Author Archives: wvk_sm9je57j

Simple precision measurements of optical beam sizes

The paper is in the top 10 most downloaded papers of Applied Optics for November and December 2018.

Applied Optics 57 9863 (2018) 

M. Mylonakis, S. Pandey, K. G. Mavrakis, G. Drougakis, G. Vasilakis, D. G. Papazoglou, and W. von Klitzing 

doi: 10.1364/AO.57.009863 

Abstract: We present a simple high-precision method to quickly and accurately measure the diameters of Gaussian beams, Airy spots, and central peaks of Bessel beams ranging from sub-millimeter to many centimeters without special- ized equipment. By simply moving a wire through the beam and recording the relative losses using an optical power meter, one can easily measure the beam diameters with a precision of 1%. The accuracy of this method has been experimentally verified for Gaussian beams down to the limit of a commercial slit-based beam profiler (3%).

Image of the setup of the beam diameter measurement

Setup of the beam diameter measurement

Plot of the real beam size calculated from the minimum transmitivity.

Real beam size as a function of the minimum transmitivity.

 

Antireflection coated semiconductor laser amplifier for Bose-Einstein condensation experiments

AIP Advances 8 095020 (2018)  

S. Pandey, H. Mas, G. Drougakis, K. G. Mavrakis, M. Mylonakis, G. Vasilakis, V. Bolpasi, and W. von Klitzing 

https://doi.org/10.1063/1.5047839

Abstract

We present a slave laser highly suitable for the preparation and detection of 87Rb Bose-Einstein condensates (BEC). A highly anti-reflection coated laser diode serves as an optical amplifier, which requires neither active temperature stabilization nor dedicated equipment monitoring the spectral purity of the amplified light. The laser power can be controlled with a precision of 10μW in 70mW with relative fluctuations down to 2 × 10^−4. Due to its simplicity and reliability, this slave laser will be a useful tool for laboratory, mobile, or even space-based cold-atom experiments. By the way of demonstration this slave laser was used as the sole 780nm light-source in the production of 3×10^4 BECs in a hybrid magnetic/dipole trap.

Figure 1: Stability of the power of a AR-coated diode lase slave.

 

Collimation of laser beams from optical fibers

An ESA milestone reached.

Our ESA Space-Optics project has reached a major milestone:  We have finished the development of a novel beam collimation technique, which works allows us to adjust the waist of the laser beam emitted from a fibre coupler to an arbitrary position simply by maximising the peak intensity of the laser beam at some other position.

ZERODUR collimator

This is a fiber collimator manufactured from the ultra-low expansion material ZERODUR.

In order to make the coupler space-compatible it is manufactured from ultra-low-expansion ceramics (ZERODUR) and has no moving parts.

Quantum Technologies in Space (QTSpace)

We have been appointed the Greek representatives of “Quantum Technologies in Space (QTSpace)”.

The scientific and technological legacy of the 20th century includes milestones such as quantum mechanics and pioneering space missions. Both endeavours have opened new avenues for the furthering of our understanding of Nature, and are true landmarks of modern science. Quantum theory and space science form building blocks of a powerful research framework for exploring the boundaries of modern physicsthrough the unique working conditions offered by experimental tests performed in space.

Space-based sources of entangled photons promise the formation of global quantum communication networks, long-distance tests of quantum theory and the interplay between relativity and quantum entanglement.

 

Long free-fall times enable high-precision tests of general relativity and tests of the equivalence principle for quantum systems.

Harnessing microgravity, high vacuum and low temperature of deep space promises allowing the study of deviations from standard quantum theoryfor high-mass test particles. Space-based experiments of metrology and sensing will push the precision of clocks, mass detectors and transducers towards the engineering of novel quantum technologies.

Matter-wave interferometers using TAAP rings

New Journal of Physics   18   075014 (2016)

P. Navez, S. Pandey, H. Mas, K. Poulios, T. Fernholz, and W. von Klitzing

doi: 10.1088/1367-2630/18/7/075014

Fig 2

Figure 2. Experimental realisation of a ring-shaped TAAP waveguide. The radius of the ring is R = 570 μm.

Abstract: We present two novel matter-wave Sagnac interferometers based on ring-shaped time-averaged adiabatic potentials, where the atoms are put into a superposition of two different spin states and manipulated independently using elliptically polarized rf-fields. In the first interferometer the atoms are accelerated by spin-state-dependent forces and then travel around the ring in a matter-wave guide. In the second one the atoms are fully trapped during the entire interferometric sequence and are moved around the ring in two spin-state-dependent `buckets’.

Figure 6.

Figure 6. Experimental realisation of arbitrary traps. The fitted radius is 440 μm and 450 μm respectively.  Note that (a) and (b) are taken with identical experimental conditions and differ only in the state of the atoms. The axis of the circular rf component and the one of the tilted modulation are not orthogonal.

Corrections to the ideal Sagnac phase are investigated for both cases. We experimentally demonstrate the key atom-optical elements of the interferometer such as the independent manipulation of two different spin states in the ring-shaped potentials under identical experimental conditions.