摘要:
针对可用于微弱红外图像探测的光学参量变频与增强技术,进行了仿真与实验探索.针对高增益光参量放大器(OPA)过程中的参量荧光背景噪声,提出了基于外接圆模型的空间滤波技术,通过仿真优化设计,利用空域、频域滤波与像传递系统相结合的方法,将参量荧光背景的抑制比例超过70%,其增强后的成像质量较之前有明显改善,峰值信噪比提升22%.基于10 Hz,355 nm的大能量皮秒紫外抽运激光,实现了红外波段到可见光波段的参量频率上转换,得到了超过1.3×108(82 dB)的光学图像增益.实验结果表明,采用高增益OPA作为光学预放大级之后,常规非制冷电荷耦合器件可实现微弱红外成像的有效探测,灵敏度可达每像素7.4个光子.该方案有望用于单光子级高灵敏红外成像场合。
Abstract:
Optical parametric frequency up-conversion and amplification, used for ultra-weak infrared image detection, is investigated both numerically and experimentally. A circum-circle model of spatial filtering is proposed to suppress the parametric fluorescence background noise. Combining the spatial filter, image relay module and band-pass filter, the fluorescence noise is suppressed by 70%. Accordingly, the image quality is significantly improved and the peak signal-to-noise ratio is increased by 22%. Based on the 10 Hz, mJ-level, 355 nm picosecond pump laser, the weak infrared image is amplified and up-converted into the visible region, and over 1.3 × 108 (82 dB) optical gain is obtained at the same time. Our experiment demonstrates that the detection sensitivity of the conventional uncooled CCD can be as high as 7.4 photons per pixel when the high gain OPA is used as an image preamplifier. The scheme in this paper is expected to be used in single-photon-level sensitive infrared imaging.
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