Young's type interference for probing the mode symmetry in photonic structures

Generalized Fano lineshapes reveal exceptional points in photonic molecules

The optical behavior of coupled systems, in which the breaking of parity and time-reversal symmetry occurs, is drawing increasing attention to address the physics of the exceptional point singularity, i.e., when the real and imaginary parts of the normal-mode eigenfrequencies coincide. At this stage, fascinating phenomena are predicted, including electromagnetic-induced transparency and phase transitions. To experimentally observe the exceptional points, the near-field coupling to waveguide proposed so far was proved to work only in peculiar cases. Here, we extend the interference detection scheme, which lies at the heart of the Fano lineshape, by introducing generalized Fano lineshapes as a signature of the exceptional point occurrence in resonant-scattering experiments. We investigate photonic molecules and necklace states in disordered media by means of a near-field hyperspectral mapping. Generalized Fano profiles in material science could extend the characterization of composite nanoresonators, semiconductor nanostructures, and plasmonic and metamaterial devices.

Fano lineshapes are found in many photonic systems where discrete and extended spectra interfere. Here, the authors extend this description and introduce generalized Fano lineshapes to describe the results from hyperspectral mapping around an exceptional point in a coupled-cavity system.

Mode Profiling of Semiconductor Nanowire Lasers

We experimentally determine the lasing mode(s) in optically pumped semiconductor nanowire lasers. The spatially resolved and angle-resolved far-field emission profiles of single InP nanowire lasers lying horizontally on a SiO2 substrate are characterized in a microphotoluminescence (μ-PL) setup. The experimentally obtained polarization dependent far-field profiles match very well with numerical simulations and enable unambiguous identification of the lasing mode(s). This technique can be applied to characterize lasing modes in other type of nanolasers that are integrated on a substrate in either vertical or horizontal configurations.

Resolving parity and order of Fabry-Pérot modes in semiconductor nanostructure waveguides and lasers: Young's interference experiment revisited

Semiconductor nanostructures such as nanowires and nanoribbons functioning as Fabry-Pérot (F-P)-type optical cavities and nanolasers have attracted great interest not only for their potential use in nanophotonic systems but also to understand the physics of light-matter interactions at the nanoscale. Due to their nanoscale dimensions, new techniques need to be continuously developed to characterize the nature of highly confined optical modes. Furthermore, the inadequacy of typical far-field photoluminescence experiments for characterizing the nanoscale cavity modes such as parity and order has precluded efforts to obtain precise information that is required to fully understand these cavities. Here, we utilize a modified Young's interference method based on angle-resolved microphotoluminescence spectral technique to directly reveal the parity of F-P cavity modes in CdS nanostructures functioning as waveguides and nanolasers. From these analyses, the mode order can be straightforwardly obtained with the help of numerical simulations. Moreover, we show that the Young's technique is a general technique applicable to any F-P type cavities in nanoribbons, nanowires, or other photonic and plasmonic nanostructures.

Ultrafast non-local control of spontaneous emission

The radiative interaction of solid-state emitters with cavity fields is the basis of semiconductor microcavity lasers and cavity quantum electrodynamics (CQED) systems. Its control in real time would open new avenues for the generation of non-classical light states, the control of entanglement and the modulation of lasers. However, unlike atomic CQED or circuit quantum electrodynamics, the real-time control of radiative processes has not yet been achieved in semiconductors because of the ultrafast timescales involved. Here we propose an ultrafast non-local moulding of the vacuum field in a coupled-cavity system as an approach to the control of radiative processes and demonstrate the dynamic control of the spontaneous emission (SE) of quantum dots (QDs) in a photonic crystal (PhC) cavity on a ∼ 200 ps timescale, much faster than their natural SE lifetimes.

Engineering the mode parity of the ground state in photonic crystal molecules

We propose a way to engineer the design of photonic molecules, realized by coupling two photonic crystal cavities, that allows an accurate control of the parity of their ground states. The spatial distribution of the fundamental mode of photonic molecules can be tuned from a bonding to an antibonding character by a local and continuous modification of the dielectric environment in between the two coupled cavities. In the systems that we investigate the transition could be experimentally accomplished by post-fabrication methods in either a reversible or an irreversible way. We notably find that the mode parity exchange is tightly related to a dramatic variation of the far field emission pattern, leading to the possibility to exploit these systems and techniques for future applications in optoelectronics.