建设良好的科研环境营造浓厚的创新氛围

江泽民同志多次强调：“创新是一个民族的灵魂．是一个国家兴旺发达的不竭动力。”创新是人类活动的本质。动物的发展是进化，而人类的发展是进步；生物进化的本质是适应．而社会进步的本质是创新。创新是一个民族进步的灵魂．作为一个国家兴旺发达的不竭动力．创新往往成为社会发展和变革的先导。对人类社会发展来说，创新涉及各种不同的领域．

Comparison of modal gain and material gain for strong guiding slab waveguides

The relations between the gain factor, defined as the ratio of modal gain to material gain, and the optical confinement factor are discussed for the TE and TM modes in slab waveguides. For the TE modes, the gain factor is larger than the optical confinement factor, due to the zigzag propagation of the modal light ray in the core layers. For the TM modes, the existence of a nonzero electric field in the propagation direction results in a more complicated relation of the gain factor and the confinement factor. For an air-Si-SiO2 strong slab waveguide, the numerical results show that the modal gain can be larger than the material gain and the higher-order transverse mode can have an even larger modal gain than the fundamental mode, The efficiency of waveguiding photodetectors can be improved by applying the modal gain or loss characteristics in strong waveguides.