Fundamental research of the optical logic gates in a sub-teraherz frequency range

这一基础研究项目的目标是实现原理证明，并建立光学逻辑门在200-400 GHz频率范围内的频率响应模型。研究结果总结如下(1)到(3)：(1)分析诊断和实验验证超高频工作下可能出现的输出波形失真。首先，根据我们的原始门模型，我们第一次解析地发现，在研究者最了解的情况下，门输出可能固有地包含弱子脉冲分量。其次，我们对分析发现进行了实验验证。因为产生亚脉冲分量的内在因素被认为存在于最近由NEC(2000-2001)、朗讯技术(2001-2002)和技术大学所做的著名的演示实验中。分别为埃因霍温(2005年至2006年)，它们的输出波形被认为包含特定的AMU…失真的Nt越大(即，子脉冲分量)。我们推测，这种失真是他们噪音水平相对较高的来源之一。[现在我们正在尝试重新设计门结构，以显著降低子脉冲组件的强度比。](2)为了了解二次弛豫时间常数的潜在影响，而不是与相应研究者社区中的传统猜测相反，我们发现，光逻辑门的二次弛豫时间常数的影响可以抑制(而不是放大)输出失真分量，这取决于输出光学组件的光谱滤波条件。发现后，我们设计并实验验证了光谱滤波条件。[这项研究成果(发表于2006年1月)很快在会议摘要论文(最近发表于2006年3月)中被引用，其中埃因霍温技术大学将光逻辑门的无差错操作比特率从创纪录的160 GB/S(包括本研究人员在内的作者在2000年首次实现)更新为320-GB/S。](3)利用光逻辑门产生超高频锁模脉冲不是直接研究超高频范围内的光逻辑门，而是可以替代地研究其在将光逻辑门的输出反馈到其输入端口时的自发脉冲产生，正如目前的研究人员在2000年理论上提出的那样。在本研究项目中，我们在这一研究方向上也取得了重大进展，利用光逻辑门和反馈环路实现了2ps、40 GHz锁模脉冲的产生。实验产生的2ps，40 GHz脉冲的值几乎等同于光复用的160 GHz时钟信号，因为脉冲宽度对于这种光复用来说足够短。在成功产生锁模脉冲的基础上，我们交替地研究了在10 GHz到160 GHz的等效频率范围内和在2ps到10ps的时间常数范围内的几种新的光学逻辑门的特性。我们在2006年5月向CLEO/QELS 2006和一家行业报纸提交了这一漂亮的研究成果。较少

The goal of this fundamental research project was to achieve a proof of principle and to establish a frequency-response model of the optical logic gate in a frequency range from 200 through 400 GHz. The outlines of the research results are summarized from (1)through (3), as follows :(1)to analytically diagnose and experimentally verify the possible output waveform distortion, under the ultrahigh-frequency operation.First, we analytically discovered, according to our original gate model, that the gate output can inherently contain weak sub-pulse components, for the first time to the investigator's best knowledge. Second, we experimentally verified the analytical discovery. Because the inherent factors which generate the sub-pulse components are supposed to exist in the recent, famous demonstration experiments done by NEC (2000-2001), Lucent Technology (2001-2002), and Technical Univ. of Eindhoven (2005-2006), respectively, their output waveforms are supposed to contain a particular amou … More nt of the distortion (i.e., the sub-pulse components). We speculate that this distortion was one of the sources of their relatively high noise level. [Now we are trying to re-design the gate structure, for significantly reducing the intensity ratio of the sub-pulse components.](2)to access the potential impacts of the secondary relaxation time constantIn contrast to the conventional speculation in the corresponding researcher's community, we discovered that the impacts of the secondary relaxation time constant of the optical logic gate can suppress (instead of enlarge) the output distortion components, depending upon the spectral filtering conditions for the output optical component. After the discovery, we designed and experimentally verified the spectral filtering conditions. [This research result (which was published in January 2006) was referred to very soon in a conference digest paper (which was published more recently in March 2006) in which the Technical University of Eindhoven renewed the record-high error-free-operation bitrate of the optical logic gate from 160 Gb/s (first achieved in 2000 by authors including the present investigator) to 320-Gb/s.](3)Ultrahigh-frequency mode-locked pulse generation with the optical logic gateInstead of directly studying the optical logic gate in a ultrahigh frequency range, we can alternatively study its spontaneous pulse generation when feedbacking the output of the optical logic gate to its input port, as the present investigator theoretically proposed in 2000. In this research project, we have made a significant progress in this research direction, as well ; we achieved 2-ps, 40-GHz mode-locked pulse generation with using the optical logic gate and the feedback loop. The value of the experimentally generated 2-ps, 40-GHz pulses is nearly equivalent to optically multiplexed 160-GHz clock signal, because the pulse width is short enough for such optical multiplexing. Based on the successful mode-locked pulse generation, we have alternatively studied several new, characteristic properties of the optical logic gate in an equivalent frequency range from 10 GHz to 160 GHz, and in a time-constant range from 2 ps to approximately 10 ps. We presented this beautiful research result to CLEO/QELS 2006 and to an industrial newspaper in May 2006. Less