Through this research, the company investigated the characteristics of many QCLs to clarify wavelength conversion process in a terahertz nonlinear QCL and found that it could apply the theory of a nonlinear optical effect, called coherent optical rectification, which had not been evaluated before. By applying this theory to the wavelength conversion mechanism using the nonlinear optical effect, the researchers optimized the anti-crossed dual-upper-state design to suppress the unwanted absorption of light inside the device, thus allowing output of the two mid-infrared light rays at longer wavelengths up to 13 to 14μm while increasing the wavelength conversion efficiency. In this way, they succeeded in outputting terahertz waves at 450μm in the terahertz range, believed to be the world’s longest wavelength available from a single semiconductor laser operating at room temperature.
Results from this research will be useful in applications such as quality testing and non-destructive inspection of drugs and foods containing components that absorb electromagnetic waves in the sub-terahertz range as well as submillimeter astronomy and high-speed and high-capacity communication over short distances.
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