Method and device for improving terahertz intensity of photoconductive antenna through laser ablation

Abstract

The invention discloses a method for improving terahertz intensity of a photoconductive antenna through laser ablation. A light source, a diaphragm arranged on one side of the light source, an attenuation piece arranged on one side of the diaphragm, a lens arranged on one side of the attenuation piece and a cavity arranged on one side of the lens are included. A light-transmitting hole is formed in the end surface, close to the lens, of the cavity; a sample is mounted at the bottom in the cavity; the material of the sample is crystal orientation lt; 100 gt; the thickness of the intrinsic gallium arsenide material is 350 microns, and the resistivity of the intrinsic gallium arsenide material is 107-108 omega.cm. According to the method for improving the photoelectric characteristic of the gallium arsenide material through laser ablation, the terahertz wave radiation intensity generated by the photoconductive antenna prepared from the material can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz waves, and in particular to a method and a device for improving the terahertz intensity of a photoconductive antenna by laser ablation. Background Art

[0002] Terahertz waves are part of the electromagnetic spectrum, located between microwaves and infrared, and have many unique characteristics, such as strong penetration, non-ionizing radiation, and transparency to many materials. And due to its special frequency band, terahertz waves have unique properties and advantages in many application fields.

[0003] Laser ablation technology is a processing method that uses a laser beam to irradiate the surface of a material, and through the absorption and conduction of laser energy, the material is locally heated to melt or evaporate. Laser ablation technology has made significant progress in various fields, especially in silicon materials, by inducing the formation of special structures on the silicon surface, thereby improving the optical properties of the material such as absorption rate and photoelectric conversion efficiency.

[0004] Terahertz photoconductive antenna is a device used to receive and transmit terahertz waves, which has excellent performance in the terahertz frequency range. Terahertz photoconductive antenna has many advantages, including high sensitivity, wide bandwidth, fast response speed and good size adjustability. However, its development in practical applications is limited by its high manufacturing cost, large energy loss and large size. Photoconductive materials are used to convert terahertz waves into electrical signals or convert electrical signals into terahertz waves. The selection of appropriate photoconductive materials has an important influence on the performance of the device. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for improving the terahertz intensity of a photoconductive antenna by laser ablation, and a method for improving the photoelectric properties of a gallium arsenide material by laser ablation, which can effectively improve the terahertz radiation intensity generated by a photoconductive antenna made of this material. In order to achieve the above-mentioned purpose and other advantages according to the present invention, a device for improving the terahertz intensity of a photoconductive antenna by laser ablation is provided, comprising:

[0006] A light source, an aperture arranged on one side of the light source, an attenuation sheet arranged on one side of the aperture, a lens arranged on one side of the attenuation sheet, and a cavity arranged on one side of the lens;

[0007] A light-transmitting hole is provided on the end surface of the cavity close to the lens, and a sample is installed at the bottom of the cavity;

[0008] The material of the sample is crystal oriented <100> , intrinsic gallium arsenide material with a thickness of 350μm and a resistivity of 107~108Ω·cm.

[0009] Preferably, the light source is a laser with a repetition frequency of 1 kHz, a pulse width of 120 fs and a wavelength of 800 nm.

[0010] Preferably, the laser generated by the laser is focused on the sample surface in the cavity through a lens with a focal length of 200 mm, the focusing radius is 100 μm, and the laser power is 300 mW, the scanning speed is 4 mm / s, and the scanning interval is 20 μm as processing parameters.

[0011] Preferably, the laser generated by the laser includes femtosecond laser or nanosecond laser.

[0012] A method for improving the terahertz intensity of a photoconductive antenna by laser ablation comprises the following steps:

[0013] S1. Install the sample in a cavity, which is fixed with a two-dimensional platform;

[0014] S2, focusing the laser through the lens, and setting the scanning path to process the sample by adjusting the stepper motor;

[0015] S3. When the laser contacts the sample surface, the scattered light interferes with the incident light beam. At this time, the formation of periodic irradiation makes the sample surface present a periodic micro-nanostructure pattern. The surface microstructures are all gully-like protrusions. The surface morphology and peak height of the material are uniform. The ripple interval is between 700nm and 800nm, which is close to the wavelength of the femtosecond laser and is perpendicular to the scanning direction.

[0016] S4. The processed sample is mounted on a PCB board and connected to a source meter via an SMA interface to control the applied bias voltage. The sample is processed into a photoconductive antenna.

[0017] Compared with the prior art, the present invention has the following beneficial effects: a method for improving the photoelectric properties of gallium arsenide materials by laser ablation, and the micro-nano structure produced by ablation improves the photoelectric properties of the material and effectively improves the terahertz intensity. The device of the present invention is simple and convenient to use, low in cost, and highly controllable, and improves the photoelectric properties of the material and enhances the terahertz intensity. By laser ablation of the surface of the GaAs material, a regular micro-nano structure is produced on the surface, thereby improving the light absorption rate and compressive strength of the material. After the material is prepared as a photoconductive antenna, the terahertz radiation intensity can be improved. Compared with the unprocessed photoconductive antenna, the photoconductive antenna processed by this method can increase the output terahertz radiation intensity by 2.24 times, and has low cost and simple operation, and has a good application prospect in the field of terahertz photoconductive antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of a method and apparatus for improving the terahertz intensity of a photoconductive antenna by laser ablation according to the present invention;

[0019] Figure 2 A micro-nano structure diagram of a method, device and method for improving the terahertz intensity of a photoconductive antenna by laser ablation according to the present invention;

[0020] Figure 3 A comparison diagram of the light transmittance of GaAs materials according to the method, device and method for improving the terahertz intensity of a photoconductive antenna by laser ablation of the present invention;

[0021] Figure 4 It is a comparison diagram of IV curves of GaAs materials of the method, device and method for improving the terahertz intensity of photoconductive antennas by laser ablation according to the present invention;

[0022] Figure 5 This is a comparison diagram of the terahertz time domain waveforms generated by a processed photoconductive antenna and an unprocessed photoconductive antenna according to the method, device and method for improving the terahertz intensity of a photoconductive antenna by laser ablation of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Reference Figure 1-5 , an aperture 1 disposed on one side of the light source, an attenuation plate 2 disposed on one side of the aperture 1, a lens 3 disposed on one side of the attenuation plate 2, and a cavity 4 disposed on one side of the lens 3;

[0025] A light-transmitting hole is provided on the end surface of the cavity 4 close to the lens 3, and a sample 5 is installed at the bottom of the cavity 4;

[0026] The material of sample 5 is crystal orientation <100> , intrinsic gallium arsenide material with a thickness of 350μm and a resistivity of 107~108Ω·cm.

[0027] Furthermore, the light source is a laser with a repetition frequency of 1 kHz, a pulse width of 120 fs, and a wavelength of 800 nm.

[0028] Furthermore, the laser generated by the laser is focused on the sample surface in the cavity through a lens with a focal length of 200 mm, the focusing radius is 100 μm, and the laser power is 300 mW, the scanning speed is 4 mm / s, and the scanning interval is 20 μm as the processing parameters.

[0029] Furthermore, the laser generated by the laser includes femtosecond laser or nanosecond laser.

[0030] A method for improving the terahertz intensity of a photoconductive antenna by laser ablation comprises the following steps:

[0031] S1. Install the sample in a cavity, which is fixed with a two-dimensional platform; cut a 1 cm×1 cm intrinsic gallium arsenide wafer into chips, and fix them on a sample holder connected to the two-dimensional platform.

[0032] S2. Focus the laser through the lens, and set the scanning path to process the sample by adjusting the stepper motor; the laser power is adjusted by controlling the rotating attenuation plate. The laser is focused on the sample surface in the cavity through a lens with a focal length of 200mm, the focusing radius is 100μm, and the processing area is 800μm×600μm. Select laser power 300mW, scanning speed 4mm / s, and scanning interval 20μm as processing parameters.

[0033] S3. When the laser contacts the sample surface, the scattered light interferes with the incident light beam, and periodic irradiation is formed at this time; this irradiation interacts with the material, causing energy to be deposited on the spatial coordinates, thereby generating a periodically changing surface electric field and forming a local field amplitude, so that the sample surface presents a periodic micro-nanostructure pattern. The surface microstructures are all gully-like protrusions, the surface morphology and peak height of the material are uniform, and the ripple interval is between 700nm and 800nm, which is close to the wavelength of the femtosecond laser and is perpendicular to the scanning direction;

[0034] S4. The processed sample is mounted on the PCB board and connected to the source meter through the SMA interface to control the applied bias voltage. The sample is processed into a photoconductive antenna. When the laser pulse is irradiated on the photoconductive antenna, the semiconductor material will be excited by the femtosecond laser to generate photogenerated carriers. When the electrode voltage bias is applied on both sides of the antenna, the carriers are driven by the bias electric field and accelerate to migrate toward the two electrodes of the antenna. This acceleration process leads to the formation of transient current, thereby generating terahertz waves radiating outward.

[0035] Figure 2 The surface after processing and SEM observation. It can be seen that there are obvious structural changes on the surface of the material. After SEM observation, the regular micro-nano structure of the surface can be seen, showing a gully shape.

[0036] Figure 3 This is a comparison chart of the light transmittance of GaAs materials. Fourier transform infrared spectroscopy was used for surface analysis. During the experiment, a Lambda750s UV / visible / infrared spectrometer was used to record the transmission spectrum data in the range of 750nm to 1150nm. From the comparison chart, it can be seen that the transmittance of the processed sample is much lower than that of the original piece, and the processed material has a stronger light trapping ability.

[0037] Figure 4 This is a comparison chart of the IV curve of GaAs materials. After installing the electrodes, the samples were tested under 50mW light irradiation. Compared with the IV curve of the original sheet, the processed samples have higher voltage resistance and can withstand higher voltage.

[0038] Figure 5 This is a comparison of the terahertz time domain waveforms generated by the processed photoconductive antenna and the unprocessed photoconductive antenna. The terahertz time domain spectroscopy system was used for testing. The operating frequency of the system was 77.6MHz, the emitted pulse wavelength was 780nm, and the pulse width was 97fs. It was connected to the source meter through the SMA interface to control the applied bias voltage. By analyzing and processing the measurement data, we can obtain the time domain waveform of the terahertz radiation pulse at different times. It can be observed that the photoconductive antenna made of the processed material exhibits superior terahertz performance compared to the original piece. The performance of the processed antenna can reach 2.24 times that of the original piece.

[0039] The number of devices and processing scales described here are used to simplify the description of the present invention, and the application, modification and variation of the present invention will be obvious to those skilled in the art.

[0040] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A device for improving the terahertz intensity of a photoconductive antenna by laser ablation, characterized in that: include: A light source, an aperture (1) arranged on one side of the light source, an attenuation plate (2) arranged on one side of the aperture (1), a lens (3) arranged on one side of the attenuation plate (2), and a cavity (4) arranged on one side of the lens (3); A light-transmitting hole is provided on the end surface of the cavity (4) close to the lens (3), and a sample (5) is installed at the bottom of the cavity (4); The material of sample (5) is crystal orientation <100> , intrinsic gallium arsenide material with a thickness of 350μm and a resistivity of 107~108Ω·cm.

2. The device for improving the terahertz intensity of a photoconductive antenna by laser ablation according to claim 1, characterized in that: The light source is a laser with a repetition frequency of 1 kHz, a pulse width of 120 fs, and a wavelength of 800 nm.

3. The device for improving the terahertz intensity of a photoconductive antenna by laser ablation according to claim 2, characterized in that: The laser generated by the laser is focused on the sample surface in the cavity through a lens with a focal length of 200 mm. The focusing radius is 100 μm. The laser power is 300 mW, the scanning speed is 4 mm / s, and the scanning interval is 20 μm as the processing parameters.

4. The device for improving the terahertz intensity of a photoconductive antenna by laser ablation according to claim 3, characterized in that: The laser light generated by the laser includes femtosecond laser or nanosecond laser.

5. A method for improving the terahertz intensity of a photoconductive antenna by laser ablation according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, installing a sample (5) in a cavity (4), wherein a two-dimensional platform is fixedly connected to the cavity (4); S2, focusing the laser through a lens (3), and setting a scanning path to process the sample by adjusting a stepper motor (5); S3. When the laser contacts the surface of the sample (5), the scattered light interferes with the incident light beam. At this time, the periodic irradiation is formed, so that the surface of the sample (5) presents a periodic micro-nano structure pattern. The surface microstructures are all gully-like protrusions. The surface morphology and peak height of the material are uniform. The ripple interval is between 700nm and 800nm, which is close to the wavelength of the femtosecond laser and is perpendicular to the scanning direction. S4. The processed sample (5) is mounted on a PCB board and connected to a source meter via an SMA interface to control the applied bias voltage, and the sample (5) is processed into a photoconductive antenna.

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