Formation of ultrashort triangular pulses in optical fibers

Specialty shape ultrashort optical pulses, and triangular pulses in particular, are of great interest in optical signal processing. Compact fiber-based techniques for producing the special pulse waveforms from Gaussian or secant pulses delivered by modern ultrafast lasers are in demand in telecommunications. Using the nonlinear Schr¨odinger equation in an extended form the transformation of ultrashort pulses in a fiber towards triangular shape is characterized by the misfit parameter under variety of incident pulse shapes, energies, and chirps. It is shown that short (1-2 m) conventional single mode fiber can be used for triangular pulse formation in the steady-state regime without any pre-chirping if femtosecond pulses are used for pumping. The pulses obtained are stable and demonstrate linear chirp. The ranges and combinations of the pulse parameters found here will serve as a guide for scheduling the experiments and implementation of various all-fiber schemes for optical signal processing

Astronomical optical frequency comb generation and test in a fiber-fed MUSE spectrograph

We here report on recent progress on astronomical optical frequency comb generation at innoFSPEC-Potsdam and present preliminary test results using the fiber-fed Multi Unit Spectroscopic Explorer (MUSE) spectrograph. The frequency comb is generated by propagating two free-running lasers at 1554.3 and 1558.9 nm through two dispersionoptimized nonlinear fibers. The generated comb is centered at 1590 nm and comprises more than one hundred lines with an optical-signal-to-noise ratio larger than 30 dB. A nonlinear crystal is used to frequency double the whole comb spectrum, which is efficiently converted into the 800 nm spectral band. We evaluate first the wavelength stability using an optical spectrum analyzer with 0.02 nm resolution and wavelength grid of 0.01 nm. After confirming the stability within 0.01 nm, we compare the spectra of the astro-comb and the Ne and Hg calibration lamps: the astro-comb exhibits a much larger number of lines than lamp calibration sources. A series of preliminary tests using a fiber-fed MUSE spectrograph are subsequently carried out with the main goal of assessing the equidistancy of the comb lines. Using a P3d data reduction software we determine the centroid and the width of each comb line (for each of the 400 fibers feeding the spectrograph): equidistancy is confirmed with an absolute accuracy of 0.4 pm

All-fiber, single-mode spectral beam combining of high power Tm-doped fiber lasers

Signal beam combining of Tm-doped fiber lasers can increase the laser output power while simultaneously maintaining the single mode beam quality. We demonstrate an all-fiber integrated dual-wavelength Tm-doped fiber laser with an output power of 36 W by using the spectral beam combining method. The constituent lasers are operating at the wavelengths 1949 and 1996 nm and an in-house-made WDM is used for combination of these two different wavelengths. All-fiber truly single mode power combining is demonstrated for the first time in this wavelength region. © OSA 2015

Single-mode spectral beam combining of high power Tm-doped fiber lasers with WDM cascades

Spectral beam combining of Tm-doped fiber lasers can increase the laser output power while simultaneously maintaining the single mode beam quality. We report on a spectral beam combining technique based on highly efficient in-house-made WDM cascade. We demonstrate continuous wave power combining employing a WDM cascade consisting of four fiber laser sources with emission wavelengths of 1920, 1949, 1996 and 2030 nm. A combined power of up to 38 W resulted in a combining efficiency of 69%. © 2016 SPIE

Innovative laser sources operating around 2 μm

We report on a variety of continuous wave and pulsed laser sources based on Thulium- and Holmium-doped materials, emitting in the spectral range around 2 μm. This includes continuous wave Thulium-doped fiber lasers which have been realized based on the beam combining technique by using tapered fused bundles and truly single mode WDM cascades, respectively. A pulsed laser source emitting nano- or picosecond pulses has been developed in a master oscillator power amplifier (MOPA) configuration, which consists of a gain-switched diode operating at a wavelength of 1.95 μm, followed by Thulium-doped fiber-based pre- and main amplifiers. Furthermore, we present a femtosecond regenerative amplifier system using Thulium:YAP and Holmium:YAG crystals with emission wavelengths around 1.95 μm and 2.1 μm, respectively. Output energies of more than 700 μJ have been generated with both systems

Innovative laser sources operating around 2 μm

We report on a variety of continuous wave and pulsed laser sources based on Thulium- and Holmium-doped materials, emitting in the spectral range around 2 μm. This includes continuous wave Thulium-doped fiber lasers which have been realized based on the beam combining technique by using tapered fused bundles and truly single mode WDM cascades, respectively. A pulsed laser source emitting nano- or picosecond pulses has been developed in a master oscillator power amplifier (MOPA) configuration, which consists of a gain-switched diode operating at a wavelength of 1.95 μm, followed by Thulium-doped fiber-based pre- and main amplifiers. Furthermore, we present a femtosecond regenerative amplifier system using Thulium:YAP and Holmium:YAG crystals with emission wavelengths around 1.95 μm and 2.1 μm, respectively. Output energies of more than 700 μJ have been generated with both systems