Optical cavity reaching 10 frequency stability with compact optical circulator based in-coupling optics.

Future space missions will benefit from highly stable and compact optical frequency references. While many promising technologies are currently under investigation, optical cavities are a well-suited technique for applications in which relative references are required. To improve the frequency stability of optical cavities, a key step in combining high performance with compactness and robustness is the further development of in-coupling optics.

Optical pilot tone correction of phase errors in photodetection chains.

The phase delay introduced by photodetectors can be affected by intensity, reverse bias, and temperature through different effects. An optical pilot tone superimposed on the detected signal allows an independent measurement of such phase errors in the complete photodetection chain and provides an opportunity to correct them. This allows to further separate readout noise from the measurement, providing a more performant and intensity-invariant phase readout.

Choice of the Miniature Inertial Optomechanical Sensor Geometric Parameters with the Help of Their Mechanical Characteristics Modelling.

In this paper, the mechanical characteristics of a miniature optomechanical accelerometer, similar to those proposed for a wide range of applications, have been investigated. With the help of numerical modelling, characteristics such as eigenfrequencies, quality factor, displacement magnitude, normalized translations, normalized rotations versus eigenfrequencies, as well as spatial distributions of the azimuthal and axial displacements and stored energy density in a wide frequency range starting from the stationary case have been obtained. Dependencies of the main mechanical characteristics versus the minimal and maximal system dimensions have been plotted.

Interferometric sphere surface metrology with cylindrical reference for precision topography.

We demonstrate a method for measuring a surface map of a spherical body with interferometric optical point sensors while rotating the test subject. The setup takes advantage of the excellent performance of heterodyne interferometry at nanometer levels and suppression of common-mode errors, as a cylindrical mirror mounted adjacent to the sphere is used as a reference. Future space based missions for gravitational wave research demand an improved inertial reference sensor with reduced acceleration noise levels.

Ultracold atom interferometry in space.

Bose-Einstein condensates (BECs) in free fall constitute a promising source for space-borne interferometry. Indeed, BECs enjoy a slowly expanding wave function, display a large spatial coherence and can be engineered and probed by optical techniques. Here we explore matter-wave fringes of multiple spinor components of a BEC released in free fall employing light-pulses to drive Bragg processes and induce phase imprinting on a sounding rocket.

Simultaneous laser frequency stabilization to an optical cavity and an iodine frequency reference.

In this Letter, we demonstrate a method to combine a molecular iodine absolute frequency reference with a high-finesse optical cavity in a single laser to take advantage of the frequency stability properties of both systems at different time scales. The result is a laser exhibiting the long-term and short-term stability levels of the iodine frequency reference and optical cavity, respectively. The method uses frequency offset side-band locking and an acousto-optical modulator driven ac-coupled servo-loop to correct the iodine's short-term frequency fluctuations.

Long-term stable optical cavity for special relativity tests in space: erratum.

We incorrectly cited a maximum acceleration sensitivity of the rigidly-mounted cavity of 2.5 × 10 1/(m s). The correct coupling factor is a factor of 100 smaller: 2.

Architecture and performance analysis of an optical metrology terminal for satellite-to-satellite laser ranging.

Interferometric laser ranging is an enabling technology for high-precision satellite-to-satellite tracking within the context of Earth observation, gravitational wave detection, or formation flying. In orbit, the measurement system is affected by environmental influences, particularly satellite attitude jitter and temperature fluctuations, imposing an instrument design with a high level of thermal stability and insensitivity to rotations around the spacecraft center of mass. The new design concept presented here combines different approaches for dynamic heterodyne laser ranging and features the inherent beam-tracking capabilities of a retroreflector in a mono-axial configuration.

In-Orbit Performance of the GRACE Follow-on Laser Ranging Interferometer.

The Laser Ranging Interferometer (LRI) instrument on the Gravity Recovery and Climate Experiment (GRACE) Follow-On mission has provided the first laser interferometric range measurements between remote spacecraft, separated by approximately 220 km. Autonomous controls that lock the laser frequency to a cavity reference and establish the 5 degrees of freedom two-way laser link between remote spacecraft succeeded on the first attempt. Active beam pointing based on differential wave front sensing compensates spacecraft attitude fluctuations.

Line of sight calibration for the laser ranging interferometer on-board the GRACE Follow-On mission: on-ground experimental validation.

The laser ranging interferometer (LRI) on board of the GRACE follow-on spacecraft, launched in May 2018, is the first laser interferometer to perform an inter-satellite range measurement. It is designed for ranging noise levels of 80 nm Hz for frequencies above 20 mHz, i.e.

Space-borne Bose-Einstein condensation for precision interferometry.

Owing to the low-gravity conditions in space, space-borne laboratories enable experiments with extended free-fall times. Because Bose-Einstein condensates have an extremely low expansion energy, space-borne atom interferometers based on Bose-Einstein condensation have the potential to have much greater sensitivity to inertial forces than do similar ground-based interferometers. On 23 January 2017, as part of the sounding-rocket mission MAIUS-1, we created Bose-Einstein condensates in space and conducted 110 experiments central to matter-wave interferometry, including laser cooling and trapping of atoms in the presence of the large accelerations experienced during launch.

Development of a compact optical absolute frequency reference for space with 10 instability.

We report on a compact and ruggedized setup for laser frequency stabilization employing Doppler-free spectroscopy of molecular iodine near 532 nm. Using a 30 cm long iodine cell in a triple-pass configuration in combination with noise-canceling detection and residual amplitude modulation control, a frequency instability of 6×10 at 1 s integration time and a Flicker noise floor below 3×10 for integration times between 100 and 1000 s was found. A specific assembly-integration technology was applied for the realization of the spectroscopy setup, ensuring high beam pointing stability and high thermal and mechanical rigidity.

Interferometric surface mapping of a spherical proof mass for ultra precise inertial reference sensors.

In the context of our investigations on novel inertial reference sensors for space applications, we have explored a design utilizing an optical readout of a spherical proof mass. This concept enables full drag-free operations, hence reducing proof mass residual acceleration noise to a minimum. The main limitations of this sensor are errors in position determination of the center of mass of the proof mass due to the surface topography and the involved path length changes upon rotation.

Dilatometer setup for low coefficient of thermal expansion materials measurements in the 140 K-250 K temperature range.

Space applications demand light weight materials with excellent dimensional stability for telescopes, optical benches, optical resonators, etc. Glass-ceramics and composite materials can be tuned to reach very low coefficient of thermal expansion (CTE) at different temperatures. In order to determine such CTEs, very accurate setups are needed.

A three-layer magnetic shielding for the MAIUS-1 mission on a sounding rocket.

Bose-Einstein-Condensates (BECs) can be used as a very sensitive tool for experiments on fundamental questions in physics like testing the equivalence principle using matter wave interferometry. Since the sensitivity of these experiments in ground-based environments is limited by the available free fall time, the QUANTUS project started to perform BEC interferometry experiments in micro-gravity. After successful campaigns in the drop tower, the next step is a space-borne experiment.

Interspacecraft link simulator for the laser ranging interferometer onboard GRACE Follow-On.

Link acquisition strategies are key aspects for interspacecraft laser interferometers. We present an optical fiber-based setup able to simulate the interspacecraft link for the laser ranging interferometer (LRI) on gravity recovery and climate experiment Follow-On. It allows one to accurately recreate the far-field intensity profile depending on the mispointing between the spacecraft, Doppler shifts, and spacecraft attitude jitter.

A phasemeter concept for space applications that integrates an autonomous signal acquisition stage based on the discrete wavelet transform.

We describe a phasemeter designed to autonomously acquire and track a heterodyne signal with low signal-to-noise ratio in a frequency band that spans from 1 MHz to 25 MHz. The background driving some of the design criterions of the phasemeter comes from studies on future space mission concepts such as orbiting gravitational wave observatories and next generation geodesy missions which all rely on tracking phasemeters in order to meet their mission goal. The phasemeter has been implemented within a field programmable gate array trying to minimize the requirement of computational resources and its performance has been tested using signal generators.

Mathematical model of thermal shields for long-term stability optical resonators.

Modern experiments aiming at tests of fundamental physics, like measuring gravitational waves or testing Lorentz Invariance with unprecedented accuracy, require thermal environments that are highly stable over long times. To achieve such a stability, the experiment including typically an optical resonator is nested in a thermal enclosure, which passively attenuates external temperature fluctuations to acceptable levels. These thermal shields are usually designed using tedious numerical simulations or with simple analytical models.

Atom interferometry in space: thermal management and magnetic shielding.

Atom interferometry is an exciting tool to probe fundamental physics. It is considered especially apt to test the universality of free fall by using two different sorts of atoms. The increasing sensitivity required for this kind of experiment sets severe requirements on its environments, instrument control, and systematic effects.

Interferometric characterization and modeling of pathlength errors resulting from beamwalk across mirror surfaces in LISA.

An alternative payload concept with in-field pointing for the laser interferometer space antenna utilizes an actuated mirror in the telescope for beam tracking to the distant satellite. This actuation generates optical pathlength variations due to the resulting beamwalk over the surface of subsequent optical components, which could possibly have a detrimental influence on the accuracy of the measurement instrument. We have experimentally characterized such pathlength errors caused by a λ/10 mirror surface and used the results to validate a theoretical model.

Note: silicon carbide telescope dimensional stability for space-based gravitational wave detectors.

Space-based gravitational wave detectors are conceived to detect gravitational waves in the low frequency range by measuring the distance between proof masses in spacecraft separated by millions of kilometers. One of the key elements is the telescope which has to have a dimensional stability better than 1 pm Hz(-1/2) at 3 mHz. In addition, the telescope structure must be light, strong, and stiff.

Ultrastable assembly and integration technology for ground- and space-based optical systems.

Optical metrology systems crucially rely on the dimensional stability of the optical path between their individual optical components. We present in this paper a novel adhesive bonding technology for setup of quasi-monolithic systems and compare selected characteristics to the well-established state-of-the-art technique of hydroxide-catalysis bonding. It is demonstrated that within the measurement resolution of our ultraprecise custom heterodyne interferometer, both techniques achieve an equivalent passive path length and tilt stability for time scales between 0.

Ultrahigh long-term dimensional stability of a sapphire cryogenic optical resonator.

We report on the ultrahigh long-term dimensional stability of a crystalline cryogenic optical resonator (CORE) cooled to liquid-helium temperature. The frequency of a Nd:YAG laser stabilized to a CORE was compared over long times with an independent laser system, a frequency-doubled Nd:YAG laser stabilized to a hyperfine line of molecular iodine at 532 nm. Over a 6-month period the drift was less than 3 kHz.

High-resolution Doppler-free molecular spectroscopy with a continuous-wave optical parametric oscillator.

We present a reliable, narrow-linewidth (100-kHz) continous-wave optical parametric oscillator (OPO) suitable for high-resolution spectroscopy applications. The singly resonant OPO with a resonated pump is based on periodically poled lithium niobate crystal and features a specially designed intracavity etalon, which permits precise tuning to any desired wavelength in a wide range. We demonstrate Doppler-free spectroscopy of a rovibrational transition of methane at 3.