Rheinmetall Waffe Munition has worked since 30 years in the area of High Energy Laser (HEL) for defence applications, starting from pulsed CO2 to pulsed glass rods lasers. In the last decade Rheinmetall Waffe Munition changed to diode pumped solid state laser (DPSSL) technology and has successfully developed, realised and tested a variety of versatile HEL weapon demonstrators for air- and ground defence scenarios like countering rocket, artillery, mortar, missile (RAMM), unmanned aerial systems (UAS) and unexploded ordnances clearing. By employing beam superimposing technology and a modular laser weapon concept, the total optical power has been successively increased. Stationary weapon platforms, military vehicles and naval platforms have been equipped with high energy laser effectors. The contribution gives a summary of the most recent development stages of Rheinmetalls HEL weapon program. In addition to the stationary 30 kW laser weapon demonstrator, we present vehicle based HEL demonstrators: the 5 kW class Mobile HEL Effector Track V, the 20 kW class Mobile HEL Effector Wheel XX and the 50 kW class Mobile HEL Effector Container L and the latest 10 kW HEL effector integrated in the naval weapon platform MLG 27. We describe the capabilities of these demonstrators against different potential targets. Furthermore, we will show the capability of the 30 kW stationary Laser Weapon Demonstrator integrated into an existing ground based air defence system to defeat saturated attacks of RAMM and UAS targets.
For some years Rheinmetall Waffe Munition has successfully developed, realised and tested a variety of versatile high
energy laser (HEL) weapon systems for air- and ground-defence scenarios like C-RAM, UXO clearing. By employing
beam superimposition technology and a modular laser weapon concept, the total optical power has been successively
increased. Stationary weapon platforms and now military mobile vehicles were equipped with high energy laser
effectors. Our contribution summarises the most recent development stages of Rheinmetalls high energy laser weapon
program. We present three different vehicle based HEL demonstrators: the 5 kW class Mobile HEL Effector Track V
integrated in an M113 tank, the 20 kW class Mobile HEL Effector Wheel XX integrated in a multirole armoured vehicle
GTK Boxer 8x8 and the 50 kW class Mobile HEL Effector Container L integrated in a reinforced container carried by an
8x8 truck. As a highlight, a stationary 30 kW Laser Weapon Demonstrator shows the capability to defeat saturated
attacks of RAM targets and unmanned aerial vehicles. 2013 all HEL demonstrators were tested in a firing campaign at
the Rheinmetall testing centre in Switzerland. Major results of these tests are presented.
We will present the setup of a 50 kW Laser Weapon Demonstrator (LWD) and results achieved with this system. The LWD is a ground based Air Defence system consisting of a Skyguard sensor unit for target acquisition and two laser equipped weapon turrets. The weapon turrets used are standard air defence turrets of Rheinmetall Air Defence which were equipped with several 10 kW Laser Weapon Modules (LWM). Each LWM consists of one 10 kW fiber laser and a beam forming unit (BFU). Commercial of the shelf fiber laser were modified for our defence applications. The BFU providing diffraction limited beam focusing, target imaging and fine tracking of the target was developed. The LWD was tested in a firing campaign at Rheinmetall test ground in Switzerland. All laser beams of both weapon turrets were superimposed on stationary and dynamic targets. Test results of the LWD for the scenarios Air Defence and C-RAMM (counter rockets, artillery, mortar and missiles) will be presented. An outlook for the next development stage towards a 100 kW class laser weapon on RWM will be given.
The paper will give an overview over the laser weapon activities at RWM (Rheinmetall Waffe Munition) over the last years. Starting from the actual scenarios for laser weapon applications as: CRAM (Counter Rocket Artillery Mortar), Air Defence and UXO (unexploded ordnance) clearing. The basic requirements of a future laser weapon as beam diameter, beam quality, tracking capability, adaptive optics were deduced.
For the UXO scenario a mobile directed energy laser demonstrator for humanitarian mine and UXO clearing based on fiber lasers is presented. Based on the parameters the system concept including the cooling system, power supply and the integration into the armoured vehicle TM 170 are explained. The contribution show first experiments of UXO and IED clearing.
Different technical approaches to achieve laser power in the 100 kW regime combined with very good beam quality are discussed to fulfil the requirements of the CRAM and Air Defence scenario. Spectral coupling and the beam superimposing both are performed by Rheinmetall Waffe Munition.
At the spectral coupling the basic technology parameters for the fiber laser and the dielectric grating as the latest results were put into context with the power levels reached at other groups.
For the beam super imposing technology the basic experiments regarding the tracking capability and compensation of the atmosphere on the test range at Unterlüß will be explained.
A generic 10 kW Laser Weapon Demonstrator based on 2 Laser Weapon Modules (LWM) from RWM each 5 kW fiber Laser with beam forming and tracking integrate by the team of RWM and RAD (Rheinmetall Air Defense) into a Ground based Air Defend system consisting of Skyguard and Millenium turret are presented.
The flight path of the UAV within the valley of the life firing range at Ochsenboden Switzerland is shown. Selected results of the successful tests against UAV’s are presented. It shows the capability of the generic 10 kW Laser Weapon Demonstrator to track and to destroy the target.
From these results the next steps of Rheinmetall Waffe Munition for a 100 kW class laser weapon are explained.
Wavelength around 940 nm lasing can be obtained by quasi-three-level operation of Nd doped laser crystal.
Diode end pumping provides the necessary high pump intensity in the laser crystal. In order to get high efficiency of the
end pumped laser system, the overlap coefficient between pump beam and laser beam should be optimized. Thermal lens
coefficient is one of the most important parameters to design the laser cavity structure. The time dependent heat
conduction equation is solved numerically in order to study the thermal lens effect in pulsed pumping laser crystal.
Calculated results showed that the thermal lens coefficients change with different pump frequencies. Experiments are
done with Nd:YAG and Nd:GSAG laser rod. The thermal lens coefficient of Nd:YAG at pump frequency 50 Hz with
pump beam diameter 1.5 mm is 10.2 Wm, while the thermal lens coefficient of Nd:GSAG at pump frequency 50 Hz with
pump beam diameter 1.75 mm is 5.9 Wm.
Water vapour absorption wavelengths have been directly generated by diode pumped Nd:YGG crystals emitting at 935 nm and with Nd:GSAG crystals emitting at 942 nm in cw and pulsed operation. In addition the 1064 nm fundamental wavelength from Nd:YAG pump lasers with pulse lengths of 10 or 20 ns was shifted using Stimulated Raman Scattering (SRS) or Ti:Sapphire (TiSa) lasers. The potential of Nd:GSAG, Nd:YGG, SRS and TiSa laser systems is compared for future incorporation into a satellite based Lidar system. High output energies are possible by recent advances of fiber coupled diode sources allowing pulsed longitudinal pumping of Q-switched solid state lasers.
Many materials e.g. diamond or silicon do not show sufficient absorption at one micron, the fundamental wavelength of Nd-based solid-state laser sources. Frequency conversion to the second and fourth harmonic allows the efficient processing of these materials. High beam quality is another important property for micro material processing with lasers. It facilitates small focus diameters and due to high Rayleigh length even at strong focusing drilling of holes with high aspect ratio. Together with high average output powers it allows fast processes with high quality. At least flexible pulse peak power and repetition rate is necessary to optimize the process. Two laser systems which fulfill these requirements are investigated. A pulse pumped Nd:YAP system which delivers an average output power of 124 W at the second harmonic and a Nd:YAG with an average output power up to 50 W in the second harmonic. Due to its active Q-switch the pulse peak power of this system is variable in a wide range. Efficient laser processing of different ceramics with these laser system are presented.
The three-dimensional measurement of the global water vapor distribution in the atmosphere considerably improves the reliability of the weather forecast and climate modeling. A spaceborne Differential Absorption Lidar (DIAL) is able to per-form this task by use of suitable absorption lines of the broad absorption spectrum of water vapor. Because no interference with the absorption of other molecules exists, the range of 935/936 nm, 942/943 nm are the most preferred wavelength ranges for a water vapor DIAL. The challenge is to develop a dedicated efficient high power laser source emitting at these wavelengths. The comparison between frequency converters based on stimulated Raman scattering (SRS) and Ti:Sapphire and the directly generated Mixed Garnet laser shows the favorable properties of each concept and helps to evaluate the most suitable concept. Development of Raman frequency converters for high pulse energies concentrates on linear resonator de-signs and seeding using the Raman material as a direct amplifier based on Raman four-wave-mixing. In addition a seeded and frequency stabilized pulsed Ti:Sapphire laser system with output pulses up to 22 mJ injection-seeded at the water vapor absorption line at 935.684 nm with a spectral purity up to 99.9 % has been developed. Direct generation of the wavelengths 935/936 nm and 942/943 nm required for water vapor detection is possible with diode-pumped, Nd-doped YGG- and GSAG-crystals. First experiments resulted in pulse energies of 18 mJ in Q-switched and 86 mJ in free-running operation at 942 nm wavelength.
Standard 200 μm multimode fibers with Ta2O5/SiO2 antireflective coatings reach a transmission of more than 99.5% below the threshold of stimulated Brillouin scattering. The laser-induced damage threshold measured at 1064 nm and 24 ns pulse duration was about half than the LIDT of uncoated fibers.
In this paper, we demonstrate a (3D) analytical solution of stimulated Brillouin scattering (SBS) for high reflectivity and fidelity phase conjugation mirrors (PCM). The results are checked with experimental ones, which were obtained with CS2 and optical fibers as nonlinear materials and high PCM reflectivities are found out. Furthermore, analytical SBS reflectivity for pumping with Gauss-Laguerre modes is demonstrated and shown to suppress high modes, when using SBS mirrors. These findings are used in some all solid-state laser (SSL) systems with SBS-PCM in order to obtain near Gaussian beams, depolarization compensation and high brightness.
To meet the industry's demand for reducing machine cycle lengths concerning laser-drilling a laser was developed at the LMTB-laboratories that emits high-power peak-pulses at excellent beam-quality. In co-operation with Technical University of Berlin (TU Berlin) a Nd:YAG Master-Oscillator Power-Amplifier (MOPA) laser system is undergoing permanent enhancements aiming at shorter pulse duration, higher fluence and improved long-term stability. Presently, the output power of the oscillator (10W@1064nm) with a beam-quality of M2=1.3 is amplified to more than 100W@1064nm with M2=2.3 and a single pulse energy up to 800 mJ. The pulse duration can be varied between 31 and 230ns. On account of the excellent beam quality, frequency conversion was carried out down to 266nm. The MOPA-System was used for laser micro scribing and drilling experiments into metals and ceramics where the influence of the beam quality on the geometrical shape of the hole is investigated and compared with applications conducted with similar laser systems. Additionally means in optimizing the drilling process such as burr-minimizing and melt-reduction were introduced. Furthermore, experiments using tapered drilling technique are undertaken. A maximum aspect ratio of 1:180 in sapphire was obtained. We achieved high ablation rates and precise structures in Al2O3 (ceramic and sapphire), AlN, ZrO2, Ni-base alloy, platinum, tungsten and many more materials. Further improvement of the system was undertaken by means of multimode fibers as phase conjugate mirrors (PCM) using the effect of stimulated brillouin scattering (SBS).
To meet the industry's demand for reducing machine cycle lengths concerning laser-drilling a Nd:YAG Master-Oscillator Power-Amplifier (MOPA)-system was developed at the LMTB-laboratories that emits high-power peak-pulses at excellent beam-quality. Presently, the output power of the oscillator (10W@1064nm) with a beam-quality of M2 = 1.3 is amplified to 95W@1064 nm with M2=2.3 and a single pulse energy up to 500 mJ. The pulse duration can be varied between 26 and 230 ns. On account of the excellent beam quality, frequency conversion resulted in 49W@532nm and 4.8@266nm. The MOPA-System is used for laser micro drilling experiments into metals and ceramics where the influence of the beam quality on the geometrical shape of the hole is investigated and compared with applications conducted with similar laser systems. Additionally means in optimizing the drilling process such as burr-minimizing and melt-reduction were introduced. Furthermore, experiments using tapered drilling technique are undertaken. A maximum aspect ratio of 1:200 in stainless steel was obtained.
Solid-state laser sources are required for numerous applications in industry and science. High output power while preserving a diffraction limited beam quality results in high brightness operation. However, conventional laser systems suffer from thermally induced phase distortions in the active medium, which considerably reduce the beam quality. Proper cooling, diode pumping, as well as active media with high quantum efficiency reduce the thermal load. But the still remaining phase distortions result in a reduction of beam quality. Phase conjugate mirrors are suitable to compensate for phase distortions in master oscillator power amplifier systems (MOPA). Stimulated Brillouin scattering (SBS) in commercial multimode silica fibers leads to reliable and stable phase conjugation. A further advantage is, that the fiber core diameter can be select in respect of the systems pulse energy to obtain the necessary intensity for high reflectivity SBS. Three systems with phase conjugators have been investigated. A pulse pumped, passively q-switched Nd:YAP System which delivers an average output power of 315 W with M2 = 2.6. The pulse energy is about 160 mJ with a pulse width of 140 ns at 2 kHz repetition rate. Another pulse pumped MOPA system based on Nd:YAG with depolarization compensation delivers an average output power up to 124 W with M2 = 2.2. Due to active q-switching the pulse repetition rate and peak power of this system are variable in a wide range. Furthermore a continuously pumped amplifier arrangement with nearly diffraction limited output of 120 W average power has been achieved at 10 kHz repetition rate.
Reflectivity and fidelity of phase conjugation by stimulated Brillouin scattering (SBS) is studied in CS2. Experimental results are presented for TEM00 and TEM01 mode pumping, at 1.06 μm. SBS reflectivity has been analytically calculated and compared with experimental data. Good healing of phase distortions was demonstrated.
To meet the industry's demand for reducing machine cycle lengths concerning laser-drilling a Nd:YAG Master-Oscillator Power-Amplifier (MOPA)-system was developed at the LMTB-laboratories that emits high-power peak-pulses at excellent beam-quality. Presently, the output power of the oscillator (10W@1064nm) with a beam-quality of M2=1.3 is amplified to 95W@1064nm with M2=2.3 and a single pulse energy up to 500mJ. The pulse duration can be varied between 26 and 230ns. On account of the excellent beam quality, frequency conversion resulted in 49W@532nm and 4.8@266nm. The MOPA-System is used for laser micro drilling experiments into metals and ceramics where the influence of the beam quality on the geometrical shape of the hole is investigated and compared with applications conducted with similar laser systems. Additionally means in optimizing the drilling process such as burr-minimizing and melt-reduction were introduced. Furthermore, experiments using tapered drilling technique are undertaken. A maximum aspect ratio of 1:200 in stainless steel was obtained.
High beam quality is one of the most important properties for micro material processing with lasers. It facilitates slight focus diameters and due to high Raleigh length even at strong focusing drilling of holes with high aspect ratio. Together with high average output powers it allows fast processes with high quality. Another important point is the wavelength of the laser radiation. Many materials e.g. diamond or silicon show no sufficient absorption at fundamental wavelength of Nd based solid-state laser sources. Frequency conversation to the second and fourth harmonic allows the efficient processing of these materials. At least flexible pulse peak power and repetition rate is necessary to optimize the process. Three laser systems which fulfill these requirements are investigated. A pulsed pumped Nd:YAG System which delivers an average output power of 315 W with M2 = 2.6 at the fudamental wavelength and 124 W at the second harmonic. Another pulsed pumped System based on Nd:YAG with an average output power up to 125 W with M2 = 2.2 at the fundamental wavelength, 49.5 W at the second harmonic and 4.75 W at 266 nm. Due to its active Q-switch the pulse peak power of this system is variable in a wide range. Furthermore, a continuously pumped amplifier arrangement with nearly diffraction limited output of 120 W average power has been achieved at 10 kHz repetition rate.
Solid-state laser sources are required for numerous applications in industry and science. High output power while preserving a diffraction limited beam quality results in high brightness operation. However, conventional laser systems suffer from thermally induced phase distortions in the active medium, which considerably reduce the beam quality. Proper cooling, diode pumping, as well as active media with high quantum efficiency reduce the thermal load. But the still remaining phase distortions result in a reduction of beam quality. Phase cojugate mirrors are suitable to compensate for phase distortions in master oscillator power amplifier systems (MOPA). Stimulated Brillouin scattering (SBS) in commercial multimode silica fibers leads to reliable and stable phase conjugation. A further advantage is, that the fiber core diameter can be select in respect of the systems pulse energy to obtain the necessary intensity for high reflectivity SBS. Three systems with phase conjugators have been investigated. A pulse pumped, passively q-switched Nd:YAP System which delivers an average output power of 315 W with M2 = 2.6. The pulse energy is about 160 mJ with a pulse width of 140 ns at 2 kHz repetition rate. Another pulse pumped MOPA system based on Nd:YAG with depolarization compensation delivers an average output power up to 124 W with M2 = 2.2. Due to active q-switching the pulse repetition rate and peak power of this system are variable in a wide range. Furthermore a continuously pumped amplifier arrangement with nearly diffraction limited output of 120 W average power has been achieved at 10 kHz repetition rate.
All-solid-state laser sources are required for numerous applications in industry and science. Scaling of average output power while preserving a diffraction limited beam quality results in high brightness operation. However, conventional laser systems suffer from thermally induced phase distortions in the active medium, which considerably reduce their beam quality. Advanced pumping geometry, diode pumping, as well as active media with high quantum efficiency can reduce the thermal load. But the remaining phase distortions result in a reduction of beam quality. Optical phase conjugate mirrors are suitable to compensate for phase distortions in master oscillator power amplifier systems (MOPA). Stimulated Brillouin scattering in conventional, commercially available silica fibers facilitates reliable and stable phase conjugation. These all-solid state devices reveal an energy reflectivity of almost 90% and require low financial efforts. Moreover, the SBS threshold is determined by the appropriate fiber core diameter. Therefore fiber phase conjugators can be applied in continuously pumped, repetitively q-switched laser systems which usually exhibit smaller peak power in comparison with pulsed pumped systems. A four-pass amplifier arrangement with birefringence compensation was developed. Nearly diffraction limited output with 32 W average power has been achieved at 10 kHz repetition rate. Power scaling up to 100 W seems to be possible.
Transversely cooled, cylindrical Nd:YAG laser rods exhibit a strong thermally induced birefringence when they are optically pumped. The birefringence leads to different refractive indices for radially and tangentially polarized light which affects the beam-quality and the degree of polarization achieved with conventional optical resonators. In spite of this drawbacks the traditional rod-geometry for Nd:YAG lasers is still of great interest because of its technological simplicity, comparatively low costs and acceptable efficiency. In the present study the limitations for the output power of single rod Nd:YAG lasers in TEM00- operation is investigated theoretically and experimentally. Furthermore the possibility of improving the brightness of Nd:YAG rod lasers beyond the traditional limits using dual rod systems with birefringence compensation is demonstrated. Birefringence compensation is established by image-relaying between two identical Nd:YAG laser rods and an additional 90 degree(s) polarization rotation. This compensation method requires specific dynamically stable optical resonators in order to achieve optimal compensation and high efficiencies. With a dual rod Nd:YAG-system up to 80 Watt TEM00 output power is achieved with a beam quality of M2 equals 2.8. The output power is approximately 8 times higher than using a single rod-system separately.
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