Living lasers : lasing from biological and biocompatible soft matter

Abstract

In recent years, the study of stimulated emission from and by biological systems has gained wide spread attention as a promising technology platform for novel biointegrated laser. However, the photonic properties and the associated physics of many biological laser systems are not yet fully understood and many promising resonator architectures and laser classes have not yet transitioned into the biological world. In this thesis, we investigate the fundamental photonic properties of lasers based on single biological cells and explore the potential of distributed feedback (DFB) gratings as novel biointegrated laser resonators. We show how the easy and flexible fabrication of DFB resonators helps to realize optofluidic and solid-state biological lasers. Lasing characteristics, such as tunable and single mode emission, are investigated and different applications are explored. Fourier-space emission studies on different biological lasers give insight in to the photonic dispersion relation of the system and the fundamental creation of lasing modes and their confinement in living systems. The first purely water based optofluidic DFB laser is demonstrated and novel sensing applications are suggested. This device shows low threshold lasing due to an optimized mode shape, which is achieved by a low refractive index substrate and the use of a mixed-order grating. Next, by integrating a high refractive index interlayer on a DFB resonator, a laser device incorporating the novel solid-state biological gain material green fluorescent protein (GFP) is realized. Lastly, we show how the thickness of organic polymer lasers can be reduced to its fundamental limit (< 500 nm) and the resulting membrane like laser devices can be applied to and operated on various body parts to potentially complement biometric identification.