Optical isolators are essential components for highly demanding applications, enabling the use of single frequency lasers. With their capability to design micro-integrated laser systems, the availability of single frequency laser diodes in the visible wavelength region, led to a demand for suitable micro-integrated optical isolators for visible wavelength, e.g. for micro-integrated ECDL laser and MOPA modules. Unlike for the near infrared, micro-integrated optical isolators for the wavelength region between 680 and 1000 nm are not available so far, limiting or even hindering use of micro-integrated laser sources for space mission with photonic, spectroscopic and quantum-technological mission payloads. To overcome this issue, a micro-optical isolator for space application for visible wavelengths has been developed. The design specifically features a low stress crystal mount with a symmetric heat removal essential for good isolation, the avoidance of beam deflection, and a large allowable temperature range. Moreover, the high homogeneity of the magnetic field enables at least 40dB single stage isolation, limited by polarizers and crystal properties. Structural and thermo-elastic analyses have been performed to ensure a space qualifiable design. The properties of the CdMnTe crystals, such as Verdet constant, transmission, optical loss, and polarization, around the generic wavelength of 780 nm have been measured. At 1064 and 780 nm an optical and thermal characterization of the CdMnTe crystals at high power (up to 1.4 W) has been carried out. The isolator design as well as the measurement results will be presented.
We present the European development of an engineering model Laser Head for LISA. This single box includes a seed laser, an electro-optical phase modulator, a fiber amplifier and all PCBs to operate the Laser Head.
This paper presents the design and breadboarding of the proof of concept demonstrator for the so called retro-reflector interferometer scheme in off-axis configuration for the ‘Next Generation Gravity Mission’ (NGGM) studied at the European Space Agency (ESA). This configuration can offer benefits in terms of overall satellite configuration compared to the transponder scheme, which is currently flying on board of GRACE-FO. However, it relies on very low received laser signal levels due to the fact that the laser light is travelling about 100 km from the master satellite to the remote satellite and is reflected back to the master satellite by a retro-reflector. In comparison to the transponder scheme, where the signal is amplified on the remote satellite using a laser, which is optically phase locked to the laser signal of the master spacecraft, this reflection does not amplify the signal. Thus, even with higher emitted laser power, instead of some nanowatt, only a few picowatt are available on the according science detector. Therefore, less than a femtowatt of straylight within the detectable heterodyne frequency and angular range is allowed on the detector to fulfil the ranging noise requirement. The paper gives insights into the main opto-mechanical design topics of the Optical Bench Assembly (OBA). It includes the optical analysis results as well as mechanical design to suppress straylight below the required limit. The optomechanical design of the OBA is complemented by the opto-mechanical design of the test setup and by the electro-optical design of the phase read-out chain. Finally, preliminary results from the test campaign are presented.
The Lidar Emitter and Multi-species greenhouse gases Observation iNstrument (LEMON) is a novel Differential Absorption Lidar (DIAL) sensor concept for greenhouse gases and water vapor measurements from space.1,2 It is based on a versatile transmitter allowing for addressing various absorption lines of different molecules. This highly flexible emitter design requires a universal frequency referencing scheme. Here we present a concept employing a 1 GHz frequency comb, which allows the absolute referencing over a spectral range from 0.95 μm to 1.15 μm. By using an intermediate frequency doubling stage, this allows for DIAL measurements on CO2, H2O/HDO, and CH4 in the 2 μm range. Absolute referencing is obtained by using a GPS disciplined oscillator as the common time base for frequency measurements. The concept of the LEMON Frequency Reference UnIT (FRUIT) is designed to match the requirements of the vibration loads associated with airborne operation to allow implementation on the airborne demonstrator for LEMON. In addition, the requirements for a future space development are considered in the design. For example, radiation critical items have been identified and radiation tested within the project and a compact wavemeter design has been implemented.
K. Nicklaus, M. Herding, A. Baatzsch, M. Dehne, C. Diekmann, K. Voss, F. Gilles, B. Guenther, B. Zender, S. Böhme, V. Mueller, D. Schuetze, G. Stede, B. Sheard, G. Heinzel
The Gravity Recovery and Climate Experiment (GRACE) is a successful Earth observation mission launched in 2002 and consisting of two identical satellites in a polar low-Earth orbit.
The French-German Methane Remote Sensing LIDAR Mission (MERLIN) planned for launch in 2020 aims to provide a global methane concentration map. The instrument is a differential absorption LIDAR (DIAL) system measuring the column-weighted dry-air mixing ratios of methane with a horizontal resolution of 50 km employing an absorption line at 1645 nm [1].
C. Dahl, A. Baatzsch, M. Dehne, F. Gilles, P. Hager, M. Herding, K. Nicklaus, K. Voss, K. Abich, C. Braxmaier, M. Gohlke, B. Guenther, J. Sanjuan, B. Zender, G. Barranco, A. Görth, C. Mahrdt, V. Müller, D. Schütze, G. Stede, G. Heinzel
The Gravity Recovery and Climate Experiment (GRACE) is a successful Earth observation mission launched in 2002 consisting of two identical satellites in a polar low-Earth orbit [1]. The distance variations between these two satellites are measured with a Micro Wave Instrument (MWI) located in the central axis. In data postprocessing the spatial and temporal variations of the Earth’s gravitational field are recovered, which are among other things introduced by changing groundwater levels or ice-masses [2, 3, 4, 5]. The Laser Ranging Interferometer (LRI) on-board the GRACE Follow-On (GFO) mission, which will be launched in 2017 by the joint collaboration between USA (NASA) and Germany (GFZ), is a technology demonstrator to provide about two orders of magnitude higher measurement accuracy than the initial GRACE MWI, about 80 nm/√Hz in the measurement band between 2 mHz and 0.1 Hz. The integration of the LRI units on both GFO S/C has been finished in summer 2016. The design as well as the functional, performance, and thermal-vacuum tests results of the German LRI flight units will be presented.
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