Fig. 1. (Color online) (a) Device structure of wavelength-tunable organic semiconductor lasers. (b) Graphical illustration of the stretching setup.

Fig. 2. (Color online) (a) Fabrication process. (b) AFM images of the PDMS gratings. The period is 280, 320, and 360 nm from left-hand to right-hand, respectively, and the groove depth are both ~60 nm.

Fig. 3. (Color online) Chemical structures of (a) T-m, (b) SPL(2)-1, (c) F8BT from top to bottom. (d) Absorption, PL and ASE spectra for a thin film of T-m (blue), SPL(2)-1 (green), F8BT (yellow).

Fig. 4. (Color online) Lasing characteristics of elastic organic DFB lasers. (a) Spectra of elastic DFB lasers based on active films of T-m, SPL(2)-1 and F8BT, respectively. (b) Chromaticity coordinates of the elastic lasers in (a) on the CIE 1931 chromaticity diagram.

Fig. 5. (Color online) (a–c) Output intensity as a function of the pump fluence and (d–f) emission spectra with pump pulse energy slightly above the lasing threshold for the three devices.

Fig. 6. (Color online) Lasing spectra measured by straining the elastic DFB lasers based on (a) T-m, (b) SPL(2)-1, and (c) F8BT.

Fig. 7. (Color online) The dependence of lasing wavelength of the elastic DFB lasers based on (a) T-m, (b) SPL(2)-1, and (c) F8BT. (d) The dependence of threshold variations of these elastic DFB lasers on the applied strain.

Fig. 8. (Color online) Chromaticity coordinates of the varied lasing wavelength for T-m, SPL(2)-1, and F8BT on the CIE 1931 chromaticity diagram (the red arrows indicate the direction of spectral shift).

Fig. 9. (Color online) Emission spectra with pump pulse energy slightly above the lasing threshold for the organic laser based on F8BT, and output intensity as a function of the pump fluence (a, b) after the first stretch, (c, d) after the second stretch and (e, f) after the third stretch, respectively.