Terahertz wave emission with 1.5 m pump from photoconductive antenna using stacked Er-doped-InAs quantum dot layers with ultrafast carrier relaxation

We fabricated a photoconductive antenna (PCA) with Er-doped InAs quantum dot (QD) layers on a GaAs substrate and demonstrated THz wave generation with 1.5 mu m pump. In terahertz time-domain spectroscopy (THz-TDS), PCAs require high mobility and short lifetimes of photocarriers since the carriers need to respond rapidly to optical pulses for broad THz generation and detection with a high time resolution. In this study, to achieve PCA operation at an optical communication wavelength band of 1.5 mu m, a substrate for a PCA was fabricated using stacked Er-doped-InAs QD layers. Then, photocurrent measurements were performed to observe optical absorption in the 1.5 mu m band. The results indicated the high capability of the PCA for THz wave generation and detection, in fact, which enabled us to generate the THz wave in the 1.5 mu m band optical system.