Principle of QCW laser
A QCW laser consists of a pump source , a gain medium and a resonator cavity. Its pulsed pump driving mechanism has two types.
- The pump source delivers energy in periodic pulses (e.g., millisecond-level pulse width, kHz-level repetition rate) rather than continuous power. It injects high energy into the gain medium within a short duration (microseconds to milliseconds), creating a population inversion.
- The gain medium stores energy during the pump pulse and releases it via stimulated emission as short, high-peak-power pulses. It accumulates significantly more energy during the pulse than a continuous-wave (CW) laser can store instantaneously.
Advantage of QCW laser
The mainly advantage of QCW laser is the HIGH-PEAK-POWER pulse output, which allows the medium to dissipate heat, reducing thermal lensing effects and damage risks while extending system lifespan.
- Once the stored energy reaches a threshold, laser oscillation forms through resonator feedback, releasing high-energy short pulses (typically microsecond-level pulse widths).
- The high repetition rate (e.g., 100 Hz to several kHz) approximates continuous output macroscopically but remains a discrete pulse train microscopically.
Comparison with CW and pulsed lasers
Feature | QCW Laser | CW Laser | YAG laser |
Operating Mode | High-repetition pulses (μs-ms) | Continuous output | Single or low-repetition short pulses (ns-level) |
Peak Power | High (exceeds CW, lower than ultrashort pulses) | Low | Extremely high |
Thermal Load | Moderate (intermittent operation) | High (requires active cooling) | Very low (low duty cycle) |
Typical Applications | Precision machining, medical procedures, nonlinear optics | Cutting, welding | Micromachining, LiDAR |
How is QCW laser manufactured
First, coil the 30-meter-long active fiber with an appropriate bending radius in a circular groove to avoid microbend loss. Next, splice an output coupler grating (OC grating) to one end of the active fiber, and connect the other end of the OC grating to a 200W fiber end cap (CPS). Simultaneously, splice a high-reflective grating (HR grating) to the opposite end of the active fiber to form a resonant cavity, then connect the HR grating to a (2+1)×1 combiner through splicing. Among the three output fibers of the combiner, two 250μm fibers are respectively connected to pump sources, while the remaining 400μm fiber is connected to a mode field adapter (MFA). A red guiding light is spliced at the output end of the MFA. Finally, output the 200W CPS through a QBH connector to complete the assembly of the entire laser system.
Of course, for special scenarios, we can design the fiber laser head in the form of a single or double head.
Typical Applications of Laser Source
QCW laser is one of the important types of fiber laser welding, and QCW based laser welding machines are widely used in Industrial Processing, such as deep Engraving and Drilling and Heat-Sensitive Components welding. For example, 200W desktop QCW laser welding uses peak power to melt materials such as gold, silver, copper, etc. High energy density pulse output, single point welding depth up to 1mm, and minimal heat affected zone, effectively avoiding material deformation, discoloration and other problems.
