1. Challenges of laser processing: from continuous light to pulsed light
In the laser processing process, we usually need the laser to output high-energy, short-pulse beams to achieve rapid melting, vaporization or stripping of materials. However, most lasers output continuous light or low-peak power beams by default, which is difficult to meet processing requirements.
At this time, we need a device that can actively control the accumulation and release of energy in the laser cavity, and the acousto-optic Q-switch is the key to solving this problem.
2. Pulse control principle of acousto-optic Q switch
The acousto-optic Q switch is installed in the laser cavity. By adjusting the Q value (quality factor) of the laser cavity, the laser oscillation is turned on and off:
Q value off stage (RF on):
When the RF signal acts on the Q switch, ultrasonic waves are generated in the crystal to form a dynamic grating. Part of the laser is diffracted out of the cavity, the loss in the cavity increases, the laser oscillation is suppressed, and the energy accumulates continuously in the gain medium.
Q value on stage (RF off):
When the RF signal is turned off, the grating disappears, the loss in the cavity decreases rapidly, the Q value rises sharply, and the accumulated energy is released in a very short time to form a high-power laser pulse.
This "energy storage first, then burst" method enables the laser to output pulses with extremely high peak power, which is very suitable for fine processing.
3. Key parameters of pulse control
In laser processing, the performance of the acousto-optic Q switch directly affects the processing effect. The following parameters are particularly critical:
| Parameters | Description | Impact on processing |
| Repetition frequency | Number of pulses per second (kHz) | Affects processing speed and heat-affected zone |
| Pulse width | Duration of a single pulse (ns) | Determines energy concentration and processing accuracy |
| Peak power | Maximum power of a single pulse | Determines processing depth and material removal rate |
| Beam stability | Energy consistency between pulses | Affects processing uniformity and quality |
4. Typical applications of acousto-optic Q switches in laser processing
- Laser marking and engraving
When marking or engraving patterns on the surface of materials such as metals, plastics, and ceramics, the laser pulse needs to have high energy, short pulse width, and high repetition frequency to achieve clear and fine processing effects. The acousto-optic Q switch can accurately control the pulse output to ensure that each marking point is uniform and clear.
- Laser cutting and drilling
When cutting thin metal sheets or drilling tiny holes, the laser pulse needs to have high peak power and good focusing. The acousto-optic Q switch controls the pulse energy to avoid excessive melting of the material or excessive heat-affected zone, thereby achieving high-precision cutting and drilling.
- Laser cleaning and stripping
When removing surface coatings, oxide layers, or contaminants, the laser pulse needs to have high energy density and controllable heat input. The acousto-optic Q switch can adjust the pulse frequency and energy to achieve non-contact, non-damaging cleaning effects.
5. Performance optimization: How to improve processing quality?
In order to obtain better pulse control effect in laser processing, the performance optimization of acousto-optic Q switch is crucial:
- Improve diffraction efficiency
High diffraction efficiency means that more light energy is effectively modulated and the pulse energy is more concentrated. The diffraction efficiency can be significantly improved by selecting suitable crystal materials (such as TeO₂) and optimizing the acoustic wave power.
- Enhance thermal stability
In high-power laser processing, crystal thermal effects will affect the beam quality and device life. Using air cooling, water cooling or conduction cooling, and optimizing the packaging structure, can help maintain beam stability.
- Optimize drive control
Using a dedicated RF driver, precise control of pulse frequency, width, and delay can be achieved, improving processing consistency and repeatability.
Conclusion: The Precision Art of Pulse Control
Acousto-optic Q switch, as the "pulse commander" in the laser processing system, gives the laser powerful processing capabilities with its high speed, precision and reliability. From marking to cutting, from cleaning to micro-machining, it plays a key role silently.