Study on carrier dynamics of transition metal oxides using broadband infrared pump-probe spectroscopy

利用宽带红外泵浦探针光谱研究过渡金属氧化物的载流子动力学

• 批准号: 16340091
• 负责人: ASHIDA Masaaki
• 金额: $ 10.62万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16340091/
• 关键词: THz time-domain spectroscopy; pump-probe spectroscopy; ultra short pulse laser; photoconductive antenna; transition metal oxide; infrared spectroscopy; carrier dynamics; ポンプ-プローブ分光

1. We investigated ultrabroadband detection of terahertz electric field with a dipole-type photoconductive (PC) antenna with 10 fs pulse laser. Ultrabroadband frequency response from 0.1 THz up to 100 THz was demonstrated using two types of generation methods: optical rectification using a thin GaSe crystal and dipole radiation using a PC antenna with a large aperture. Comparison between the spectrum obtained with the PC antenna and the calibrated one with a combination of a monochromator and an MCT detector suggests that PC antenna detection has potential for detecting a frequency region much higher than 100THz.2. We utilized rapid scanning method to ultrabroadband terahertz detection using photoconductive antennas. Measurement time was reduced to one tenth of the conventional method. Ultrabroadband terahertz spectrum from 0.1 to 15 THz was observed. This technique provides significant improvement in THz timedomain spectroscopy.3. We measured transmittance of SrTiO_3 thin films deposited on MgO in broadband THz region from 0.1 THz to 10THz. Then we calculated the complex dielectric constant of the thin films directly from amplitude and phase of the transmittance. At room temperature, broad soft-mode (TO1) dispersion is observed around 3 THz and TO2 mode at 5 THz. The resonant frequencies of both modes are almost independent of the thickness at room temperature. On the other hand, at cryogenic temperature (15K), dielectric dispersion is strongly dependent on the thickness. The previously reported softening of the SrTiO_3 thin films deposited on SrRuO_3 substrate is similar to the obtained one. This fact indicates the existence of the intrinsic size effect in SrTiO_3 thin films, since the softening is independent of the substrate. However, the broadening is only observed in extremely thin films deposited on MgO, suggesting that the strain from the substrate strongly affects the width of the soft mode dispersion.

1.研究了利用10ps脉冲激光的偶极型光导天线对太赫兹电场的超宽带探测。利用两种产生方法：利用薄GaS晶体的光学整流和使用大口径PC天线的偶极辐射，实现了从0.1 THz到100 THz的超宽带频率响应。将PC天线与单色仪和MCT探测器相结合得到的校准频谱进行比较，表明PC天线检测具有检测远高于100THz2的频率区域的潜力。我们利用快速扫描的方法，利用光导天线进行超宽带太赫兹探测。测量时间缩短到传统方法的十分之一。观察到0.1~15太赫兹的超宽带太赫兹光谱。这项技术大大改进了太赫兹时间域谱。在0.1~10THz的宽带太赫兹范围内，测量了生长在氧化镁衬底上的钛酸锶薄膜的透过率。然后由透过率的幅值和相位直接计算出薄膜的复介电常数。在室温下，在3THz附近观察到较宽的软模(To1)色散，在5THz处观察到TO2模色散。在室温下，这两种模式的谐振频率几乎与厚度无关。另一方面，在低温下(15K)，介电色散强烈地依赖于厚度。以前报道的在SrRuO_3衬底上沉积的SrTiO_3薄膜的软化现象与所获得的结果相似。这一事实表明，由于薄膜的软化与衬底无关，因此在薄膜中存在本征尺寸效应。然而，只有在沉积在氧化镁上的超薄薄膜中才能观察到展宽，这表明来自衬底的应变强烈地影响了软模色散的宽度。

项目成果

Sensitivity of Photoconductive Antenna for Ultrabroadband Terahertz Radiation : Feasibility of detection over 100THz

光电导天线对超宽带太赫兹辐射的灵敏度：检测超过 100THz 的可行性

• 发表时间: 2005
• 期刊: International Quantum Electronics Conference 2005 and the Pacific Rim Conference on Laser and Electro-Optics 2005 (IQEC/CLEO-PR), Technical Digest
• 作者: 伊藤;山口;渡部;M.Ashida
• 通讯作者: M.Ashida

Four-wave mixing and direct terahertz emission with two-color semiconductor lasers

• DOI: 10.1063/1.1737486
• 发表时间: 2004-04
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: S. Hoffmann;M. Hofmann;E. Bründermann;M. Havenith;M. Matus;J. Moloney;A. S. Moskalenko;M. Kira;S. W. Koch;S. Saito;K. Sakai

Intense terahertz radiation from longitudinal optical phonons in GaAs∕AlAs multiple quantum wells

• DOI: 10.1063/1.2033138
• 发表时间: 2005-08
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: K. Mizoguchi;T. Furuichi;O. Kojima;M. Nakayama;S. Saito;A. Syouji;K. Sakai

物質・現象・新技術(3)強相関電子系

材料、现象与新技术（3）强相关电子系统

• 发表时间: 2005
• 期刊: オプトロニクス 279
• 作者: S.Miyauchi;Y.Watanabe;芦田昌明
• 通讯作者: 芦田昌明

Ultrabroadband Detection of Terahertz Radiation from 0.1 to 100 THz with Photoconductive Antenna

• DOI: 10.1007/978-0-387-49119-6_41
• 发表时间: 2007
• 作者: H. Shimosato;M. Ashida;T. Itoh;S. Saito;K. Sakai