Ahmad Bawamia

Corrigendum: STE-QUEST—test of the universality of free fall using cold atom interferometry (2014 Class. Quantum Grav. 31 115010)

The theory of general relativity describes macroscopic phenomena driven by the influence of gravity while quantum mechanics brilliantly accounts for microscopic effects. Despite their tremendous individual success, a complete unification of fundamental interactions is missing and remains one of the most challenging and important quests in modern theoretical physics. The spacetime explorer and quantum equivalence principle space test satellite mission, proposed as a medium-size mission within the Cosmic Vision program of the European Space Agency (ESA), aims for testing general relativity with high precision in two experiments by performing a measurement of the gravitational redshift of the Sun and the Moon by comparing terrestrial clocks, and by performing a test of the universality of free fall of matter waves in the gravitational field of Earth comparing the trajectory of two Bose–Einstein condensates of 85Rb and 87Rb. The two ultracold atom clouds are monitored very precisely thanks to techniques of atom interferometry. This allows to reach down to an uncertainty in the Eötvös parameter of at least 2 × 10−15. In this paper, we report about the results of the phase A mission study of the atom interferometer instrument covering the description of the main payload elements, the atomic source concept, and the systematic error sources.

Micro-integrated extended cavity diode laser with integrated optical amplifier for precision spectroscopy in space

GaAs diode laser-based hybrid micro-integration technology meets the demand for precision spectroscopy applications in space for compact, robust, and energy-efficient laser modules. It supports applications at wavelengths ranging from 630 nm to 1200 nm and is already used for quantum optics experiments in space [1].

Determination of the thermal lensing in a broad area semiconductor laser amplifier

The local refractive index in the active medium of semiconductor lasers is affected by heat generated from the injection of carriers, non-radiative recombination and absorption of photons. Temperature gradients arising from generation and diffusion of the heat induce a refractive index distribution and contribute to the formation of a positive lens in the lateral dimension of the active area. The thermal lens may be approximated by the coefficient γ which relates the local refractive index across the laser diode to the effective refractive index as: n(x) = n0(1-γ2X2/2), (1) where n0 is the effective refractive index and x the lateral coordinate. This thermal lens significantly influences the propagation of lateral optical modes through the amplifier. Using the amplifier as part of a diode laser with internal or external resonator, the thermal lens may also determine the properties of the lateral modes generated and hence may effect beam quality.