Figure 3
From: On the Existence of Low-Mass Dark Matter and its Direct Detection
Illustration of the suggested experiment, the hardware for which can be provided by the proposed ‘MAQRO’ space-craft23.
(a), Location of the space-craft at Lagrange point 2 in the context of our solar system (not to scale). (b), Close-up of the optical arrangement: a compound objective lens provides high numerical aperture focusing for laser light to create a gradient-force dipole trap for a micron-scale particle. Light, which diverges strongly after the particle, is collected by a lens. Interference between the laser light and the light scattered coherently by the particle gives rise to a difference in intensity across the cross-section which, when measured by balanced photodiodes (PDs), provides sub-wavelength position information in three dimensions25. (c), A further close-up, showing s-wave scattering of a χ DM particle, with an approximately plane-wave incident wavefunction and an example scattering outgoing direction with the associated recoil of the test particle.
