The integration of laser pointer technology with various industries has become increasingly close. Femtosecond ultrafast lasers, as an ideal light source for high-end micro-nano processing and life sciences, have been widely used in industrial precision microprocessing and medical micro precision treatment. Femtosecond laser refers to a pulsed laser with a pulse width <1ps. Under normal circumstances, the material acted by the laser will absorb the energy of the photon and transition to a high energy level within 100 fs; in order to achieve equilibrium, the electron will transfer energy to the crystal lattice within 1 ps; at 10 ps Over time, this energy will be gradually transferred to the inside of the material.
Femtosecond laser because the pulse is short enough, electrons do not have enough time to transfer energy to the lattice. The process is different from traditional laser processing linear absorption, which mainly involves multi-photon absorption, and only the irradiated area that exceeds the multi-photon absorption threshold will a clear processing behavior appear. Therefore, based on the light intensity dependence of multiphoton absorption, femtosecond laser processing can achieve precision processing smaller than the focal spot size. Based on the characteristics of extremely narrow pulse width, concentrated energy, and short thermal diffusion time of femtosecond laser, its ultra-small damage and strict spatial positioning are very suitable for ultra-fine cutting of biological tissues.
Especially in eye surgery such as glaucoma surgery, hyperopia surgery for retinal imaging, and cataract surgery, the femtosecond laser and corneal tissue are unfolded through a photolysis effect, and the tissue instantly becomes plasma under the action of the femtosecond laser. Since the intensity of the electromagnetic field generated by the plasma is several times greater than the force of the nucleus on the surrounding electrons, the tissue will eventually generate tens of thousands of tiny bubbles through photolysis blasting, and finally achieve its precise tissue cutting effect. Very accurate corneal flap thickness and reduce the probability of corneal flap complications. The principle is roughly as follows:
The optical transmission principle of femtosecond laser surgery:
Before the operation, the doctor enters the patient’s basic information and surgical data into the computer (including the depth of green laser pointer focus, that is, the distance from the bottom of the cone lens to the laser focus point; the diameter of the corneal flap, the size and width of the pedicle; the energy of laser cutting, etc. ). During the operation, the doctor operates the femtosecond laser machine and fixes the cornea with a cone lens to maintain the precise distance between the laser head and the laser focus point in the corneal tissue.
The depth of laser focus, that is, the distance from the bottom of the conical lens to the laser focus point. The femtosecond laser machine transmits laser pulses according to the pattern set by the doctor to perform various targeted ablation on the cornea. In brief, the optical transmission principle of femtosecond lasers impressed us the most with the precise directionality and precise positioning of optical transmission.