I think everyone has heard the slogan "Femtosecond laser treatment of myopia", but I believe many people do not understand what is a femtosecond laser, the same is the nanosecond laser, picosecond laser, these strange seconds and our common What is the difference between lasers? Today, let's take a look at the features and applications of these kinds of laser pointers.
In fact, nanoseconds, picoseconds, and femtoseconds are all time units, 1 ns = 10-9 s, 1 ps = 10-12 s, and 1 fs = 10-15 s. This time unit represents the pulse width of a laser pulse, in short, a pulsed laser is output in such a short period of time. Such a laser is called an ultrafast laser because its output single pulse time is very short. When the laser energy is concentrated in such a short period of time, a huge single pulse energy and a very high peak power are obtained, and in the material processing, the long pulse width and the low intensity laser pointer are largely prevented from melting the material. Continuous evaporation (heat effect) can greatly improve the processing quality.
In the industry, the laser pointer is usually divided into four categories: continuous wave (CW), quasi-continuous (QCW), short pulse (Q-Switched), and ultra-short pulse (Mode-Locked). Continuous wave is represented by multimode continuous fiber laser, which occupies a large part of the current industrial market. It is widely used in cutting, welding, cladding and other fields, and has the characteristics of high photoelectric conversion rate and fast processing speed. Quasi-continuous waves, also known as long pulses, can generate pulses of the order of ms to μs with a duty cycle of 10%, which makes pulsed light have more than ten times higher peak power than continuous light. For applications such as drilling and heat treatment. Very beneficial. Short pulses refer to pulses of the order of ns, which are widely used in laser marking, drilling, medical, laser ranging, second harmonic generation, military and other fields. Ultrashort pulses are what we call ultrafast lasers, including pulsed lasers of the order of ps and fs.
When the laser pointer acts on the material with a pulse time of the order of picoseconds and femtoseconds, the processing effect changes significantly. The femtosecond laser can focus on a smaller area than the diameter of the hair, making the intensity of the electromagnetic field several times higher than the force of the nucleus to its surrounding electrons, thus enabling many other methods that do not exist on Earth. Extreme physical conditions are also not available. As the pulse energy rises sharply, the high power density laser pulse can easily strip off the outer electrons, causing the electrons to break away from the atom and form a plasma. Since the interaction time between the laser and the material is extremely short, the plasma has not been able to transfer energy to the surrounding material, and has been ablated from the surface of the material without causing thermal influence on the surrounding material, so ultra-fast laser processing is also Known as "cold processing." At the same time, ultrafast lasers can process almost all materials, including metals, semiconductors, diamonds, sapphire, ceramics, polymers, composites and resins, photoresists, films, ITO films, glass, solar cells, and more.