Deep‐Red‐Emissive Flexible Optical Waveguide with High Elastic Performance Based on an Organic Crystal

Abstract Organic crystals with elasticity and light‐guiding properties have been used for spatial control of light output for photonic devices and circuits. However, the emission wavelengths of organic crystals for active optical waveguides are still too short for practical applications; the elastic performance of organic crystals should be further improved. Here, we develop an organic crystal of the compound 5‐[4‐(dimethylamino)phenyl]‐1‐(4‐fluorophenyl)penta‐2,4‐dien‐1‐one (DPFP) with an emission wavelength near 675 nm. The crystal is very soft and has an elastic modulus of 323.95 MPa. The properties suggest that it has value as an active optical waveguide. It also undergoes a crystalline transition process. After the transition, both the elastic and emission properties are retained so that it can be used as an optical waveguide. These phenomena were then studied via both experimental and theoretical methods.