Fully-coherent terahertz detection method and system (Phase I)

在广泛的背景下，太赫兹（THz）科学和技术的目标是在红外和微波之间的频率间隙中开发新的研究领域，通常指的是0.1太赫兹到10太赫兹的频率范围。近年来，非线性光学的发展提供了大量创新和高效的产生和检测方案，使该领域重新焕发活力。太赫兹科学中常用的主要探测方法被称为空气偏置相干探测（ABCD），它基于太赫兹场诱导二次谐波（TFISH）技术，允许以极大的带宽（bbb20太赫兹）记录太赫兹场。该系统由一对悬浮在空气中的电极组成，电极之间的距离接近1毫米，这两个电极对应于太赫兹和光束聚焦的部分。在该区域，在光学聚焦上施加强烈的交流外偏置，以产生偏置场并诱导二次谐波脉冲。外部偏置越高，信号越好。不幸的是，小型化和集成仍然难以捉摸。现有系统不仅难以小型化（尺寸为几厘米或更小），而且电流检测系统需要使用高压放大器（通常是kV源），从而影响了该技术的可及性。此外，由于检测发生在空气中，高电压的使用受到空气击穿的限制。我们的发明建议克服这些限制，首先将检测装置小型化，其次用中心对称材料代替空气，在这种情况下是二氧化硅SiO2。该探测器采用CMOS兼容制造工艺制造，其特点是两个金属电极相距几十微米，并填充非线性高击穿电压介质。这种设备的原理证明已经被证明，这就是为什么，在这个项目中，我们打算改进和优化制造过程，目的是建立一个原型，并充分表征其商业化。因此，这个概念的简单性将导致成本效益和大规模可复制的特征，这是成功商业化的先决条件。

Terahertz (THz) science and technology aims, in a broad context, at developing new research fields in the frequency gap between the infrared and microwaves, typically referred to as the frequencies ranging from 0.1 THz to 10 THz. Recent progresses in nonlinear optics have offered a great number of innovative and efficient generation and detection schemes, which have lately revitalized the field. The main detection method commonly used in THz science and named Air Biased Coherent Detection (ABCD), is based on the Terahertz Field Induced Second Harmonics (TFISH) technique, and allows to record THz fields with extremely large bandwidth (>20 THz). The system is composed of a pair of electrodes suspended in air and separated by a distance close to 1 millimeter, which correspond to the section where THz and optical beams are focused. In this region an intense AC external bias is applied to the optical focus in order to generate a bias field and to induce a second harmonic pulse. The higher the external bias, the better the signal. Unfortunately miniaturization and integration remains elusive. Not only the existing systems cannot be easily miniaturized (dimension of few cm or less) but current detection systems require the use of high voltage amplifiers (typically kV sources) thus affecting the accessibility to this technique. Moreover, since the detection occurs in air, the use of high voltage is limited by air breakdown. Our invention proposes to overcome these limitations by first miniaturizing the detection device, and second substituting the air by a centro-symmetric material, in this case the silica SiO2. The detector, fabricated using a CMOS compatible fabrication process, features two metallic electrodes separated by a distance of few tens of micrometers and filled with a nonlinear, high breakdown voltage medium. A proof of principle of such a device has already been demonstrated, that is why, in this project, we intend to improve and optimize the fabrication processes, with the aim to build and fully characterize a prototype in view of its commercialization. The simplicity of this concept will thus lead to the cost performance and mass-reproducible characteristics that are prerequisite to a successful commercialization.