The solution to the noise of the fiber laser marking machine

Fiber laser marking machine is one of the most widely used laser equipment in the development of laser technology. It is used in many industries, such as hardware tool industry, auto parts industry, mold industry and so on. There may be some noise during the use of the fiber laser marking machine. Let's take a look at the reasons for the noise and the solutions.

The reason for the noise of fiber laser marking machine, the noise mainly comes from the mutual coupling of different longitudinal modes. There are three main changes in the longitudinal mode of the laser when noise is generated: one is that when some longitudinal modes appear and sometimes disappear, the laser output has noise; There is noise; the third is that when the longitudinal modes are coupled with each other and the amplitudes of different longitudinal modes are randomly superimposed, the output power of the laser has an instantaneous peak, and the noise is greater.

The first two cases are mainly caused by spatial hole burning effect, laser mechanical or thermal instability; laser marking machine and the last one is caused by multiple longitudinal modes It is formed by mutual coupling in the frequency doubling crystal. In the green laser without frequency selection measures, the number of longitudinal modes is large, and the coupling phenomenon is quite significant.

The straightforward way to eliminate or reduce the noise of the laser output is to force the laser to operate in a single longitudinal mode. However, an all-solid-state laser that does not operate in a single longitudinal mode can also be in a stable low-noise state under certain conditions

One method is to reduce the number of longitudinal modes, such as when the laser has only 2 to 3 longitudinal modes. , By adjusting the cavity length, controlling the frequency and other means, the fiber laser marking machine keeps the number, amplitude and frequency of the longitudinal modes of the laser relatively stable, and obtains low-noise operation of the laser in several longitudinal modes; the other is to reduce the longitudinal mode. Coupling, by selecting appropriate frequency doubling crystal and matching type to reduce the coupling between longitudinal modes, low noise output can also be obtained.

Reducing the number of longitudinal modes: In a high-power laser, the number of longitudinal modes is large, and the mutual coupling is quite complicated. At this time, the method of longitudinal mode selection can be used to suppress the In addition to the center frequency, as many longitudinal modes as possible, and by adjusting the cavity length (that is, L), controlling the frequency and other means, the number, amplitude and frequency of the longitudinal modes of the laser are kept relatively stable, and the fiber laser marking machine can obtain the laser's quality. Low noise operation.

Frequency interval of different longitudinal modes: △qu003dC/2L′C is the speed of light, L′u003dηL L is the cavity length η is the refractive index of the medium in the cavity, that is, △q u003dC/2ηL Change the cavity length so that the larger the interval, the smaller the number of longitudinal modes. Inserting the device makes other longitudinal modes in the cavity have a certain loss, thereby suppressing other longitudinal modes (such as Brinell sheets) and reducing longitudinal mode coupling. As mentioned earlier, the main noise is from the mutual coupling between different longitudinal modes. According to the coupled wave theory, two valuable conclusions can be drawn: one is that the smaller the interval between two longitudinal modes, the greater the possibility of coupling; the other is that the coupling probability of vertical two longitudinal modes is greater than that of two mutually parallel longitudinal modes.

(This article is edited by the editor, please be sure to indicate the source:)

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