stabilized Nd:YAG based two-wavelength-two-frequency-lasers for refraction corrected length measurement

基于稳定 Nd:YAG 的双波长双频率激光器，用于折射校正长度测量

• 批准号: 273245890
• 负责人: Professor Dr.-Ing. Eberhard Manske
• 金额: --
• 依托单位: Institut für Prozessmess- und Sensortechnik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/273245890?language=en
• 关键词: stabilized; Nd; YAG; based; two

For many interferometric measuring tasks, a compensation of the refractive index of air is either not sufficiently possible at present or would require a disproportionately high amount of technical equipment. In recent years, the two wavelength method has been in the centre of intensive investigations. However, it has not been possible so far to make it applicable because of the unavailability of a suitable laser source.This application aims to eliminate this deficit by combining various physical approaches for generating two wavelengths of two frequencies each, using a Nd:YAG laser thus allowing good stabilization in an easy way. So far, the photoelastic effect occurring in Nd:YAG crystals has been examined intensively for the application as force sensor with a linearity over 12 decades.Conversely, another main focus of this application is to provide a constant beat frequency of the orthogonally polarized laser modes resulting from the application of a piezoelectric force. Thus, in the second step, these two modes can be used for two mode stabilization in this case on an unsaturated absorption peak of a gas absorption cell as it has been the case with HeNe lasers for a long time already. This kind of frequency stabilization promises clearly better relative and absolute stabilities (goal: better 10-9) than the side of fringe technology applied so far. Also, the approach proposed is considerably simpler than stabilization methods on saturated absorption lines.Here, the necessary decoupling of the mechanically and optically coupled closed loop control system from the beat and absolute frequency regulation is a task representing a particularly high scientific challenge. The force controlled beat frequency, which is the prerequisite for the 2 mode stabilization, can now be used in the interferometer directly for the heterodyne technique. The frequency doubling by means of KTP crystal, as it has been used with the Nd:YAG lasers for a long time already, finally results in the stabilized wavelength at 532 nm (which is necessary for the two wavelength method), synchronously to the 1064 nm, with the beat frequency being regulated automatically, too. The goal of this project is to create the scientific technological bases for realizing low cost stabilized two wavelength two frequency lasers, which can well be used for industrial measuring tasks, presenting an absolute frequency uncertainty of 10-9. These lasers should potentially be suitable for a variety of applications of refractive index-compensated interferometric length measurement, in particular for suppressing the effect of air turbulences occurring in long baseline interferometry.

对于许多干涉测量任务，空气折射率的补偿目前还不够可能，或者需要不成比例的大量技术设备。近年来，双波长方法一直是深入研究的中心。然而，由于缺乏合适的激光源，迄今为止还不可能使其适用。该应用旨在通过结合各种物理方法来消除这种缺陷，使用 Nd:YAG 激光器产生两个频率的两个波长，从而以简单的方式实现良好的稳定性。到目前为止，Nd:YAG 晶体中发生的光弹性效应已被深入研究，用于作为线性度超过 12 个十年的力传感器。相反，该应用的另一个主要焦点是提供由施加压电力产生的正交偏振激光模式的恒定拍频。因此，在第二步中，这两种模式可以用于气体吸收池的不饱和吸收峰的双模式稳定，就像长期以来HeNe激光器的情况一样。这种频率稳定明显比目前应用的边缘技术具有更好的相对和绝对稳定性（目标：更好的 10-9）。此外，所提出的方法比饱和吸收线的稳定方法要简单得多。在这里，机械和光学耦合闭环控制系统与拍频和绝对频率调节的必要解耦是一项代表特别高科学挑战的任务。力控制的拍频是 2 模式稳定的先决条件，现在可以直接在干涉仪中用于外差技术。通过 KTP 晶体进行倍频，因为它已经与 Nd:YAG 激光器一起使用了很长时间，最终导致波长稳定在 532 nm（这是双波长方法所必需的），与 1064 nm 同步，拍频也自动调节。该项目的目标是为实现低成本稳定的二波长二频激光器奠定科学技术基础，该激光器可以很好地用于工业测量任务，呈现出10-9的绝对频率不确定度。这些激光器可能适用于折射率补偿干涉长度测量的各种应用，特别是用于抑制长基线干涉测量中发生的空气湍流的影响。