Enhanced nonlinear optical response from dihydroxy(5,10,15,20-tetraphenyl porphyrinato)tin(iv) or SnTPP in a fully plastic photonic crystal microcavity

Mild Sol-Gel Conditions and High Dielectric Contrast: A Facile Processing toward Large-Scale Hybrid Photonic Crystals for Sensing and Photocatalysis

Solution processing of highly performing photonic crystals has been a towering ambition for making them technologically relevant in applications requiring mass and large-area production. It would indeed represent a paradigm changer for the fabrication of sensors and for light management nanostructures meant for photonics and advanced photocatalytic systems. On the other hand, solution-processed structures often suffer from low dielectric contrast and poor optical quality or require complex deposition procedures due to the intrinsic properties of components treatable from solution. This work reports on a low-temperature sol-gel route between the alkoxides of Si and Ti and poly(acrylic acid), leading to stable polymer-inorganic hybrid materials with tunable refractive index and, in the case of titania hybrid, photoactive properties. Alternating thin films of the two hybrids allows planar photonic crystals with high optical quality and dielectric contrast as large as 0.64. Moreover, low-temperature treatments also allow coupling the titania hybrids with several temperature-sensitive materials including dielectric and semiconducting polymers to fabricate photonic structures. These findings open new perspectives in several fields; preliminary results demonstrate that the hybrid structures are suitable for sensing and the enhancement of the catalytic activity of photoactive media and light emission control.

Norepinephrine exhibits thermo-optical nonlinearity under physiological conditions

Norepinephrine (NE), a crucial modulatory neurotransmitter, plays a significant role in human physiology. Here, we use the Z-scan technique to investigate the nonlinear properties of NE at physiological conditions. Results reveal that NE exhibits thermo-optical nonlinearity. Outcomes can be utilized to investigate noradrenergic processes in correlation with various diseases.

Strategies for Dielectric Contrast Enhancement in 1D Planar Polymeric Photonic Crystals

Historically, photonic crystals have been made of inorganic high refractive index materials coupled to air voids to maximize the dielectric contrast and in turn the light confinement. However, these systems are complex, costly, and time-demanding, and the fabrication processes are difficult to scale. Polymer structures promise to tackle this issue thanks to their easy solution and melt processing. Unfortunately, their low dielectric contrast limits their performance. In this work, we propose a concise but exhaustive review of the common polymers employed in the fabrication of planar 1D photonic crystals and new approaches to the enhancement of their dielectric contrast. Transfer matrix method modeling will be employed to quantify the effect of this parameter in standardized structures and to propose a new polymer structure for applications dealing with light management.