18 research outputs found
Vanishing tilt-to-length coupling for a singular case in two-beam laser interferometers with Gaussian beams
The omnipresent tilt-to-length coupling in two-beam laser interferometers,
frequently a nuisance in precision measurements, vanishes for the singular case
of two beams with identical parameters and complete detection of both beams
without clipping. This effect has been observed numerically and is explained in
this manuscript by the cancellation of two very different effects of equal
magnitude and opposite sign.
This paper was published in Applied Optics and is made available as an
electronic reprint with the permission of OSA. The paper can be found at the
following URL on the OSA website:
[http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-54-5-1010]. Systematic or
multiple reproduction or distribution to multiple locations via electronic or
other means is prohibited and is subject to penalties under law
A brief comparison of optical pathlength difference and various definitions for the interferometric phase
To this paper we discuss that the phase readout in low noise laser interferometers can significantly deviate from the underlying optical pathlength difference (OPD). The cross coupling of beam tilt to the interferometric phase readout is compared to the OPD. For such a system it is shown that the amount of tilt to phase readout coupling depends strongly on the involved beams and their parameters, as well as on the detector properties and the precise definition of the phase. The unique single element photodiode phase is therefore compared to three common phase definitions for quadrant diodes. It is shown that neither phase definition globally shows the least amount of cross coupling of angular itDeutsches Zentrum fĂĽr Luft- und Raumfahrt (DLR)/No 50 OQ 130
Sub-system mechanical design for an eLISA optical bench
We present the design and development status of the opto-mechanical sub-systems that will be used in an experimental demonstration of imaging systems for eLISA. An optical bench test bed design incorporates a Zerodur® baseplate with lenses, photodetectors, and other opto-mechanics that must be both adjustable - with an accuracy of a few micrometers - and stable over a 0 to 40°C temperature range. The alignment of a multi-lens imaging system and the characterisation of the system in multiple degrees of freedom is particularly challenging. We describe the mechanical design of the precision mechanisms, including thermally stable flexure-based optical mounts and complex multi-lens, multi-axis adjuster mechanisms, and update on the integration of the mechanisms on the optical bench
The Lunar Lander Neutron and Dosimetry (LND) Experiment on Chang'E 4
Chang'E 4 is the first mission to the far side of the Moon and consists of a
lander, a rover, and a relay spacecraft. Lander and rover were launched at
18:23 UTC on December 7, 2018 and landed in the von K\'arm\'an crater at 02:26
UTC on January 3, 2019. Here we describe the Lunar Lander Neutron \& Dosimetry
experiment (LND) which is part of the Chang'E 4 Lander scientific payload. Its
chief scientific goal is to obtain first active dosimetric measurements on the
surface of the Moon. LND also provides observations of fast neutrons which are
a result of the interaction of high-energy particle radiation with the lunar
regolith and of their thermalized counterpart, thermal neutrons, which are a
sensitive indicator of subsurface water content.Comment: 38 pages, submitted to Space Science Review
Geometric tilt-to-length coupling in precision interferometry: mechanisms and analytical descriptions
Tilt-to-length coupling is a technical term for the cross-coupling of angular
or lateral jitter into an interferometric phase signal. It is an important
noise source in precision interferometers and originates either from changes in
the optical path lengths or from wavefront and clipping effects. Within this
paper, we focus on geometric TTL coupling and categorize it into a number of
different mechanisms for which we give analytic expressions. We then show that
this geometric description is not always sufficient to predict the TTL coupling
noise within an interferometer. We, therefore, discuss how understanding the
geometric effects allows TTL noise reduction already by smart design choices.
Additionally, they can be used to counteract the total measured TTL noise in a
system. The presented content applies to a large variety of precision
interferometers, including space gravitational wave detectors like LISA
Experimental demonstration of reduced tilt-to-length coupling by a two-lens imaging system
Method Comparison for Simulating Non-Gaussian Beams and Diffraction for Precision Interferometry
In the context of simulating precision laser interferometers, we use several examples to compare two wavefront decomposition methods—the Mode Expansion Method (MEM) and the Gaussian Beam Decomposition (GBD) method—for their precision and applicability. To assess the performance of these methods, we define different types of errors and study their properties. We specify how the two methods can be fairly compared and based on that, compare the quality of the MEM and GBD through several examples. Here, we test cases for which analytic results are available, i.e., non-clipped circular and general astigmatic Gaussian beams, as well as clipped circular Gaussian beams, in the near, far, and extremely far fields of millions of kilometers occurring in space-gravitational wave detectors. Additionally, we compare the methods for aberrated wavefronts and their interaction with optical components by testing reflections from differently curved mirrors. We find that both methods can generally be used for decomposing non-Gaussian beams. However, which method is more accurate depends on the optical system and simulation settings. In the given examples, the MEM more accurately describes non-clipped Gaussian beams, whereas for clipped Gaussian beams and the interaction with surfaces, the GBD is more precise