Difference between pulsed and continuous laser cleaning

The laser cleaning technology involves the stimulation of laser radiations from an electromagnetic source onto a substrate. The substrate refers to the surface or item being cleaned. The laser beam is propagated straight to clean the surface effectively.

Hence, laser cleaning refers to using laser beams in a non-destructive manner. The lasers only rip off the material’s surface, removing dust, smoke, or coatings from the bulk of the material. The process is non-destructive because the power and intensity of the whole process are controlled. The user can choose how far the process will go and how much power to use.

However, different cleaning techniques are applied depending on the material of the substrate. Otherwise, the substrate could either be destroyed or not thoroughly cleaned. The two primary laser cleaning techniques are pulsed and continuous laser cleaning.

Overview of Continuous Laser Cleaning

LASER is an acronym for light amplification by stimulated emission of electromagnetic radiation. The light is emitted at a constant power output if the wave is continuous. The active medium used in the laser will determine the strength of the waves. Such lasers include xenon fluoride, CO2, argon fluoride, and (YAG) yttrium aluminum garnet.

These lasers are widely applied in the aerospace, automobile, and welding industries. They are ideal for drilling and cutting projects, besides containment of dirt. Oil extraction companies find such lasers helpful in maintaining the drill heads and softening rocks during drilling. Medical engineering companies also adopt this technique to keep medical devices. They are also relevant in repairing damaged parts and manufacturing medical implants and other components.

Continuous lasers are the best choice if you’re looking for a more powerful, faster cleaning technique. They are also ideal when working on a budget and your workshop has weight restrictions.

The Drawbacks of Continuous Laser Cleaning

• It is not a versatile cleaning technique. This is because quite several machines can operate with pulsed waves.
• The process can damage the substrate because of high energy production.
• They cannot be used for high-precision cleaning because of the high energy produced.

Overview of Pulsed Laser Cleaning

Pulsed lasers emit power in pulses at a constant time interval. Unlike the previous technique, pulsed lasers cannot operate continuously when required to produce strong waves. Hence, they are used in high-precision scenarios requiring heat control stringency. Q-switched lasers are an excellent example of pulsed lasers. As such, they have nanosecond pulses. However, there are more examples of pulse-generating lasers.

Pulsed laser applications

• Flash lamps:Involves the pumping of some solid-state bulk lasers in a free-running mode. It gives longer pulse durations and higher energy emissions.
• Gas and metal vapor lasers:Nitrogen and copper vapor lasers are good examples of lasers that cannot operate in continuous-wave mode. As such, they are driven with current pulses.
• Picosecond diode lasers:These are semiconductor lasers with short pulses (nanosecond and picosecond pulses). They also operate with relatively low energy.
• Actively or passively, Q-switched lasers:They emit pulses with either nanosecond or sub-nanosecond duration regime. Typically, they are primarily solid-state bulk lasers, emitting high-pulse energy. The energy mainly falls in the millijoule or multi-joule zone.
• Excimer pulses:Pumped with short pulse durations. They operate in the ultraviolet spectral zone. They are also pumped with relatively short electric pulses.
• Mode-locked lasers:These are either semiconductor lasers, fiber lasers, or solid-state bulk lasers. They have ultrashort pulses falling under the femtosecond and picosecond pulse duration domain. Their pulse repetition rate is mostly in megahertz or gigahertz, producing relatively low energy. Cavity-dumped lasers are an excellent alternative for higher-energy pulses.
• Quasi-continuous-wave-operation and laser diodes: Used to generate rather long pulse durations.

The Drawbacks of Pulsed Laser Cleaning

In some applications, short pulse duration doesn’t give the best result. For instance, long pulse durations will prevent laser-induced damage because of low optical linewidth. Such also have meager peak power.

Pulse Quality

Look out for only reproducible pulse parameters. They include bandwidth, energy duration, and center wavelength. Also, consider the optical power and time. Some applications only need a constant evolution of the optical phase.

Some scenarios will not need any pre-pulses or post-pulses to avoid unnecessary evaporation of the target. As such, an intense laser pulse should strike the target at once. It is mainly applicable in high-intensity physics experiments like laser-induced nuclear fusion.

Look out for the pulse timing. Some scenarios may require a minimal timing jitter. For example, mode-locked lasers.

Bottom Line

We hope your knowledge about both lasers is enriched. Pulsed lasers are used for low-energy, high-precision applications. On the other hand, continuous lasers are applicable in high-energy scenarios. Remember to check the pulse quality using the pulse parameters and timing. Click here to find out more about pulsed and continuous laser cleaning.