MOPA Fiber Laser Knowledge

Everything about Fiber Laser you should know

In the current digital world, we need to have manufacturing and industrial processes that get done quickly but with efficiency and high precision. Fiber laser technology has made this possible for most sectors including medical, manufacturing, mining, construction, food production, aeronautics, among others.

Carbon dioxide (CO2) lasers have been used to cut sheet metal since the 1980s. However, in recent years, fiber laser technology has emerged causing a major disruption in the metalworking market. This technology is seen to be a revolutionary and disruptive as it has affected operations in sheet metal fabrication in a positive way. Fiber laser technology has advanced exponentially within a short time to ease the cutting of plates and metal sheets. It has taken fiber lasers have taken just five years to achieve the 4kW cutting standard that CO2 lasers achieved in 20 years. Fiber lasers have achieved other thresholds that CO2 lasers have never achieved.

What is a Fiber Laser?

This is a laser that uses optical fiber as the active medium, which is made with rare elements such as erbium, thulium, ytterbium, holmium, praseodymium, or dysprosium. The type of rare earth elements used should not concern you much, the most important thing to know is that this laser machine uses optical fiber at its main component.

Advantages of Fiber Laser

  • Fiber lasers are advantageous because unlike other laser types, fiber lasers generate and deliver laser light through a flexible medium, allowing easy delivery to the target and location. This is mostly beneficial to laser welding, cutting, and polymers and metal folding.
  • The fiber laser has high output power in comparison to other laser types. Fiber lasers can accommodate several kilometers of active regions, thus providing high optical gain. Their surface area to volume ratio is high, which permits efficient cooling. Its waveguide properties eradicates or decreases thermal alteration of the optical way; producing a premium, diffraction-limited optical ray.
  • When compared to gas or solid-state lasers, fiber lasers are more compact since the fiber can be coiled or bent to save space.
  • Fiber lasers are dependable and display high vibrational and temperature steadiness and extended lifetime. Their nanosecond pulses and high peak power enhance engraving and marking. The improved beam quality and additional power produce faster cutting speeds and cleaner cut edges.
  • Fiber laser technology is used in various applications including processing material in medicine, telecommunications, directed energy weapons, and spectroscopy.

Types of Fiber Laser

Classification by Light Emitting Mode

1. QCW Fiber Lasers

These are the most recent fiber lasers. They have a lower average power and high peak power, and are manufactured at a lower cost than continuous wave (CW) version. QCW fiber lasers are most suited for various industrial applications that require high peak power and pulse duration, such as, seam welding, spot welding and drilling. They are designed to dislodge YAG lasers because of their necessary low up-front and maintenance costs. They are easily retrofitted into various systems, with multimode and single-mode versions available.

2. CW Fiber Lasers

This is a laser that produces a continuous laser beam while observing controlled heat output, as beam intensity and duration. CW lasers mainly focus on high output and power; therefore, you will most likely find them in industrial settings. The industries that mostly use CW fiber lasers are aerospace, electronics, and automotive, medical sector and semi-conductor industries. They are most efficient when laser cutting, laser drilling, and laser welding.

3. Pulsed Fiber Lasers

These refer to lasers that do not fall under the continuous wave classification. Their optical power is illustrated in timed pulses at a repetitive rate. Pulse lasers encompass a variety of technologies that address different motivations. Some of them are pulsed for not being able to operate in continuous mode.

In other scenarios, the application needs pulses to be produced that have as much energy as possible. As the pulse energy is equivalent to the standard power over the repetition rate, the goal is achieved by bringing down the pulse rate to build more energy between pulses. In other instances, peak pulse power is used instead of pulse energy, particularly when obtaining nonlinear optical effects.

Classification by Light Mode

1. Multimode Kilowatt Fiber Lasers

Manufacture of fiber lasers that are kilowatt-class and higher is done through the combination of various fiber lasers in single-mode, in parallel and then launch them via a step-index fiber that is in larger-core-diameter. When it gets to this point, the laser ceases to be in single-mode, but the ensuing beam quality has better quality compared to other kilowatt-class lasers used commercially. The deviation of kilowatt-class fibers continues to improve as a result of utilizing high-power single-mode modules continuously.

2. Single-mode Fiber Lasers

These fiber lasers are found commercially up to 3000 Watts of output. The devices have continuous operation, but they can be adjusted to over 50 kHz. The adjusted mode allows the devices equal peaks to the average CW power. Emission leaves through a single-mode fiber that has an M2 below 1.1.

The profile is a task of single-mode fiber, instead of the thermal operating point, like it happens with traditional solid-state lasers; fiber lasers produce the same profile throughout the operating range. The adjustment is achieved through turning of the pump diodes on and off, which allows the device to be adjusted in single-pulse operation or at high frequency.

3. Few-mode Fiber

The mode division multiplexing (MDM) systems utilizes restricted orthogonal modes within few mode fibers (FMF). They use this as an independent way to transmit information to multiply the system’s transmission capacity. Few mode optical fiber applies varied modes to demonstrate a new level of freedom; the system’s spectrum efficiency can be successfully enhanced by FMF. Since FMF contains a huge mode field area, it has a better nonlinear tolerance that SMF. This not only enhances the capability of optical transmission system, it also evades the nonlinear effects. MDM systems that are based on FMF can help in solving bandwidth crisis for single mode fibers in the future.

Brief History of Laser Fiber

The laser celebrates 60 years of inception in 2020. Laser technology was made possible because of an awareness that light is a type of electromagnetic radiation. Max Planck discovered elementary energy quanta, which earned him a Physics Nobel Prize in 1918. He was working in thermodynamics while trying to understand why blackbody radiation did not equally emit all frequencies of light during heating. His most important discovery was published in 1900 where he implied that there exists a relationship between radiation frequency and energy.

This meant that emission or absorption of energy could occur in discrete chunks, quanta, even if they were tiny. This marked a defining moment in physics, which inspired emerging physicists like Albert Einstein. Later in 1905, Einstein released a paper of the effect of photoelectric; proposing that light also conveys energy in chunks, discrete quantum particles known as photons.

Laser technology has become critical to many industries and applications, amplifying the effect of light. Lithography that utilizes laser power now plays a major role in the production of semiconductors. Ranging systems that use laser technology provide necessary information in safely navigating autonomous vehicles. Although there is small market today for these types of vehicles, projections indicate that by 2026, the market will increase to $550 billion. Every sector that is impacted by lasers is expected to continue increasing, they include, medical laser market, data centers, and long-haul fiber.

In 1951, while at Columbia University, Charles Townes conceives the maser idea. In 1954, in collaboration with Herbert Zeiger and James Gordon, they demonstrated the initial maser at Columbia University. The ammonia maser was based on Einstein’s forecasts, derived the first generation and amplification of electromagnetic waves through stimulated emission.

In 1960, while working as a physicist, Theodore H. Maiman constructed the first laser with a synthetic ruby cylinder with a 1cm diameter and 2cm length. The laser had silver-coated ends for reflection and was able to function as Fabry-Perot resonators. Photographic flashlamps were used as the pump source. In November 1960, Mirek Stevenson and Peter Sorokin, showcased the uranium laser, and in December 1960, the helium neon laser was developed by William Bennet Jr, Ali Javan and Donald Herriot; it was the first laser to produce a light beam at 1.15 µm continuously.

Lasers began to appear on the commercial market in 1961, through companies such as Perkin-Elmer, Trion Instruments Inc, and Spectra-Physics. In the same year, doctors performed the first medical procedure using a laser on humans to remove a retinal tumor.

In 1962, Q-switching is introduced through giant formation technique for use in applications such as spring welding in watches. The same year saw the development of a gallium-arsenide laser which is a semiconductor that directly converts electrical energy into infrared light, although its cooling happens cryogenically.

Laser fiber technology continues to evolve with the highest-energy and largest laser ever developed unveiled in 2009. It began firing 192 laser beams onto its targets. Recently, MIT researchers have developed a way of using lasers to convey whispers to listeners. This technique allows people to receive secret messages; it is best applied in advertising and the military.

What is Fiber Laser used for?

Fiber lasers are used in industrial processing materials in almost all low- and high-power markets, which include sintering, scribing, cutting and welding, marking, heat treating, and drilling. Single-mode lasers can accomplish high fluency levels and focus on micron-sized spots to change past beliefs that relate to process parameters.

The kilowatt level of the laser fiber has achieved higher speeds of weld penetration and cutting than other technologies while operating under similar conditions. The fiber laser’s compact size, single-mode operation, and wavelength choice provide a variety of medical applications to the medical community. The applications rely on particular fiber and wavelength delivery. It operation is maintenance-free making it acceptable to doctors and other professionals working in the medical field.

Fiber laser is used in many complicated applications because of their many great qualities which include wavelength range, polarized and unpolarized emissions. Other factors are narrow line widths, single-mode operation, short pulse durations, compact size and disregard of environmental conditions.

How does Fiber Laser Work

As stated earlier, the main medium used in laser fiber is doped in hard-to-find earth elements, which in most cases, it is Erbium. The reason for doing this is due to the usefulness of the energy levels in the earth elements’ atom levels, which allow the use of a low-end diode laser pump source that still produces high output energy.

For instance, when fiber is doped in Erbium, an energy level absorbing photon with a 980nm wavelength decays to a meta-stable equal to 1550nm. This means that a 980nm laser pump source can be used, and achieve high energy, high quality and high laser beam power of 1550nm.

Erbium atoms functions as the medium for the doped fiber, and the emitted photons stay inside the fiber core. To create the photon entrapping cavity, there is addition of Fiber Bragg Grating. This is basically a glass section with stripes, where alteration of the refractive index occurs. When light goes through a boundary between two refractive indexes, it refracts back a small amount of light. Basically, Bragg Grating enables the optical fiber laser to function like a mirror.

The pump laser focuses on cladding sitting near the fiber core, since it is too small to focus a low-quality diode later on. When the laser is pumped into the cladding near the core, it bounces around inside, and whenever it passes the core, the core continues to absorb more pump light.

How long does a Fiber Laser Last?

A fiber laser has a higher life expectancy than other laser solutions. The diode module found in a fiber laser functions three times longer than other laser technologies. Majority lasers last for about 30,000 hours equating to about 15 years. However, with fiber lasers lasting three times more, their life expectancy is around 100,000 hours or about 45 years. Although it is unlikely that we will still be using the same fiber lasers 45 years from now, it is still a cost effective option.

Advantages of MOPA Fiber Laser

Master Oscillator Power Amplifier (MOPA) fiber lasers are efficient and reliable marking machines. Their other advantages include:

  • High beam quality
  • Low power consumption but efficient operation
  • Long diode life (about 100,000 hours)
  • Basically maintenance-free
  • Long pulse durations and high peak power enabling deep engraving and aggressive marking applications
  • Compact design
  • Easy integration within other operations
  • Maximum application flexibility
  • Easy to service
  • No alignment or adjustment problems

Final Word

Fiber laser technology has eased the way we work as it touches almost all industries. The food industry has not been left behind as there are thermometers that apply laser fiber technology. The Thermopro Meat Thermometer is one such product that is equipped with high-quality receivers and long probes to observe meat temperature from a 300-feet distance. It has an alarm alert and a large backlit LCD for you to achieve the best cooking outcomes.

Nelson James
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