Femtosecond lasers, with their ultra-short pulse duration (10⁻¹⁵ s level) and extremely high peak power (up to terawatt level), possess "cold processing" characteristics — the heat-affected zone can be controlled at the sub-micron level. They are core processing equipment in high-end precision manufacturing and cutting-edge scientific research, widely used in semiconductor wafer dicing, transparent material modification, biomedical device processing, aerospace precision drilling, etc. A femtosecond laser system is a coordinated system of optical, mechanical, and control components. The photon properties and material interaction mechanisms of different wavelength bands vary significantly, and the parameter matching of core components directly determines the processing performance and service life of the equipment. This article provides a professional selection reference from multiple dimensions: basic logic, component selection by wavelength band, collaborative matching principles, mainstream brand selection, and common misunderstanding avoidance.
I. Key Considerations for Selecting Complete Femtosecond Laser Systems
The peak power of femtosecond lasers is far higher than that of continuous-wave or nanosecond pulsed lasers. Even a femtosecond laser with only 10W average power can reach a peak power of 10⁹W magnitude, imposing much higher requirements on the damage threshold and optical uniformity of all optical components compared to ordinary laser equipment. The core logic of system selection is: determine the laser wavelength based on processing requirements, determine the aperture and damage threshold of optical components based on laser parameters, and determine the precision of control and scanning systems based on accuracy requirements. All components must be custom-matched around the laser wavelength — there is no universal femtosecond system solution for all wavelengths.
The mainstream application wavelengths of femtosecond lasers can be divided into five categories:
1030/1064nm near-infrared femtosecond: Main industrial processing band
515/520nm green femtosecond: Photovoltaic, bio-imaging applications
343/355nm ultraviolet femtosecond: Core equipment for advanced semiconductor packaging
257/266nm deep ultraviolet femtosecond: High-end micro/nano processing
1550nm/2μm mid-infrared femtosecond: Medical surgery, polymer processing
II. Detailed Selection of Core Components for Band-Split Femtosecond Lasers
2.1 1030/1064 nm near-infrared femtosecond band
1030nm (YDF fiber femtosecond, Yb:KGW crystal femtosecond) and 1064nm (Nd:YAG femtosecond) are the most widely used femtosecond bands in industrial applications. They have relatively low cost and high technological maturity, mainly used for metal drilling, ceramic cutting, internal modification of transparent materials (e.g., glass cover plate blind engraving, photovoltaic silicon cutting). Average power ranges from 10W to 100W, pulse width from 100fs to 1ps.
2.2 515/520 nm green-light femtosecond band
Green femtosecond lasers are visible-band lasers obtained through second harmonic generation (SHG) of fundamental femtosecond lasers, with photon energy of approximately 2.4eV. They combine the penetration of near-infrared and the high absorption of ultraviolet, making them especially suitable for processing highly reflective metals such as copper and gold, as well as photovoltaic solar cell scribing. Average power ranges from 5W to 40W, pulse width <300fs.
2.3 343/355 nm ultraviolet femtosecond band
Ultraviolet femtosecond lasers are obtained through third harmonic generation of fundamental femtosecond lasers, with photon energy reaching 3.5-3.6eV. They are typical ultra-cold processing tools that can directly break most material molecular bonds, with a heat-affected zone <1μm. They are core equipment for advanced semiconductor packaging, chip marking, and flexible circuit board (FPC) 3D cutting. Average power ranges from 2W to 20W, pulse width <200fs.
2.4 257/266 nm deep-ultraviolet femtosecond band
Deep ultraviolet femtosecond lasers are obtained through fourth harmonic generation of fundamental femtosecond lasers, with photon energy reaching 4.6-4.8eV. Their absorption rate for hard and brittle transparent materials such as sapphire, quartz glass, and diamond is much higher than that of UV femtosecond lasers. They are high-end equipment for semiconductor wafer drilling, biochip preparation, and quantum device micro-machining. Average power is generally 1W-10W, pulse width <150fs.
2.5 The 1550 nm/2 μm mid-infrared femtosecond band
Mid-infrared femtosecond lasers belong to the eye-safe wavelength band, with special absorption characteristics for organic tissues, polymers, and silicon-based optoelectronic materials. They are mainly used in medical femtosecond surgery, polymer 3D processing, and infrared transparent material modification. Average power ranges from 5W to 30W, pulse width from 100fs to 1ps.
III. General Principles for the Coordination and Matching of Core Components
In addition to the component parameter requirements for each wavelength band, system selection must follow the following collaborative matching principles to avoid individual components being qualified but overall performance falling short.
3.1 The principle of damage threshold redundancy
The damage threshold of all optical components (beam expanders, galvo mirrors, focusing lenses) must be at least 50% higher than the actual peak power density of the laser, leaving sufficient safety margin. Femtosecond lasers have extremely high peak power — even minor impurity defects can cause mirror damage. 50% redundancy is the minimum requirement.
3.2 The principle of the proportion of calibre filling
The diameter of the expanded laser beam must match 80%-85% of the galvo's entrance aperture: filling factor less than 70% will result in longer focal depth, larger spot size, and decreased processing accuracy; filling factor greater than 90% will cause laser energy to overflow the galvo, heating the mirror mount and causing thermal drift, and will also lose more than 10% of energy.
3.3 The principle of repetition frequency synchronisation
The trigger frequency of the control card must match the repetition rate of the laser, with an error <1‰, to avoid missed pulses or double pulses that could cause processing gaps or over-burning.
3.4 The principle of focal length matching
The focal length of the focusing lens is selected based on processing requirements: the greater the processing depth and the larger the field, the longer the focal length; the higher the accuracy requirement, the shorter the focal length. The focal length must match the dynamic focusing range, which needs to cover 120% of the focal length variation range to ensure accurate focusing across the entire field.
IV. Guide to Selecting Leading Brands
4.1 Laser Brands
波段类型 | 进口品牌 | 国产品牌 | 适用场景 |
|---|
近红外飞秒 | 德国通快(TRUMPF)、美国相干(Coherent)、光谱物理(Spectra-Physics) | 安扬激光、大族激光、锐科激光 | 工业批量加工选国产，高端科研选进口 |
绿光飞秒 | 德国通快、美国NKT Photonics | 安扬激光、华工激光 | 光伏、3C加工可选国产头部品牌 |
紫外飞秒 | 美国相干、德国TOPTICA | 大恒光电、安扬激光 | 先进封装高端选进口，批量加工选国产 |
深紫外飞秒 | 日本滨松(Hamamatsu)、德国TOPTICA | 上海激光所、凯普诺 | 几乎都选进口，国内仅科研级产品可选 |
中红外飞秒 | 美国Thorlabs、德国Menlo Systems | 武汉锐科、中科院光机所 | 医疗高端选进口，工业选国产 |
V. Avoiding Common Mistakes in Selection and Configuration
Misconception 1: Replacing femtosecond laser components with nanosecond laser components
Many users think that components can be shared if the femtosecond and nanosecond wavelengths are the same. In reality, the peak power of femtosecond lasers is 100-1000 times higher than that of nanosecond lasers. The damage threshold of nanosecond components is far from sufficient, and mirror damage will occur in a short period, even if the average power is the same.
Misconception 2: Blindly pursuing high power whilst neglecting beam quality
The core of femtosecond processing is peak power, not average power. Under the same average power, the smaller the beam quality M², the higher the focused peak power, and the better the processing effect. Blindly increasing average power only increases cost without improving processing quality.
Misconception 3: Ignoring the impact of temperature control on the overall precision of the machine
Femtosecond laser processing is extremely sensitive to temperature. When the ambient temperature fluctuation exceeds ±1°C, the focal point drift can exceed 2μm. High-precision processing must be equipped with a system-wide temperature control system, not relying solely on the galvo's own heat dissipation compensation.
Misconception 4: Incorrect choice of beam expansion factor
Either the magnification is too small and the spot cannot fill the galvo, reducing processing accuracy; or the magnification is too large and the spot overflows, losing energy and burning components. The matching must be precisely calculated based on the 80%-85% filling factor.
Conclusion
Femtosecond laser system selection is a systematic engineering effort. The core principle is: "wavelength determines the foundation, parameters determine the matching, and application scenario determines the brand." Different wavelength bands have inherently different requirements for the materials, coatings, and precision of all core components. The rules for selecting components by wavelength band must be strictly followed, with sufficient damage threshold and accuracy redundancy, to balance processing performance, equipment lifespan, and procurement cost.
Currently, the domestic femtosecond laser industry chain has gradually matured. Except for ultra-high-end scenarios such as deep ultraviolet, most industrial scenarios can use domestic components, reducing equipment cost by 30%-40% while meeting performance requirements. For scientific research and medical applications pursuing ultimate precision, imported brands still have advantages in stability and consistency, but domestic brands have shown strong competitiveness in cost-effectiveness and customized services.
