Highly stable fiber amplifier development and environmental component-testing for the space-based gravitational wave detector LISA

Abstract

For a study of the European Space Agency ESA, Fraunhofer ILT developed and built single-frequency, linearly polarized, power-stabilized fiber amplifiers as elegant breadboard (EBB) with an output power <3 W for the future space-based gravitational wave detector LISA (Laser Interferometer Space Antenna). The fiber amplifier developed at Fraunhofer ILT in a previous phase has fulfilled most of the optical performance requirements, except the relative intensity noise (RIN) [1]. In this paper, we present our revised and optimized fiber amplifier which now, in addition to the earlier demonstrated parameters, fulfills the LISA RIN requirements. Currently, the engineering model (EM) of the chosen fiber amplifier concept is being implemented by our project partner SpaceTech GmbH. Furthermore, since the Technology Readiness Level (TRL) of the components has to be confirmed for the EM, Fraunhofer ILT conducted 1000hours operational long-term tests of the components installed in a thermal-vacuum chamber and 2-weeks nonoperational tests in a thermal cycling chamber to qualify them for space applications.

Narrow-linewidth single-stage fiber amplifier with an output power of 15 W at 1064 nm

“…Figure 5 shows the measured RIN with respect to the analyzed frequency at an output power 15.8 W. The measurement shows that the RIN is below 10 -3 Hz -1/2 at frequencies between 10 mHz and 1 Hz even without an active power stabilization. With our previously demonstrated setup, which features an active power stabilization, we fullfilled the LISA requirements at 3 W output power [2]. We expect to achieve comparable results, when we implement an active power stabilization for our here presented setup, which currently does not include any stabilization scheme yet, and additionally does not have any protective housing.…”

“…Figure 5. The measured relative intensity noise of the single-stage fiber amplifier and our earlier published fiber amplifier [2] at maximum output power…”

“…Our here presented single-frequency fiber amplifier is based on our previous design for the LISA study [1,2]. In comparison to our previous setup, we revised our single-stage fiber amplifier concept to scale a narrow-linewidth seed signal to higher output power without significant amplified spontaneous emission (ASE) and without the occurrence of nonlinear effects, e.g.…”

“…It requires a single frequency narrow-linewidth linearly polarized highly stable single-mode laser with an output power >2 W with high efficiency. For this, in a pre-study of the European Space Agency (ESA) on the future space-based gravitational wave detector LISA, a power-stabilized, narrow-linewidth fiber amplifier with an output power of 3 W was developed and built at the Fraunhofer Institute for Laser Technology ILT [1,2].…”

Ultra-Low-Noise, Single-Frequency, All-PM Thulium- and Holmium-Doped Fiber Amplifiers at 1950 nm and 2090 nm for Third-Generation Gravitational Wave Detectors

“…For the space-based gravitational wave detector LISA, compact systems with an output power of approx. 2 W at a wavelength of 1064 nm are under development [9,10]. For wavelengths at approx.…”