Published in：2019-01-25Views：1378 Times
The femtosecond laser is a laser that operates in pulses and has a very short duration of only a few femtoseconds. A femtosecond is 10 negative 15ths of a second, or 1/1000 trillion seconds.
Can femtosecond lasers break through the problem of glass soldering?
Femtosecond lasers have very high instantaneous power and can reach terawatts. The third characteristic of a femtosecond laser is that it can focus on a smaller spatial area than the diameter of the hair, making the electromagnetic field stronger than the nucleus's surrounding electrons.
How are these characteristics of femtosecond lasers achieved?
The high-power femtosecond laser system consists of four parts: an oscillator, a stretcher, an amplifier, and a compressor. Within the oscillator, a femtosecond laser pulse is obtained using a special technique. The stretcher pulls this femtosecond seed pulse apart at different wavelengths. The amplifier gives this broadened pulse full energy. The compressor recombines the amplified spectra of the different components and returns to the femtosecond width to form a femtosecond laser pulse with high instantaneous power.
It is well known that matter is composed of molecules and atoms, but they are not static and move rapidly. This is a very important basic attribute of microscopic matter. The advent of femtosecond lasers has allowed humans to observe this ultrafast motion process at the atomic and electronic levels.
Based on these scientific findings, femtosecond lasers have been widely used in fields such as physics, biology, chemical control reactions, and optical communication. It is worth mentioning that due to the fast and high resolution characteristics of femtosecond lasers, it has its advantages and irreplaceable role in the early diagnosis of lesions, medical imaging and biological living detection, surgical medicine and the manufacture of ultra-small satellites.
Substances can be very strange under the action of high-intensity femtosecond lasers: gaseous, liquid, and solid matter become plasma in a flash. This plasma can radiate laser light of various wavelengths of radiation. High-power femtosecond lasers collide with electron beams to produce hard X-ray femtosecond lasers that produce beta-ray lasers that produce positive and negative electron pairs.
High-power femtosecond lasers have good prospects for medical, ultra-fine micromachining, high-density information storage and recording. High-power femtosecond lasers can also break down the atmosphere, creating discharge channels and enabling manual lightning protection to avoid catastrophic damage caused by lightning strikes on aircraft, rockets, and power plants.
The use of femtosecond lasers accelerates electrons and compresses the size of the accelerator. High-power femtosecond lasers interact with matter to produce a sufficient number of neutrons for fast ignition of laser-controlled nuclear fusion. This will open up a new way for mankind to realize a new generation of energy.
Femtosecond lasers are one of the powerful new tools developed in the past by laser science. The femtosecond pulse is so short that it has reached 4fs. 1 femtosecond (fs), which is 10-15s, is only 1 petath of a second. If 10fs is used as a geometric mean to measure the universe, its lifetime is only 1min; the femtosecond pulse is so strong, adopting The maximum pulse peak power obtained by multi-stage chirped pulse amplification (CPA) technology can reach the order of terawatts (TW, ie 1012W) or even watts (PW, ie 1015W), which can focus the intensity of the sun to the earth. The energy density of all the light that is focused to a needle-like size is even higher.
The application of femtosecond pulsed lasers is that people use it as a light source to form a variety of time-resolved spectroscopy techniques and pump/detection techniques. Its development directly led the research of physics, chemistry, biology, materials and information science into the micro-superfast process field, and opened up some new research fields, such as femtosecond chemistry, quantum control chemistry, and semiconductor coherence spectroscopy. The combination of femtosecond pulsed lasers and nanomicroscopy allows one to study the carrier dynamics in semiconductor nanostructures (quantum wires, quantum dots, and nanocrystals).
In biology, people are using the differential absorption spectroscopy and pumping/detection technology provided by femtosecond laser technology to study the energy transfer, transduction and charge separation processes of photosynthetic reaction centers. Ultrashort pulse lasers are also used in the transmission, processing and storage of information.
The successful operation of the desktop terawatt laser using chirped pulse amplification technology began in 1988, marking the beginning of a femtosecond glare physics study in the laboratory.
In this field of research, since the role of the ultrashort laser field has been equivalent to or greatly exceeds the bound field of electrons in the atom, the perturbation theory has not been established, and new theoretical processing needs to be developed. At a light intensity of 1020 W / cm 2 , the study of simulating astrophysics can be achieved.
Professor Zhao Quanzhong from the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, focused on femtosecond laser technology and its applications in a keynote speech on femtosecond laser welding glass. Professor Zhao Quanzhong said: "Glass welding is considered to be a major problem in the welding field. This is mainly because the laser energy is difficult to be absorbed by the transparent material, the glass material is hard and hard to process, and the thermal effect will affect the glass permeability. Compared with the ultraviolet laser welding Femtosecond laser welding is becoming an effective solution for glass soldering because the multiphoton absorption effect of femtosecond lasers only reacts at the focal position."
Femtosecond laser welding glass is mainly used to weld the glass together by focusing the laser on the glass joint and adjusting the femtosecond laser pulse energy and scanning speed to form a melting effect on the glass surface. With the development of integration, glass is often required to be soldered with materials such as semiconductors and metals. Femtosecond lasers are expected to achieve further breakthroughs in these soldering fields.