Since the laser’s pulse duration is smaller than the destination object’s conduction period, the ultra-short pulse laser provides innovative material processing opportunities. It effectively implies that cold processing of things is achievable, with substance taken out through sublimation.
Such a vaporization processing approach has benefits that are impossible with conventional procedures. Nevertheless, because these technologies are costly, people should thoroughly review the lasers and platform selection.
The three most common forms of laser technology are nanosecond laser, picosecond laser, and femtosecond laser. Each one has various uses and benefits in laser technology. This article will go through the three types of lasers and how they work.
What is Nanosecond Laser?
Nanosecond lasers, often known as nanolasers, are the most prevalent type of q-switched pulsed lasers. The utilization of an increased speed shutter inserted into the optical cavity to briefly enhance cavity wastage till the gain substance’s metastable state is completely saturated is known as Q-switching.
When the switch is turned on, every laser beam becomes discharged simultaneously. The depletion period for many laser amplification substances is in the wavelength range of several nanoseconds (10-9s), leading to the creation of nanosecond laser pulses.
Numerous operations need optical properties of a laser beam having a pulse duration in the nanosecond range, such as laser ablation of materials, scanning electron microscopy, measuring distances, and satellite imagery. They are produced with lasers in many situations through Q-switched or gain-switched mode.
Q-switched ones may generate massive laser energy, such as many millijoules from small solid-state lasers and many joules from bigger machines. Based on design parameters, the output may occur in a specific longitudinally state of the laser resonant, resulting in an extremely small linewidth.
Gain-switched nanosecond laser can produce nanosecond pulses at considerably lower pulse energy levels. Maximum strength in semiconductor lasers is frequently restricted to the range of 1 W.
One of several significant advantages is the high degree of flexibility in altering both the high repetition rates and the laser pulse duration mechanically and maintaining the laser pulse duration stable. In contrast, the high repetition rates are adjusted across a wide variety. Furthermore, such systems can be manufactured at a lower price.
Nanosecond laser is produced in many different wavelengths from ultraviolet to infrared, pulse energy ranging from nJ to J, and high repetition rates ranging from Hz to MHz due to the extensive spectrum of gain techniques and materials. Such lasers’ substantial maximum output and laser pulse duration make them useful for various uses such as LIBS, nanosecond laser ablation, laser identification, and marking.
What is Picosecond Laser?
Picosecond lasers generate optical laser pulses with pulse durations ranging from one (10-12s) to tens of picoseconds. As a result, it falls within the ultrafast or ultrashort laser pulses.
Specific laser-based generators of picosecond laser pulses and wavelength, such as continuously pumped OPOs, are often referred to as picosecond lasers, though they are not technically picosecond lasers.
Several laser systems can generate Picosecond laser pulses, with several other laser efficiency parameters ranging widely. They may be used in various uses, including laser ablation of materials, medicinal applications, OPO pumping, etc.
What is Femtosecond Laser?
A femtosecond laser generates optical pulses with laser pulse durations far below 1 picosecond in the femtosecond (10-15 s) region. It’s therefore classified as an ultrafast or ultrashort pulse laser.
The method of latent mode-locking is almost typically used to generate these brief femtosecond laser pulses. As a result, pulse patterns with significant pulse energy and repetition frequencies in the MHz or GHz frequency range are produced.
It, formed with the constrained mean output power, results in relatively short pulse energy, frequently in the nanojoule range. Utilizing an optical amplification device that contributes to a femtosecond laser allows for much larger pulse energy at a lesser repetition frequency, typically by several times greater magnitude.
The Importance of Ultrashort Laser Pulses
Laser micromachining and laser ablation have long been attempted. Laser ablation is the technique of removing material from an irradiated region using a laser light focused on the surface of the material. Several technological applications have explored and employed the laser ablation process.
Nevertheless, the materials constantly dissolve and evaporate because of the laser’s longer pulses width and lower efficiency power. Even though the laser pulses may be focused into a limited area, the heat effect on the substance is still significant, limiting cutting precision.
The only way to increase processing quality is to reduce the heat-affected zone. The operating performance changes dramatically when a laser pulse of picosecond duration strikes a substance. The high laser power generated by the abrupt rise in pulse energy is sufficient to tear off the electrons in the outer shell.
Since the contact period between the laser pulses and the base material is so brief, ions are efficiently removed with laser ablation of the specimen surface before transmitting laser pulse energy to the surrounding surface, resulting in negligible heat effect on the underlying metal. For that, it is also termed “cold working.” Nanosecond pulses, femtosecond laser pulses, and picosecond lasers have penetrated industrial output and usage due to the benefits of cold working.
The ultrashort laser pulse generating power is rapidly fed into a limited activity region. The immediate high power density application modifies electron reception and mobility, eliminates the consequences of laser-straight absorption, pulse energy movement, and diffusion, and significantly modifies the laser-matter reaction mechanism.
Nanosecond vs. Femtosecond vs. Picosecond Laser
Following centering, an increased energy laser beam irradiates the material’s substrate. It is basically a thermal processing mechanism, but the process is more effective because of the short response period, generally within several nanoseconds. As a result, the heat-affected zone is limited, and the laser-induced impact and speed are ensured.
The picosecond and femtosecond laser having reduced laser pulse durations have significant advantages in the laser ablation sector and are now referred to as greater precision ultra-fast laser ablation techniques. Because the picosecond laser has ultra-short laser pulse duration and the reaction period of a single frequency is only a few picoseconds, its thermal load is very modest, if not non-existent.
Unlike the nanosecond laser micromachining, the picosecond laser doesn’t rework the materials throughout the process. The procedure is smoother, and the laser energy consumption is less reliant on the substance or wavelength. Simultaneously, the operation duration is reduced, the precision is increased, and the processing power is increased.
The picosecond laser process outperforms the nanosecond laser in terms of processing efficiency and quickness. The picosecond laser even has an enormous potential application scope. In addition, nanosecond laser continues to dominate the significant laser ablation and processing business. The massive expense of picosecond laser cutting devices is the cause.
Picoseconds and femtosecond laser will be the key focus. These lasers specialize in working with materials with thicknesses as thin as 0.01 in (250 microns). Denser substances can be treated, but Buyers should carefully consider processing time. The operational variations among the picosecond and femtosecond laser might be minor in some cases and evident in others.
The distinction is slight when utilized to treat metals. The femtosecond laser has no rough topside edges, significantly more specified details, and decreased surface irregularity. The femtosecond laser also can work with a wider variety of polymers. Picosecond lasers generally need a green or UV spectrum to treat polymers efficiently.
The contrast between picosecond and femtosecond laser performance is compared to the material. A femtosecond laser is an apparent option when only the highest quality is required. Picosecond lasers, on the other hand, tend to process quicker.
There are several ultra-short high laser energy pulsed laser wavelength options, with some performing better for specific materials. Picosecond and the femtosecond laser each include infrared, green, and ultraviolet spectrum options. Different wavelengths perform well for other substances, which people can sometimes choose depending on the area of the necessary features and advantages.
The lowest possible focus point area is proportional to the wavelength. Consequently, providing all other variables stay constant, a UV laser will concentrate to a surface area one-third the size of an IR laser. Every femtosecond and picosecond laser may provide numerous wavelengths from the same laser device.
For femtosecond laser, the purpose and reasoning for various wavelengths suited to specific metals are less evident. Several experts first assumed that with such a small pulse duration, the conventional absorption dependence on wavelength might no longer happen and that the multiple photon absorption process would take over.
It has not been demonstrated for specific polymers, such as polymer catheters. Not only do femtosecond laser pulses improve processing performance and materials cutting precision rate, but it also has a broader processing area and ablation threshold than infrared. The green spectrum can give a more stable system for cutting tiny or blind details on polymers, even to the precision micron scale.
Production incorporation of femtosecond laser pulses and the capacity of such lasers to operate materials with enhanced dimensional precision is their distinguishing attribute. As a result, the initial design criterion is that that degree of accuracy is supported.
Nevertheless, even the most powerful technology on the planet will not offer a reliable system if the surroundings wherein the machine is located are unstable, particularly in terms of temperature variation. Temperature variations of more than several degrees will lead to problems with fittings and phases and with the laser’s aiming accuracy and precise removal. As a result, the equipment must be kept in a climate-controlled and air-conditioned environment.
Parts testing is the only way to identify the ideal laser for the operation. Some firms would often perform experiments on the nanosecond, picosecond, and femtosecond laser and different photon energy for all the lasers to specify the purpose and equipment.
Conclusion
Studies on the laser processing quality, ablation speeds, and pulse duration must be balanced against the three lasers. The average cost of an ultra-short pulsed laser is high. While going down that route, customers must evaluate their profit on the investment to validate the total amount of expense in terms of cost-saving advantages and precision processing capacity.
