Basic research on the optical pulse transmission and nonlinear phenomina in the photonic crystal slab waveguide

众所周知，二维光子晶体平板波导具有显著的光传输特性。一个典型的例子是，光可以通过这些线缺陷WG的突然弯曲的角落，而没有任何明显的损失，从而对超小和低能量的光学集成电路（PIC）非常有吸引力。这是由以下事实引起的：PC板WG具有分别由于全内反射而垂直地和由于光子带隙（PBG）效应而横向地紧密光限制的优点。此外，群速度vg^<WG>小使得WG内部的功率大了n_g=（vg^<0>/vg^<WG>）倍，这非常有利于光学非线性（ONL）现象。到目前为止，无源PC器件已经研制成功，而有源器件如全光开关、缓冲存储器、光放大器等，除了少数几种情况外，还很少有人研制成功。发展我们的最佳途径之一 ...更多信息 超快有源元件是有效利用ONL现象，例如受激拉曼散射（SRS）和由于瞬时光学克尔效应引起的自或交叉相位调制（SPM或XPM）。基于AlGaAs的PC WG具有避免双光子吸收（TPA）的优于基于Si的PC WG的优点。与Si不同的是，在AlGaAs中，通过增加Al的含量，可以避免TPA的产生，从而提高了禁带宽度。由于非线性折射率n_2引起的SPM（或相移）导致随着输入脉冲功率P_1的增加而显著的光谱演化<in>。我们测量了光脉冲通过Al_<0.26>Ga_<0.74>As基样品的光谱，改变入射光脉冲的功率，T_0（脉冲宽度）= 1.6ps。结果表明，随着P_（1/2）的增加，谱线变宽<in>，进一步增加，谱线出现双峰结构，对应相移为1.3 π。对于1.0 mm长的样品，该偏移所需的功率估计为1.4 W。估算的n_2值为1.3 × 10 ~（13）<-13>cm ~ 2/W。另一方面，SRS具有开发光放大器和紧凑光源的潜力。然而，到目前为止，还没有关于PC板WG的SRS的实验工作被报道。在这方面，我们提到，关于SRS的几个成功的工作已经在基于GaP和基于Si的线WG上被报道。因此，我们在Al_ Ga_As基PhC板条WG中进行了1,550 nm附近光的SRS放大的泵浦-探测实验<0.26><0.74>。结果，在有效样品长度为10.5 mm的情况下，我们观察到超过6 dB的信号放大，其中泵浦脉冲能量为22 pJ，这对应于10.3 dB的净增益。这一结果鼓励我们在未来开发超快速全光开关。少

It is well known that two-dimensional (2D) photonic-crystal (PC) slab waveguides (WGs) exhibit the noticeable light propagation characteristics. A typical example is that the light can pass through an abruptly bent corner of those line-defect WGs without any appreciable loss, resulting in being very attractive for ultra-small and low-energy optical integrated circuits (PIC). This is caused by the fact that the PC-slab WG has the advantage of tight light confinement vertically due to total internal reflection and laterally due to photonic band gap (PBG) effect, respectively. Moreover, that the group velocity vg^<WG> is small makes the power inside the WG larger by a factor n_g= (vg^<0>/vg^<WG>), being very advantageous to optical nonlinear (ONL) phenomena. So far, passive PC components have already been successfully developed, active components such as all-optical switch, buffer memory and optical amplifier have seldom been developed except a few cases. One of the best ways to develop u … More ltra-fast active components is to make efficient use of ONL phenomena such as stimulated Raman scattering (SRS) and self-or cross-phase-modulation (SPM or XPM) due to instantaneous optical Kerr effect. AlGaAs-based PC WGs have the advantage over the Si-based ones of avoiding two-photon absorption (TPA). Different from the case of Si, the TPA in the AlGaAs is practically avoided by increasing Al-content, thus increasing the electronic band gap.In this work, we first observed the SPM-induced spectral broadening for PC-slab WGs in a wavelength range from 1,460 to 1,535 nm; the SPM (or a phase shift) due to the nonlinear refractive index n_2 leads to a marked spectral evolution as the input pulse power P_<in> is increased. We have examined the spectrum of the light-pulse transmitted through an Al_<0.26>Ga_<0.74>As-based sample, by varying the power of incident pulse with T_0 (pulse duration) =1.6 ps. As a result, we found that the spectrum gets broader with increase of P_<in>, and on further increasing, develops a double-peak structure, corresponding to a phase shift of 1.3 π. The power required for this shift is estimated to be as small as 〜1.4 W for a 1.0 mm-long sample. The estimated n_2-value is 〜1.3 X 10^<-13>cm^2/W. On the other hand, the SRS has the potential for developing a light amplifier and a compact light source. Until now, however, no experimental work has been reported yet on SRS for the PC-slab WG In this connection we mention that several successful works on SRS have already been reported on GaP-based-and Si-based wire-WGs. So, we performed a pump-probe experiment of SRS amplification of light around 1,550 nm in an Al_<0.26>Ga_<0.74>As-based PhC-slab WG As a result, we observed more than 6 dB signal amplification with pump pulse energy of 22 pJ in an effective sample-length of 〜0.5 mm, which corresponds to a net gain of 〜3 dB. This result encourages us to develop an ultra-fast all-optical switch in future. Less