12 research outputs found
A Photonic Thermalization Gap In Disordered Lattices
The formation of gaps - forbidden ranges in the values of a physical parameter - is common to a variety of physical systems: from energy bandgaps of electrons in periodic lattices and their analogues in photonic, phononic and plasmonic systems to pseudo-energy gaps in aperiodic quasicrystals. Here, we predict a thermalization gap for light propagating in finite disordered structures characterized by disorder-immune chiral symmetry - the appearance of the eigenvalues and eigenvectors in skew-symmetric pairs. In these systems, the span of sub-thermal photon statistics is inaccessible to input coherent light, which - once the steady state is reached - always emerges with super-thermal statistics no matter how small the disorder level. We formulate an independent constraint of the input field for the chiral symmetry to be activated and the gap to be observed. This unique feature enables a new form of photon-statistics interferometry: the deterministic tuning of photon statistics via controlled excitation symmetry breaking realized by sculpting the amplitude or phase of the input coherent field
Coherence measurements of scattered incoherent light for lensless identification of an object’s location and size
In absence of a lens to form an image, incoherent or partially coherent light
scattering off an obstructive or reflective object forms a broad intensity
distribution in the far field with only feeble spatial features. We show here
that measuring the complex spatial coherence function can help in the
identification of the size and location of a one-dimensional object placed in
the path of a partially coherent light source. The complex coherence function
is measured in the far field through wavefront sampling, which is performed via
dynamically reconfigurable slits implemented on a digital micromirror device
(DMD). The impact of an object -- parameterized by size and location -- that
either intercepts or reflects incoherent light is studied. The experimental
results show that measuring the spatial coherence function as a function of the
separation between two slits located symmetrically around the optical axis can
identify the object transverse location and angle subtended from the detection
plane (the ratio of the object width to the axial distance from the detector).
The measurements are in good agreement with numerical simulations of a forward
model based on Fresnel propagators. The rapid refresh rate of DMDs may enable
real-time operation of such a lensless coherency imaging scheme.Comment: 9 pages, 7 figure