We present a high-performance Alexandrite laser for LIDAR applications with repetition rates up to 20 kHz in cavity-dumped Q-switched operation continuous-wave diode-pumped in the red spectral ...region. With a double-pass pump configuration, short pulses with 2.8 ns duration at repetition frequencies ranging from 1 kHz to 20 kHz could be demonstrated. At 5 kHz a - to our knowledge - record pulse energy of over 500 µJ could be achieved at 755 nm in TEM
. Furthermore, a stability measurement at an energy of around 350 µJ with 5 kHz showed no degradation over 150 Mega-shots. The influence of the crystal temperature on the laser performance is also investigated, first in continuous-wave and secondly in cavity-dumped Q-switched operation.
Understanding the gain dynamics of fiber amplifiers is essential for the implementation and active stabilization of low noise amplifiers or for coherent beam combining schemes. The gain dynamics of ...purely Er
or Yb
doped fiber amplifiers are well studied, whereas no analysis for co-doped systems, especially for Er
:Yb
co-doped fiber amplifiers has been performed, so far. Here, we analyze for the first time the gain dynamics of Er
:Yb
co-doped fiber amplifiers theoretically and experimentally. It is shown that due to the energy transfer between the Yb
and Er
ions a full analytical solution is not possible. Thus, we used numerical simulations to gain further insights. Comparison of experimental and numerical results shows good qualitative agreement. In addition, we were able to determine the Yb
-Er
transfer function of the energy transfer experimentally.
In this work, we studied the interlock requirements in a seed failure scenario for Er 3+ :Yb 3+ doped fiber amplifiers (EYDFAs) pumped with high intensities in the MWcm −2 range at 9XX nm. We fed a ...time-dependent FEM-tool with the data from backwards directed amplified spontaneous emission (ASE) transients of different commercially available core-pumped single-mode fibers. In the FEM-tool, the Er 3+ :Yb 3+ system is defined as a bi-directional energy transfer process and described by the corresponding rate equations. The power evolution of the pump, seed, and ASE signal is computed by differential equations taking into account the transient population densities of the relevant energy levels. With the model, we computed the temporal evolution of the corresponding energy levels after a seeder failure to take place within tens to hundreds of µs and calculated the associated gain. The fibers under test provide a critical total gain of 30 dB after ∼ 80 µs within the Yb 3+ band and after ∼300 µs within the Er 3+ band. This time decreases with increasing pump power and doping concentration. The results can be extrapolated to high-power cladding-pumped EYDFAs to meet the challenging requirements of engineering-level systems.
We report on theoretical and experimental investigations of gain dynamics in Raman fiber lasers in the frequency range of 1 Hz-1 MHz. An analytical solution of the problem is due to the nonlinear ...nature of the Raman effect not feasible. Thus, we used a numerical simulation to gain general insights. Experimentally and numerically obtained results for a Raman fiber laser emitting at 1180 nm show good qualitative agreement. We also present a potential physical interpretation of the observed dynamical properties. In addition, we report on an experimental proof-of-principle of a passive pump-to-Stokes RIN suppression scheme for the main Stokes order in cascaded Raman fiber lasers utilizing an additional parasitic Stokes order. Again, results from numerical and experimental studies of a cascaded Raman fiber laser at 1180 nm and 1240 nm show good agreement and confirm the passive pump-to-Stokes RIN suppression at 1180 nm. The dependencies between the resonator design and the parameters of the noise suppression are investigated. In addition, it is shown that the scheme can also be applied to cascaded Raman fiber lasers with more then two Stokes shifts. This opens the possibility to design for example low-noise Raman fiber lasers at 1480 nm to pump low-noise Er(3+) doped fiber amplifiers.
We present a space environmental test campaign of functionally coated, high-quality Alexandrite laser crystals developed in the course of the Horizon 2020 project GALACTIC. The campaign comprises ...gamma and proton irradiation as well as thermal cycling tests. As the result of a detailed qualification procedure consisting of transmittance measurements, LIDT, tape-lift, and functional laser tests in a diode-pumped configuration before and after environmental testing, their suitability for space applications could be demonstrated.
We report on a passively mode-locked ytterbium-doped fiber laser with a repetition rate of 1.8 MHz. The laser was hybridly mode-locked via nonlinear polarization evolution and a semiconductor ...saturable absorber mirror. It generated chirped 3.8 ps long pulses with a pulse energy of 1.0 nJ which could be dechirped to a pulse duration of 93 fs.
We report on a diode-pumped double-slab Yb:KYW regenerative amplifier with combined gain spectra and intracavity dispersion compensation. At repetition rates > 20 kHz an average power of up to 5 W ...after compression was generated, resulting in a maximum pulse energy of 250 µJ. Pulse durations of around 190 fs were achieved by using a GRISM compressor with a transmission efficiency of 90%.
We performed two simulation studies that investigated dimensionality recovery in NPD tetrachoric correlation matrices using parallel analysis. In each study, the NPD matrices were rehabilitated by ...three smoothing algorithms. In Study 1, we replicated the work by Debelak and Tran on the assessment of dimensionality in one- or two-dimensional common factor models. In Study 2, we extended the Debelak and Tran design in three important ways. Specifically, we investigated: (a) a wider range of factors; (b) models with varying amounts of model error; and (c) models generated from more realistic population item parameters. Our results indicated that matrix smoothing of NPD tetrachoric correlation matrices improves the performance of parallel analysis with binary data. However, these improvements were modest and often of trivial size. To demonstrate the effect of matrix smoothing on an empirical data set, we applied parallel analysis and factor analysis to Adjective Checklist data from the California Twin Registry.
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