| Summary: | Biological microlasers have positioned themselves as a potent tool for the
detection and identification of biomolecules in the last decade. The key
advantages of laser-based detection over fluorescence-based methods
include signal amplification, tighter linewidth, and superior signal-to-noise
ratio, culminating in a remarkable increase in detection sensitivity. Moreover,
due to the nonlinearity of the signal at the lasing threshold, laser emission
can offer improved axial spatial resolution. The vast diversity in laser
parameters such as threshold, intensity, and transverse mode makes lasers
suitable candidates for anti-counterfeiting techniques. Despite of recent
progress in achieving lasing for molecular biosensing and anti-counterfeiting
labeling, the challenges in raw material fabrication and physical property
limitations often lead to micro-lasers that lack versatility and functionality in
real world applications. Therefore, this dissertation explores the potential of
using reconfigurable materials hydrogels to develop a platform that is
versatile and well-suited for both chemical sensing and physical anticounterfeiting.
For better understanding of this dissertation, we begin with a brief review with
the introduction of biological lasers and characteristics of hydrogels, then we
introduce the background of applications in biochemistry and security
techniques (Chapter 1 and Chapter 2). In Chapter 3 and 4, we successfully
developed a Whispering Gallery Mode (WGM) hydrogel biological microlaser,
capable of detecting variations in molecular distances and differentiating
molecular sizes based on lasing threshold. The study also demonstrates the
microlaser's ability to encapsulate and analyze living organisms with superior
sensitivity compared to traditional fluorescence analysis. Moving to physical
applications in Chapter 5 and Chapter 6, we harnessed the inherent
properties of hydrogels to create tunable microlasers for anti-counterfeiting
purposes. Through enzyme-based reactions, the hydrogel's internal structure
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and its corresponding lasing emission were manipulated, enabling a novel
approach for information encoding and encryption. Furthermore, the fusion of
Förster Resonance Energy Transfer (FRET) lasers and hydrogel's structural
randomness yielded a high-capacity optical encoding method, adding an
advanced layer of security against counterfeiting. These key findings of this
research underscores the immense potential and versatility of hydrogel
microlasers, bridging the fields of biophotonics and information security and
opening new avenues for future applications and investigations.
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