48 research outputs found
Sub-pm/ non-reciprocal noise in the LISA backlink fiber
The future space-based gravitational wave detector Laser Interferometer Space
Antenna (LISA) requires bidirectional exchange of light between its two optical
benches on board of each of its three satellites. The current baseline foresees
a polarization-maintaining single-mode fiber for this backlink connection.
Phase changes which are common in both directions do not enter the science
measurement, but differential ("non-reciprocal") phase fluctuations directly do
and must thus be guaranteed to be small enough. We have built a setup
consisting of a Zerodur baseplate with fused silica components
attached to it using hydroxide-catalysis bonding and demonstrated the
reciprocity of a polarization-maintaining single-mode fiber at the 1
pm/ level as is required for LISA. We used balanced
detection to reduce the influence of parasitic optical beams on the reciprocity
measurement and a fiber length stabilization to avoid nonlinear effects in our
phase measurement system (phase meter). For LISA, a different phase meter is
planned to be used that does not show this nonlinearity. We corrected the
influence of beam angle changes and temperature changes on the reciprocity
measurement in post-processing
Real-time phasefront detector for heterodyne interferometers
We present a real-time differential phasefront detector sensitive to better
than 3 mrad rms, which corresponds to a precision of about 500 pm. This
detector performs a spatially resolving measurement of the phasefront of a
heterodyne interferometer, with heterodyne frequencies up to approximately 10
kHz. This instrument was developed as part of the research for the LISA
Technology Package (LTP) interferometer, and will assist in the manufacture of
its flight model. Due to the advantages this instrument offers, it also has
general applications in optical metrology
Measurement of the non-reciprocal phase noise of a polarization maintaining single-mode optical fiber
Polarization maintaining single-mode optical fibers are key components in the interferometry of the Laser Interferometer Space Antenna (LISA). LISA's measurement principle relies on the availability of space qualified fibers of this type which influence the phase of light with a wavelength of 1064 nm passing in opposite directions through them with differences smaller than 6 prad/. We present a measurement scheme suitable to sense these non-reciprocal phase changes, as well as results obtained using this setup on samples of commercially available fibers. The experimental setup for the fiber characterization consists of a quasi-monolithic interferometer which constitutes a representative cut-out of the local interferometry on-board LISA concerning the fiber. Several noise sources are identified and improvements to the setup are presented to overcome them. The noise level achieved using this setup is between approximately 40 prad/ and 400 prad/ in the frequency range between 1 mHz and 1 Hz. It is also verified that this noise level is limited by the setup and not introduced by the fiber.DLR/50 OQ 060
Digital laser frequency control and phase stabilization loops for a high precision space-borne metrology system
We report on the design, implementation and characterization of fully digital
control loops for laser frequency stabilization, differential phase-locking and
performance optimization of the optical metrology system on-board the LISA
Pathfinder space mission. The optical metrology system consists of a laser with
modulator, four Mach-Zehnder interferometers, a phase-meter and a digital
processing unit for data analysis. The digital loop design has the advantage of
easy and flexible controller implementation and loop calibration, automated and
flexible locking and resetting, and improved performance over analogue
circuitry. Using the practical ability of our system to modulate the laser
frequency allows us to accurately determine the open loop transfer function and
other system properties. Various noise sources and their impact on system
performance are investigated in detail.Comment: 10 pages, 7 figures; draft only, for edited version see journal lin
Sub-pm√Hz⁻¹ non-reciprocal noise in the LISA backlink fiber
The future space-based gravitational wave detector laser interferometer space antenna (LISA) requires bidirectional exchange of light between its two optical benches on board of each of its three satellites. The current baseline foresees a polarization-maintaining single-mode fiber for this backlink connection. Phase changes which are common in both directions do not enter the science measurement, but differential (non-reciprocal) phase fluctuations directly do and must thus be guaranteed to be small enough. We have built a setup consisting of a Zerodur baseplate with fused silica components attached to it using hydroxide-catalysis bonding and demonstrated the reciprocity of a polarization-maintaining single-mode fiber at the 1 pm√Hz-1 level as is required for LISA. We used balanced etection to reduce the influence of parasitic optical beams on the reciprocity measurement and a fiber length stabilization to avoid nonlinear effects in our phase measurement system (phase meter). For LISA, a different phase meter is planned to be used that does not show this nonlinearity. We corrected the influence of beam angle changes and temperature changes on the reciprocity measurement in post-processing
Emerging Paths of Family Entrepreneurship Research
This futuristic commentary reviews family business research since its beginning more than 30 years ago. Prior to 2000, disciplinary roots, professional organizations, and early milestones are identified. More recent books, journals, and special issues are noted, and conceptualizations, theories, and databases are compared and contrasted. Lastly, current and future research paths or directions are identified and discussed, and researchers are challenged to move ahead into new and different research arenas