Dispersion Measurement of Ultra-High Numerical Aperture Fibers covering Thulium, Holmium, and Erbium Emission Wavelengths

We present broadband group velocity dispersion (GVD) measurements of commercially available ultra-high numerical aperture fibers (UHNA1, UHNA3, UHNA4, UHNA7 and PM2000D from Coherent-Nufern). Although these fibers are attractive for dispersion management in ultrafast fiber laser systems in the 2 {\mu}m wavelength region, experimental dispersion data in literature is scarce and inconsistent. Here we demonstrate the measurements using the spectral interferometry technique covering the typically used erbium, thulium and holmium emission bands. The results are characterized in terms of the standard-deviation uncertainty and compared with previous literature reports. Fitting parameters are provided for each fiber allowing for the straightforward replication of the measured dispersion profiles. This work is intended to facilitate the design of ultrafast fiber laser sources and the investigations of nonlinear optical phenomena

Low noise all-fiber amplification of a coherent supercontinuum at 2 \mu m and its limits imposed by polarization noise

We report the amplification of an all-normal dispersion supercontinuum pulse in a Thulium / Holmium co-doped all-fiber chirped pulse amplification system. With a -20 dB bandwidth of more than 300 nm in the range 1800-2100 nm the system delivers high quality 66 fs pulses with more than 70 kW peak power directly from the output fiber. The coherent seeding of the entire emission bandwidth of the doped fiber and the stability of the supercontinuum generation dynamics in the silicate glass all-normal dispersion photonic crystal fiber result in excellent noise characteristics of the amplified ultrashort pulses

Challenges in the development of the Laser Metal Deposition process for use in microgravity at the Einstein-Elevator

This paper is about the challenges in developing the Laser Metal Deposition process with metal powder for use in microgravity. The modified gravitational conditions are set up for a few seconds using a drop tower, the Einstein-Elevator of the Leibniz University Hannover. In addition to the drop tower, the specially adapted setup of the experiment will be explained. The samples produced in microgravity during this project will demonstrate the influence of gravity on this additive manufacturing process and on the materials used. Thermal analyses using the Ansys software show how the temperature distribution of the manufactured specimens looks over time and what this means for the execution of the experiment

Generalized spectral phase-only time-domain ptychographic phase reconstruction applied in nonlinear microscopy

Nonlinear microscopy has evolved over the last few decades to become a powerful tool for imaging and spectroscopic applications in biological sciences. In this study, I$^2$PIE, a novel spectral phase control technique, was implemented in order to compress broad-bandwidth supercontinuum light pulses generated in an all-normal-dispersion (ANDi) photonic crystal fiber (PCF). The technique, based on time-domain ptychography, is demonstrated here in a nonlinear microscopy application for the first time, to the best of our knowledge. The first real-world application of this technique for second-harmonic generation and two-photon excitation fluorescence microscopies in biological samples is presented. We further show that in our implementation, I$^2$PIE leads to improved contrast and signal-to-noise ratios in the generated images, compared to conventional compression techniques used in nonlinear microscopy.Comment: Copyright 2020 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibite

Novel time domain ptychography, i2PIE, for improved contrast in nonlinear microscopy

We present a novel nonlinear microscopy modality using a time-domain ptychographic phase measurement, i2PIE, to compress 80 MHz supercontinuum pulses from an ANDi PCF used as excitation source, improving contrast at reduced average power

Signal-to-noise ratio of temperature measurement with Cernox sensors at various supply currents

The Karlsruhe Institute of Technology (KIT) has developed a new thermal method for flow measurement, which is particularly suitable for the application in cryogenic systems. In this method, the stability and the resolution of temperature measurement is important, rather than precision. In other words, constant offsets in temperature measurements can be ignored, and the temperature sensors can be operated at supply currents beyond their nominal design value in order to gain resolution. For this application, the performance of two Cernox TM type CX-1050-SD-HT-1.4L sensors was measured in a temperature range between 300 K and 4 K. The experiments were carried out in the calibration cryostat at the Institute for Technical Physics. Sensors were connected to a Lake Shore Model 121 current source and a Keithley 2701/E digital multimeter for voltage measurements. At constant calibration temperatures, the supply currents were varied such that the resulting voltage drops lay in-between 10 mV and 100 mV. The influence on both the noise and the temperature offset are presented

Noise Fingerprints of Fiber Supercontinuum Sources

We present a novel technique for measuring unique ”noise fingerprints” of fiber supercontinuum (SC) sources, revealing a strong dependence of SC relative intensity noise not only on the dispersion of the fiber, but also on its cross-sectional geometry

All-fibre heterogeneously-integrated frequency comb generation using silicon core fibre

Originally developed for metrology, optical frequency combs are becoming increasingly pervasive in a wider range of research topics including optical communications, spectroscopy, and radio or microwave signal processing. However, application demands in these fields can be more challenging as they require compact sources with a high tolerance to temperature variations that are capable of delivering flat comb spectra, high power per tone, narrow linewidth and high optical signal-to-noise ratio. This work reports the generation of a flat, high power frequency comb in the telecom band using a 17 mm fully-integrated silicon core fibre as a parametric mixer. Our all-fibre, cavity-free source combines the material benefits of planar waveguide structures with the advantageous properties of fibre platforms to achieve a 30 nm bandwidth comb source containing 143 tones with 30 dB OSNR over the entire spectral region

All-fibre heterogeneously-integrated frequency comb generation using silicon core fibre.

Originally developed for metrology, optical frequency combs are becoming increasingly pervasive in a wider range of research topics including optical communications, spectroscopy, and radio or microwave signal processing. However, application demands in these fields can be more challenging as they require compact sources with a high tolerance to temperature variations that are capable of delivering flat comb spectra, high power per tone, narrow linewidth and high optical signal-to-noise ratio. This work reports the generation of a flat, high power frequency comb in the telecom band using a 17 mm fully-integrated silicon core fibre as a parametric mixer. Our all-fibre, cavity-free source combines the material benefits of planar waveguide structures with the advantageous properties of fibre platforms to achieve a 30 nm bandwidth comb source containing 143 tones with 30 dB OSNR over the entire spectral region