Day: September 23, 2025

Novel approach to high-energy ultrashort pulses

A team of Swiss researchers successfully generated high-energy ultrashort pulses with single-mode beam quality by applying nonlinear beam cleaning within a multimode laser cavity. Previously, mode-locked fiber lasers with single-mode optical fibers were thought to support only temporal modes.

Advantages and drawbacks of single-mode fiber lasers

Mode-locked single-mode fiber laser systems are considered to be very advantageous. The benefits include high-gain doping, intrinsically single-spatial mode, and compact setups. High-power mode-locked fiber lasers have some disadvantages, such as high nonlinearity because of the compact core size of optical fibers.

Nonlinear beam cleaning in multimode laser systems

A team of researchers from Switzerland presented a novel technique for producing high-energy, ultrashort pulses with single-mode laser beam quality. They develop nonlinear laser beam cleaning in a multimode laser system cavity. The conventional technique generates low-power ultrashort laser oscillators to solve the problem.

Then it is necessary to increase the laser beam power levels by several amplifiers, but the process of external amplification makes the cost and complexity higher. Researchers prefer applying multimode optical fibers (graded-index) in fiber laser systems because of their low modal dispersion and periodic self-focusing of the light inside.

Spatiotemporal mode-locking technique

The researchers claim that it is possible to perform spatial laser beam cleaning, wavelength conversion, and spatiotemporal mode-locking using graded-index multimode optical fibers. The spatiotemporal technique mode-locking is a relatively new one that allows for creating ultrashort pulses by fiber lasers.
The technique produces “a balance between spatial and temporal effects within a multimode laser system cavity, which supports multiple paths to guide light.” A big multimode core leads to a decrease in the cavity nonlinearity; the fiber laser can achieve high pulse energy without external amplification. High-power mode-locked fiber laser systems suffer from a low-quality output laser beam because of multimode fibers.

Results and practical applications

Finally, the researchers tested the developed fiber laser technology and it demonstrated nonlinear beam cleaning in a multimode laser for the first time. The nonlinear laser beam cleaning promotes the creation of high-energy, ultrashort pulses with single-mode beam quality. The fiber laser technology directs a high-quality laser beam when mode-locking is reached.

Development of a microcavity fiber laser

A team of scientists from Australia developed a microcavity laser system that emits energy-saving and user-safe laser beams with low pump power. This fiber laser technology has an excellent potential for nanoscale applications, especially in biology and medicine.

Challenges of nanosized fiber lasers

It is necessary to look deep inside tissue for biosensing and bioimaging research at the intracellular level. This is the reason why nanosized fiber laser systems have several challenges for these biological applications. These fiber lasers allow for directing the luminescent emitters included in individual nanoparticles to interact with one another.

Operating principle of nanoparticle fiber lasers

Electrons are accumulated at particular energy levels, and laser systems help to overcome the limits of the generally low pump laser beam power’s insufficiency in producing nanoparticles able to lase. These nanoparticles of the new fiber laser system will emit laser beams at pretty low pump powers.

The fiber laser technology has already been tested by the researchers and showed a two orders of magnitude lower pumping threshold compared to that generally accessible. The operating principle of the laser system is based on the binding surface of the nanoparticle matrix to create a cavity surface with a uniform single layer.

Applications in biosensing and bioimaging

The researchers claim that it is possible to include the NIR microcavity fiber laser in thick tissues and single cells. Thus, the fiber laser system helps to detect environmental indicators such as temperature, pH, and refractive index. These factors play a crucial role because their change demonstrates the health status of the tissues or cells, leading to the opportunity of early-stage disease detection.

Potential for medical applications

Fiber laser technology is very promising for biological applications. The researchers could point a nanoparticle fiber laser “inside a cell and illuminate an area of interest inside the compartments of a cell.” Additionally, the opportunity to reduce pump power results in low tissue damage as the laser system penetrates the sample.

Accuracy and limitations

A narrow laser beam allows for more accurate detection. Nevertheless, interference greatly influences fluorescence-based sensing. According to test results, a single nanoparticle can operate like a fiber laser at low power with a sharp laser beam signal.

Application of fiber lasers in welding

The application of laser systems is widespread when it comes to the welding process. Specialists claim that fiber lasers will soon replace traditional welding technologies. The diode-pumped fiber laser systems are most popular due to their low cost, including the ongoing cost of maintenance, spare parts, and being environmentally friendly.

Continuous-wave lasers and beam focusing

Continuous-wave laser systems enable the transmission of uninterrupted laser beam lights that are highly valued in welding. The combination of a fiber laser with the right optics makes the size of the laser beam more focused, for example, a 51μm diameter spot that is 10 times smaller than that of a pulsed laser system.

Advantages of oscillating head technology

Fiber laser systems with an oscillating head provide better welds by applying mirrors that can handle high-power laser beams of 1.5kW. The benefits of lasers with an oscillating head help to achieve high power density that can melt most metal materials and even vaporize them if needed.

Welding types and related issues

There are two types of welds: conduction-limited and keyhole welding. Additionally, the molten pool interacts with the beam of the fiber laser, resulting in inefficient welds when left uncontrolled. The problem appears in deep and narrow keyhole welding, as well as in small welds.

Plasma formation and its influence

Plasma formation also influences the laser beam and leads to scattering effects that degrade welds. The solution to the problem requires the opinions of specialists. Effects such as thermal lens focusing or reflection focusing on the molten pool can lead to a temperature increase in the laser system.

Flexibility and precision of fiber laser technology

“When a gas is heated to a high temperature, it can be ionized and turn into a plasma, where metal vapor and dust can be aggregated, which generates a ‘plasma ball’ scattering the incoming laser beam in multiple directions.” It also decreases the quality of the fiber laser system.
Finally, fiber laser technology is considered to be very flexible compared to fixed fiber optics. It allows for controlling weld depth and width independently. It needs careful attention to such parameters as power, amplitude, frequency, and average speed. Low heat distortion plays a crucial role in laser systems.