Guide wave spatial filter

本发明涉及到一种用来接收输入辐射并输出对应的滤波输出辐射的导波空间滤波器(300)，滤波器包括串联连接的第一和第二波导段(30，L3，L5)，用波导段：(a)相互配合发射出现在输入辐射中的基本模式辐射分量通过，提供输出辐射；并且(b)相互失配来阻止出现在输入辐射中的高阶模式辐射分量传播通过，防止其影响输出辐射。空间滤波器(300)是用肋波导实现的，用具有比较深和比较浅的蚀刻结构的各段(20，310，320)为各段提供辐射模式滤波特性。按照本发明的空间滤波器能够装入光学分光器和光学调制器来提高其性能，并且降低它们对注入其中的高阶模式辐射的灵敏度。 The invention concerns a guided wave spatial filter ( 300 ) for receiving input radiation and outputting corresponding filtered output radiation, the filter comprising first and second waveguide sections ( 30, L 3, L 5 ) connected in series, the sections: (a) mutually matched for transmitting fundamental mode radiation components present in the input radiation therethrough to provide the output radiation; and (b) mutually mismatched for hindering higher-order mode radiation components present in the input radiation from propagating therethrough and contributing to the output radiation. The spatial filter ( 300 ) is implemented using rib waveguides ( 30 ) for the sections with associated relatively deeply and relatively shallowly etched structures ( 20, 310, 320 ) for imparting to the sections their radiation mode filtration characteristics. The spatial filter according to the invention can be incorporated into optical splitters and optical modulators to enhance their performance and desensitise them to higher-order mode radiation injected thereinto.