Electron-Lattice Synergistic Coordination for Boosting the Electro-Optic Response of the Crystal

The electro-optic (E-O) response is fundamental where the refractive index of materials can be modulated by the external electric field. Up to now, E-O modulation has become a critical technology in photonics, quantum optics, modern communication, etc. However, the design of E-O crystals with broadband availabilities and large E-O effect is still challenging since the E-O response is contributed by both electrons and phonons. Here, an electron-lattice synergistic coordination strategy is proposed for boosting the E-O response, and with the langasite as the subject, a novel crystal La₃Zr_0.5Ga₅Si_0.5O₁₄ (LZGS) is designed. By the rational introduction of the Zr⁴⁺ ion in the octahedral site, it is found that the E-O response can be obviously improved attributed to the active 4d orbitals of the Zr⁴⁺ ion and the optical phonons of the flexible (ZrO₆) unit. This crystal also has advantages in transparency, laser damage threshold and E-O coefficient compared with the well-known E-O crystals. Moreover, broadband E-O modulation is also demonstrated in the lasers at wavelengths from 639 to 1991 nm. These findings not only demonstrate an excellent E-O crystal for the development of modern devices in classical and quantum fields but also provide a design strategy for boosting the E-O response.