Abstract
AbstractOptical pumping conditions for organic solid‐state lasers (OSLs) are discussed with particular emphasis on the use of gallium nitride based light‐emitting diodes (LEDs) as pump sources. LEDs operate in a regime where the pump should be optimized for a short rise time and high peak intensity, whereas fall time and overall pulse duration are less important. Lasers pumped with this approach need to have very low thresholds which can now be routinely created using (one‐dimensional) distributed feedback lasers. In this particular case stripe‐shaped excitation with linearly polarized light is beneficial. Arrays of micron‐sized flip‐chip LEDs have been arranged in an appropriate stripe shape and the array dimensions were chosen such that the divergence of LED emission does not cause a loss in peak intensity. These micro‐LED arrays have successfully been used to pump OSLs with thresholds near 300 W/cm2 (∼9 ns rise time, 35 ns pulse duration), paving the way for compact arrays of indirectly electrically pumped OSLs.
Highlights
Organic chromophores have always played an important role in photonics
Various aspects of optical pumping conditions of organic solid-state lasers (OSLs) have been discussed with particular emphasis on using GaN light-emitting diodes (LEDs) as pump sources
Simulation results show that the pump pulse duration and the pulse shape and in particular its rise time have a strong influence on the laser threshold
Summary
Organic chromophores have always played an important role in photonics. Considerable efforts are undertaken to exploit them for solid-state laser sources because they offer simple fabrication methods and access to the whole visible spectrum (including schemes for mechanical and electrical laser wavelength tuning) as well as potential for mechanically flexible devices. This article will concentrate on optical pumping and in particular the use of GaN light-emitting diodes (LEDs) as pump sources Such an approach aims to make a virtue of optical pumping and enable compact devices which closely mimic the properties a directly electrically driven device would have. We present the systematic improvement of organic lasers and pumping conditions with the particular objective to use arrays of micron-sized flip-chip GaN LEDs [15, 16] as pump source. This LED format was chosen because it holds potential for enhanced functionality in future devices such as pattern programmability and potential for integration with CMOS control electronics [16]. This effort led to the demonstration of an OSL pumped by micro-LEDs
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