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

众所周知，二维(2D)光子晶体平板光波导(WGS)具有显著的光传输特性。一个典型的例子是，光可以穿过那些有线路缺陷的WG的突然弯曲的角落，而没有任何明显的损失，因此对超小型和低能量光学集成电路(PIC)非常有吸引力。这是由于PC-Splet WG具有垂直方向由于全内反射和横向由于光子带隙(PBG)效应而受到严格限制的优点。此外，由于群速度Vg^&lt；Wg&gt；较小，使得WG内部的功率增大了一倍n_g=(Vg^&lt；0&gt；/Vg^&lt；Wg&gt；)，这对光学非线性现象非常有利。到目前为止，无源PC器件已经开发成功，而有源器件如全光开关、缓冲存储器和光放大等，除了少数情况外，还很少被开发出来。开发u…的最佳方式之一更多的LTRA-FAST有源元件是为了有效地利用ONL现象，如受激拉曼散射(SRS)和由于瞬时光克尔效应而产生的自或交叉相位调制(SPM或XPM)。在避免双光子吸收(TPA)方面，AlGaAs基PC WGS比硅基PC WGS具有更大的优势。与Si的情况不同，增加Al含量实际上可以避免AlGaAs中的TPA，从而增加电子带隙。在本工作中，我们首先观察到了在1,460-1,535 nm波长范围内由SPM引起的光谱展宽；由于非线性折射率n_2引起的SPM(或相移)导致了显著的光谱演化，随着输入脉冲功率的增加。通过改变入射脉冲的功率T_0(脉冲宽度)=1.6ps，我们研究了通过Al_(0.26)；Ga_(t；0.74)As基样品的光脉冲光谱。结果发现，随着P&lt；In-gt；的增加，光谱变宽，并且进一步增加，形成双峰结构，对应的相移为1.3π。对于1.0 mm长的样品，这种漂移所需的功率估计只有~1.4W。N_2值估计为~1.3×10~(-13)cm~2/W。另一方面，受激拉曼散射具有发展光放大器和紧凑型光源的潜力。然而，到目前为止，还没有关于PC板材WG的SRS的实验工作的报道。在这方面，我们提到已经有几个关于GaP基和Si基线WG的SRS的成功工作被报道。因此，我们在Al&lt；0.26；Ga_&lt；0.74&gt；As基PHC板条WG中进行了1,550 nm附近受激喇曼散射放大的泵浦探测实验，在有效抽运脉冲能量为22pJ的情况下，在~0.5 mm的有效采样长度下，我们观察到了超过6dB的信号放大，相当于~3dB的净增益。这一结果鼓励我们在未来开发一种超高速全光开关。较少

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