IPG Photonics

About: IPG Photonics is a based out in . It is known for research contribution in the topics: Laser & Fiber laser. The organization has 903 authors who have published 1241 publications receiving 63339 citations.

Darcy flow around a two-dimensional permeable lens

Abstract: The flow in and around a fracture modelled as a two-dimensional permeable lens immersed in an infinite porous medium of different permeability is analytically solved by means of conformal mapping and Fourier transform. When the lens is more permeable than the surrounding medium, singularities occur at angular points for flow parallel to the lens, while velocities vanish at these points for flow perpendicular to the lens. In the opposite case, when the lens is less permeable than the surrounding medium, singularities are exchanged and flows parallel and perpendicular to the lens are regular and singular, respectively. Predictions are successfully compared with data obtained by a numerical code.

A new Late Triassic-Liasic Palaeomagnetic pole from superimposed and juxtaposed magnetizations in the Saharan craton

Abstract: SUMMARY Palaeomagnetic measurements, in the Late Triassic-Liasic Zarzaytine formations of the La Recul6e area, showed the existence of superimposed and juxtaposed magnetizations. The separation of the juxtaposed magnetizations yielded Late Triassic-Liasic magnetization directions of normal and reversed polarities. The new corresponding palaeomagnetic pole agrees well with a Pangea A configuration. It confirms, from Autunian to Lias, a latitudinal displacement of stable Africa towards the north, with important anti-clockwise rotation contrary to Laurussia which did not undergo significant rotation. This transition of Pangea from A2 to A ended before the Late Triassic. It corresponds to dextral movements in the HercynoAppalachian collision area, and perhaps to part of the northwards drift of microcontinents of Gondwanian origin located north of the Arabian promontory.

Mid-IR Kerr-lens mode-locked polycrystalline Cr:ZnS and Cr:ZnSe lasers with intracavity frequency conversion via random quasi-phase-matching

Abstract: Cr2+ doped ZnS and ZnSe possess a unique blend of physical, spectroscopic, and technological parameters. These laser materials feature ultra-broadband gain in 1.9 – 3.3 μm mid-IR range, low saturation intensities, and large pump absorption coefficients. The II-VI semiconductor hosts provide a low phonon cut-off, broad IR transparency, and high second and third order nonlinearity. Cr:ZnS and Cr:ZnSe are available in polycrystalline form: the material consists of a multitude of microscopic single-crystal grains with a broad distribution of grain sizes and orientations, which results in random quasi-phase-matching (RQPM). The distinctive features of RQPM are a linear dependence of the conversion yield with length of the medium and ultra-wide bandwidth of three-wave mixing. We review resent experimental results on optically pumped mid-IR ultrafast lasers based on polycrystalline Cr:ZnS and Cr:ZnSe. We demonstrate that Kerrlens mode-locking of polycrystalline Cr:ZnS and Cr:ZnSe lasers allow for generation of few-cycle mid-IR pulses with MW-level peak power. This opens several avenues for efficient nonlinear frequency conversion of short optical pulses directly in the laser gain medium via RQPM process. We implemented Kerr-lens mode-locked Cr:ZnS oscillators, which feature high power (up to 0.25 W), spectrally broad (up to 22 THz) second harmonic generation (SHG) in the laser medium. We also demonstrate simple and robust ultrafast source based on single-pass continuously pumped polycrystalline Cr:ZnS laser amplifier: mid-IR pulses with 6.8 W average power and the spectrum spanning 2.0–2.6 μm as well as SHG pulses with 0.52 W average power and 1.05 – 1.25 μm spectral span were obtained.

Intensity noise limit in a phase-sensitive optical time-domain reflectometer with a semiconductor laser source

Abstract: In the present paper we perform, for the first time, the analysis of the average intensity noise power level at the output of a coherent phase-sensitive optical time-domain reflectometer (phase-OTDR) with a semiconductor laser source. The origin of the considered intensity noise lies in random phase fluctuations of a semiconductor laser source field. These phase fluctuations are converted to intensity noise in the process of interference of backscattered light. This intensity noise inevitably emerges in every phase-OTDR spatial channel and limits its sensitivity to external phase actions. The analysis of intensity noise in a phase-OTDR was based on the study of a fiber scattered-light interferometer (FSLI) which is treated as the constituent part of OTDR. When considered independently, FSLI has a broad intensity noise spectrum at its output; when FSLI is treated as a part of a phase-OTDR, due to aliasing effect, the wide FSLI noise spectrum is folded within the spectral band, determined by the probe pulse repetition frequency. In the analysis one of the conventional phase-OTDR schemes with rectangular dual-pulse probe signal was considered, the FSLI, which corresponds to this OTDR scheme, has two scattering fiber segments with additional time delay introduced between backscattered fields. The average intensity noise power and resulting noise spectrum at the output of this FSLI are determined by the degree of coherence of the semiconductor laser source, the length of the scattering fiber segments and by the additional time delay between the scattering segments. The average intensity noise characteristics at the output of the corresponding phase-OTDR are determined by the analogous parameters: the source coherence, the lengths of the parts constituting the dual-pulse and the time interval which separates the parts of the dual-pulse. In the paper the expression for the average noise power spectral density (NPSD) at the output of FSLI was theoretically derived and experimentally verified. Based on the found average NPSD of FSLI, a simple relation connecting the phase-OTDR parameters and the limiting level of full average intensity noise power at its output was derived. This relation was verified by experimental measurement of the average noise power at the output of phase-OTDR. The limiting noise level, considered in the paper, determines the fundamental noise floor for the phase-OTDR with given parameters of the source coherence, probe pulse length and time delay between two pulses constituting the dual-pulse.

Energy scaling of nanosecond gain-switched Cr2+:ZnSe lasers

Abstract: In this paper, we report record nanosecond output energies of gain-switched Cr:ZnSe lasers pumped by Q-switched Cr:Tm:Ho:YAG (100 ns @ 2.096 μm) and Raman shifted Nd:YAG lasers (7 ns @ 1.906 μm). In these experiments we used Brewster cut Cr:ZnSe gain elements with a chromium concentration of 8x10 18 cm -3 . Under Cr:Tm:Ho:YAG pumping, the first Cr:ZnSe laser demonstrated 3.1 mJ of output energy, 52% slope efficiency and 110 nm linewidth centered at a wavelength of 2.47 μm. Maximum output energy of the second Cr:ZnSe laser reached 10.1 mJ under H 2 Raman shifted Nd:YAG laser pumping. The slope efficiency estimated from the input-output data was 47%.