量子集成光学芯片上的器件设计

发布时间：2017-12-28 22:12

本文关键词：量子集成光学芯片上的器件设计　出处：《中国科学技术大学》2017年博士论文　论文类型：学位论文

【摘要】：在当今社会中,人们的日常生活越来越离不开电子产品,不论是笔记本电脑,还是平板电脑,尤其是人手一份的移动手机。随着信息量的爆炸式增长,集成电子学的飞速发展,其物理学瓶颈也日益显现,比如,当集成度高到电路仅能容一个电子传输时,电子的隧穿效应等便不能忽视。而以光子为信息载体的集成光学芯片,因其编码自由度高、响应速率快、传输速度快、并行性高、相容性好等诸多优势,迅速进入了人们的视野。但是,为了适应未来更高信息量的要求,同时拥有更快信息处理速度和更低能量消耗,发展基于量子力学的量子集成光学芯片成为了必然趋势。事实上,早在一个世纪前,普朗克、爱因斯坦等科研先驱首先从光中发现量子概念开始,就注定了光学与量子力学的密不可分性。一个功能性的集成光学芯片与集成电子芯片一样,也包含光源、光传输、光探测、光调制、门操作等各种元器件。本论文致力于量子集成光学芯片上的器件设计的研究,一方面是线性的光学元器件,实现对光子态的操纵,另一方面是基于非线性光学相互作用制成的集成元器件,实现对光子态的制备。具体的研究内容包括:(1)我们从量子光学中的受激拉曼绝热通道概念得到启发,提出了一个偏振旋转器的设计,该器件在以光子偏振编码的量子信息处理中可以用作Pauli X门。偏振旋转器的结构包含一个信号波导和一个辅助波导,信号波导中的两个正交偏振模式和辅助波导中的辅助模式,形成了一个A型三能级系统。通过控制信号波导的宽度和两个波导之间的距离,便可以在信号波导中绝热地实现两个正交模式间的相互转化。所需的波导长度仅为150μm,而水平和竖直偏振间的相互转化效率均可达到99%以上。并且,这样的偏振旋转器设计对于加工误差不敏感,因而旋转器的结构参数的容错度都很高。这个工作表明,我们可以用特定结构的波导对一些相干的量子现象进行光学模拟,同时也启发我们将这些量子现象应用到实际的光学器件设计中。.(2)同样是利用绝热模式转化的思想,我们提出了一个集成的能量吸收器的设计,用于将集成光学芯片上的杂散光吸收掉,其工作原理是引入金属,利用表面等离激元的吸收损耗。在40μm长的器件内,入射光(1550nm)的吸收效率高达99.8%,即反射率和透射率均小于0.1%。由于是绝热的转化,所以其工作效率对入射波长不敏感,在300nm的带宽范围内均保持稳定,并且对周围的工作环境和温度也不敏感。而且,金属的使用令器件可以非常小,散热的问题也更容易解决。这样的器件对于集成光学芯片很重要,因为芯片上常常会用到高功率的泵浦光,或者会有杂散光影响弱光测量。而在光子态制备方面,则需要借助非线性光学相互作用。比如利用二阶非线性光学效应(二倍频、参量下转换等),能够产生相互关联、相互纠缠的光子对;或者需要用三阶非线性光学效应(四波混频等),将原本不相关的光子关联起来。对于硅基非线性器件,最低阶只有三阶非线性光学效应,且功耗相对较高,所有我们主要关注的是二阶非线性光学材料,如氮化铝和铌酸锂,它们的二阶非线性系数都很高,并且线性传输损耗也都很低,最重要的是,它们的加工工艺与CMOS兼容,是非常棒的替代硅基非线性器件的材料。(1)我们提出用集成的宽度变化的氮化铝波导,在光子学芯片上实现了基于二阶非线性光学效应的光子频率转换。我们证实,在绝热锥形波导中,频率转换谱更宽带,并且在有效带宽范围内,非线性转换效率几乎不变,这对于短脉冲的频率转换是非常有利的。这样一个简单却有效的设计,不仅对误差的容错度更高,也使得我们可以调整器件的工作带宽。我们还用解析方法以及数值方法证明了频率转换过程中的"面积定则",可以用于以后设计非线性集成光学器件的通用法则。用我们的方法,在集成芯片上对短脉冲进行高效的、波形可保持的频率转换成为了可能,为未来可扩展的集成光学信息处理打下了基础。(2)我们展示了在刻蚀的薄膜铌酸锂微纳波导中实现的相位匹配的二倍频过程。集成的薄膜铌酸锂芯片最近初露锋芒,有望用于下一代可密集封装、可批量生产的高效率的频率转换系统。我们采用了两种机制:首先是在波导宽度恒定的均匀波导中进行了模式相位匹配,然后在宽度周期调制的波导中进行了准相位匹配。我们对两种波导均进行了理论分析和实验验证。实验证明,我们的微纳波导的线性传输损耗(～3.0dB/cm)使得归一化的非线性转换效率可以高达41%W-1cm-2。
[Abstract]:In today's society, people's daily life is more and more inseparable from electronic products, whether laptops or tablet computers, especially mobile phones with human hands. With the explosive growth of information and the rapid development of integrated electronics, its physical bottlenecks are also emerging. For example, when the integration level is high enough to only allow one electron transmission, the electron tunneling effect can not be ignored. The integrated optical chip based on photon as information carrier has rapidly entered the field of vision because of its many advantages, such as high coding freedom, fast response speed, fast transmission speed, high parallelism and good compatibility. However, in order to adapt to the future higher information requirements and have faster information processing speed and lower energy consumption, the development of quantum integrated optical chip based on quantum mechanics has become an inevitable trend. In fact, a century ago, the pioneers of Planck and Einstein first discovered the concept of quantum from light, and they doomed the inseparability between optics and quantum mechanics. A functional integrated optical chip, like integrated electronic chips, also includes a variety of components such as light source, light transmission, light detection, light modulation, gate operation and so on. This paper is devoted to the research of device design on quantum integrated optical chip. On the one hand, it is a linear optical component, which realizes the manipulation of photon state. On the other hand, it is an integrated component based on nonlinear optical interaction to realize the preparation of photon state. The specific research contents include: (1) inspired by the concept of stimulated Raman adiabatic passage in quantum optics, we propose a design of polarization rotator, which can be used as Pauli X gate in quantum information processing based on photon polarization encoding. The structure of the polarization rotator includes a signal waveguide and an auxiliary waveguide. The two orthogonal polarization modes in the signal waveguide and the auxiliary mode in the auxiliary waveguide form a A type three level system. By controlling the width of the signal waveguide and the distance between the two waveguides, the mutual transformation between the two orthogonal modes can be adiabatic in the signal waveguide. The required waveguide length is only 150 m, and the mutual conversion efficiency between the horizontal and vertical polarization can reach more than 99%. Moreover, the design of such a polarizer is not sensitive to the machining error, so the fault tolerance of the structural parameters of the revolver is very high. This work shows that we can simulate the phenomena of some coherent quantum with the waveguide of specific structure, and enlighten us to apply these quantum phenomena to the design of practical optical devices. (2) similarly, the idea of transforming adiabatic mode is applied. We propose an integrated energy absorber designed to absorb stray light on the integrated optical chip. Its working principle is to introduce metal and use surface plasmon absorption loss. In the 40 m long device, the absorption efficiency of the incident light (1550nm) is as high as 99.8%, that is, the reflectivity and the transmittance are less than 0.1%. Because of the adiabatic transformation, its working efficiency is insensitive to the incident wavelength, and remains stable in the bandwidth range of 300nm, and it is also not sensitive to the surrounding working environment and temperature. Moreover, the use of metal makes the device very small, and the problem of heat dissipation is easier to solve. Such devices are important for integrated optical chips, because a high power pump is often used on the chip, or there will be a stray light that affects weak light measurements. In the fabrication of photon states, the nonlinear optical interaction is needed. For example, the two order nonlinear optical effect (two frequency doubling, parameter down conversion, etc.) can produce correlated and entangled photon pairs, or the three order nonlinear optical effect (four wave mixing, etc.) can be used to associate the previously uncorrelated photons. For silicon based nonlinear devices, the lowest order only three order nonlinear optical effect, and the power consumption is relatively high, all our main concern is the two order nonlinear optical materials, such as aluminum nitride and lithium niobate, two order nonlinear coefficient are very high, and the linear transmission losses are very low, and most importantly, processing technology with their CMOS compatible, is an alternative to silicon based nonlinear devices very good material. (1) we present a photonic frequency conversion based on the two order nonlinear optical effect on a photonics chip using an integrated width varying aluminum nitride waveguide. We confirm that in adiabatic tapered waveguide, the frequency conversion spectrum is wider, and the nonlinear conversion efficiency is almost unchanged within the effective bandwidth range, which is very beneficial for short pulse frequency conversion. Such a simple but effective design not only has a higher error tolerance, but also allows us to adjust the bandwidth of the device. We also use the analytical method and numerical method to prove the "area rule" in the frequency conversion process, which can be applied to the general rule of designing nonlinear integrated optical devices later. With our method, efficient and constant frequency conversion of short pulses on integrated chips is possible, which lays the foundation for future scalable integrated optical information processing. (2) we show the two frequency doubling process of phase matching in an etching thin film lithium niobate waveguide. Thin film lithium niobate chip integrated recently is expected to be used in high efficiency can begin to display talents, dense packaging and batch production of the next generation of frequency conversion system. We have adopted two mechanisms: first, mode phase matching is performed in uniform waveguide with constant waveguide width, and then quasi phase matching is performed in a wide frequency modulated waveguide. We have carried out theoretical analysis and experimental verification on all two kinds of waveguides. The experimental results show that the linear transmission loss (~ 3.0dB/cm) of our nanofilm waveguide makes the normalized nonlinear conversion efficiency possible
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O413;TN256

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