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超低噪声光纤干涉仪稳频激光器实验研究
其他题名Experimental research on ultra-low noise fiber interferometer stabilized laser
董靖
学位类型博士
导师刘亮
2016
学位授予单位中国科学院上海光学精密机械研究所
关键词超稳激光 亚赫兹线宽 光学干涉仪 光纤本征热噪声
摘要本学位论文的内容是围绕作者在攻读博士学位期间的两项主要工作。包括超低噪声光纤干涉仪稳频激光的实验研究以及利用超稳激光和光纤干涉仪对光纤本征热噪声进行测量。 光钟是目前精度最高的时间频率标准,而超稳激光作为光钟的本地振荡器,其性能水平直接影响光钟的精度水平。虽然是应光钟的诞生而诞生,但是超稳激光也是许多领域的重要工具。超稳激光可通过光学频率梳产生超低噪声的微波信号,可用来探测引力波,精密验证相对论,进行精密光谱测量。传统超稳激光技术是利用PDH(Pound-Drever-Hall)方法将激光锁定到超稳高精细度的法布里-玻罗(Fabry-Perot)腔上,该方法要求需要光路和腔的空间模式精确匹配,高真空,甚至低温恒温,光学结构复杂,系统昂贵,体积巨大,不容易对激光器的频率进行调节。为了解决这些问题,一个很有前景的方案就是将激光锁定到光纤干涉仪上,相对于高精细度稳腔超稳激光有系统简单,稳定,价格便宜,体积小,容易对频率进行调谐等诸多优势。本实验搭建了两套光纤干涉仪稳频激光系统,并且对其性能通过拍频的方法进行了评估,测量了包括拍频线宽、频率稳定度和频率噪声。测量结果是拍频线宽小于0.67Hz,短期(0.1-1s)频率稳定度小于7E-15 ,频率噪声在1Hz频偏处小于0.8 Hz2/Hz (-1 dB Hz2/Hz),从200Hz到1KHz,达到0.016 Hz2/Hz (-18 dB Hz2/Hz)。性能主要受限于光纤的本征热噪声。 目前,存在两种不同类型的理论来解释光纤本征热噪声,一个是由K.H.Wanser提出的来自于光纤内部热传导的温度弛豫而产生的噪声,在高频区域,能够与实验数据符合的非常好。另外一个Duan Lingze提出,源自于布朗运动的内部摩擦而产生的光纤长度的自发起伏,可以解释光纤本征热噪声的的低频区域特性,但是缺少实验数据的支撑。有许多基于光纤的系统,比如光纤干涉仪式传感器、光纤激光器以及光纤延迟线稳频激光器,其本征分辨率或频率稳定度受限于光纤本征热噪声,因此,对光纤本征热噪声进行理论和实验探究具有十分重要的意义。本论文开展了光纤本征热噪声的测量工作。将测量扩展至次声波段,这对于人们认识次声波段的光纤热噪声特性提供了第一个实验数据;在次声波段,发现光纤热噪声仍然符合1/f的噪声特性;验证了光纤热噪声跟光纤长度的正比光纤;确定了光纤热噪声跟载波光功率无关;发现利用聚酰亚胺涂层的光纤,可降低光纤低频区域的热噪声;实验中并没有观察到现有的热机械噪声模型所预测的共振峰,这预示着该模型可能修改或者加以完善。
其他摘要The content of this thesis mainly include two topics that the author gets involved in his Ph.D works. One topic is experimental research on ultra-low fiber interferometer stabilized laser, and the other is the measurement of fundamental thermal noise of the fiber, using ultra-stable laser and fiber interferometer. Currently, the most precise or accurate frequency standards are optical clocks. The precision or accuracy is directly determinated by the ultra-stable lasers, which act as local oscillators of optical clocks. They are also important tools for many other applications, such as generation of ultralow phase noise microwave signals, upgrade of fountain clock, optical communication network. Moreover, they play key roles in modern precision measurement, such as gravitational wave detection, precision testing of the theory of relativity. Currently, the lowest noise lasers are realized by stabilizing laser frequency onto an ultra-stable high-finesse Fabry–Perot cavity with the Pound–Drever–Hall (PDH) method. However, this approach requires stable and precise alignment of free-space optical elements, the system is bulky, fragile, and expensive, and they are not easy to tune the frequency. A radical alternative is to use an optical fiber delay line as a frequency reference to stabilize laser frequency. By comparing two identical laser systems, a 0.67 Hz (0.25Hz RBW, resolution bandwidth ) line-width beat note signal is achieved, and we obtain the fractional frequency instability of 7E-15 at short timescales (0.1-1 s). The frequency noise power spectral density (PSD) of two identical lasers is below -1 dB Hz2/Hz at 1 Hz and it reaches -18 dB Hz2/Hz from 200 Hz to 1 kHz. The frequency noise was limited by the fundamental thermal noise of the optical fiber. There are two type of theory models which interpreting the fundamental thermal noise , Wanser’s theory and Duan’s theory, the noise comes from spontaneous fluctuations of the local temperatures , according to Wanser’s theory, and it proved to be consistent with the measurement data at high frequencies, while Duan’s theory can explain thermal noise of the fiber at low frequencies ,but there is no experimental proof. The noise comes from the internal friction of the fiber. In many fiber-based systems, such as interferometric fiber-optic sensors, fiber lasers, and fiber-delay-line stabilized lasers, the fundamental resolution or frequency stability is limited by the intrinsic thermal noise inside optical fibers. Thus, it is important to have both an experimental and theoretical understanding of the thermal noise in optical fibers. We expanded the measurement to the range of infrasonic frequencies, and found the 1/f noise spectrum characteristic in the infrasonic frequencies, we provided the evidence that the fundamental thermal noise was proportional to the fiber length, and there has no relations between the thermal noise and the power of light source. When measuring the thermal noise of the polyimide (PI) coating fiber , we found that the thermal noise is lower than the SMF-28 of the same length in the low frequencies, which indicate a possible way reduce the thermal noise in optical fiber at low Fourier frequencies. The resonance peaks of the thermomechanical noise predicted by Duan have not been observed in the experiment, this inconsistence between the experimental and the model proposed by Duan indicates, perhaps, a new physical mechanism need to be further investigated.
语种中文
文献类型学位论文
条目标识符http://ir.siom.ac.cn/handle/181231/15947
专题学位论文
推荐引用方式
GB/T 7714
董靖. 超低噪声光纤干涉仪稳频激光器实验研究[D]. 中国科学院上海光学精密机械研究所,2016.
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