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High-Power Laser Beam Propagation in Slightly Wet Atmosphere
Issue:
Volume 10, Issue 6, December 2022
Pages:
215-222
Received:
26 October 2022
Accepted:
9 November 2022
Published:
14 November 2022
DOI:
10.11648/j.jeee.20221006.11
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Abstract: The use of high-power lasers in the industry has been rapidly advanced by incorporating flexible-fiber-based beam delivery. In order to deliver high-power laser beam to a distant place, the laser beam must propagate through the atmosphere. When the laser beam propagates through a medium, a fraction of the laser energy is absorbed by the medium. This absorbed power heats the medium and alters the index of refraction of the path, and leads to a distortion of the beam itself. This phenomenon is called thermal blooming. Thermal blooming at λ0 = 1.08 μm is caused by the absorption of water vapor. In this article, high-power laser beam propagation in a slightly wet atmosphere at λ0 = 1.08 μm was theoretically investigated. At First, the absorption coefficient (α) of air at 10% relative humidity was estimated. Then, simulation of thermal blooming of Gaussian laser beam with an initial power of 1 kW and a radius of 5 mm was conducted using this α. Under the condition of no wind, the beam intensity decreases rapidly with increasing length z. At z = 16 m, the intensity of laser beam became 1/5 of the initial intensity at z = 0 m. When laser beam propagated in the moist air with transverse air flow, thermal distortion of the beam was not symmetrical around the z axis because of the asymmetry introduced by the one-dimensional wind velocity v. Under the condition of calm uniform wind with v = 0.05 m/s, laser beams propagated only 25 to 30 m at most without damaging the initial beam shape. On the other hand, the beams propagated 65 to 70 m at most without beam-shape deformation under the condition of light uniform wind with v = 0.5 m/s.
Abstract: The use of high-power lasers in the industry has been rapidly advanced by incorporating flexible-fiber-based beam delivery. In order to deliver high-power laser beam to a distant place, the laser beam must propagate through the atmosphere. When the laser beam propagates through a medium, a fraction of the laser energy is absorbed by the medium. Thi...
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Numerical Simulation of Thulium Doped Fiber Laser with Dispersion Compensation Technology
Yansong Yang,
Xiaodan Chen,
Ning Zhang
Issue:
Volume 10, Issue 6, December 2022
Pages:
223-228
Received:
31 October 2022
Accepted:
8 December 2022
Published:
15 December 2022
DOI:
10.11648/j.jeee.20221006.12
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Abstract: When the laser transmits in the fiber, it will produce dispersion, and the dispersion is usually expressed by the time delay difference. The reason for dispersion is that the propagation speed of light with different frequencies in the fiber is different with the increasing transmission distance during the transmission of optical signals in the fiber. The light emitted by all light sources has a certain bandwidth, and the optical transmission delay at different frequencies is different, which leads to delay difference. Time delay difference is the time difference caused by different modes or different wavelength components transmitting the same distance in an optical pulse. Because of this time difference, the laser pulse will be broadened, which is a physical effect. For an optical communication system, dispersion will affect the transmission capacity of the system, and also adversely affect the relay distance. The existence of dispersion will also affect the confusion of optical signals at the receiver, cause mutual interference between optical signal numbers, and generate wrong signal codes. This increases the bit error rate of optical signal reception, which is extremely harmful to the optical communication system. We must find ways to eliminate this adverse effect. By analyzing the causes of dispersion, a thulium doped fiber laser based on dispersion compensation is designed, a method of laser dispersion compensation is proposed, and a scheme of laser dispersion compensation is presented. The experimental results show that the intracavity dispersion can be changed by introducing a dispersion compensation system, so that the optical pulse signal can basically restore the original pulse shape. The design scheme proposed in this paper can compensate the dispersion to some extent, and the proposed dispersion compensation method is effective.
Abstract: When the laser transmits in the fiber, it will produce dispersion, and the dispersion is usually expressed by the time delay difference. The reason for dispersion is that the propagation speed of light with different frequencies in the fiber is different with the increasing transmission distance during the transmission of optical signals in the fib...
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Study on High Power Thulium Doped Fiber Laser with Multistage Amplification
Xiaodan Chen,
Yansong Yang,
Ning Zhang
Issue:
Volume 10, Issue 6, December 2022
Pages:
229-233
Received:
2 November 2022
Accepted:
8 December 2022
Published:
15 December 2022
DOI:
10.11648/j.jeee.20221006.13
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Abstract: In recent years, with the continuous progress of science and technology, fiber lasers have been greatly developed. Fiber laser technology combines the waveguide characteristics of fiber and the pumping characteristics of semiconductor. It is simple in structure, high in energy conversion efficiency, good in beam quality, low in threshold, good in heat dissipation and easy to maintain. Fiber lasers can be developed on the basis of fiber amplifiers. Tm doped fiber lasers can emit relatively large wavelengths and have important application value in medical surgery. Therefore, people attach great importance to Tm doped fiber lasers. However, the output power of Tm doped fiber laser is relatively small, which can not meet the requirements for laser applications. In the fields of industry, agriculture and medical application, high power laser is required. High power fiber lasers have many important applications and can meet the needs of all walks of life. In order to obtain high power laser with excellent performance, laser amplification technology has been developed rapidly. Tm doped fiber laser is studied, several different laser amplification systems are analyzed, and a new laser amplification scheme is designed. In the design scheme, a small power Tm doped fiber laser with excellent performance is used as the seed source, and the seed laser is injected into a single-stage or multi-stage fiber amplifier system to finally realize the laser output of high power amplification. The simulation results show that the designed laser amplification scheme is effective.
Abstract: In recent years, with the continuous progress of science and technology, fiber lasers have been greatly developed. Fiber laser technology combines the waveguide characteristics of fiber and the pumping characteristics of semiconductor. It is simple in structure, high in energy conversion efficiency, good in beam quality, low in threshold, good in h...
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Study of Tm Doped Silica Fiber Lasers Pumped by LD
Ning Zhang,
Yansong Yang,
Xiaodan Chen
Issue:
Volume 10, Issue 6, December 2022
Pages:
234-238
Received:
3 November 2022
Accepted:
8 December 2022
Published:
15 December 2022
DOI:
10.11648/j.jeee.20221006.14
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Abstract: Fiber laser has many advantages. First of all, fiber lasers are relatively simple in structure, with fewer components than traditional solid state lasers, smaller volume, and easy to integrate into a small area. In addition, the energy conversion efficiency of fiber lasers is very high. The gain medium is rare earth doped glass, which is rich and cheap. Rare earth doped glass has very high beam quality and is widely used in industry, agriculture, laser communication, atmospheric detection, remote sensing, laser radar, medical surgery and other fields. Now fiber laser has become the mainstream of laser technology development and the main technology of laser industry application. Tm doped silica fiber lasers have been studied. The gain spectrum range of Tm ions is very wide, and its emission wavelength can cover 1800nm-2100nm. This range is just near the peak of the absorption spectrum of water molecules, which has great application value. This paper analyzes the structural characteristics of Tm doped fiber lasers, designs a new type of Tm doped silica fiber lasers, gives the equation of laser pulse, and then simulates the laser to obtain the mode locked pulse of the laser. The simulation results show that the designed Tm doped silica fiber lasers are feasible.
Abstract: Fiber laser has many advantages. First of all, fiber lasers are relatively simple in structure, with fewer components than traditional solid state lasers, smaller volume, and easy to integrate into a small area. In addition, the energy conversion efficiency of fiber lasers is very high. The gain medium is rare earth doped glass, which is rich and c...
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Study on Pumping Technology of Thulium Doped Fiber Laser
Huijuan Sun,
Ning Zhang,
Yansong Yang,
Xiaodan Chen
Issue:
Volume 10, Issue 6, December 2022
Pages:
239-245
Received:
21 December 2022
Accepted:
Published:
23 December 2022
DOI:
10.11648/j.jeee.20221006.15
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Abstract: Fiber laser is a small volume laser using rare earth doped fiber as laser medium. If the fiber laser can emit laser, it must be provided with a certain amount of energy by the outside world. The technology that provides energy for fiber lasers is laser pumping technology. With the continuous development of laser technology and laser devices, there is a growing demand for high power, high efficiency, high beam quality and compact lasers in various fields. Compared with traditional gas and solid state lasers, fiber laser has been developed rapidly because of its high efficiency, miniaturization, excellent beam quality and good heat dissipation performance. Laser pumping is a technology to obtain energy from external energy sources. In order for the fiber laser to output laser, the pump power that provides energy must be higher than the laser threshold of the laser. In order to obtain higher laser power, it is necessary to continuously increase the laser pump power. However, due to the structural characteristics of the optical fiber, the diameter of the optical fiber is usually very small. When the external pump power is relatively large, the optical fiber will generate higher temperature after absorbing energy, which will lead to the damage of the optical fiber. In order to improve the laser output power of the fiber without damaging the fiber material, various laser pumping methods have been developed. The appearance of double clad fiber is undoubtedly a breakthrough in the field of laser pumping, which makes the production of high power fiber lasers and high power optical amplifiers come true. The structure of optical fiber is analyzed, and various laser pumping modes are discussed. The simulation of laser pumping is carried out. The results show that the dual symmetric simultaneous pumping mode is a superior method.
Abstract: Fiber laser is a small volume laser using rare earth doped fiber as laser medium. If the fiber laser can emit laser, it must be provided with a certain amount of energy by the outside world. The technology that provides energy for fiber lasers is laser pumping technology. With the continuous development of laser technology and laser devices, there ...
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