设计了一种双正方形中空表面等离子体光波导(SPW)。采用频域有限差分法，对这种波导所支持的基模的传输特性进行了研究。结果表明，基模沿纵向的能流密度主要分布在双正方形空气芯的中心区域。通过调节2个正方形空气孔的边长、中心距离以及工作波长的大小，可以调节基模的场分布范围以及场与金属银相互作用的大小，从而调节有效折射率、传播距离和模式面积等传输特性。通过与双圆形中空表面等离子体光波导的比较发现，在730~800 nm工作波长范围内，双正方形表面等离子体光波导的传输特性要优于后者。因此双正方形表面等离子体光波导有可能用于光子器件集成领域和传感器领域。

A kind of surface plasmonic waveguide (SPW) with a double-square-shaped air core was designed. The propagation properties of the fundamental mode supported by this SPW are analyzed using the finite-difference frequency-domain method. The result shows that the longitudinal energy flux density of the fundamental mode distributes mainly in the central area of the double-square-shaped air core. Adjusting the sides of the two squares, the center to center distance of the two squares and the working wavelength, the field distribution range as well as the degree of the interaction of field with silver can be adjusted, then the effective index, propagation length and mode area of the fundamental mode can be adjusted. Compared with the SPW with a double-circle-shaped air core, it is found that the propagation properties of this kind of SPW are better than the latter within 730~800 nm working wavelength range. This double-square-shaped SPW can be applied to the field of photonic device integration and sensors.