Highly Nonlinear Metal‐Organic Framework Microcrystal for Ultrabroadband and Multiwavelength Coherent Light Emission

Abstract Nonlinear optical (NLO) crystals are critical for developing coherent light sources that advance fundamental research and technological applications, including metrology, communication, precision machinery, and surgery. While NLO crystals offer unmatched bandwidth and efficiency, their miniaturization contradicts the phase‐matching and crystal size requirements. Here, a non‐centrosymmetric metal–organic framework (MOF) crystal is reported that enables broadband, multi‐wavelength coherent light generation on a microscale. By overcoming the limitations of the most conventional NLO crystals, MOF microcrystal of a fixed orientation supports simultaneously a wide range of NLO effects, initiated by two pump wavelengths in a free space. The second‐ and the third‐order optical nonlinearities in arbitrary direction, coupled with a 1.5 nm 3 unit cell and the huge hyperpolarizability of this MOF, facilitates simultaneously a set of the sum‐frequency generation and cascaded processes that span over 350 nm with 7 to 32 coherent peaks of uniform intensity and a quality factor up to 180. Discovered counterintuitive light–matter interaction for MOF microcrystals highlights a new molecular design strategy of NLO microcrystals for miniaturized optoelectronic and communication devices.