The difference between Q-switching technology and MOPA technology in fiber lasers
At present, the types of pulsed fiber lasers used in laser marking on the market mainly include two types: Q-switching technology and MOPA technology. MOPA (Master Oscillator Power-Amplifier) laser refers to a laser structure in which a laser oscillator and an amplifier are cascaded. In industry, MOPA laser refers to a unique, more "intelligent" nanosecond pulsed fiber laser composed of a semiconductor laser seed source and fiber amplifier driven by electrical pulses. Its "intelligence" is mainly reflected in the independent adjustable output pulse width (the range can reach 2ns-500ns), and the repetition frequency can be as high as megahertz. The seed source structure of the Q-switched fiber laser is to insert a loss modulator in the fiber oscillating cavity, which generates a nanosecond pulse light output with a certain pulse width by periodically modulating the optical loss in the cavity. For this problem that often troubles everyone, we will make a simple analysis from the internal structure of the laser, output optical parameters and application scenarios.
Laser Internal Structure
The difference in the internal structure of the MOPA fiber laser and the Q-switched fiber laser is mainly in the way of generating the pulsed seed optical signal. The MOPA fiber laser pulse seed optical signal is generated by the electric pulse driving the semiconductor laser chip, that is, the output optical signal is modulated by driving the electric signal, so it has a strong ability to generate different pulse parameters (pulse width, repetition frequency, pulse shape and power, etc.). flexibility. The pulsed seed optical signal of the Q-switched fiber laser generates pulsed light output by periodically increasing or decreasing the optical loss in the resonator, and has a simple structure and a price advantage. However, due to the influence of Q-switching devices, etc., the pulse parameters are limited.
The schematic diagram of the internal structure of MOPA fiber laser and Q-switched fiber laser is as follows:
Schematic diagram of the structure of MOPA and Q-switched fiber laser
Output Optical Parameters
The output pulse width of MOPA fiber laser is independently adjustable. The pulse width of the MOPA fiber laser is arbitrarily tunable (ranging from 2 ns to 500 ns). The narrower the pulse width, the smaller the heat-affected area, and the higher the machining accuracy can be obtained. 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. MOPA fiber lasers have a wider repetition frequency range. The repetition frequency of MOPA laser can reach the high frequency output of MHz. High repetition frequency means high processing efficiency, and MOPA can still maintain high peak power characteristics under high repetition frequency conditions. The Q-switched fiber laser is limited by the working conditions of the Q switch, and the output frequency range is narrow, and the high frequency can only reach ~100 kHz.
Comparison of optical parameters between MOPA fiber laser and Q-switched fiber laser
Application scenarios
MOPA fiber laser has a wide range of parameter adjustment. Therefore, in addition to covering the processing applications of conventional nanosecond lasers, it can also use its unique narrow pulse width, high repetition frequency, and high peak power to achieve some unique precision processing applications. for example:
Alumina sheet surface stripping application
Today's electronic products are getting thinner and lighter, and many mobile phones, tablets, and computers use thin and light alumina as the outer shell of the product. When using a Q-switched laser to mark conductive potential on a thin aluminum plate, it is easy to cause deformation of the material and produce a "convex hull" on the back, which directly affects the aesthetics of the appearance. The parameters of the MOPA laser with a smaller pulse width can make the material not easily deformed, and the shading will be more delicate and brighter. This is because the MOPA laser uses a small pulse width parameter to make the laser stay in the material shorter, and the energy is high enough to remove the anode layer, so for the process of stripping the anode on the surface of the thin aluminum oxide plate, MOPA Lasers are a better choice.
Anodized Aluminum Blackening Application
Use laser to mark black trademark, model, text, etc. on the surface of anodized aluminum material. This application has gradually been widely used in electronic product casings by Apple, Huawei, ZTE, Lenovo, Meizu and other electronics manufacturers in the past two years. , used to mark the trademark, model, etc. of the black mark. For such applications, currently only MOPA lasers can process them. Since the MOPA laser has a wide range of pulse width and pulse frequency adjustment, the parameters of narrow pulse width and high frequency can be used to mark the black effect on the surface of the material, and different grayscale effects can also be marked by different parameter combinations.
Color Laser Marking
Color laser marking is a new type of laser marking process. At present, only MOPA lasers can mark color patterns on metal materials such as stainless steel, chromium, and titanium. When coloring the stainless steel material, the color change of the surface layer of the material can be changed by adjusting the laser beam, so as to obtain the decorative effect of different colors. For the stainless steel product industry, the color of the marking pattern can be added, and various kinds of Text pattern, convenient and easy to operate: environmental protection and no pollution; fast marking speed, which can greatly increase the added value of stainless steel products and enhance the market competitiveness of stainless steel products. Add added value to the product.
Electronics, semiconductor, ITO precision processing applications
In precision processing such as electronics, semiconductors, and ITO, fine scribing applications are often required. Due to its own structure, the Q-switched laser cannot adjust the pulse width parameters, so it is difficult to make fine lines. Since the MOPA laser can flexibly adjust the pulse width and frequency parameters, it can not only make the scribed lines fine, but also make the edges smooth and not rough.
In general, the pulse width and frequency of the MOPA fiber laser are independently adjustable, and the adjustment parameter range is large, so the processing is fine and the thermal effect is low. Achieve the effect that the Q-switched fiber laser cannot achieve. The Q-switched fiber laser is characterized by strong marking strength and has certain advantages in deep metal engraving processing, but the marking effect is relatively rough. In common marking applications, MOPA pulsed fiber lasers are compared with Q-switched fiber lasers, and their main features are shown in the table below. The user can select the appropriate laser correctly according to the actual needs of marking materials and effects.
Performance characteristics of MOPA laser marking machine
MOPA laser marking machine (aluminum black laser marking machine, color laser marking machine) belongs to the category of laser marking machine. Compared with the Q fiber laser, the pulse frequency and pulse width of the MOPA fiber laser are independently controllable. Through the adjustment and matching of the two laser parameters, the high-speed scanning galvanometer system can achieve a constant high peak power output and can be applied to a wider range of standards. Engraved substrate. With high-quality laser beam, the use cost is low, 100,000 hours maintenance-free, suitable for aluminum oxide blackening, 304 stainless steel coloring, stripping anode, stripping coating, semiconductor and electronic industry, plastic and other sensitive materials marking and PVC plastic In the pipe industry, the marked pattern fonts are environmentally friendly and comply with ROHS standards.
Compared with ordinary laser marking machines, the pulse width of MOPA laser marking machine M1 is 4-200ns, and the pulse width of M6 is 2-200ns. The pulse width of the ordinary laser marking machine is 118-126ns. From this, it can be seen that the pulse width of the MOPA laser marking machine can be adjusted in a wider range, so it is understood why some products cannot be marked by ordinary fiber laser marking machines. effect, but MOPA's laser marking machine can do it.
However, when many customers purchase a MOPA laser marking machine, they expect its processing speed to be the same as that of an ordinary fiber laser marking machine, but this is obviously counterproductive. The two techniques are different, when engraving color effects, the machine needs to mark at high frequencies with minimal shadowing effects, which allows high resolution engraving, but at the same time the engraving speed is relatively slow. In addition, in metal deep engraving, MOPA laser marking machine may have no advantage, because there is no advantage in single pulse energy, but in terms of delicate effect, it is much better than ordinary laser marking machine. Therefore, customers need to understand the advantages and disadvantages of this type of laser marking machine before choosing to buy a MOPA laser marking machine.
MOPA laser marking machine is suitable for fine marking process of metal and non-metal materials, such as laser engraving of digital product parts, mobile phone back cover, IPAD, aluminum black, mobile phone buttons, plastic light-transmitting buttons, electronic components, integrated circuits ( IC), electrical appliances, communication products, sanitary ware, tool accessories, knives, glasses and clocks, jewelry, auto parts, luggage buckles, cooking utensils, stainless steel products and many other industries.
