【作者】 潘海峰；

【导师】 曾和平； 陆卫；

【作者基本信息】 华东师范大学 ， 光学， 2008， 博士

【摘要】 红外单光子探测具有非常重要的意义,在光通信、光雷达、激光测距、激光制导、量子信息学、物质检测与分析等诸多实际应用中发挥着重要的作用,既具有民事技术的普遍性,又有国防科技的特殊性。然而现今的铟镓砷雪崩光电二极管红外单光子探测器性能却差强人意,其探测效率、工作速率和背景噪声等指标与硅雪崩光电二极管可见光单光子探测器相比具有相当大的差距。单光子频率上转换技术是利用非线性光学的方法将红外单光子信号频率上转换为可见光波段的“镜像”光子,而且初始光子与“镜像”光子被证明是具有相同的量子态。这使得我们可以使用性能更好的硅雪崩光电二极管代替铟镓砷雪崩光电二极管实现红外单光子信号的高效探测。本文主要围绕如何实现长时间稳定的单光子频率上转换,如何实现高效率的单光子频率上转换过程,如何实现精确可控的单光子上转换波长调谐,如何降低单光子频率上转换的背景噪声等一系列关键问题开展研究,发展了多种新方案,构建了高性能的单光子频率上转换系统,并对其中一些新的量子特性和机制进行了探索。利用激光器腔内高强度,高稳定的光场作为泵浦光,利用腔内的周期极化的铌酸锂(PPLN)晶体实现了高效率的光通信波段单光子频率上转换。这种新方案充分发挥了固体激光器性能稳定,结构简单的优点,不需要使用复杂的伺服控制装置来锁定泵浦光强度。实验上我们获得几个小时内强度非常稳定的和频单光子信号,强度抖动的标准方差约为2.2%。通过使用激光模式控制技术对泵浦光的空间模式和光谱线宽等参数进行进一步的优化,可以有效提高泵浦光束质量和利用效率。使用单向环行腔激光器腔内泵浦的方案,实现了1.55μm单光子频率上转换,达到了迄今为止最高的单光子频率上转换效率——96%。由于强度均匀分布的泵浦光抑制了纵模竞争和光折变效应,和频信号的强度在几个小时内保持稳定,上转换抖动标准方差仅约为2%,稳定性指标在国际同类系统中领先。利用成熟的固体激光器的波长调谐技术,本文提出了可实时控制的高精度频率可调谐的上转换探测的实现方法。利用腔内标准具在PPLN晶体准相位匹配带宽内实现了频率可调谐的单光子频率上转换过程,经过实验研究确定了实现频率调谐的工作条件和参数允许范围。为了探索降低背景噪声的方法,本文使用掺铒光纤激光器和放大器作为泵浦源,实现了超低噪声的1.06μm单光子频率上转换过程。基本上消除了上转换荧光的非线性噪声影响,在93%单光子转换效率的条件下背景噪声仅为150/s。报导了迄今为止上转换探测器中最低的噪声等效光子数。由于背景噪声是限制上转换探测器性能的最重要因素之一,这项研究对提升上转换探测器的探测效率和灵敏度具有重要价值。最后,本论文通过分析多纵模泵浦条件下的单光子频率上转换过程,对其中一些新的物理机制开展了研究。入射光子的量子态会依据泵浦光的纵模分布而演化成相应的频率叠加态,这提供了一种通过控制经典的泵浦光来操控单光子量子态的手段,本文发展了一种简便的非破坏性的量子态路由器模型。更多还原

【Abstract】 Efficient infrared photon counting probe is of great importance in variable practical applications, such as optical communications, optical time domain reflectometer, laser ranging, laser-guided techniques, quantum information, and so forth. Compared with the visible single-photon detectors based on Si-avalanch photodiodes (APDs), however, the current infrared photon counters based on InGaAs APDs are just passable, especially in quantum efficiency, working repetition rate and background noise. Single-photon frequency up-conversion technology provides an another solution to detect the infrared single-photons, which is the use of nonlinear optical method to convert the infrared signal photons into visible "mirror" photons. The original photon and the "mirror" photon would share the identical quantum feature. Thereby, Si-APDs with better performance can replace the InGaAs-APDs for the enhanced infrared single-photon counting. We focused on a series of key issues in frequency up-conversion detection, such as how to realize long-term stable conversion process, how to achieve unitary conversion efficiency, how to achieve precise frequency tuning, how to reduce the background noise, and so forth. A number of new methods were developed for upgrading the performance of the single-photon frequency converter, and some new quantum properties and mechanisms were investigated.Taking the advantage of the high-intensity and high-stability intracavity laser beam as the pump field, the efficient frequency up-conversion of the c-band single photon was achieved in bulk periodically poled lithium niobate (PPLN). The advanced method could give full play to the merits of solid-state lasers as stable and robust in single-photon frequency up-conversion system, so that the complex servo system was not necessary for sustaining the high pump intensity. In our experiments, the intensity of the SFG signal remained very stable in a few hours, where the standard deviation of the intensity fluctuation was measured to be only 2.2%.The mature technologies on the laser mode control could optimize the spatial mode and spectral line-width to improve the beam quality and the efficiency of the pump field. A unidirectional ring laser was built to improve the performance of the intracavity frequency up-conversion of 1.55μm single photons. So far the highest conversion efficiency of 96% was reported, which could maintain within a few hours. Because the mode hopping and the photorefractive effects were suppressed by the uniform-intensity pump field, the stability of the SFG signal was further improved.On the other hand, the flexible solid-state laser wavelength tuning technique allowed a high-precision real-time frequency control of pump field. Using an intracavity etalon, we demonstrated the wavelength-tunable single-photon frequency conversion process within the spectral bandwidth of the quasi-phase-matching interaction. The working condition and the tolerant parameter values were experimentally investigated in our frequency-tunable single-photon upconversion system.The efficient frequency up-conversion of the 1.06μm single photon with ultra-low background noise was successfully operated by using the Er-doped mode-locking fiber laser and amplifier as the pump source. The single-photon conversion efficiency was 93%, and the corresponding background noise was only 150 /s. We achieved so far the lowest noise equivalent power among the reported up-conversion detectors. Since the background noise was one of the most important factors which restricted the performance of the up-conversion detector, our research is of great significance to upgrade the up-conversion detection technology.In the end, the efficient single-photon frequency upconversion was demonstrated under strong multi-longitudinal-mode pump, where the incident single-photon state was converted to a superposition state according to the intensity distribution of the multi-mode pump field. This new phenomenon allowed us to manipulate the quantum state by having control on the classical laser beam, based on which we developed a simple non-destructive quantum state router model.更多还原