Cellular dye lasers: lasing thresholds and sensing in a planar resonator.

Matjaž Humar,Malte C Gather,Seok-Hyun Yun

doi:10.1364/oe.23.027865

Abstract

Biological cell lasers are promising novel building blocks of future biocompatible optical systems and offer new approaches to cellular sensing and cytometry in a microfluidic setting. Here, we demonstrate a simple method for providing optical gain by using a variety of standard fluorescent dyes. The dye gain medium can be located inside or outside a cell, or in both, which gives flexibility in experimental design and makes the method applicable to all cell types. Due to the higher refractive index of the cytoplasm compared to the surrounding medium, a cell acts as a convex lens in a planar Fabry-Perot cavity. Its effect on the stability of the laser cavity is analyzed and utilized to suppress lasing outside cells. The resonance modes depend on the shape and internal structure of the cell. As proof of concept, we show how the laser output modes are affected by the osmotic pressure.

Highlights

The unique spectral and spatial characteristics of lasers make them useful for probing or stimulating biological cells in sensing and therapy applications
Exploiting the fact that GFP and other fluorescent proteins can be produced by a wide variety of live organisms, live cells have been incorporated into cavities to enable lasing: For instance, GFP expressing E. coli bacteria were used as biological gain medium in Fabry-Perot [11] and microdroplet cavities [12], and we have shown the first biological lasers based on single human cell expressing GFP [8] or cells containing fluorescent dyes [13], using a Fabry-Perot type cavity
We have demonstrated protocols to make a cell laser based on standard cell cultures and using conventional dye staining procedures

Summary

Introduction

The unique spectral and spatial characteristics of lasers make them useful for probing or stimulating biological cells in sensing and therapy applications. A recent new concept is to generate laser light within a biological material [1] by generating optical gain and resonant feedback with biomolecules, biopolymers, natural structures or synthetic biocompatible materials. Such bio-lasers have been shown to have potential for highly sensitive chemical and biological analysis [2]. As a further control we exchanged the solution without changing osmolarity by injecting the same FITC-dextran in PBS mixture In this case, the changes of the lasing modes were minimal, but an overall shift of the spectrum in Fig. 8(c) indicates that the cavity path length changes when the medium is exchanged. After equilibrium was reached again, the modes were nearly identical to the modes before addition of the medium, indicating that the previously observed effect in Fig. 8(a) was caused by the variation in osmotic pressure and by the flow of the liquid

Methods

Results

Conclusion