A research team of the National Institutes of Natural Sciences, National Institute for Fusion Science and Akita Prefectural University has successfully demonstrated a broadband mid-infrared (MIR) source with a simple configuration. This light source generates highly-stable broadband MIR beam at 2.5-3.7 μm wavelength range maintaining the brightness owing to its high-beam quality. Such a broadband MIR source facilitates a simplified environmental monitoring system by constructing a MIR fiber-optic sensor, which has the potential for industrial and medical applications.