Random lasing and amplified spontaneous emission from silk inverse opals: Optical gain enhancement via protein scatterers

Abstract

Gain amplification and coherent lasing lines through random lasing (RL) can be produced by a random distribution of scatterers in a gain medium. If these amplified light sources can be seamlessly integrated into biological systems, they can have useful bio-optical applications, such as highly accurate sensing and high-resolution imaging. In this paper, a fully biocompatible light source showing RL and amplified spontaneous emission (ASE) with a reduced threshold is reported. Random cavities were induced in a biocompatible silk protein film by incorporating an inverse opal with an inherent disorder and a biocompatible dye for optical gain into the film. By choosing the appropriate air-sphere diameters, clear RL spikes in the emission spectra that were clearly distinguished from those of the ASE were observed in the silk inverse opal (SIO) with optical gain. Additionally, the RL output exhibited spatial coherence; however, the ASE did not. The high surface-to-volume ratio and amplification of the SIO led to highly efficient chemosensing in the detection of hydrogen chloride vapor. Moreover, SIO could be miniaturized to be made suitable for injection into biological tissues and obtain RL signals. Our results, which open the way for the development of a new generation of miniaturized bio-lasers, may be considered as the first example of engineered RL with biocompatible materials.

Biocompatible Polymer and Protein Microspheres with Inverse Photonic Glass Structure for Random Micro‐Biolasers

“…The threshold energy is comparable to other polymeric random lasers based on photonic glass structure [ 8 ] and inverse opals. [ 18 ]…”

“…[ 13 ] To date, random microlasers are highly limited to semiconductor‐based structure such as the clusters of ZnO nanoparticles, [ 14 ] and ZnO microwires [ 15 ] whereas organic random lasers generally have a larger size in a range of millimeter scale. [ 16–18 ] Compared with semiconductor random microlasers, organic random microlasers may have several advantages including low‐cost fabrication, flexible properties, and lightweight. [ 19–21 ] However, obtaining small organic random microlasers is challenging as organic materials tend to have low refractive index and a highly disordered medium requires careful optimization.…”

Toward Electrically Pumped Organic Lasers: A Review and Outlook on Material Developments and Resonator Architectures

“…Random lasing from the fully biofriendly silk inverse opals (SIOs) comprising silk protein and fluorescein sodium was also applied as a sensor for vapors of hydrogen chloride. [ 156 ]…”

Silk Nanocrack Origami for Controllable Random Lasers

“…Previously, silk inverse opal RLs were fabricated by applying SF solution on an array of polymer spheres, and then the spheres were etched to use remaining voids as scatterers. [27,35] Moreover, random lasing was analyzed in terms of pore alignment by using SF scaffolds. [36] In another study, SF was utilized as a sacrificial scaffold to prepare porous monoliths to obtain RLs.…”