Category: Applications of Fiber Lasers

Advantages of Fiber Lasers in Micromachining

Over the last years, the fiber laser technology and its potential have been sparking the interest of laser manufacturers, as well as researchers and industrial users. Lasers have an excellent beam quality, providing observable advantages and enhancements in high precision and material processing at the micro scale.
Micromachining is concerned with making small characteristic features using such ordinary machining operations as drilling, cutting, scribing, and slotting—but on a smaller scale. There is no official scale to identify when an operation is micromachining, but a golden rule is that you can see the results, but without seeing the details.

Laser Parameters and Process Capabilities

Up-to-date laser micromachining techniques are used in the automobile and medical industries, the production of semiconductors, and solar cell processing. Lasers for micromachining suggest a wide range of wavelengths, pulse width (from femtoseconds to microseconds), and repetition frequency (from a single pulse to Megahertz). These values allow micromachining with high resolution in depth and lateral dimensions. The sphere of micromachining consists of manufacturing methods like drilling, cutting, welding, ablation, and material surface texturing, where it is possible to attain very fine surface structures ranging in the micrometer.

Cost Efficiency and Performance Benefits

Nowadays, there is a new innovative micromachining technology, including advanced laser markers with superior beam quality. It is being used to achieve results similar to traditional machining technologies, but cheaper, faster, and more flexible.
Recent developments in the use of a fiber laser marker for micromachining can create desired features not normally associated with this equipment. The major benefit of this approach is that fiber laser markers are two to three times less expensive than standard equipment used for micromachining.
The fiber laser micromachining technology can be used for a wide variety of applications, such as selective plating removal for solder barrier, solar cell scribing and hole drilling, hole drilling of stainless steels for medical hypo tubes and fluid flow control systems, and cutting of sub-0.02in.-thick metals for fast part prototyping.

Ultraviolet (UV) Laser Sources and Types

Numerous photonics applications in research and industry require ultraviolet (UV) laser light. Only a few types of conventional laser systems provide UV light, and those emit at fixed wavelengths. Gas lasers, laser diodes, and solid-state lasers can be manufactured to emit ultraviolet light, and lasers are available that cover the entire UV range. The nitrogen gas laser uses electronic excitation of nitrogen molecules to emit a beam that is mostly UV. The strongest ultraviolet lines are at 337.1 nm and 357.6 nm, wavelength. Another type of high-power gas laser is the excimer laser. They are widely used lasers emitting in ultraviolet and vacuum ultraviolet wavelength ranges.

Applications of Excimer Lasers in Industry and Research

Excimer lasers have been widely used for many photonics applications, such as polymer laser micromachining, ranging from microelectronics, medical, life sciences, automotive, printing, and other industrial applications. Excimer lasers produce high-energy UV radiation. They are suited for machining polymers, which exhibit good absorption at these wavelengths. These pulsed lasers produce high average UV power from a few to hundreds of watts at relatively low repetition rates, and from tens of pulses per second up to a few thousand pulses per second. Each pulse duration can range from a few nanoseconds to hundreds of nanoseconds, and their pulse energy ranges from a few millijoules to a few joules. The UV laser beams generated by these excimer lasers are generally incoherent, wide, and multimodal.

Advantages and Considerations of Excimer Lasers

Excimer lasers are available at much higher average power levels than ultrafast lasers, and their initial cost is lower, especially if normalized to their power output. However, they require more maintenance and have higher operating costs. Excimer lasers can achieve much higher throughput for high-volume manufacturing, especially for high-density patterns. For low-density patterns such as machining a few holes in each part, the choice is often more complex. High repetition rate, low power excimer lasers are now available with low operating costs and can be used economically for these applications.

Optromix Company offers compact and powerful excimer lasers with a wavelength range of 193 nm to 308 nm. CL-5000 is equipped with high high-voltage switch – a high resource cold cathode thyratron. The laser has an average power stabilization system, which makes it easy and convenient to use. Moreover, CL-5000 provides a longer-lasting time for the gas mixture. The ultraviolet excimer laser is a perfect source for ophthalmic systems. It is also a great solution for various industrial purposes, namely manufacturing diffractive structures in optical fibers, micro marking, processing of certain materials, and laser deposition.

Optical Tweezers: Principles and Scientific Applications

Optical tweezers, also known as optical traps, were first introduced in 1986 and since then have been widely used in different applications, being particularly successful in the field of biological studies, where optical tweezers are used to study DNA sequences, interactions of proteins, etc.
Optical tweezers have been used in numerous studies involving optical tweezers in order to trap single atoms, viruses, single-cell organisms, strands of DNA, bacteria, carbon nanostructures, and many others. The manipulation and assembly of structures on a nanoscale are the most promising advances right now.

How Optical Tweezers Work

The main principle of optical tweezing lies in the fact that light carries momentum that is in proportion to its energy, and the direction of light is the same as the direction of propagation. After interacting with an object, the light beam changes its momentum; the same happens with an object after interaction with a beam of light – it undergoes a change of momentum by an equal amount. These interactions result in a reaction force, which acts on the object.
In most optical tweezer setups, light is emitted by a laser beam that is focused on a particular spot. A trap that is able to hold a small dielectric object appears in the spot. The scattering force, which occurs when light hits the object and scatters off its surface, produces a momentum transfer that leads to the object being pushed by the beam of light. This method allows for trapping an object in all dimensions.

Ytterbium Lasers in Optical Tweezer Systems

Lasers used to create an optical trap must be highly stable. Ytterbium lasers are often used in optical tweezer systems as they produce a stable and high-power laser beam, which allows for interference-free optical trapping. Other properties of Yb lasers include:

• a simple electronic level structure;
• a small quantum defect, which provides an opportunity for high power efficiency;
• Yb lasers have a capacity for wide wavelength tuning;
• a low-noise beam that allows for the creation of an optical trap in a precise spot.

All of these characteristics make Ytterbium lasers one of the most optimal options for light emitters in optical tweezer systems. These lasers have already been used in multiple studies that utilize optical trapping for capturing micron-sized particles and living cells, with superior pointing stability being the main reason these lasers are chosen over other types.

What Are Tunable Fiber Lasers and How They Work

Tunable fiber lasers’ main characteristic is the ability of the wavelength to tune or adjust. This process is referred to as wavelength tuning. Tuning of the fiber laser may occur over a wide range, which is highly desired for certain applications.

Wavelength Tuning and Speed Requirements

Tunable fiber lasers are called wavelength agile if the wavelength tuning may be performed at high speed. Fast wavelength tuning is important for dynamic environments in which the laser may be used. Generally, single-frequency fiber lasers can be continuously tuned over a certain range; other laser types can be tuned to only access discrete wavelengths. Tuning of non-single-frequency lasers over a large range leads to mode hops.
Among fiber lasers, rare-earth-doped fiber lasers can be tuned over a wide range of wavelengths. For example, ytterbium fiber lasers are tunable over tens of nanometers. Widely tunable fiber lasers are Raman fiber lasers.

Key Applications of Tunable Fiber Lasers

Tunable fiber laser systems are used in a variety of different applications:

1. Spectroscopy. A high-frequency resolution of transmission recording is possible by using tunable lasers. Tunable fiber lasers are also used in LIDAR.

2. Laser cooling. Some methods of laser cooling require tunable lasers that can be adjusted very precisely.

3. Isotope separation. The process of isotope separation with the use of a tunable laser consists of adjusting the laser wavelength to atomic resonances first and later tuning it to a particular isotope to ionize it and deflect it with an electric field.

4. Optical fiber communications. Tunable fiber lasers are often used as a spare laser in case the main fixed wavelength laser breaks down. In this situation, a wavelength-tunable laser is tuned to the wavelength of a particular channel that has failed.

5. Optical frequency metrology. In optical frequency metrology, the laser needs to be stabilized to a certain standard, e.g., an absorption cell, an optical reference cavity.

Fiber-Laser Optical Sensing Systems and Their Advantages

The optical sensing systems based on fiber laser technology are important tools for various fields of applications, like oil and gas exploitation, pipeline monitoring, wind detection, and perimeter security. The advantages that these systems provide make them highly desirable: the systems are passive, lightweight, and small in size, reliable, and provide the ability to be multiplexed to interrogate large sensor arrays.

How Fiber-Laser Optical Sensing Detects Events

In optical sensing systems, the optical fiber acts as a long sensor that is sensitive to the acoustic perturbations. The light traveling through the fiber changes its path due to the change in the optical path length in the fiber. After the interrogation by coherent laser light and recombination with reference light from the fiber laser source, an acoustic “fingerprint” is produced.
The fingerprint provides information about an event that took place somewhere along the fiber. To reduce the irrelevant noise that may be caused by rain droplets and aircraft, sophisticated algorithms are used; such practice is often used in perimeter monitoring. The optical sensing systems based on fiber laser technology are crucial to pipeline integrity monitoring, as pipelines are also potential targets for intrusion. Therefore, the demand for fiber laser systems is increasing, and a need for low RIN lasers has emerged.

Why Low RIN Lasers Are Essential

Low RIN lasers tend to be compact, efficient, reliable under most environmental conditions, and easy to use. The main advantages of low RIN lasers include low phase noise and narrow spectral linewidth. One of the important requirements that are expected from low RIN lasers is the ability to be interrogated over long distances. Low phase noise ensures the high sensitivity of optical systems. In general, single-frequency fiber lasers have low RIN.
The low RIN lasers are required in various fields, including:

1. Subsea systems – low RIN lasers are used in the location of oil and gas below the sea level via interrogation of fiber optic hydrophone arrays. The low RIN lasers are key to obtaining clear images and solid data.
2. Wind LIDAR – lasers with low relative intensity noise are needed for the detection of weak backscatter from particles carried by the wind.
3. Satellite missions – various measuring equipment mounted on satellites utilizes low RIN lasers.

Laser Beam Welding: Principles and Advantages

Laser beam welding is a technique of material welding through the use of a laser beam. Laser beams provide a concentrated source of heat that allows for narrow welds and high welding rates. Laser beam welding is frequently used in high-volume applications that are automated, for example, in the automotive industry.

How Laser Beam Welding Works

The high power density of laser beam welding results in small areas being affected by heat, which in turn leads to high heating and cooling rates. The laser spot size varies between 0.2 mm and 13 mm; however, large spot size lasers are not typically used in welding. The depth of penetration depends on the amount of power supplied. Picosecond lasers and femtosecond lasers are used to weld thin materials, like razors, whereas continuous wave lasers are used in deep welding.
Laser welding is a versatile process that is capable of welding many different metals, including carbon steels, stainless steel, and aluminum. The main advantages of laser beam welding are 1) transmission of the laser beam through air rather than requiring a vacuum; 2) the process is widely automated; 3) the welds are of high quality.

The Role of High Beam Quality

High beam quality is an important factor in laser beam welding. High beam quality can be defined as a measure of how tightly a beam of a laser can be focused. The ability to tightly focus a laser beam allows for a more precise weld that is required when working with small objects and tight seams between the metals. The use of high beam quality lasers in laser beam welding provides an opportunity for a large working distance. This can be highly desirable to protect the optics against debris and fumes.
High beam quality fiber lasers are most often based on single-mode fibers. Among other laser types that have high beam quality are gas lasers, like CO2 lasers. High beam quality fiber lasers are increasingly being used for robotic industrial welding due to the many advantages that they provide.
The high optical quality of high beam quality fiber lasers is a result of the fiber’s waveguiding properties. They reduce thermal distortion of the optical path, resulting in the production of a diffraction-limited optical beam. High beam quality fiber lasers are also able to have high output power – they can support kilowatt levels of continuous output power.

Choosing the Right Fiber Laser for High-Quality Micromachining

The goal of micromachining is to achieve high-quality results in the shortest time possible and in the most economical way. Laser machining can achieve all of these goals — it can achieve localized, high-quality, precise machining. However, the right choice of laser is crucial to achieving a high-yield, economical process.
Laser micromachining is heavily used in mobile devices, where the demand to make smaller, lighter, lower-cost mobile devices has required laser processes that can meet this challenge. Other areas of application include medical device manufacturing,  clean energy, automotive, and aerospace.

How Pulse Width Shapes Precision, Quality, and Throughput

One of the most important factors that affects the machining results is the laser pulse width. It affects the precision, quality, and economics of the process. The most used fiber laser types that are used in micromachining are femtosecond fiber lasers, picosecond fiber lasers, and nanosecond fiber lasers.
Nanosecond fiber lasers result in higher throughput due to a higher rate of material removal when compared to picosecond fiber lasers and femtosecond fiber lasers, because most of the material removal takes place by melting. After being heated to its melting temperature, the material evaporates. The precision of nanosecond fiber lasers may suffer due to the melted material clinging to the edges of the machined feature and its solidification. In addition, some of the melted material often splashes around the machined feature, which creates poor quality of machining.

Picosecond Lasers — Improved Edge Quality and Reduced Heat Effects

The use of picosecond fiber lasers improves molten material splashing around the laser-machined edges and molten material buildup. Moreover, the material removal threshold is much lower for picosecond fiber lasers. However, cutting and drilling processes are executed at a much higher fluence than the material removal threshold, and nanosecond fiber lasers provide higher throughput than picosecond lasers.

Femtosecond Lasers — Premium Quality for Sensitive Materials

The choice between femtosecond and picosecond lasers depends on the material used, quality requirements, and economic considerations. Generally, femtosecond fiber lasers provide higher quality micro machining, but the higher costs of femtosecond lasers are a serious consideration. Both femtosecond and picosecond lasers provide high peak power and lower material removal.
Overall, the choice of the right fiber laser wavelength depends on the materials to be processed, the desired quality, and cost requirements. Generally, nanosecond lasers offer an economical, higher-throughput solution, whereas picosecond and femtosecond lasers provide high-quality machining of thin, transparent materials.