A powerful new tool developed from ultrashort pulse laser technology

In the past 20 years, femtosecond laser is a powerful new tool developed in laser technology. Such short femtosecond pulses are already within 4fs. 1 femtosecond (fs), or 10-15s, is only 1,1. If the universe is measured with 10fs as the geometric mean, its lifetime is only 1 minute; femtosecond pulses are so powerful that the maximum pulse peak power obtained using multi-stage chirped pulse amplification (CPA) technology reaches 100 terawatts (TW). This is 1012W, or even 1015W of petawatts (PW, that is, 1015W), and its focusing intensity is higher than that of all the light radiated by the sun to the earth after focusing it to the size of a needle tip. Femtosecond laser is definitely a miracle of mankind.

In the past 20 years, from dye lasers to Kerr mirror-locked titanium sapphire femtosecond lasers, as well as diode-pumped all-solid-state femtosecond lasers and femtosecond fiber lasers, the pulse width and energy records have been continuously refreshed, but the biggest progress is that it has become easier to obtain super-femtosecond pulses. In the past 10 years, ultra-high-speed (ultra-high-speed) technology has made significant progress. At present, titanium sapphire lasers and fiber lasers have made this type of (femtosecond laser) laser simple and stable. Today, people can buy this kind of laser, but 10 years ago, you had to build it yourself. For example, all the components for high-power femtosecond pulses are integrated in one box. Using fiber femtosecond laser as the seed source, the design does not need to be adjusted, forming the world's unique, ultra-stable, ultra-compact CPA2000 series titanium sapphire chirped pulse amplification system. This practical system does not require professional femtosecond flight operation and can be widely used in scientific research and industrial production.

Based on the ultra-short and ultra-strong characteristics of femtosecond lasers, the application research field can usually be divided into ultrafast transient phenomena and ultra-speed phenomena research. And it deepens and develops with the shortening of laser pulse width and the increase of pulse energy.

Using femtosecond pulse laser as the light source, forming a variety of spectral time resolution technology and pumping detection technology is the most direct application. Its development has directly promoted physics, chemistry, biology, materials, information and other disciplines into the field of microscopic ultrafast processes, creating new fields such as femtosecond chemistry, quantum controlled chemistry, and semiconductor-related spectroscopy. Femtosecond pulse lasers and nano-microscopy techniques can be used to study semiconductor nanostructures (quantum wires, quantum dots, and nanocrystals). In the biological field, people use the differential absorption spectrum and pump/probe techniques provided by femtosecond laser technology to study the transfer and charge separation processes of photosynthetic reaction centers. Ultrashort pulse laser beams are also used for information transmission, processing, and storage.

In 1988, the first desktop terawatt laser was developed using pulse amplification technology, marking the beginning of femtosecond ultra-intense light physics research in the laboratory. At present, the effect of ultrashort laser fields is equal to or far exceeds the beam field of electrons in atoms, and the perturbation theory is no longer valid, so it is necessary to further develop new theoretical treatments. Using a light intensity of 1020W/cm2, it is possible to study the physical phenomena of simulated celestial bodies. Ultra-strong lasers generated by thermal electrons (200keW/cm2 thermal electrons (200keV).

Another important application area is femtosecond lasers. Generally, the duration of laser pulses exceeds 10 picoseconds (equivalent to the heat conduction time) and is a long pulse, which is used for processing materials. Thermal effects will change the surrounding materials, thus affecting the processing accuracy. The pulse width is only one quadrillionth of a second. Femtosecond laser pulses have special material processing properties such as small melting range or no processing aperture; metals can be micro-machined and engraved on various materials, such as semiconductors, transparent materials and even biological tissues; the processing area can be smaller than the focus, diffraction limit, etc. Now, some automakers and heavy equipment manufacturers are studying the use of femtosecond lasers to make better engine nozzles. Ultrashort pulse lasers can form micropores several hundred nanometers wide on the metal surface. IBM's Hitt said at the recent American Optical Society meeting in Orlando that IBM has applied a femtosecond laser system to the lithography process of large integrated circuit chips, with almost no heat transfer femtosecondLaser Cutting.

It can be said with certainty that with the further development of ultrashort pulse laser technology and the further improvement of high reliability of femtosecond laser technology, it will be more widely used in more fields.