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.

High-power narrowed-linewidth fiber laser system

Abstract: A high-power narrow-linewidth fiber laser system includes a seed oscillator with multiple resonant cavities and an amplifier stage. The seed oscillator includes a gain fiber, a pump source to introduce pump light into the gain fiber, a single-mode output fiber arranged at the end of the active gain fiber, a first resonant cavity including the active gain fiber, and a second resonant cavity including the active gain fiber. The first and second resonant cavities cooperate to minimize the synchronization of longitudinal modes and thereby reduce modal beating. The amplifier preferably includes an active multimode gain fiber capable of supporting a single fundamental mode at the signal wavelength, wherein the single mode output fiber of the seed oscillator and the multimode gain fiber of the amplifier are mode-matched and coupled without a mode converter.

Two regimes in the regularity of sunspot number

Abstract: Sunspot numbers WN display quasi-periodical variations that undergo regime changes. These irregularities could indicate a chaotic system and be measured by Lyapunov exponents. We define a functional λ (an "irregularity index") that is close to the (maximal) Lyapunov exponent for dynamical systems and well defined for series with a random component: this allows one to work with sunspot numbers. We compute λ for the daily WN from 1850 to 2012 within 4 yr sliding windows: λ exhibit sharp maxima at solar minima and secondary maxima at solar maxima. This pattern is reflected in the ratio R of the amplitudes of the main versus secondary peaks. Two regimes have alternated in the past 150 yr, R1 from 1850 to 1915 (large λ and R values) and R2 from 1935 to 2005 (shrinking difference between main and secondary maxima, R values between 1 and 2). We build an autoregressive model consisting of Poisson noise plus an 11 yr cycle and compute its irregularity index. The transition from R1 to R2 can be reproduced by strengthening the autocorrelation a of the model series. The features of the two regimes are stable for model and WN with respect to embedding dimension and delay. Near the time of the last solar minimum (~2008), the irregularity index exhibits a peak similar to the peaks observed before 1915. This might signal a regime change back from R2 to R1 and the onset of a significant decrease of solar activity.

Timing recovery for partial-response maximum likelihood sequence detector

Abstract: An embodiment of the present invention is a technique for timing recovery. A frequency acquisition loop locks a voltage controlled oscillator (VCO) clock of a multi-band VCO to a reference clock. The frequency acquisition loop generates first and second feedback clocks from the VCO clock. A data lock phase loop generates a driving signal corresponding to a phase error signal from interleaved partial response signal (PRS) samples based on the second feedback clock. The driving signal controls the multi-band VCO in a data phase lock mode. A lock detect controller detects a frequency lock condition in a frequency lock mode and a data lock condition in the data phase lock mode based on the first feedback clock and the reference clock.

Multi-kilowatt peak power pulsed fiber laser with precise computer controlled pulse duration for materials processing

Abstract: We have developed pulsed fiber laser with computer controlled pulse duration and multi-kilowatt output peak power in a diffraction-limited beam. The diode laser as a master oscillator and Yb-based fiber amplifiers were used in a MOPFA configuration. The output pulse duration can be arbitrary selected in the range from 4ns to over 200ns with 1ns resolution. Pulse duration does not depend on the repetition rate and remains the same for all operational frequencies in the range from 10kHz to over 140kHz. The short length of the large mode area Yb-doped fiber was used to amplify the generated pulses to over 40kW peak power and several watt of the average power. The output pulse-to-pulse energy instability was less than 1% for all operational frequencies. Due to the single mode design of the delivery fiber, the measured output beam quality M2 was found to be smaller than 1.05. The developed laser presents a solid-state design to be used in the industrial environment for applications where primary requirements are the beam quality, high repetition rate, small pulse-to-pulse energy instability and reliable laser operation on the real factory floor.