Organic dye-based distributed feedback (DFB) lasers are widely tunable laser light sources in the visible wavelength range and exhibit low-cost, simple fabrication, low threshold and single-mode emission . Precise emission wavelength modeling is essential for understanding and optimization of DFB lasers. Here, we present a simple yet precise model for calculating the emission wavelength of multilayer DFB lasers. We ¯nd that experimental and calculated wavelength values are in compelling agreement for hybrid nanoimprinted Ormocomp-TiO2 (doped with Pyrromethene 597) ¯rst order DFB lasers . Applying the model, we explain the occurrence of di®erent laser light polarization, i.e., transvers electric (TE) or transvers magnetic (TM) emission. We further explore hybrid Ormocomp-TiO2 second order DFB lasers as highly sensitive refractive index sensors featuring narrow linewidth and thus high quality spectral resolution. Design guidelines for high performance sensing are given and the in°uences of layer thicknesses and grating period on wavelength and wavelength shifts are discussed in this context . This is used for optimizing the laser sensors towards highest sensitivity and thus lowest detection limits. We show that the additional TiO2 layer can increase the sensitivity by a factor of 5 making the laser sensors competitive with state-of-the-art photonic crystal sensors. In addition, single-mode biological second order distributed feedback dye lasers are presented . The active core of these lasers consists of vitamin B2 doped gelatin which is spin-coated onto a nanoimprinted grating structure in low-index polymer. These single-mode biological lasers represent a next step towards all-biological lasers where the resonator is formed from structured biological material. Such devices could be biocompatible and eventually biodegradable laser light sources and laser sensors.