Following the idea of a circular bioeconomy, the use of side streams as substitutes for cultivation media (components) in bioprocesses would mean an enormous economic and ecological advantage. Costly compounds in conventional media for the production of the triterpene squalene in thraustochytrids are the main carbon source and complex nitrogen sources. Among other side streams examined, extracts from the spent mycelium of the basidiomycete Pleurotus ostreatus were best-suited to acting as alternative nitrogen sources in cultivation media for thraustochytrids. The total nitrogen (3.76 ± 0.01 and 4.24 ± 0.04%, respectively) and protein (16.47 ± 0.06 and 18.57 ± 0.18%, respectively) contents of the fruiting body and mycelium were determined. The fungal cells were hydrolyzed and extracted to generate accessible nitrogen sources. Under preferred conditions, the extracts from the fruiting body and mycelium contained 73.63 ± 1.19 and 89.93 ± 7.54 mM of free amino groups, respectively. Cultivations of Schizochytrium sp. S31 on a medium using a mycelium extract as a complex nitrogen source showed decelerated growth but a similar squalene yield (123.79 ± 14.11 mg/L after 216 h) compared to a conventional medium (111.29 ± 19.96 mg/L, although improvable by additional complex nitrogen source).
We report on an ytterbium-doped monolithic fiber laser at a wavelength of 1018 nm with an output power of 200 W in continuous wave operation. The optimal parameters for setting up such a high-power fiber laser with an ytterbium-doped fiber are investigated and discussed in detail. An in-house-developed pump light stripper and a single-mode fused fiber coupler were applied to use the fiber laser for core-pumping of ytterbium-doped high-power fiber amplifiers in a monolithic setup.
Fused-type mode-selective fiber couplers exciting the LP(11) mode are fabricated by well-defined fiber cladding reduction, pretapering and fusion. At a wavelength of 905 nm 80 % of the injected power in the single-mode fiber was transmitted in the few-mode fiber selectively exciting the LP(11) mode. The coupling behavior was experimentally investigated for the case of strong as well as weak fusion. Numerical simulations based on the super-mode coupling approach were used to estimate fabrication parameters and to discuss the modal evolution in arbitrarily fused couplers. The influence of changes in the coupler geometry on the super-modes and their modal weighting are analyzed by calculations of the effective refractive index and by modal decomposition.
We developed a fused fiber coupler (FFC) capable of multiplexing wavelengths in the range of 795 nm and 2 µm. A simple 2D simulation model to calculate the pretaper length for matching the propagation constants in the coupling region was established. Based on the numerical data, we fabricated an asymmetric FFC consisting of two different fibers with single-mode guidance for the respective wavelength, achieving a transmission of 90% in the signal fiber for both wavelengths. In order to demonstrate the application, we integrated the FFC into a core pumped thulium-doped fiber amplifier.
Optical Fibers , Thulium , Lasers , Optical Phenomena
We present a mode-locked all-normal dispersion ytterbium fiber oscillator with output pulse energies beyond 0.5 µJ. The oscillator is mode-locked using nonlinear polarization rotation, and stable single-pulse operation is achieved by spectral filtering inside the resonator. The oscillator generates strongly chirped output pulses at a repetition rate of 4.3 MHz which can be compressed down to 760 fs.
We investigated an all-fiber picosecond Raman shifter, pumped by an amplified gain switched laser diode in detail. The Raman shifter emitted ps pulses simultaneously at 8 different central wavelengths in the region between 1.06 µm and 1.59 µm.
Amplifiers, Electronic , Fiber Optic Technology/instrumentation , Lasers, Solid-State , Spectrum Analysis, Raman/instrumentation , Equipment Design , Equipment Failure Analysis
We present a mode-locked, all-normal-dispersion erbium-doped fiber oscillator generating output pulses with broadband spectra covering the range from 1475 to 1620 nm. The oscillator operates at a repetition rate of 109 MHz with output pulse energies of 1.6 nJ. Mode-locked operation is achieved by use of nonlinear polarization evolution in combination with a birefringent filter. The output pulses are dechirped with an external prism compressor to a duration of 50 fs.
We demonstrate output pulse energies of 20 nJ from an erbium-doped fiber oscillator that contains only positive dispersion fibers and is mode locked by use of nonlinear polarization evolution and stabilized with a birefringent filter. The fiber oscillator operates at a repetition rate of 3.5 MHz with a central wavelength of 1550 nm. The positively chirped output pulses have a duration of 53 ps and are compressed to 750 fs. The large positive chirp of the output pulses and the steep side edges of the pulse spectrum indicate dissipative soliton operation.
