用于天体生物探测的虚拟成像相位阵列光谱技术研究

The search for life beyond earth is an important part of astrobiology, with the spectroscopic studies of atoms, molecules and their isotopes one of the main technical tools. Such spectroscopic studies are mainly in the radio band, since it is easier to distinguish molecules and their isotopes in the long wavelength range. It is of practical significance to advance extraterrestrial life detection to visible band because of the advantages of higher signal intensity, more information and higher spatial resolution. However, the spectral resolution of current astronomical spectroscopy technologies is not higher enough . In order to solve this problem, we propose a new astronomical spectroscopy technology based on Virtual Imaged Phased- Array and laser frequency comb, which can provide a spectral resolving power of 1 million level and a spectroscopic precision of 10^(-10) level, with a compact and low-cost setup. This astronomical spectroscopy technology together with the 12-meter optical / infrared telescope, which is already among the China's Major Scientific and Technological Infrastructure Construction "13th Five-Year Plan", will provide powerful technical means and research tools for extraterrestrial life detection in visible / near-infrared band. The project intends to explore the principle and key techniques of this high resolution astronomical spectroscopy technology. The aim is a systematically understanding of the physical mechanisms, critical techniques and the law of the parameter adjustment of the technology, and then proceeding the practical applications of the technology in the study of extraterrestrial life detection.

地外生命探测是天体生物学重要组成部分，基于原子、分子及其同位素的光谱研究是其主要技术手段之一；由于长波波段更易区分各种分子及其同位素特征，此类光谱研究目前主要集中在射电波段。由于在信号强度、光谱信息量及信号定位精度方面的优势，将地外生命探测推进到可见波段具有现实意义。然而，目前主流天文光谱技术在分辨能力方面很难满足地外生命探测要求，为解决此问题，本项目书提出一种基于虚拟成像相位阵列及激光频率梳的新型天文光谱技术，其可具有100万量级光谱分辨能力及10^(-10)量级光谱定标精度，且结构紧凑，造价低。该技术与2016年进入我国重大科技基础设施建设“十三五”规划的12米光学/红外望远镜结合，将为我国可见/近红外波段地外生命探测提供强大的技术手段和研究工具。本项目拟对该光谱技术原理及关键技术进行探索性研究，系统掌握其物理机制、技术要点及调节规律，为后续在地外生命探测研究中的实际应用奠定坚实基础。

光谱探测是天文观测最重要的技术手段之一。光栅色散能力不足导致目前天文观测常用的光栅光谱仪在高分辨高精度光谱观测时面临尺寸大、造价高的问题。为解决这一问题，色散能力更高的新型色散器件及相关光谱技术的研究成为必要。本项目研究了以虚拟成像相位阵列（VIPA）为主色散器件的光谱技术。在充分理解VIPA的色散机理、色散特性基础上，对VIPA光谱装置进行了数值模拟及设计，并搭建了两套实验装置和一套原理样机。该类实验装置能提供100万光谱分辨率，配合激光频率梳定标，波长重复性定标精度在10分钟时间尺度内可达到10cm/s量级。而在校正像差影响后，使用大靶面探测器获得100nm光谱探测范围，使用多通道探测，探测光谱范围可以更宽。项目还研究了多模光纤输入下VIPA色散特性，发现VIPA分辨能力几乎不受光纤芯径影响，这相对于光栅更具优势。本项目研究为VIPA光谱装置在天文观测、窄线宽激光光谱表征、布里渊散射谱测量等应用奠定了基础。