Lasers for LISA
The Laser Interferometer Space Antenna (LISA) mission aims for detection and characterization of gravitational waves in the frequency range between 30 μHz and 1 Hz. These wavelengths are generated by galactic or cosmic events happening in massive black holes or binary galaxies. Thus, LISA will provide a new observation window and addresses a multitude of cosmological and astrophysics questions.
Artist's impression of one of the three LISA satellites (source: AEI/MM/exozet/NASA/Henze)
SpaceTech’s development for the LISA mission
Gravitational waves are detected by displacement measurements using laser interferometers. In LISA three satellites are arranged in a triangular shape with an arm length of 5 million kilometers. Two active laser systems will be onboard of each satellite sending their light to the two remote S/C and forming an interferometer between two S/C, respectively. The laser light is the only link between the satellites. It will be used to detect tiny displacements at picometer level caused by gravitational waves, but also for data transfer, and for inter-S/C ranging. To achieve this, LISA requires (among other laser requirements) ultra-stable laser sources in power and frequency.
At SpaceTech, we develop the laser as prime contractor to ESA. STI is leading a consortium of Ferdinand-Braun-Institute (seed laser), Fraunhofer ILT (fiber amplifier), and Airbus Defence & Space and DLR Bremen for testing. SpaceTech is responsible for the overall system, electronics, and integration.
The current contract covers the development from laser concept up to the Engineering Model. Phase 1 – breadboarding – has been completed with the laser meeting or even exceeding almost all requirements.
LISA key laser components
- Seed laser based on the micro-integrated ECDL platform of FBH, providing frequency and power stabilities matching the performance so far only demonstrated with NPRO technology. In addition it features a much higher output power and a higher electro-optical efficiency.
- Fiber amplifier to scale the optical output power to more than 2 W, while maintaining the spectral and power noise parameters. The design is optimized for high efficiency and low non-linearities to allow further power scaling, which is also relevant e.g. for future optical communication in space.
- Control & drive electronics relying on the ultra-low noise current driver of STI to enable the demanding frequency and power stability of the whole system.
The design follows the STI approach to develop laser building blocks to allow easy re-use of individual elements for other applications/missions, such as NGGM, optical telecommunication or quantum technological systems like optical clocks at different wavelengths.
LISA key laser parameters and features
- Wavelength 1064 nm with ultra-stable long-term frequency stability; see orange graph in the right figure
- Tuning range of ± 2 GHz with a slew rate of 638 MHz/s (the latter number refers to the seed laser)
- High phase coherence with phase modulation capabilities
- 2 W output power delivered out of a polarization-maintaining optical fiber with excellent stability; see blue graph in the right figure
For more technical details on STI’s laser development please check out the conference proceedings listed below.
The launch of the 3 LISA satellites is planned for 2034.
More LISA mission details
The activity “Gravitational Wave Observatory Metrology Laser” is funded by the European Space Agency (ESA), Contract No. 4000119715/17/NL/BW. The view expressed herein can in no way be taken to reflect the official opinion of the European Space Agency.