A Novel Light Routing Device with Phase Encoding using Liquid Crystal Spatial Light Modulator

提出了一种新型空间变光互联方案，该方案仅通过改变嵌入在空间光调制器（SLM）上的相位编码模式来改变节点间的空间路由模式，并通过实验检验了其一维路由模式的基本性能。用分段液晶SLM对相干光的空间相位轮廓进行整形，使远场模式与期望的路由模式相匹配。同时，用m系列码对激光束进行编码，并将其转换为准噪声空间图形。用不同m系列编码的各种路由模式进行多路复用并在空间中发送。在接收端，只有一个期望的路由模式可以用相同的m系列相位掩模选择。剩余的复用信号以噪声形式存在，并被一些阈值检测器消除。通过理论和实验研究，我们得到了以下结论：(1)假设在16个灰度级的128x128分段SLM，可以使用长度为127 m系列相位码复用100多个路由模式。(2)利用128一维SLM和HeNe激光器进行了概念验证实验。用另一个SLM相位掩码成功地解码了嵌入在SLM上的双编码空间路由模式。计算了不同m系列码长下的信损比。(3)我们证明了非相干光的光谱相位编码的空间模式可以通过光纤发送，并通过形成光谱全息来恢复。这种时间到空间的转换方案可以开辟新的光互连和通信。(4)为了在光纤互连和通信中使用光谱全息技术，我们演示了1.3mm波长的全息技术。全息图首先由1.3mm的SHG激光写入，然后由基束读取。

A novel space variant optical interconnection, where the spatial routing pattern among nodes is variable only by changing the phase encoding pattern embedded on a spatial light modulator (SLM), is proposed and experimentally examined its basic performance for one-dimensional routing patterns. The spatial phase profile of a coherent light is shaped with a segmented liquid crystal SLM so that the far-field pattern matches to a desired routing pattern. At the same time, the laser beam is encoded with a M-series code and converted to a quasi noise spatial pattern. Various routing patterns encoded with different M-series are multiplexed and send in space. At a receiver, only a desired routing pattern can be selected with an identical M-series phase mask. The rest of multiplexed signals remain as noise and eliminated by some threshold detectors. We obtained following conclusions through theoretical and experimental studies.(1) Assuming a 128x128 segmented SLM at 16 gray levels, one can multiplex more than 100 routing patterns using length-127 M-series phase codes.(2) Proof-of-concept experiments was conducted with a 128 one-dimensional SLM and a HeNe laser. Doubly encoded spatial routing pattern embedded on the SLM was successfully decoded with another SLM phase mask. The signal-to-loss ratio were evaluated for different M-series code lengths.(3) We demonstrated that a spatial pattern encoded for the spectral phase of an incoherent light can be sent through a fiber and recovered by forming a spectral holography. This time-to-space conversion scheme can open up new optical interconnections and communications.(4) In order to use spectral holography technologies in fiber delivered interconnections and communications, we demonstrated holography at 1.3mm wavelength. The hologram was first written by a SHG of 1.3mm laser and then read by the fundamental beam.