2. The high-efficiency spin terahertz emitter according to claim 1, characterized in that: The substrate is a quartz substrate.

3. The high-efficiency spin terahertz emitter according to claim 1, characterized in that: The number of the one-dimensional photonic crystal primitives is 10-15.

4. The high-efficiency spin terahertz emitter according to claim 1, characterized in that: The magnetic layer is a cobalt layer; the non-magnetic layer is a platinum layer.

5. The high-efficiency spin terahertz emitter according to claim 4, characterized in that: The cobalt layer and the platinum layer have the same thickness.

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