Over the last two decades the cold-atom physics has matured from proof-of-principle demonstrations to a versatile platform for precision measurements and study of quantum phenomena. Ultra-cold atomic ensembles have been used both for technological and fundamental science applications. To fully exploit their potential, a precise measurement and control of the atom number in the ensemble is crucial. We report on a precise, minimally destructive measurement technique that can be used to prepare an atomic ensemble with a desired atom number. The measurement relies on the dispersive light-atom interaction; thus it is expected to have a negligible effect on the ensemble temperature and to induce minimal decoherence in the atomic quantum state. As a result, it can be used to perform quantum-enhanced measurements and prepare the atom-number state at the start of an interferometer sequence.
Optical communications (OC) is an emerging transformative technology for scientific, commercial, and defense applications. Compared to radio-frequency (RF) communications, it can offer higher bandwidth, lower power consumption, and reduced size and mass of transceivers. Narrow, directed beams of light, OC can in principle increase link security and enable optical quantum communication, which provides absolute physical security. Free-space optical satellite networks will employ both satellite-satellite and satellite-Optical Ground Station (OGS) optical links. Optical Communication terminals (OCT) on-board a satellite have to comply to volume and energy limitations, restricting the available optical power and optical system parameters. In this paper, we perform an optical link design trade-off between an OGS and a Low Earth Orbit (LEO) satellite. We study the feasibility of utilizing Skinakas Observatory in Greece as an OGS, for realistic OCT specifications and based on the criterion of link budget. We model an optical downlink and compute the results for various critical parameters of the OCT. Our results confirm the feasibility of such a link for optical communication purposes.
We report a novel Optical Beam Steering Technique (OBST) for fiber to free-space to fiber coupling with extreme stability of the coupling efficiency and high tolerance to temperature fluctuations. The compact optical system is based near monolithic (ZERODUR) fiber couplers and relies on optical wedges and plates to perform the fine-steering of the optical beam. In our approach, we use coarsely aligned fiber couplers and then perform the fine alignment using the wedges and plates. This separation of fine and course tuning significantly reduces the manufacturing and assembly requirements of the fiber couplers. At the same time, it results in a much-reduced sensitivity to drifts increases the stability and reliability of the breadboard. OBST achieves a coupling efficiency (CE) of 94% with long-term fluctuation of 0.1% RMS at stable temperatures and 1.4% under repeated vacuum temperature cycling over a 30K range. Even under extreme mechanical stress (random vibrations of up to 8.3g) the RMS vibration of the coupling efficiency were less than 0.3% RMS. The optical breadboard technology has therefore achieved TRL5.
We present the theoretical analysis of a novel optical beam steering technique (OBST) for fiber to free-space to fiber coupling schemes on optical breadboards. This technique uses glass wedges and plates to correct misalignments in the position and angle of beams on the breadboard. It can be used in any application where stable and robust coupling of light from an input to an output fiber is required, such as laser distribution boards for cold atom experiments in space. We examine the optical performance in terms of coupling efficiency (CE) for a number of different OBST systems and compare the results. Coupling efficiencies above 95% and positional and angular resolution of smaller than 5 μm and 5 μrad can be achieved using this technology.
We present a novel optical beam steering technique (OBST) for fiber to free-space to fiber coupling schemes on optical breadboards, which uses glass wedge pairs and plates to correct for angular and translational misalignments respectively. This technique finds application in proposed missions for atom quantum experiments in space, e.g. where laser beams are used to cool and manipulate atomic clouds. The key advantage compared to the conventional beam steering is that OBST permits extremely fine adjustments whilst being far less sensitive to alignment errors and mechanical drifts. Beam steering resolutions of better than 5 μrad and 2 μm are achieved, resulting in a resolution in coupling efficiency (CE) of 0.1%. The inclusion of OBST on an optical breadboard reduces the requirements on the pointing and position precision adjustment of the fiber couplers, leading to a much-simplified design. The simpler construction of the couplers combined with the reduced sensitivity to drifts increases the stability-reliability of the breadboard and reduces the production duration and cost. We demonstrate CE of up to 90%, with a stability of 0.2% in a stable temperature environment and 2% over a temperature range from 10-40 degrees Celsius. We do not observe any change in the performance after large temperature changes.
Thomas Fernholz, Robin Stevenson, Michael Hush, Igor Lesanovsky, Thomas Bishop, Fabio Gentile, Sindhu Jammi, Tadas Pyragius, Mark Bason, Hèctor Mas, Saurabh Pandey, Georgios Vasilakis, Konstantinos Poulios, Wolf von Klitzing
We discuss a scheme to implement a gyroscopic atom sensor with magnetically trapped ultra-cold atoms. Unlike standard light or matter wave Sagnac interferometers no free wave propagation is used. Interferometer operation is controlled only with static, radio-frequency and microwave magnetic fields, which removes the need for interferometric stability of optical laser beams. Due to the confinement of atoms, the scheme may allow the construction of small scale portable sensors. We discuss the main elements of the scheme and report on recent results and efforts towards its experimental realization.
KEYWORDS: High power lasers, Chemical species, Semiconductor lasers, Laser systems engineering, Modulation, Rubidium, Tunable lasers, Single mode fibers, Laser stabilization, Diodes
Since the introduction of laser-cooling techniques for neutral atoms, the enhancement of high-power lasers with excellent spectral and spatial quality has been an important research subject. We report a new principle of using high-power laserdiodes directly in an external cavity. The very compact design offers an output power of up to 1 W and an excellent beam quality (M2 < 1.2). The coupling efficiency for a single mode fiber exceeds 60%. The center wavelength can be tuned between 775 nm and 785 nm. This laser operates single mode with a mode-hop free tuning range of up to 15 GHz without current modulation and a side-mode suppression better than 55 dB. Demonstrating the suitability for neutral atom cooling we used this laser as light source in the production of a BEC of over a million 87Rb atoms.
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