Fabrication of disordered photonic crystal structures for organic random lasing devices

In this work we show the fabrication of disordered structures for organic random lasing devices by means of the combined use of two high resolution techniques, namely electron beam lithography (EBL) and nano imprint lithography (NIL). We have developed a model for random lasing disordered structures by introducing a well defined degree of disorder in a regular photonic crystal (PC) pattern. Before the fabrication of the device, a preliminary modelling of the ordered 2D-PC has been realized by a finite difference time domain (FDTD) based simulation software. Subsequently, random point defects were introduced in the ordered pattern in order to study the influence of disorder on the reflection spectra and to establish the presence of localized modes. The engineered random pattern was transferred through EBL and reactive ion etching (RIE) onto a Si substrate, thus obtaining an hard master used in the following imprint process of polyfluorene (PFO). Preliminary optical characterization collected from one edge of the structure show the occurrence of localized modes which have been attributed to random scattering in the patterned organic layer.