【作者】 陈玉和；

【导师】 杨立森；

【作者基本信息】 内蒙古师范大学 ， 光学， 2007， 硕士

【摘要】 光子晶体在光通信、集成光学中具有非常广阔的应用前景。阵列波导是(2+1)维光子晶体的特殊形式。它可应用在控制光的传播路径、光学互连以及研究光在光子晶体中的传播行为等诸多方面。目前关于阵列波导的制作方法的研究比较多,但大多工艺都比较复杂。用全光学方法在光折变晶体中构造阵列波导是一种最简便可行的方法。光诱导(光感应)光折变实时制作阵列波导技术的出现,改善了传统制作阵列波导的局限性,从而使得对于(2+1)维光子晶格的构造更具有实时性,因此对于光在光子晶格中的传播行为的研究变得更容易,目前(2+1)维光子晶格中分立衍射和分立孤子的研究成为非线性光学的一个研究热点。在自聚焦光折变晶体中光诱导波导阵列比较容易,但不易保存且材料价格昂贵。因此,研究在自散焦光折变晶体中用全光学方法写入波导阵列的机理和阵列光束与写入晶格的相互作用规律,是构造出所需的光子晶格是首先要解决的基础课题。本论文工作中,我们使用输出波长为532nm的YAG激光器和输出波长为632.8nm的He-Ne激光器作为光源,在厚度不同的自散焦光折变晶体——LiNbO3:Fe晶体中利用多种光感应方法(光学傅立叶变换法、干涉法、成像法)实时成功地制作了多种不同晶格周期的(2+1)维非线性光子晶格。实验结果表明:选择合适的振幅掩模,用光学傅立叶变换法,适当地控制辐照时间,可以制作周期较小的(2+1)维波导阵列;但是制作的波导阵列的面积较小。用干涉法可以很容易地写入大面积的一维波导阵列,但制作(2+1)维波导阵列的光路比较复杂;用成像法制作光子晶格时,虽然可以容易地在光子晶格中引入“缺陷”,但是晶格周期较大,且需要的写入时间较长。但只要能制作出较高质量的振幅掩模一般都能够写入光子晶格,还可以根据需要制作合适形状的掩模来制作带有相应形状的缺陷的光子晶格。在制作光子晶格和研究光在光子晶格中的传播行为时,我们首次观察到了一种空间频率的倍频现象。在用光学傅立叶变换法和干涉法制作光子晶格时,发现在双光束写入过程中干涉条纹会一分为二、在四光束写入过程中干涉图样会一分为四的一些新的实验现象。我们对此现象进行了仔细的研究,证明这是一种空间频率的倍频现象,是入射的阵列光束与写入的光子晶格相互作用的结果,并用相位分裂的观点给予了初步解释,它是光折变光子晶格非线性的重要表现。从其产生的物理机制来分析,入射的阵列光束与写入的光子晶格相互作用不但可以产生空间二次谐波,而且还可以产生空间高次谐波。利用这一特性可以写入倍频光子晶格和空间高次谐波光子晶格。这一特性的发现对光折变光子晶格和光学微结构的制作是非常有意义的,这将有利于进一步研究在自散焦晶体中用阵列光束写入波导阵列及光学微结构的机理以及阵列光束与写入晶格的相互作用。在用傅立叶变换法制作光子晶格的基础上,观察了不同晶格的分立衍射现象。实验中我们除了观察到常见的分立衍射外还发现一种新的分立衍射现象,并对此作了初步分析。另外,还对引入缺陷模形成分立孤子的问题作了初步研究。更多还原

【Abstract】 Photonic crystal has very wide application foreground in optical communications and integration optics. Array wave-guides is the extremely format of (2+1)-dimensional photonic lattices. It can be applied to control the light-transmitting path, control optics interlinkage and study the transmitting action of light in photonic crystal, etc.At present, there are many studys on fabricating methods of wave-guide arrays, but most of the techniques are very complex. All optical method is a kind of the simplest, most convenient and most feasible method to fabricate wave-guide arrays in the photorefractive crystal. With the development of real-time fabricating wave-guide arrays using light induced technology, it improves the conventional techniques of wave-guide arrays fabrications, it makes fabricating (2+1)-dimensional photonic lattices even more real-time, therefore, the study on the transmitting action of light in photonic crystal become even easier. At present, the study on discrete diffraction and discrete soliton in (2+1)-dimensional photonic lattices becomes the research focus of nonlinear optics. Fabricating wave-guide arrays by light induced technology in self-focus photorefractive crystal is easier, but it is not easy to preserve photonic lattices, moreover, the materials are expensive. So the most important basal research problems for fabricating needful photonic lattices in the field of nonlinear optics are the study on the mechanism of fabricating wave-guide arrays using array beam of light, the study on interaction of array beam of light with photonic lattices fabricated in self-defocus photorefractive crystal and the study on fabricating needful photonic lattices.In the work of this thesis, using YAG laser and He-Ne laser as the light source, which output wavelength are 532nm and 632.8nm, we successfully real-time fabricate various periodic (2+1)-dimensional nonlinear photonic lattices in the self-defocus photorefractive crystal LiNbO3: Fe of different thickness by diverse light induced methods that include the method of optical Fourier transform, the method of imaging and the method of interference. The experimental result shows that using the method of optical Fourier transform, the short periods wave-guide arrays can be fabricated by controlling irradiation time, but the area of wave-guide arrays fabricated is smaller. Using the method of interference, one-dimensional wave-guide arrays can be fabricated easily, but the light-pathway of fabricating two-dimensional wave-guide arrays is more complex. Using the method of imaging fabricating photonic lattices, the lattices periods are bigger and the writing time is longer though the defect modes are imported easily in photonic lattices. But once the good quality amplitude mask is fabricated, the photonic lattices can be fabricated generally, but also the photonic lattices that contain corresponding defect modes can be fabricated by choosing suitable amplitude mask.In the process of fabricating photonic lattices and studying the transmiting action of light in photonic crystal, for the first time we observe a phenomenon of spacial frequency doubling. Using the method of optical Fourier transform and interference fabricate photonic lattices in self-defocus photorefractive crystal LNbO3:Fe, We first find the new experiment phenomenon that dual-beam interference fringes are divided into two each, and four-beam interference fringes are divided into four each. We carefully study this phenomenon and prove that it is a phenomenon of spacial frequency doubling. This phenomenon is the result of the interaction between the entrance array beam and the fabricated photonic lattices. It can be explained tentatively by the theory of phase transfer and phase abruption, and it is the important representation of nonlinear character of photorefractive photonic lattices. We analyze its physical mechanism and think the interaction between the entrance array beam and the fabricated photonic lattices can even produce spacial high-order harmonics besides spacial second-harmonic. Using this character, spacial frequency-doubling photonic lattices and spacial frequency high photonic lattices can be fabricated. The discovery of this character is very significant for the fabrication of photorefractive photonic lattices and optical micro-structure, and it is helpful to study the mechanism of fabricating the wave-guide array and optical micro-structure in self-defocus photorefractive crystal by array light beam and the interaction between the array light beam and fabricated photonic lattices.Base on the fabrication of nonlinear photonic lattices using the method of optical Fourier transform, we observe the discrete diffraction phenomena of different photonic lattices. In the experiment, besides common discrete diffraction, we also find a new discrete diffraction phenomenon, and make some basic analysis about it. In addition, we study discrete soliton generation after importing defect mode preliminarily.更多还原