Since the demonstration of lasing in organic solid-state thinfi lms, much effort has been devoted to this fi eld. [1][2][3][4] Organic lasers in general offer broad tuning ranges and only a few active materials are needed to cover the entire visible spectrum. [ 5,6 ] Electrically pumped organic lasing still remains the ultimate scientifi c goal, which is driving signifi cant work to address this challenge. [7][8][9][10] On the other hand, there are applications where optically pumped organic lasers might be favorable because they are easy to fabricate and require no elaborate device processing. In particular, organic lasers pumped by an inorganic laser diode, [ 11 ] or even a light emitting diode, [ 12,13 ] have recently received considerable attention. With reports of their use ranging from explosives detection [ 14,15 ] to lab-on-achip biospectroscopy, [ 16,17 ] organic lasers today address a broad scope of applications.A very compact setup of an organic laser is achieved using a distributed feedback (DFB) geometry. The period of the DFB resonator and the effective refractive index set the lasing wavelength.Therefore, there is the prospect that "soft" DFB lasers could be optically tuned on every spot of the surface simply by mechanical stretching. This feature would launch a wide range of novel applications. Aside from applications in biology, pharmaceuticals, and chemistry, other applications such as conformable sensitive optical skins for the monitoring of the structural health of civil infrastructure are imaginable.We present a fundamentally new approach to form DFB gratings on the surface of elastomeric poly(dimethylsiloxane) (PDMS) by self-organization. Hard skins compressed by their soft substrates exhibit wrinkles, whether as deposited fi lms [ 18 ] or as plasma-hardened surfaces [ 19 ] . Such wrinkles are common: they are created without order, vary in size and orientation, and contain defects and cracks. In contrast, we have achieved wrinkles so precisely periodic and parallel that they form sinusoidal DFB gratings. The DFB resonators have well-controlled periodicity, low dislocation density, and enable organic lasers with thresholds as low as 28 μ J cm − 2 . At the same time, uniaxially stretching the laser by 2.2% continuously tunes its emission wavelength from 633.6 nm to 638.3 nm (4.7 nm). Mechanically, the lasers can be stretched by about 10% and therefore they have a potential tuning range of up to 20 nm if mode-hopping can be avoided.We present how the gratings are prepared and how the organic gain medium is placed on top of the gratings. The characteristics of the resulting lasers will be shown fi rst in the relaxed state and then during stretching. We fi nish by placing our results in the context of earlier work and discuss the potential for further improvements.To fabricate self-organized gratings, the PDMS elastomer was prestretched, oxygen plasma treated to harden its surface, and then again relaxed. During relaxation of the PDMS its plasma-hardened skin was compressed and buckled to waves....
