Ultrashort electromagnetic pulse radiation from YBCO thin films excited by femtosecond optical pulse

• Published in: Japanese Journal of Applied Physics 1996-05, Vol.35 (5A), p.2624-2632
• Main Authors: TONOUCHI, M, TANI, M, WANG, Z, SAKAI, K, TOMOZAWA, S, HANGYO, M, MURAKAMI, Y, NAKASHIMA, S.-I
• Format: Article
• Language: English
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Miscellaneous; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.35.2624

We have observed ultrashort electromagnetic pulse radiation from YBa 2 Cu 3 O 7-δ thin-film dipole antennas. The supercurrent transient is created by the excitation of the supercarriers into quasiparticles with a femtosecond laser pulse, and freely propagated electromagnetic pulses are measured and characterized. A pulse with 0.5 ps full width at half-maximum was obtained, containing frequency components up to 2.0 THz. A femtosecond time-resolved characterization of the spectra revealed that they strongly depend on the excitation conditions, and the quasiparticle recombination time becomes longer with increase in the excitation intensity. It is also observed that the radiation power increases in proportion to the square of both the bias current and the laser power in the region of weak excitation, which is consistent with the classical theory based on a two-fluid model. In the region of strong excitation, deviation from the classical theory was observed.