Optics (physics.optics)

Abstract: In this paper, we present a study on partially pumped, single wavelength random lasing with tunability controlled by temperature in a solid-state random laser based on DCM (4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran) doped PMMA (polymethyl methacrylate) dye. By carefully shaping the spatial profile of the pump, we achieve low-threshold, single-mode random lasing with excellent rejection of side lobes. Notably, we observe that varying the temperature induces changes in the refractive index of the PMMA-DCM layer, resulting in a blue-shift of the lasing wavelength. Moreover, we demonstrate continuous tunability of the lasing wavelength over an impressive bandwidth of 8 nm.

Abstract: We report on a comprehensive study carried out to reveal the impact of surface roughness on the incident light absorption. In practice, we have used analytical approach of solving Maxwell equations by modifying boundary conditions that take into account the surface roughness in metallic or dielectric films. Our approach reveals interference linked terms that modify the absorption dependence on the surface roughness characteristics, light wavelength,polarization and incidence angle. We have discussed the limits of our approach that hold valid from optics to microwave region. Polarization and angular dependences of roughness induced absorption are revealed. Existence of an incident angle and a wavelength for which the absorptance of rough surface becomes equal to the absorptance of flat surface is predicted. Relaying on this phenomena a method of determination of roughness correlation length is suggested.

Abstract: Miniaturized spectrometry system is playing an essential role for materials analysis in the development of in-situ or portable sensing platforms across research and industry. However, there unavoidably exists trade-offs between the resolution and operation bandwidth as the device scale down. Here, we report an extreme miniaturized computational photonic molecule (PM) spectrometer utilizing the diverse spectral characteristics and mode-hybridization effect of split eigenfrequencies and super-modes, which effectively eliminates the inherent periodicity and expands operation bandwidth with ultra-high spectral resolution. These results of dynamic control of the frequency, amplitude, and phase of photons in the photonic multi-atomic systems, pave the way to the development of benchtop sensing platforms for applications previously unfeasible due to resolution-bandwidth-footprint limitations, such as in gas sensing or nanoscale biomedical sensing.