Development of Narrow-band Laser Interferometer Gravitational Wave Antenna

有几个项目正在进行中，旨在使用激光干涉仪进行引力波探测：日本的TAMA项目，美国的LIGO项目，法国-意大利的VIRGO项目和德国-英国的GEO项目。引力波很有可能在几年内被探测到。然而，为了建立引力波天文学，还需要进一步提高天线的灵敏度。共振边带提取技术（RSE）是在有限频带内提高干涉仪灵敏度的先进技术之一。在本项目中，我们对RSE干涉仪的性能进行了基础研究，RSE干涉仪需要在传统的功率回收型法布里-珀罗迈克尔逊干涉仪的检测端口处增加一个反射镜。这种信号提取镜使得从臂腔中提取引力波信号成为可能， ...更多信息 否则的话与传统的干涉仪相比，RSE干涉仪的优点是在循环腔中的激光功率较低，可以避免由于反射镜的热透镜效应而导致的灵敏度下降。此外，RSE干涉仪可以在有限的频带内以更好的灵敏度工作，只需将信号提取镜移动一小部分光波长即可。迄今为止，已有几个关于RSE干涉仪的基本实验，但它们都是在空中进行的桌面实验，并且都使用多调制方案进行信号提取。由于RSE干涉仪需要臂腔的极高精细度，因此需要反射镜的极高反射率，因此在空气中操作干涉仪不是优选的，因为反射镜在空气中可能劣化。此外，桌面实验使用固定在桌子上的镜子，这与真实的引力波天线中的悬挂镜子非常不同。此外，多重调制方案使得干涉仪的控制更加复杂，因此在本研究中，我们使用小型悬浮系统在真空系统中进行实验，这使得有可能有一个更好的和更真实的环境。在信号提取方面，我们还提出了一种单一的调制方式，保证了控制系统的简单性。去年，我们终于在世界上首次成功地在悬镜真空系统中用单调制方法操作了RSE干涉仪。在此基础上，提出了一种在保持单一调制方式的前提下，利用三次谐波解调进行信号提取的方法。我们从理论上分析了这种新的方法，并通过仿真发现，这种方法在不损失tlte系统简单性的情况下，工作得更好。我们计划明年通过实验验证这个新方案。去年，我们终于在世界上首次成功地在使用悬镜的真空系统中使用单一调制方法操作RSE干涉仪。在此基础上，提出了一种在保持单一调制方式的前提下，利用三次谐波解调进行信号提取的方法。我们从理论上分析了这种新的方法，并使用仿真，我们发现，该方法将工作得更好，而不会失去系统的简单性。我们计划明年通过实验验证这个新方案。少

There are several projects going on which aim at gravitational wave detection using laser interferometers : the Japanese TAMA project, the American LIGO project, the French-Italian VIRGO project, and the German-British GEO project. It is quite possible that gravitational waves could be detected in several years. However, it is necessary to improve the sensitivity of the antennas further in order to establish the gravitational wave astronomy. The resonant sideband extraction (RSE) is one of the advanced technologies which could improve the sensitivity of the interferometer in a limited frequency band. In this program we performed a basic research to investigate the performance of the RSE interferometer.The RSE interferometer requires an additional mirror placed at the detection port of the conventional power-recycled Fabry-Perot Michelson interferometer. This signal extraction mirror makes it possible to extract the gravitational wave signal from the arm cavity, which would be cancelled … More out otherwise. The RSE interferometer has an advantage that the laser power in the recycling cavity is lower compared with the conventional interferometer, which could avoid the degradation of sensitivity due to the heating lens effect of the mirrors. Moreover, the RSE interferometer can be operated with better sensitivity in a limited frequency band by simply displacing the signal extraction mirror by a fraction of the wavelength of the light.There has been several basic experiments on the RSE interferometer so far, but they were all performed as table-top experiments in the air, as well as they were all using multi-modulation schemes for signal extraction. Since the RSE interferometer requires an extremely high finesse of the arm cavity, thus, extremely high reflectivty of the mirrors, it is not preferable to operate the interferometer in the air because of possible degradation of the mirrors in the air. Also the table-top experiment uses mirrors fixed to the table, which are very different from the suspended mirrors in a real gravitational wave antenna. Moreover the multi-modulation scheme makes the interferometer control even more complicated.Therefore in this research, we performed the experiment in the vacuum system using a small suspension system, which made it possible to have a better and more realistic environment. Also we invented a single modulation method for signal extraction, which ensures the simplicity of the control system. In the last year we finally succeeded in operating the RSE interferometer using the single modulation method in a vacuum system using suspended mirrors for the first time in the wotld. After that we found a better way for signal extraction using the third harmonic demodulation maintaining the single modulation scheme. We analyzed this new method theoretically and using the simulation we found that the method would work even better without losing the simplicity of tlte system. We plan to verify this new scheme by experiment next year.In the last year we finally succeeded in operating the RSE interferometer using the single modulation method in a vacuum system using suspended mirrors for the first time in the wotld. After that we found a better way for signal extraction using the third harmonic demodulation maintaining the single modulation scheme. We analyzed this new method theoretically and using the simulation we found that the method would work even better without losing the simplicity of the system. We plan to verify this new scheme by experiment next year. Less