The term MOPA is an abbreviation for Master Oscillator Power Amplifier. The master oscillator produces the beam while the optical amplifier is used for boosting the output power.
Q-switched laser is a technique for obtaining energetic short (but not ultrashort) light pulses from a laser by modulating the intracavity losses and thus the Q factor of the laser resonator. The technique is mainly applied for the generation of nanosecond pulses of high energy and peak power with solid-state bulk lasers.
The light of marking lasers is generated in pulses. Generally, the pulse duration is non-adjustable. What is special about a MOPA laser is that its pulse duration is variable: Long or short pulses can be adjusted in steps between 2 and 500 ns.
The output pulse width of the Q-switched fiber laser is not adjustable, and the output pulse width is generally unchanged at a fixed value of 80 ns to 140 ns.
Furthermore, there is a difference regarding the pulse frequency itself: While the range of the pulse frequency of Q-switched fiber laser lies between 1 and 200 kHz, it lies between 1 kHz and 4000 kHz for a MOPA laser.
Summarizing, the MOPA laser offers more flexibility regarding the adjustment of laser parameters. Thus, the MOPA laser is extremely versatile and can be adapted to the material very accurately if needed.
Differences of MOPA and Q-switched Fiber Lasers in Various Applications
1. Surface Stripping for Aluminium Oxide Thin Plate
In order to cater for the light-weight tendency, phones and laptops are now gradually adopting aluminium oxideplates as their covers. In this case when marking the covers, Q-switched fiber lasers will easily cause the deformation of the material and thus produce many small convex bulges which badly affect the appearances of the products.
However, by using MOPA laser, pulses with ultra-short pulse widths have enough energy to strip anodic layer yet the short laser residence time on material. This gives no deformation of the plate itself, leaves a smooth and bright surface after stripping, and makes MOPA a better choice for the marking of aluminium oxidethin plates.
2. Anodized Aluminum Oxide Black Marking
Many electronics makers such as Apple and Huawei are adopting laser to mark their logos, model numbers and characters in black colour on their product covers.
To achieve this, MOPA fiber laser is the exclusive choice. With its wide pulse width tuning range and pulse frequency tuning range, MOPA fiber laser can mark in black color by using pulses with narrow pulse width and high frequency. Tuning and recombining different parameters can even make different grey scales realisable.
3. Electronics, semiconductors and ITO Precision Machining
In the areas stated above, precise lining is frequently needed. It is difficult to achieve precise lining by using a Q-switched fiber laser due to its unchangeable pulse width. Alternatively, a MOPA fiber laser is able to finish the job well and ends up with smooth edges with its flexibly tuned pulse width and frequency.
In addition to the above several application cases, there are many different applications of MOPA laser and Q-switch laser, here are some typical examples of applications with the following table:
|Applications||Q-Switched Laser Marking System||MOPA Laser Marking System|
|Alumine Sheet Stripped Surface||Easy SeformationRough Marking||No Deformation,Fine Marking|
|Alumine Sheet Black Color Marking||Disable||Marking Different Black Colors by Setting the Parameters|
|Metal Depth Marking||Rough Marking||Fine Marking|
|Stainless Steel Color Marking||Difficult to Set Parameters and out of Focus||Marking Different Colors by Setting The Parameters|
|PC.ABS Plastic||Rough Marking with Yello Edge||Smooth without Yellow Edge|
|Light Transmission Paint Keyboard||Disable||Easy to Make it Pervious to Light|
Components,ITO Precision Machining
|Higher Pulse Width and Power||The Pulse can be Adiusted to Get The Best Facula. and Make The Power Balance|
In a word, MOPA fiber laser has wider laser parameter coverage, more flexible adjustment and more comprehensive application range than Q-switched fiber laser. In the case of the same power, Q-switched fiber lasers have more cost advantages. Therefore, these two laser structures present a complementary state in the application market of nanosecond pulsed laser processing.