Development of Efficient Si-nanocrystal-sensitized optical waveguide amplifiers

以硅纳米晶为敏化剂的掺Er SiO_2薄膜已被用于高效率的光放大。我们用平板波导在1.55μm波长用可变条长方法测得光放大增益为991 cm~(-1)。在平板光波导中，在60μm的辐照长度范围内，观察到了声速测量中的放大现象。研究发现，硅纳米晶的尺寸(即由退火温度控制)对于减小硅纳米晶中产生的激子引起的波导损耗是非常重要的。含有直径小于2.7 nm的纳米硅的芯膜具有正的增益(即放大)，这是因为上述的波导损耗很低。开发光学放大器的溅射和微制造工艺是核心图案的沉积和RIE(反应离子刻蚀)。在4英寸硅片上获得了均匀的芯膜(面积为4cmx8 cm)，光致发光强度和膜厚均匀度为±10%。利用RIE技术在二氧化硅薄膜中制作了6μm深的图案，可用于制作光学放大器。如果能在1.55μm波长实现实用的平面光波导放大器，就可以开发出各种新型的光子器件，因为无源硅基光波导器件增加了一种新的功能。

Er doped SiO_2 films containing Si nanocrystals as sensitizers have been investigated for an application to an efficient optical-amplifier. We demonstrate an optical-amplifier gain of 991cm^<-1> measured by the VSL (variable strip length) method at a wavelength of 1.55 μm using a slab waveguide. The amplification in the VSL measurement is observed within irradiation length of 60 μm in the slab waveguide. It has been found that the silicon-nanocrystals size (that is controlled by the annealing temperature) is very important to decrease the waveguide loss caused by excitons generated in the silicon nanocrystals. Core films containing silicon nanocrystals whose diameter is less than 2.7 nm show positive gain (that is amplification), because the above mentioned waveguide-loss is low. Sputtering and microfabrication processes to develop the optical amplifiers are deposition and RIE (reactive ion etching) of core patterns. A uniform core-film (4cmx8cm area) has been achieved on a 4 inch silicon wafer with a uniformity of ± 10 % in the photoluminescence intensity and the film thickness. 6 μm deep patterns in silica films have been fabricated using RIE, which can be used to fabricate the optical amplifiers. If the practical planar waveguide amplifier is realized at the wavelength of 1.55 μm used in optical telecommunication networks, a variety of novel photonic devices can be developed, because a new functionality is added to passive silica-based waveguide components.