Femtosecond coherent control of terahertz radiation by transient nanophotonic structures

瞬态纳米光子结构对太赫兹辐射的飞秒相干控制

• 批准号: 231727808
• 负责人: Professor Dr. Tobias Kampfrath
• 金额: --
• 依托单位: Institut für Experimentalphysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/231727808?language=en
• 关键词: Femtosecond; coherent; control; terahertz; radiation

Coherent radiation with frequencies ranging from 0.3 to 30 THz has recently become accessible by femtosecond laser technology. Terahertz (THz) waves have many applications, in particular for spectroscopy of low-frequency excitations (such as molecular vibrational/rotational modes, phonons and spin waves in solids), for imaging as well as short-range wireless communication at THz bit rates. THz light can be manipulated by static elements such as lenses, polarizers, and filters. However, ultrafast modulation of THz radiation is required as well, for instance in ultrafast optical switches or frequency shifters, whose development is just at the beginning. In this proposal, we will realize an extremely flexible approach towards the ultrafast manipulation of THz radiation by transient nanophotonic structures. For this purpose, we irradiate a semiconducting slab with a visible femtosecond laser beam whose spatial profile can be shaped arbitrarily by a light modulator. Through light absorption in the semiconductor, the beam pattern is translated into a density pattern of an electron-hole plasma in the slab. Irradiated areas become metallic whereas dark areas remain dielectric. Since features much smaller than the THz wavelength (roughly 300 micrometers) can be realized with optical radiation, we can switch on a tailored nanooptical structure for THz radiation on a femtosecond timescale.Using this approach, we will realize and study transient periodic structures, namely metamaterials and photonic crystals with three objectives:(1) We will realize transient polarizers and waveplates by generating metamaterials with a highly anisotropic unit cell, which brings about the required birefringence. We will also realize transient photonic crystals and investigate the extent to which we can tune their dispersion relation to realize large band gaps and slow light. Ohmic loss of THz radiation by free charge carriers will also be addressed.(2) By varying the charge-carrier density in the transient structures, we will test the validity of basic optical concepts. For example, at which carrier density does a structure become metallic at THz frequencies? How metallic must an array of transient disks be such that it exhibits an appreciable coupling to the magnetic-field component of the THz wave?(3) Finally, we will coherently manipulate THz radiation on-the-fly, that is, we will ultrafast modify an optical nanostructure whilst a THz pulse propagates within. An important application of such ultrafast nanostructures is frequency shifting of THz pulses, which will allow us to access the underexplored frequency window from 5 to 8THz. In addition, we plan to adiabatically compress the spectrum of a THz pulse (spectral lensing).

频率范围从0.3到30 THz的相干辐射最近已经可以通过飞秒激光技术获得。太赫兹（THz）波具有许多应用，特别是用于低频激发（诸如固体中的分子振动/旋转模式、声子和自旋波）的光谱学，用于成像以及THz比特率的短距离无线通信。太赫兹光可以通过静态元件如透镜、偏振器和滤光器来操纵。然而，THz辐射的超快调制也是必需的，例如在超快光学开关或移频器中，其发展才刚刚开始。在这个建议中，我们将实现一个非常灵活的方法对瞬态纳米光子结构的太赫兹辐射的超快操纵。为此，我们用可见飞秒激光束照射半导体板，其空间轮廓可以通过光调制器任意成形。通过半导体中的光吸收，光束图案被转换成板中的电子-空穴等离子体的密度图案。辐射区域变成金属，而暗区域保持电介质。由于特征远小于太赫兹波长（大约300微米）可以用光辐射实现，我们可以在飞秒时间尺度上打开定制的太赫兹辐射纳米光学结构。使用这种方法，我们将实现和研究瞬态周期结构，即超材料和光子晶体，有三个目标：（1）我们将通过产生具有高度各向异性晶胞的超材料来实现瞬态偏振器和波片，这导致所需的双折射。我们也将实现瞬态光子晶体，并研究我们可以在多大程度上调整它们的色散关系，以实现大带隙和慢光。太赫兹辐射的自由电荷载流子的欧姆损失也将得到解决。(2)通过改变瞬态结构中的电荷载流子密度，我们将测试基本光学概念的有效性。例如，在太赫兹频率下，一个结构在多大的载流子密度下会变成金属？一个瞬态圆盘阵列必须有多强的金属性才能与太赫兹波的磁场分量产生明显的耦合？(3)最后，我们将相干操纵太赫兹辐射的飞行，也就是说，我们将超快修改光学纳米结构，而太赫兹脉冲内传播。这种超快纳米结构的一个重要应用是THz脉冲的频移，这将使我们能够访问从5到8 THz的未探测频率窗口。此外，我们还计划对太赫兹脉冲的光谱进行几何压缩（光谱透镜效应）。

项目成果

Subcycle control of terahertz waveform polarization using all-optically induced transient metamaterials

• DOI: 10.1038/lsa.2014.36
• 发表时间: 2014-02-01
• 期刊: LIGHT-SCIENCE & APPLICATIONS
• 影响因子: 19.4
• 作者: Kamaraju, N.;Rubano, Andrea;Kampfrath, Tobias
• 通讯作者: Kampfrath, Tobias

Terahertz conductivity and ultrafast dynamics of photoinduced charge carriers in intrinsic 3C and 6H silicon carbide

• DOI: 10.1063/1.4890619
• 发表时间: 2014-07
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: A. Rubano;M. Wolf;T. Kampfrath

Ultrafast dynamics of fluctuations in high-temperature superconductors far from equilibrium.

• DOI: 10.1103/physrevlett.114.067003
• 发表时间: 2014-07
• 期刊: Physical review letters
• 影响因子: 8.6
• 作者: L. Perfetti;Bruno Sciolla;Giulio Biroli;C. J. V. D. Beek;C. Piovera;Martin Wolf;T. Kampfrath

Terahertz-field-induced optical birefringence in common window and substrate materials.

• DOI: 10.1364/oe.23.028985
• 发表时间: 2015-11
• 期刊: Optics express
• 影响因子: 3.8
• 作者: M. Sajadi;M. Wolf;T. Kampfrath