SHINHOP laser

What is high reflectivity?
Generally speaking, high reflectivity refers to the low absorption rate of near-infrared laser due to the low resistivity and smooth surface of the processed material. As shown in the figure, this is the absorption coefficient of common metal elements, which leads to a large amount of laser emission. Since most laser applications are perpendicular to the material or at a slight angle, this causes the returning laser to re-enter the output head, and some of the returning light may couple into the energy transmission fiber, transmitting back to the interior of the laser, causing the core components inside the laser to remain at a high temperature.

Specific implementation plan for anti-high reflectivity:
When processing high reflectivity materials, if excessive returning laser enters the interior of the laser, there is a certain risk of damage to the cutting head, welding head, and the laser itself, especially for high-power fiber laser products, where the returning laser power is significantly higher than that of low-power laser products, resulting in a higher risk of damage. During the cutting process of high reflectivity materials, when the material has not penetrated, there will be a high power of returning light back to the interior of the laser, damaging the laser. Laser researchers have designed a four-level anti-high reflectivity light protection design to address the above issues, and have also added various returning light monitoring functions to ensure real-time protection of the laser during abnormal processing.Taking the commonly used Raycus high reflectivity laser as an example, analyzing how brand lasers resist high reflectivity.
1. Four-level anti-high reflectivity light design
1. Anti-high reflectivity light design for optical cable output head
The QBH, QD, and QP fiber output heads designed by brand lasers can efficiently convert uncontrollable returning light into absorbable light and heat, while enhancing the heat absorption and dissipation capabilities of the output head, thus maximizing the avoidance of returning light's impact on internal components. For laser processing systems, returning laser first affects the output optical cable head, posing a risk of heating or even damage to the output optical cable. To ensure the safety of the output optical cable, we have integrated a first-level returning light stripping device inside the output optical cable based on the original design. The anti-high reflectivity light design added to the output end of the optical cable can strip away most of the returning laser immediately, reducing damage to the optical structure inside the laser, while effectively absorbing the stripped returning laser through a water cooling design, avoiding thermal impact on the optical cable output head.

2. Two-level anti-high reflectivity light design in the combining module
Multi-module high-power laser products are mainly formed by combining multiple unit modules. When cutting high reflectivity materials, the returning light may still have some light transmitted back to the combining module after passing through the first-level anti-high reflectivity design at the optical cable. Therefore, to ensure the safety and reliability of the optical devices and optical path design inside the combining module, two-level anti-high reflectivity protection designs have been added inside the combining module, using a step-by-step method to strip returning laser, ensuring the safety of anti-high reflectivity protection optical devices while reducing the impact of returning laser on the laser's optical path structure.

3. Anti-high reflectivity light design in the unit module
Due to the presence of an optical resonant cavity inside the unit module, low-power returning laser, once entering the unit module, is continuously amplified by the resonant cavity, which can severely affect the optical stability of the laser and increase the risk of damage to the laser. To further enhance the stability and reliability of the laser during high reflectivity cutting, an anti-high reflectivity light device has been added to the unit module based on the optical path design inside the unit module, improving the reliability of the module.

2. Multiple high reflectivity software monitoring design (to be gradually introduced)
High reflectivity software protection mainly refers to high reflectivity monitoring protection, which means that when the laser processes high reflectivity materials, the strong returning light generated enters the optical system of the laser, causing instability in the operation of the laser or damage to optical devices, and a monitoring or protection mechanism for the operating state of the laser is implemented.
Although the anti-high reflectivity light device can ensure that the laser can still operate normally without damage within a certain returning laser power threshold, there is still a risk of damage to the laser if this threshold is exceeded. Therefore, to ensure timely protection of the laser when the returning laser is too high, multiple high reflectivity software protection designs have been added inside the multi-module high-power laser products:
1. Output optical cable high reflectivity protection design
When the returning light power is high, part of the returning laser will return along the original optical path to the output optical cable fiber, while another part will directly enter the front end of the output optical cable. Through research on the transmission issues of returning laser and the integration of monitoring functions, we have integrated multiple detection functions inside the output optical cable, including optical cable temperature monitoring, laser monitoring, and returning light monitoring, for real-time monitoring of returning laser. Once the returning laser power exceeds the range that the laser can withstand, the laser will promptly shut off the output and issue an alarm, ensuring that the laser will not be damaged and also alerting the customer that there is an abnormality in the processing.
2. High reflectivity protection design for combining and optical modules
Considering that returning laser includes both core laser and cladding laser, in addition to adding high reflectivity protection design to the output optical cable, we have also added a high reflectivity detection module inside the combining module to detect the power of the reverse transmitted laser and monitor the power of returning laser in real-time. This high reflectivity detection module can detect both cladding laser and core laser, effectively avoiding the risk of damaging the laser when only detecting cladding returning laser while core returning laser still poses a risk. Once there is a high returning laser inside the laser, it can also promptly shut off the laser and issue an alarm, ensuring the safety and reliability of the laser.
3. Cutting test
Due to the low laser absorption rate and high thermal conductivity of purple copper, the surface of purple copper remains in a mirror state, continuously reflecting laser back to the fiber output head, thereby verifying the anti-high reflectivity capability of the new fiber output head.

Aluminum plate cutting↑
As long as the operation is proper, whether it is aluminum plates, brass, purple copper, or other high reflectivity materials, the anti-high reflectivity laser can handle them efficiently, cutting with good edge quality. The abnormal processing test for high reflectivity is to test the anti-high reflectivity capability of the laser by making lines back and forth on the purple copper plate without penetrating it. At this time, the returning light is extremely high, yet the laser can still operate normally, indicating that this type of laser has strong anti-high reflectivity capability.

Signal display↑
From the above high reflectivity test, it can be seen that during the cutting process, the high reflectivity monitoring signal can be transmitted to the display screen in real-time. When there is an abnormal processing state, the high reflectivity signal can be detected, and this signal is within the threshold of the laser. When the high reflectivity exceeds a certain threshold, it will trigger a machine alarm, reminding the staff to check if there is an operational error.
For cutting high reflectivity materials, SHINHOP laser process engineers suggest:
(1) When cutting brass, copper, and other materials, keep the speed conservative, leave some space, and do not push it to the limit.
(2) Copper must be cut with oxygen, and cannot be cut with nitrogen or air.
If the following problems occur, please stop the machine immediately for inspection.
(1) The lower protective lens is contaminated.
(2) The perforation of high reflectivity materials did not penetrate.
(3) The perforation of high reflectivity materials penetrated, but the cutting did not go through.