Lasers are becoming an integral part of countless devices and industries. When a laser beam interacts with the surface of a nanoscale material, it emits a wave of light known as a "plasmon," and the properties of a given plasmon can convey information. In optical transmission, the laser pumps light into a component called a "saturable absorber" to produce an optical signal.
Laser technology also has a wide range of uses in industrial processing, such as precision cleaning of components, high-power cutting and welding, and micromachining such as drilling, scribing, fine grinding, polishing, cutting, texturing, stripping, and isolating. In the field of industrial manufacturing, engineers tried to utilize lasers for micromachining a long time ago. However, due to the long pulse widths and low laser intensity of lasers causing the material to melt and continue to evaporate, although the laser beam can be focused into a very small spot, the thermal impact on the material is still significant, limiting the accuracy of the process. The only way to improve machining quality is to reduce the thermal impact. When accuracy of one micron is required, ultrashort pulsed lasers are the best tool for precision cleaning, high-precision polishing, surface resurfacing and welding, or otherwise modifying large amounts of material.
Ultra-short pulsed lasers are pulsed lasers whose output laser pulse widths are in the picosecond (10-12 seconds) class, or less than the picosecond class. Depending on the pulse width of the output laser, ultrashort-pulse lasers can be further categorized into picosecond lasers, femtosecond lasers, and attosecond lasers. Ultrashort pulsed lasers increase the energy of high pulses to dramatically change the light-object response. In general, the narrower the pulse width, the higher the processing accuracy.
When the laser is applied to the material with pulse times on the order of picoseconds, the processing results change dramatically. As the pulse energy rises dramatically, the high power density is sufficient to strip the outer layer of electrons. Due to the short duration of the laser interaction with the material, the ions are ablated from the surface of the material before the energy is transferred to the surrounding material, with no thermal effect on the surrounding material, hence the term "cold processing".
When a laser is applied to a material surface in femtosecond pulses, the laser can output an average power of up to the order of kilowatts, with pulse widths on the order of a few hundred femtoseconds (fs). At repetition frequencies on the order of 1 kHz to 100 MHz, the pulse energy can span the millijoule (mJ) to nano-joule (nJ) order of magnitude, and the peak pulse power can be as high as the GW to TW order of magnitude.
This combination of high pulse energy, high peak pulse power, and high pulse repetition frequency allows for the efficient processing of mechanical structures that are much finer than continuous or long pulsed lasers.
Ultrashort pulse processing energy is injected extremely quickly into a small area of action, and instantaneous high energy density deposition causes a change in the way electrons are absorbed and move, avoiding the effects of linear laser absorption, energy transfer, and diffusion, and fundamentally changing the mechanism of laser-matter interaction. As with generalized laser processing, which is contactless, the use of ultrashort pulsed lasers offers unique advantages in micromachining, including enhanced dimensional accuracy and tighter tolerances, reduced damage and the removal of subsequent processing steps.
This black technology has significant applications for ultrashort pulsed lasers in a wide range of fields such as basic research, industrial processing and optical communications, and is currently being researched intensively by major countries as a way of realizing technological advancements.
R&D Progress in Various Fields
01. Communications
Recently, Yu Yao, Associate Professor of Electrical Engineering at Arizona State University, and her research team at the Arizona State University Photonics Innovation Center designed a faster, more energy-efficient nanoscale laser element called a graphene-plasma hybrid metastructured saturable absorber, or GPSMA for short.GPSMAs have potential applications in industries such as communications, information processing, spectroscopy and biomedicine. The absorber can be used to improve speed, efficiency and overall performance to advance data transmission, information processing, biomedical sensing and imaging technologies.
Due to its beneficial properties in optical modulation and saturable absorption, Yu Yao's team incorporated a synthetically engineered metal-graphene hybrid into their development process.
By designing an optical antenna array that focuses light into the material's nanoscale gaps, known as hot spots, to promote absorption, and by focusing laser light on these hot spots, they observed improved performance and reduced energy consumption. Their new technique will open up new opportunities for infrared laser spectroscopy and high-speed optical signal communications (fiber optic cables andcommunications).
02. Military
A lasersounds like a very sci-fi application. Today, the United States now has the emergence of an ultra-short pulsed laser, and many people have been paying sustained attention to this weapon, which produces pulses of light that are all less than one nanosecond, and it is really expected when you look at it through this mode of calculation that it is known as the Ultra-Short Pulsed Light Laser Weapon. It is reported that the pulses of light produced by thisare less than a nanosecond, through this mode of calculation look down, it is called ultra-short pulse light laser weapon, also really in the unexpected range. The power enhancement of 1 million times, such an advantageous presentation creates more possibilities, in the subsequent development and utilization process, the performance will be more and more obvious.
03. Research and Development
The research team of High Power Fiber Laser Technology Laboratory, Shanghai Institute of Optics and Precision Machinery, Chinese Academy of Sciences, has proposed a nonlinear optical gain modulation technique that can convert a single-frequency continuous laser into highly coherent femtosecond pulses. The method is a brand new technical means to obtain wavelength-flexible ultrafast pulses.
Xi'an Institute of Optical Machinery Photonic Manufacturing Systems and Applications Research Center continues to research in high power and large energy ultrashort laser pulse amplification technology research, the research team used a special glass fiber cascade single crystal fiber hybrid amplification technology, to achieve the 100 kilohertz re-frequency ultrashort pulse amplification of nearly millijoule energy output, the maximum amplified output power of 92.9 watts, corresponding to the energy of a single pulse up to 929 microjoule, the Through the temperature gradient based broadband large dispersion chirped fiber grating and high diffraction efficiency grating to the compressor precision dispersion matching, the center wavelength of 1030 nm, spectral width of only 2.4 nm of the ultrashort pulse compression to 335 femtoseconds (Lorentz fitting Fourier transform limit pulse width of 325 femtoseconds), compressed output pulse energy up to 800 microJoule, corresponding to the peak power of more than 2.38 gigawatts. The output pulse energy is 800 microJoules, corresponding to a peak power of more than 2.38 GW, which is the largest peak power of ultrashort pulse output obtained based on a single-crystal fiber at a repetition frequency of 100 kilohertz, and the quality of the output laser beam is tested, and the beam quality factor (M²) is better than 1.3.
This research work has been supported by the National Natural Science Foundation of China under the major project topic, the Western Young Scholars Program of the Chinese Academy of Sciences (CAS), the Two Chain Integration Special Project of Shaanxi Province, the Hongguang Special Project of the Chinese Academy of Sciences (CAS), and the New Star of Science and Technology of Shaanxi Province. The research results can provide new and efficient light source technology means for scientific and technological research, ultrafast laser processing and other fields. Translated with www.DeepL.com/Translator (free version)
