Optical frequency conversion by ultra-fine waveguide and their application to phtonic integration

该研究项目涉及材料中具有多维光子周期结构的光子晶体的特性。特别地，研究了光子晶体光纤的非线性特性，通过在单个折射率导引的光子晶体光纤(PCF)中形成的几个小纤芯上泵浦140ps脉冲来表征与位置有关的非线性光学特性。基于反射法实现了光子晶体光纤上泵浦位置的分配，实现了光子晶体光纤输入端面相对于准直激光束固定焦点的光波导结构的原位观测。泵浦采用波长在800 nm左右的钛宝石激光器。在这些小核上的一系列输入峰值功率依赖谱显示了从红外到可见光直到紫外光的宽光谱相干光的产生，这从核尺寸变化的角度进行了讨论。可见光发生器…纤芯尺寸越小，反常色散程度越大，纤芯越小，反常色散程度越大。设计了一套独特的测量装置来研究多纤芯型光子晶体光纤中光纤长度相关的能量转换。利用该系统观察到了通过5m长光子晶体光纤产生的一些峰的光谱渐变。这些峰及其移位被识别为孤子和孤子的自频移。另一方面，短波长区的峰值既不是由孤子发射和捕获的色散波，也不是由四波混频或和频移产生的空闲波。利用光谱条纹相机和20 mm长光子晶体光纤在飞秒钛宝石激光脉冲照射下产生的超连续光，测量了5m长光子晶体光纤的波长色散分布，并制作了空气包覆型小型芯波导结构，利用光刻技术研究了光子晶体光纤的短长度限制。在硅脊结构尖端制作了35微米长的二氧化硅细丝。在810 nm钛宝石激光泵浦下，观察到了795 nm附近波长转换的新光谱。这些结果对发展光子集成功能器件具有很好的应用前景。较少

The research project concerns characteristics of photonic crystal that has multi-dimensional photonic periodic structures in the material. Especially, nonlinear properties of a photonic crystal fiber were investigated.Site dependent nonlinear optical properties are characterized by pumping 140 fs pulses at independently addressable several small cores formed in a single index-guiding photonic crystal fiber (PCF). The positional assignment of pumping site onto the PCF is achieved based on the reflection method to observe in situ the waveguiding structure of PCF input facet relative to the fixed focal point of the collimated laser beam. Pumping was done by Ti-sapphire laser with the wavelength around 800nm. A series of input peak power dependent spectra at these small cores demonstrate generation of a wide spectrum coherent light (supercontinuum light) from infra-red to visible light down to the violet, which were discussed from the viewpoint of core-size variation. Visible light generat … More ion at smaller core is principally due to an increase of the degree of anomalous dispersion by decreasing the core size.A unique measurement setup has been designed to examine the fiber-length-dependent energy conversion in multi-core-type PCFs. Gradual spectral change of some peaks generating through 5 m-long PCF has been observed by using this system. Those peaks and their shifts have been identified as solitons and soliton self-frequency shift. On the other hand, the origin of peaks in shorter-wavelength regime is neither dispersive waves which are emitted and trapped by solitons nor idler waves generated by four-wave mixing or sum-frequency shift. Wavelength dispersion profiles of 5m-long PCF have been determined by measuring chromatic dispersion using a spectroscopic streak camera and the supercontinuum light, which is generated from a 20-mm-long PCF under illumination of a femto-second Ti-sapphire laser pulse.An air-cladding type small core waveguide structures were fabricated to investigate the shorter length limit of PCF using photolithographic techniques. The 35 micrometer-long SiO2 thin wire on the sharp edge of the Si ridge structure was fabricated. A wavelength converted new spectrum around 795nm was observed with this waveguide under pumping with 810nm light from Ti-sapphire laser. These results are promising for developing photonic integrated functional devices. Less