基于亚波长偏振光栅的空间光桥接器设计

Design of optical hybrids based on a subwavelength polarization grating

为了研究自由空间的相干光探测,基于亚波长偏振光栅的衍射和偏振特性,提出了一种新的2×4的90°空间光桥接器。该桥接器主要由一个亚波长偏振光栅、两个λ/2波片和两个偏振分束器构成。结果表明,通过亚波长偏振光栅将信号光束和本振光束进行空间光桥接,通过左旋和右旋圆偏振光在偏光分离时的相位性质实现所需的相位关系,避免了传统空间光桥接器中对分光元件的相位要求,易于实现稳定的相位输出,在空间激光相干探测系统中有潜在应用。

For the coherent detection of laser beams in free space, a new 2×4 90° optical hybrid for freely propagating laser beams was proposed based on the diffraction and polarization characteristics of a subwavelength polarization grating. ｜t mainly consists of a subwavelength polarization grating, two half-wave-plates and two polarization splitters. The split and 4＇ recombination of the signal beam and the local oscillator beam are achieved through the subwavelength polarization：grating. The desired phase relation is obtained when orthogonally polarized beam components of the left-circularly and right-circularly polarized light are spatially separated under given conditions so that the rigid phase requirement for the beam splitters in traditional space optical hybrids is avoided and stable phase output can be obtained easily. It has potential applications in field of free-space laser coherent communication.