Spatial-polarization-independent (SPI) parametric conversion is the basis of many optical applications, such as SPI frequency interfaces for communication channels carried by vector modes and up-conversion detection for polarization-resolved imaging. However, realizing such conversion remains a challenge. In the proof-of-principle study presented here, we demonstrate SPI parametric up-conversion using a polarization Sagnac nonlinear interferometer based on type-II second-harmonic generation. Our results show that the vector profile (including both polarization and intensity) and associated spin-orbit-coupling state of the vector signal beam can be transferred to the frequency-doubled beam with high fidelity. The principle lays the foundation for a SPI frequency interface for quantum and classical channels based on vector modes and also paves the way for up-conversion detection of polarization-resolved images in the mid- and far-infrared regions.

中文翻译：

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向量结构光的与空间极化无关的参数上转换

独立于空间偏振的（SPI）参数转换是许多光学应用的基础，例如，矢量模式承载的通信通道的SPI频率接口以及用于偏振分辨成像的上转换检测。但是，实现这种转换仍然是一个挑战。在此处提出的原理验证研究中，我们使用基于II型二次谐波的偏振Sagnac非线性干涉仪演示了SPI参数上变频。我们的结果表明，矢量信号光束的矢量轮廓（包括偏振和强度）以及相关的自旋轨道耦合状态可以高保真地传输到倍频光束。