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Precise knowledge of the local density of optical states (LDOS) is fundamental to understanding nanophotonic systems and devices. Complete LDOS mapping requires resolution in energy, momentum, and space, and hence a versatile measurement approach capable of providing simultaneous access to the LDOS components is highly desirable. Here, we explore a modality of cathodoluminescence spectroscopy able to resolve, in single acquisitions, the dispersion in energy and momentum of the radiative LDOS. We perform measurements on a titanium nitride diffraction grating, bulk molybdenum disulfide, and silicon to demonstrate that the technique can probe and disentangle the dispersion of coherent and incoherent cathodoluminescence signals. The approach presented raises cathodoluminescence spectroscopy to a versatile tool for subwavelength design and optimization of nanophotonic devices in the reciprocal space.

Hyperuniform geometries feature correlated disordered topologies which follow from a tailored k-space design. Here, we study gold plasmonic hyperuniform disordered surfaces and, by momentum spectroscopy, we report evidence of k-space engineering on both light scattering and light emission. Even if the structures lack a well-defined periodicity, emission and scattering are directional in ring-shaped patterns. The opening of these rotational-symmetric patterns scales with the hyperuniform correlation length parameter as predicted via the spectral function method.

Here, we investigate the mechanism of a random-lasing-based sensor which shows p H sensitivity exceeding by 2 orders of magnitude that of a conventional fluorescence sensor. We explain the sensing mechanism as related to gain modifications and lasing-threshold nonlinearities. A dispersive diffusive lasing theory matches the experimental results well, and it allows us to predict the optimal sensing conditions and a maximal sensitivity as large as 200 times that of an identical fluorescence-based sensor. The lack of complex alignment and the high sensitivity make this mechanism promising for future biosensing applications.

Lasing from cells has recently been subject of thorough investigation because of the potential for sensitive and fast biosensing. Yet, lasing from individual cells has been studied in high-quality resonators, resulting in limited dependence of the lasing properties on the cellular microenvironment. Here, lasing is triggered by cells floating in a low quality factor resonator composed of a disposable poly(methyl methacrylate) (PMMA) cell counting-slide, hence in absence of conventional high-reflectivity optical cavities. The exceptional spectral narrowing and the steep slope increase in the input–output energy diagram prove occurrence of laser action in presence of cells. The observed biolasing is an intrinsically dynamic signal, with large fluctuations in intensity and spectrum determined by the optical properties of the individual cell passing through the pump beam. Numerical simulations of the scattering efficiency rule out the possibility of optical feedback from either WGM (whispering gallery mode) or multiple scattering within the cell, and point to the enhanced directional scattering field as the crucial contribution of cells to the laser action. Finally, principal component analysis of lasing spectra measured from freely diffusing cells yields spectral fingerprints of cell populations, which allows discriminating cancer from healthy Rattus glial cells with high degree of confidence.

The understanding of the phenomena underlying the interaction of photons with dielectric, metallic and hybrid microand nano-structures and the development of advanced fabrication tools have paved the way to the realization of complex, nanostructured photonic structures, with tailored and exotic absorption and emission properties. Among such nanostructured materials, polymer nanofibers have intriguing and specific properties: they can embed molecular and quantum dot light sources, they can transport light among distant emitters and they can be arranged in 2-dimensional and 3-dimensional architectures in a controlled fashion, forming complex networks of interacting light emitters. However, coupling of light with polymer nanofibers depends on many variables, being often limited by the arrangement and positioning of the nanoscale light-sources, and by the fiber geometry. Here we report on the fabrication of active polymer nanofibers with improved surface properties and controlled geometry by electrospinning. Polarization and momentum spectroscopy of light emitted by molecular compounds and single quantum dots embedded in electrospun polymer fibers, evidence that efficient, nanostructured photon sources with targeted polarization and coupling efficiency can be realized in nanofiber-based photonic environments.