Markus Karl

University of St Andrews · School of Physics and Astronomy

Fluorescent proteins have emerged as an attractive gain material for lasers, especially for devices requiring biocompatibility. However, due to their optical properties, integration with distributed feedback (DFB) resonators is not readily achievable. Here, a DFB laser with enhanced green fluorescent protein (eGFP) as the gain material is demonstra...

Organic single crystals are of interest for optoelectronic applications due to their highly ordered molecular stacking and small defect concentration, giving the possibility of high mobility and luminescence efficiency. To achieve lasing in large flat single crystals, a simple “pick and place” method of mounting organic single crystals onto distrib...

We report the application of semiconductor nanodisk lasers within living cells. Our lasers have volumes 1000-fold smaller than eukaryotic nuclei, ultralow pulse energy lasing thresholds (Eth≈0.13pJ), and provide excellent spectral stability.

Organic semiconductors enable the fabrication of a range of lightweight and mechanically flexible optoelectronic devices. Most organic semiconductor lasers, however, have remained rigid until now, predominantly due to the need for a support substrate. Here, we use a simple fabrication process to make membrane-based, substrate-less and extremely thi...

Molecular dyes, plasmonic nanoparticles and colloidal quantum dots are widely used in biomedical optics. Their operation is usually governed by spontaneous processes, which results in broad spectral features and limited signal-to-noise ratio, thus restricting opportunities for spectral multiplexing and sensing. Lasers provide the ultimate spectral...

Nanophotonic objects like plasmonic nanoparticles and colloidal quantum dots can complement the functionality of molecular dyes in biomedical optics. However, their operation is usually governed by spontaneous processes, which results in broad spectral features and limited signal-to-noise ratio, thus restricting opportunities for spectral multiplex...

Biological single cell lasers have shown great potential for fundamental research and next generation sensing applications. In this study, the potential of fluorescent biological cells as refractive index landscapes and active optical elements is investigated using a combined Fourier- and hyperspectral imaging technique. We show that the refractive...

Direct laser writing of photonic boxes into active layers of biologically produced recombinant fluorescent protein in optical microcavities is demonstrated. Irradiation with laser light above the photobleaching threshold induces photonic confinement potentials on the order of 40 meV. The technique provides high spatial selectivity and enables room-...

Reliable methods to individually track large numbers of cells in real time are urgently needed to advance our understanding of important biological processes like cancer metastasis, neuronal network development and wound healing. It has recently been suggested to introduce microscopic whispering gallery mode lasers into the cytoplasm of cells and t...

We demonstrate an evanescently pumped water-based optofluidic distributed feedback (DFB) laser with a record low pump threshold of ETH=520 nJ. The low threshold results from an optimized mode shape, which is achieved by a low refractive index substrate, and from the use of a mixed-order DFB grating. Investigating the photonic band structure via a...

We report on a laser that is fully embedded into a single live cell. By harnessing natural endocytosis of the cell we introduce a fluorescent whispering gallery mode (WGM) micro-resonator into the cell cytoplasm. On pumping with nanojoule light pulses, green laser emission is generated inside the cells. Our approach can be applied to different cell...

Abstract The degradation of non-encapsulated, small-molecule organic solar cells based on ZnPc (zinc phthalocyanine)/C60 with an aluminum top electrode is investigated under different climate conditions and correlated with the water barrier performance of the aluminum electrode layer. The degradation of the solar cells turns out to be dominated by...