[en] In this work we demonstrate a high-power, high-repetition rate chirped pulse amplification system operating at 1560 nm center wavelength. The system consists of a mode-locked Er-fiber oscillator, a grating-based pulse stretcher, a two-stage amplifier and a grating compressor. The system provides over 2.5 W of average output power with nearly transform limited, linearly polarized 390 fs pulses and 12.6 nJ pulse energy at 200 MHz repetition rate. The whole design is based on single-mode fibers, which allows excellent beam quality to be maintained. (paper)

[en] One of the most important parts of a fiber-laser vibrometer is demodulation electronic section. The distortion, nonlinearity, offset and added noise of measured signal come from electronic circuits and they have direct influence on finale measuring results. Two main parameters of an investigated vibrating object: velocity V(t) and displacement s(t), influence of detected beat signals. They are: the Doppler frequency deviation f(t) and phase shift φ(t), respectively. Because of wide range of deviations it is difficult to use just one demodulator. That is the reason why we use three different types of demodulators. The first one is the IQ demodulator, which is the most sensitive one and its output is proportional to the displacement. Each IQ channel is sampled simultaneously by an analog to digital converter (ADC) integrated in a digital signal processor (DSP). The output signals from the two FM demodulators are proportional to the frequency deviation of heterodyne signals. They are sensitive directly to the velocity of the object. The main disadvantage of scattered light interferometry system is a ''speckle effect'', appearing in relatively large amplitude fluctuation of a heterodyne signal. To minimize ''speckle effect'' influence on quality of beat signals we applied the automatic gain control (AGC) system. Data acquisition, further signal processing (e.g. vibration frequency spectra) and presentation of results is realized by PC via USB interface.

[en] A widely tunable, fully monolithic, mid-infrared difference frequency generation source and its application in the dispersion-spectroscopy-based laser trace gas detection of methane and ethane, near 2938 and 2998 cm⁻¹, is presented. Utilizing a fiber pigtailed nonlinear crystal module radically simplified the optical setup, while maintaining a superb conversion efficiency of 20% W⁻¹. Seeded directly from two laser diodes, the source delivered ∼0.5 mW of tunable radiation, which was used in a chirped laser dispersion spectroscopy setup, enabling the highly sensitive detection of hydrocarbons. (letter)

[en] An all-polarization maintaining, erbium-doped fiber laser based on a graphene saturable absorber is presented. The graphene layers were grown on copper foils by chemical vapor deposition (CVD) and transferred onto the fiber connector tip. The laser was capable of generating scalar solitons with sub-600 fs duration at 46 MHz repetition rate. The center wavelength of the emission could be continuously tuned from 1556 to 1560 nm by changing the intra-cavity losses. Thanks to the all-polarization maintaining cavity design the laser was self-starting, environmentally stable and could operate for long periods of time. The degree of polarization (DOP) of the output pulses was at the level of 99.8%. (paper)

[en] In this work we demonstrate for the first time, to our knowledge, a chirped pulse amplification (CPA) setup utilizing a graphene mode-locked femtosecond fiber laser as a seed source. The system consists of a mode-locked Er-fiber oscillator operating at 1560 nm wavelength, a grating-based pulse stretcher, two-stage amplifier and a grating compressor. The presented setup allows the amplification of the seed up to 1 W of average power (1000 times amplification) with linearly polarized 810 fs pulses and 20 nJ pulse energy at a 55 MHz repetition rate. The whole design is based on single-mode fibers, which allows one to maintain excellent beam quality, with M² less than 1.17. (letter)