Diode laser modules Diode laser modules of the DLM series are produced with an output power of up to 100 W. These lasers are distinguished by their compact design, high reliability and cost-effectiveness. They operate at a wavelength of about 970 nm, have a plug-in efficiency of 40-45%, are designed for conductive or forced air cooling, and do not require replacement of any elements during their entire service life. The radiation is output via a flexible optical fiber with a diameter of 0.1...0.3 mm, protected by a metal casing. For ease of operation of the modules, low-power radiation from a pilot laser in the red or green range can be added to the invisible operating radiation.

The control circuit of the laser module provides functions for turning on/off the output radiation, controlling the output power, monitoring module parameters, and controlling the pilot laser. Allowable modulation frequencies of output radiation are up to 50 kHz. The modules are powered from low-voltage DC sources.

Main advantages
- Compact design
- Fiber radiation delivery
- Efficiency up to 45%
- Conduction or air cooling
- Radiation modulation with frequencies up to 50 kHz
- High reliability and long service life
- No maintenance required

Areas of use
- Soldering
- Welding of plastics
- Heat treatment
- Surface cleaning
- Medical devices
- Laser pumping
- Scientific research

Options
- Green/red pilot laser

Typical specification

CW Ytterbium Lasers

The ILM series of ytterbium continuous wave lasers is designed for integration into end-user equipment for various applications and is designed for harsh operating conditions - with high levels of vibration and contamination, humidity up to 90%, and large temperature differences. Compact, maintenance-free, diode-pumped ytterbium fiber lasers generate radiation in the spectral range of 1030-1080 nm, which is delivered directly to the affected area using single-mode fiber in a protective metal sleeve. At the customer's request, a collimating lens or optical connector can be installed at the end of the fiber.

Low power consumption (efficiency “from the socket” is more than 25-30%), compact design, lack of adjustable elements, air cooling, high reliability and long service life at extreme operating conditions provide fundamental advantages of ytterbium fiber lasers compared to lasers of other types for this spectral region . The output power of the radiation can be modulated in amplitude with a frequency of up to 5 kHz. The ILM series lasers are powered from a 24 V DC network.

Main advantages
- Output power up to 120 W
- Beam quality M2

Options
- Linear polarization
- Fiber length up to 20 m

Areas of use
- Soldering
- Microwelding
- Heat treatment
- Engraving
- Medical devices
- Scientific instrumentation

Typical specification

CW erbium lasers

Erbium fiber lasers of the ELM series are unique instruments that have all the advantages of fiber lasers and operate in an eye-safe spectral range (1530-1620 nm). These lasers, due to their wide output power range, high efficiency, high reliability and a wide range of options, are the best solution for a variety of tasks in materials processing, telecommunications, medicine, and scientific instrumentation. The devices are controlled through an interface, which allows the ELM to be used as part of a technological installation, medical or scientific complex.

Main advantages
- Emission wavelength from 1530 to 1620 nm
- Efficiency from the outlet is more than 10%
- Excellent beam quality
- Air or water cooling

Options
- Power modulation
- Linear polarization
- Output fiber length up to 20 m

Areas of use
- Material processing
- Telecommunications
- Medical devices

- Environmental monitoring
- Scientific instrumentation

Typical specification

CW thulium lasers

Thulium fiber lasers of the TLM series operate in continuous mode at the lowest transverse mode (M2

Main advantages
- Single-mode operating mode (M2

Options
- Linear polarization
- Output fiber length up to 20 m

Areas of use
- Material processing
- Medical devices
- Pumping mid-IR solid-state lasers and optical parametric oscillators
- Environmental monitoring
- Scientific instrumentation

Typical specification

Pulsed ytterbium lasers

Pulsed lasers of the ILI series are characterized by low consumption from a 24 V DC network and are air-cooled using built-in fans.

The main area of ​​application of the ILI series lasers is laser marking and engraving. They are also used for precision cutting, micromachining, and laser milling.

Main advantages:
- Output power up to 50 W
- Beam quality M2

Areas of use:
- Engraving
- Marking
- Microprocessing
- Precision cutting
- Scientific instrumentation

Typical specification

These lasers can very conditionally be distinguished as a separate type, since they use approximately the same mechanism for excitation of the active medium (pumping) as gas or solid-state lasers.

Laser diodes are also used as pumping. These sources were developed for fiber telecommunication systems, where they are used as signal amplifiers. Imagine that the crystal in which useful laser radiation is generated is stretched over several tens of meters and represents a fiber core with a diameter of several microns, which is located inside a quartz fiber. The diode radiation is directed into the quartz fiber, and optical pumping of the core occurs along its entire length.

The use of laser glass as an active element in solid-state lasers has been known for a long time. Unlike crystals, laser glasses have a disordered internal structure. Along with the glass-forming components SiO 2, B 2 O 3, P 2 O 5, BeF 2, they contain Na 2 O, K 2 O, Li 2 O, MgO, CaO, BaO, Al 2 O 3, Sb 2 O 3 . Active impurities most often serve as neodymium ions Nd 3+; gadolinium Gd 3+, erbium Er 3+, holmium Ho 3+, ytterbium Yb 3+ are also used. The concentration of neodymium ions Nd 3+ in glasses reaches 6% (by weight).

Laser glasses achieve a high concentration of active particles. Another advantage of such glasses is the ability to manufacture large-sized active elements of almost any shape and with very high optical homogeneity. Glasses are obtained in platinum or ceramic crucibles. The disadvantages of using glasses as laser materials include a relatively wide lasing band (310 nm) and low thermal conductivity, which prevents rapid heat removal under high-power optical pumping.

Fiber lasers have a very high (up to 80%) efficiency in converting laser diode radiation into useful radiation. To ensure their operation, air cooling is sufficient. These laser sources are very promising for systems for digital recording of printed forms.

In Fig. Figure 3.22 shows a diagram of the operation of a semiconductor-pumped fiber laser and in general view the entire optical path right down to the material being processed. The main feature of this laser is that the radiation here is generated in a thin, with a diameter of only 68 microns, fiber (core; for example, the active medium can be ytterbium), which is located inside a quartz fiber with a diameter of 400-600 microns. Radiation from laser pump diodes is introduced into a quartz fiber and propagates along the entire complex composite fiber, which is several tens of meters in length.

Figure 3.22 – Optical system with fiber laser:

1 – core, doped with ytterbium, diameter 6-8 microns; 2 – quartz fiber, diameter 400-600 microns; 3 – polymer shell; 4 – external protective coating; 5 – optical pumping laser diodes; 6 – optical pumping system; 7 – fiber (up to 40 m); 8 – collimator; 9 – light modulator; 10 – focusing optical system

The radiation optically pumps the core, and it is here, on the ytterbium atoms, that physical transformations occur, leading to the appearance of laser radiation. Near the ends of the fiber, two so-called diffraction mirrors are made on the core in the form of a set of notches on the cylindrical surface of the core (diffraction gratings) - this is how a fiber laser resonator is created. The total fiber length and number of laser diodes are selected based on the required power and efficiency. The output is an ideal single-mode laser beam with a very uniform power distribution, which makes it possible to focus the radiation into a small spot and obtain a greater depth of field than in the case of high-power solid-state Nd:YAG lasers.

It is also worth noting that a number of properties of fiber laser radiation, such as the nature of the beam polarization, make it convenient and reliable to control this radiation using acousto-optical devices and allow the implementation of multi-beam image recording schemes.

Since optical pumping occurs along the entire length of the fiber, there are no effects typical of conventional solid-state lasers, such as a thermal lens in the crystal, wavefront distortion due to defects in the crystal itself, instability of the beam over time, etc., which have always prevented the achievement of the maximum capabilities of solid-state systems. However, the very principles of the structure and operation of a fiber laser guarantee high performance characteristics and make these devices perfect converters of light radiation into laser radiation.

The laser's core, just a few micrometers thick, is made of ytterbium and functions as a resonator. The best quality can be achieved with a radiation wavelength of 1110 nm, while the length of the fiber optic cable can reach 40 m. Lasers with powers from 1 to 100 W are commercially produced, with an efficiency of about 50%. Fiber optic lasers generally do not require special cooling. The minimum spot size of modern fiber optic lasers is about 20 microns, and with the use of correction mechanisms it can be reduced to 5 microns. The focal depth is 300 microns, which allows you to successfully work with plate materials of various thicknesses without an autofocus mechanism.

A fiber laser is a laser with a fully or partially fiber-optic implementation, where the gain medium and, in some cases, the resonator are made of optical fiber.

A fiber laser is a laser with a fully or partially fiber optic implementation, where optical fiber A a gain medium and, in some cases, a resonator are made. Depending on the degree of fiber implementation, a laser can be all-fiber (active medium and resonator) or discrete fiber (fiber only resonator or other elements).

Fiber lasers can operate in continuous wave as well as nano- and femtosecond pulsed pulses.

Design laser depends on the specifics of their work. The resonator can be a Fabry-Perot system or a ring resonator. In most designs, an optical fiber doped with ions of rare earth elements - thulium, erbium, neodymium, ytterbium, praseodymium - is used as the active medium. The laser is pumped using one or more laser diodes directly into the fiber core or, in high-power systems, into the inner cladding.

Fiber lasers are widely used due to a wide selection of parameters and the ability to customize the pulse over a wide range of durations, frequencies and powers.

The power of fiber lasers is from 1 W to 30 kW. Optical fiber length – up to 20 m.

Applications of fiber lasers:

– cutting metals and polymers in industrial production,

– precision cutting,

– microprocessing metals and polymers,

– surface treatment,

– soldering,

– heat treatment,

– product labeling,

– telecommunications (fiber optic communication lines),

– electronics production,

– production of medical devices,

– scientific instrumentation.

Advantages of fiber lasers:

– fiber lasers are a unique tool that opens a new era in materials processing,

– portability and the ability to select the wavelength of fiber lasers allow for new effective applications that are not available for other types of currently existing lasers,

– superior to other types of lasers in almost all significant parameters important from the point of view of their industrial use,

– possibility to customize the pulse in a wide range of durations, frequencies and powers,

– the ability to set a sequence of short pulses with the required frequency and high peak power, which is necessary, for example, for laser engraving,

– wide choice of parameters.

Comparison of different types of lasers:

2000w cw opto raycus pulsed fiber ytterbium laser 50w 100kw buy manufacturer
fiber solid-state lasers
metal cutting plywood awesome cernark engraving modes of deep engraving with fiber laser
ytterbium fiber laser device
fiber machine sell laser
principle of operation production Fryazino 1.65 microns technology ytterbium buy price ipg hp 1 optical for cutting metal engraving pulse principle of operation machine optical applications power do it yourself device diagram wavelength welding manufacturer cuts in waves

Demand factor 902

THOMAS SCHRIEBER, ANDREAS TUNNERMANN and ANDREAS THOMS

By identifying problems with high-power fiber lasers and optimizing the optical fiber, a single-mode power of 4.3 kW was achieved, with future possible scaling and new ultra-fast laser applications in development.

If there is one clear trend in laser technology, it is the rise of fiber lasers. Fiber lasers have taken market share from high-power CO2 lasers, as well as volumetric solid-state lasers in high-power cutting and welding. Major fiber laser manufacturers are now turning to a number of new applications to capture even more markets.

Among high-power lasers, single-mode systems offer features that make them desirable: they have the highest brightness and can be focused down to a few microns and to the highest intensities. They also exhibit the greatest depth of focus, making them most suitable for remote processing.

However, they are difficult to manufacture, and only market leader PHG Photonics (Oxford, MA) offers a 10 kW single-mode system (2009).

Unfortunately, there is no data available on these beam characteristics, particularly on any possible multimode components that might correspond to a single-mode beam.

A team of researchers in Germany demonstrated 4.3 kW single-mode power from a fiber laser in which the output was limited only by the input pump power.

Funded by the German government and in collaboration with TRUMPF (Ditzingen, Germany), Active Fiber Systems, Jenoptik and the Leibniz Institute for Photonic Technology, a team of scientists from the Friedrich Schiller University and the Fraunhofer Institute for Applied Optics and Precision Engineering (all in Jena, Germany) analyzed the challenges for scaling such lasers, and then developed new fibers to overcome the limitations. The team successfully completed a series of tests showing a single-mode output of 4.3 kW, in which the fiber laser output was limited only by the input pump power.

Containment effects for single-mode fiber laser scaling

What are the challenges for such a single mode high power fiber laser? These can be grouped into three fields: a) improved pumping, b) development of low optical loss active fiber operating in single mode only, and c) proper measurement of the resulting radiation.

In this article, we will assume that a) is solved using high-brightness laser diodes and appropriate decoupling techniques, and focus on the other two areas.

In the development of active fiber for high-power single-mode operation, two general sets of parameters are used for optimization: doping and geometry. All parameters must be determined for minimum loss, single-mode operation and, finally, high-power gain. The ideal fiber amplifier will provide high speed over 90% conversion, excellent beam quality and output power limited only by available pump power.

However, upscaling a single-mode system to higher powers can result in higher power densities within the active core, increased thermal load, and a number of nonlinear optical effects such as stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS).

Depending on the size of the active core, several transverse modes can be excited and amplified. For a given index step between core and shell, the smaller the active cross-section of the active cell, the smaller the number of such modes. However, a smaller diameter also means higher power density. A few tricks, such as fiber bending, add losses for higher modes.

However, for larger core diameters and thermal loads, other behavior may occur. These modes are subject to interaction during amplification—without optimal propagation conditions, the output profile may become spatially or temporally unstable.

Transverse mode instabilities

Ytterbium (Yb)-doped fibers are a typical working medium for high-power single-mode fiber lasers. But beyond a certain threshold, they show a completely new effect - so-called transverse mode instabilities (TMI).

At a certain power level, higher modes or even cladding modes suddenly appear, energy is dynamically transferred between these modes, and the beam quality is reduced.

The beam begins to oscillate at the exit.

Since TMI was discovered, it has been observed in a variety of fiber designs from pitch index fibers to photonic crystal fibers. Only its threshold value depends on the geometry and doping, but a rough estimate suggests that this effect exceeds 1 kW power output.

Meanwhile, the effect was found to be due to thermal effects within the fiber, with a strong relationship to photodarkening effects. Moreover, the susceptibility of fiber lasers to TMI appears to depend on the core composition.

The geometry of the step index leads to a number of parameters for optimization. The core diameter, pump shell size and refractive index difference between the core and pump shell can be customized. This setting depends on the dopant concentration, i.e. the concentration of Yb ions can be used to control the absorption length of the pump radiation in the active fiber. Other additives can be added to reduce thermal effects and control the refractive index stage.

But there are some contrary requirements. To reduce nonlinear effects, the fiber must be shorter. However, to reduce the thermal load, the fiber must be longer. Photo-darkening increases with the square of the dopant concentration, so longer fibers with lower doping will also be better.

Applications in Ultrafast Science

After about a decade of stagnation in the scaling of high-power single-mode fiber lasers, it now seems feasible to develop a new generation of kilowatt-class fiber lasers with excellent beam quality.

Output powers of 4.3 kW are shown, limited only by pump power.

The main limitations for further scaling have been identified, and ways to overcome these limitations have been identified.

It should be noted that it was a thorough investigation of all known effects and subsequent optimization of parameters that led to advances in fiber design and, ultimately, new records in power output.

Further scaling and adaptation of the fiber for other applications appears feasible and will be pursued further.

This opens up a number of interesting prospects.

On the one hand, the transfer of results into industrial products is desirable by project partners, but will require additional major development efforts.

On the other hand, this technology is very important for scaling other optical fiber laser systems such as femtosecond fiber amplifiers.

REFERENCES

1. F. Beier et al., “Single-mode 4.3 kW output power from a directly diode-pumped Yb-doped fiber amplifier,” to be published in Opt. Express.
2. T. Eidam et al., Opt. Lett., 35, 94–96 (2010).
3. M. Müller et al., Opt. Lett., 41, 3439–3442 (2016).

Translation by Sergei Rogalev

The term "fiber laser" usually refers to a laser with an optical fiber as the gain medium, although some lasers with a semiconductor gain medium and a fiber resonator are also called fiber lasers. In most cases, the gain medium of fiber lasers is a fiber doped with rare earth ions such as erbium (Er 3+), neodymium (Nd 3+), ytterbium (Yb 3+), thulium (Tm 3+) or praseodymium (Pr 3+). . One or more laser diodes are used for pumping.

Fiber laser cavity

To create a linear resonator of a fiber laser, it is necessary to use some kind of reflector (mirror), or create a ring resonator (ring fiber laser).

Fiber laser line cavities use different types of mirrors:

· In simple laboratory setups, conventional dielectric mirrors can be attached to the perpendicularly cleaved ends of the fiber, as shown in Figure 1. This approach, however, is not very practical for mass production and is also not very reliable.

· The Fresnel reflection from the end of the fiber is often sufficient for use as the output mirror of a fiber laser cavity. In Fig. 2 shows an example.

· It is also possible to apply dielectric coatings directly to the fiber ends, usually by sputtering. Such coatings can be used for reflection over a wide range.

· Many fiber lasers use fiber Bragg gratings formed directly into the doped fiber, or into an undoped fiber bonded to the active layer. Figure 3 shows a distributed Bragg reflector (DBR) laser with two fiber gratings, but there are also DBR lasers. feedback with a single grating in doped fibers with a phase shift in the middle.

· Best Features according to power you can get by using a collimator to output light from the fiber and reflecting it back using a dielectric mirror (Fig. 4). The intensity at the mirror is significantly reduced due to the much larger beam area. However, a small offset can lead to significant reflection losses, polarization-dependent losses, etc.

· Another option is to use a mirror in the form of a fiber loop (Figure 5), based on a fiber coupling (eg 50:50 split ratio) and a piece of passive fiber.

Most fiber lasers are pumped by one or more fiber output diode lasers (laser diode light is coupled into the fiber). Light can be pumped directly into the fiber core or into the inner cladding of the fiber in high-power lasers.