Those familiar with myopia surgery may also hear about the femtosecond laser frequently, as we mentioned in our previous lecture: there are two options for creating a corneal flap for LASIK surgery: the microkeratome or the femtosecond laser. So, what exactly is a femtosecond laser? What are the advantages of the femtosecond laser for corneal flap creation? Today, let’s discuss these topics together. We are going to start by understanding what is a laser? What is a femtosecond? What is a laser? The original Chinese name for laser is “radium” or “lasing”, which is a transliteration of its English name LASER, which is taken from the English word Light Amplification by Stimulated Emission of Radiation. LASER is an acronym derived from the first letter of each word of Light Amplification by Stimulated Emission of Radiation. It means “expansion of light by stimulated emission”. The full name of laser has completely expressed the main process of manufacturing laser, and in 1964, according to the suggestion of our famous scientist Qian Xuesen, the “light stimulated emission” was renamed “laser”. What is femtosecond? A femtosecond (femtosecond), also called a femtosecond, or fs, is a unit of measurement that measures the length of time. 1 femtosecond is only one trillionth of a second, i.e., 1e?15 seconds or 0.001 picosecond (1 picosecond is, 1e?12 seconds). Even the speed of light, which travels 300,000 kilometers per second, can only travel 0.3 microns in one femtosecond, less than one hundredth of a hair. In one second, light can travel 7.5 times around the earth; in 100 femtoseconds, light can only travel through one hair strand. Power = energy/time, and with a very short time, you can get a very high power using very low energy. What is a femtosecond laser? A femtosecond laser is a laser that operates in pulses of very short duration, only a few femtoseconds. One femtosecond is 10 minus 15 seconds, or 1/1000 trillionth of a second, which is thousands of times shorter than the shortest pulses obtained using electronic methods. What are the characteristics of femtosecond laser? Femtosecond laser is the shortest pulse we can obtain under experimental conditions, its accuracy is ± 5 microns; 2, femtosecond laser has a very high instantaneous power, its instantaneous power can reach a trillion watts, hundreds of times more than the total power of the world’s electricity generation; 3, matter under the action of femtosecond laser will produce a very strange phenomenon, gaseous matter, liquid matter, solid matter Femtosecond lasers have the characteristics of precise targeting and focusing, and can be focused to the ultra-fine space area which is much smaller than the diameter of a hair; 5, surgery with femtosecond lasers has no thermal effects and shock waves, and there is no tissue damage during the entire light course.