中文摘要：

光学涡旋的产生、传输与应用是当前光学领域的研究热点之一.光学涡旋具有轨道角动量,作为一种全新的自由度,丰富了目前光通信的方式.利用面向目标的共轭对称延拓傅里叶计算全息技术,基于空间光调制器,用单束激光直接产生混合光模式阵列进行编码通信.采用由单光涡和复合光涡构成的4种易于识别的模式组成2×2混合光模式阵列,进行灰度图像的编码传输.在接收端提取混合光模式阵列图的信息并进行解码,实现零误码的灰度图像再现.以传输一幅Lena图像为例,使用2×2混合光模式阵列进行编码通信,相对于传统单光涡编码通信,其信息容量可增加4倍.该方法光路简单易行,可扩展性强,进一步拓展使用4×4混合光模式阵列进行编码通信,信息容量提升16倍.提出的混合光模式阵列编码通信方法对于提高信息传输容量具有重要价值.

英文摘要：

The generation,propagation and application of optical vortex have been hot research topics in recent years.Optical vortex carries orbital angular momentum（OAM） that potentially increases the capacity and the spectral efficiency of optical communication system as a new degree of freedom.The optical vortex can be used not only as information carrier for space-division multiplexing,but also for encoding/decoding.We present a novel free-space optical communication system based on hybrid optical mode array encoding/decoding.The array includes four modes that can easily be identified by image processing.The four modes are Gaussian beam,single optical vortex,and two different composite optical vortices.In this paper,the computer generated hologram（CGH） of the hybrid optical mode array is generated based on the object-oriented conjugate-symmetric extension Fourier holography.When the CGH is loaded onto the electronic addressing reflection-type spatial light modulator（SLM）,a single light beam illuminates the SLM,and the desired hybrid optical mode array is generated.In the experiment,a 32 pixel × 32 pixel Lena gray image is transferred.At the transmitter,the Lena gray image is scanned line by line.The gray value（0-255） of each pixel with 8-bit information is extracted from the image and converted into a 2 × 2 hybrid optical mode array,which is encoded into the CGH.Hence,the 32 pixel × 32 pixel Lena gray image is corresponding to a sequence with 1024 CGHs.By switching the CGHs loaded onto the SLM,the Lena gray image is transmitted in the form of the hybrid optical mode array.At the receiver,each hybrid optical mode array is decoded to a pixel value.To distinguish different modes conveniently,two cross lines are set at the center of each mode.By counting the peaks of two intensity distribution lines,the modes can easily be identified.We demonstrate the image reproduction of Lena with zero bit error rate（BER）.The experimental result shows the favorable performance of the free-space optical communicatio