Fully-coherent terahertz detection method and system (market study)

目前的提案涉及一项市场研究，涉及开发太赫兹频率的完全相干外差探测系统，特别是使用中心对称材料进行太赫兹探测。THz科学中常用的主要检测方法称为空气偏置相干检测（ABCD），其基于太赫兹场诱导二次谐波（TFISH）技术，并且允许记录具有极大带宽（>20 THz）的THz场。该系统由一对悬浮在空气中的电极组成，它们之间的距离接近1毫米，对应于THz和光束聚焦的部分。在该区域中，将强AC外部偏压施加到光学焦点以产生偏置场并感生二次谐波脉冲。外部偏置越高，信号越好。不幸的是，微型化和集成化仍然难以实现。不仅现有系统不能容易地小型化（几厘米或更小的尺寸），而且电流检测设置需要使用高压放大器（通常是kV源），从而影响该技术的可及性。此外，由于检测发生在空气中，所以高电压的使用受到空气击穿的限制。在这里，我们建议通过采用间隙宽度为几十微米的金属狭缝，并填充有非线性，高击穿电压介质，在这种情况下SiO2，来克服这些限制。然后用外部电压源对狭缝施加偏压，以便将ABCD的概念应用于沉积在电极之间的非线性材料层。该思想的优点在于能够容易地解决在电流检测系统中遇到的问题，即需要强的施加电压、差的信噪比以及需要使用800 nm的强脉冲。这一概念的简单性也可能导致成功商业化的先决条件的成本性能和大规模可再生特性，因此我们坚信，对这一创新技术的市场研究是非常及时的，将有助于加强加拿大THz产业在国际舞台上的影响。

The current proposal is concerned with a market study related to the development of a fully coherent heterodyne detection system at Terahertz (THz) frequencies and in particular, with the use of centro-symmetric materials for THz detection. 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 remain elusive. Not only the existing systems cannot be easily miniaturized (dimension of few cm or less) but current detection set-ups 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. Here we propose to overcome these limitations by employing metallic slits with a gap width of few tens of micron and filled with a nonlinear, high breakdown voltage medium, in this case SiO2. The slits are then biased with an external voltage source in order to apply the concept of ABCD to the layer of nonlinear material that is deposited between the electrodes. The advantages of this idea consists in the ability to readily solve the problems encountered in the current detection systems i.e. the need of a strong applied voltage, a poor signal to noise ratio, as well as the need to use intense pulses at 800 nm. The simplicity of this concept may as well lead to the cost performance and mass-reproducible characteristics that are prerequisite to successful commercialization, hence we strongly believe that a market study for this innovative technology is extremely timely and will contribute to reinforce the impact of the Canadian THz Industry on the international scene.