Lane Martin

Anderson localization in optical waveguide arrays with off-diagonal coupling disorder

We observe the transition from extended to Anderson-localized states in silica waveguide arrays exhibiting off-diagonal coupling disorder.

Octave-spanning coherent perfect absorption in a thin silicon film

Although optical absorption is an intrinsic materials property, it can be manipulated through structural modification. Coherent perfect absorption increases absorption to 100% interferometrically but is typically realized only over narrow bandwidths using two laser beams with fixed phase relationship. We show that engineering a thin films photonic environment severs the link between the effective absorption of the film and its intrinsic absorption while eliminating, in principle, bandwidth restrictions. Employing thin aperiodic dielectric mirrors, we demonstrate coherent perfect absorption in a 2 μm thick film of polycrystalline silicon using a single incoherent beam of light at all the resonances across a spectrally flat, octave-spanning near-infrared spectrum, ≈800-1600  nm. Critically, these mirrors have wavelength-dependent reflectivity devised to counterbalance the decline in silicons intrinsic absorption at long wavelengths.

Basis-neutral Hilbert-space analyzers

Interferometry is one of the central organizing principles of optics. Key to interferometry is the concept of optical delay, which facilitates spectral analysis in terms of time-harmonics. In contrast, when analyzing a beam in a Hilbert space spanned by spatial modes – a critical task for spatial-mode multiplexing and quantum communication – basis-specific principles are invoked that are altogether distinct from that of ‘delay’. Here, we extend the traditional concept of temporal delay to the spatial domain, thereby enabling the analysis of a beam in an arbitrary spatial-mode basis – exemplified using Hermite-Gaussian and radial Laguerre-Gaussian modes. Such generalized delays correspond to optical implementations of fractional transforms; for example, the fractional Hankel transform is the generalized delay associated with the space of Laguerre-Gaussian modes, and an interferometer incorporating such a ‘delay’ obtains modal weights in the associated Hilbert space. By implementing an inherently stable, reconfigurable spatial-light-modulator-based polarization-interferometer, we have constructed a ‘Hilbert-space analyzer’ capable of projecting optical beams onto any modal basis.

Hanbury Brown and Twiss anticorrelation in disordered photonic lattices

We report measurements of Hanbury Brown and Twiss correlation of coherent light transmitted through disordered one-dimensional photonic lattices. Although such a lattice exhibits transverse Anderson localization when a single input site is excited, uniform excitation precludes its observation. By examining the Hanbury Brown\char21{}Twiss correlation for a uniformly excited disordered lattice, we observe intensity anticorrelations associated with photon antibunching\char22{}a signature of non-Gaussian statistics. Although the measured average intensity distribution is uniform, transverse Anderson localization nevertheless underlies the observed anticorrelation.

Two-photon discrete speckle in Anderson-disordered lattices

Two photons in an entangled, spatially correlated (anti-correlated) state transmitted through an Anderson disordered lattice maintain their correlation (anti-correlation) but exhibit coincidence-map speckle in the Fourier plane.

Transition from Anderson co-Localization to anti-co-Localization of Entangled Photon Pairs in Disordered Photonic Waveguide Arrays

We experimentally and theoretically investigate the evolution of different types of two photon entangled states in disordered photonic waveguide arrays. We present a transition from Anderson co-localization to Anderson anti-co-localization.

Observation of Anderson co-localization of spatially entangled photon pairs

We report the first observation of Anderson co-localization of spatially entangled photon pairs propagating through random optical waveguide lattices with controllable off-diagonal disorder.