Sun Yi, Tu Haohua, You Sixian, Zhang Chi, Liu Yuan-Zhi, Boppart Stephen A
Opt Lett. 2019 Sep 1;44(17):4391-4394. doi: 10.1364/OL.44.004391.
We present a detection method based on optical parametric amplification to amplify and detect near-infrared (NIR) optical imaging signals. A periodically poled lithium niobate crystal is employed as an optical parametric amplifier (OPA), which provides excellent quasi-phase-matching conditions for the optical parametric amplification process. A weak reflectance imaging signal at 1465 nm is amplified by the OPA with a high gain of up to 92 dB, and the amplified optical signal is detected with a low-cost photodetector under ambient light conditions. Such a high gain leads to a detection limit of 23 pW under a 5 MHz detection bandwidth, which is remarkably lower than the theoretical value of a NIR photomultiplier tube (PMT). By exploiting the advantages of the OPA, the incident power needed for microscopy or imaging is reduced by 40-60 dB. The high imaging gain of the OPA also significantly enhances the imaging penetration depth by selectively detecting the weak signal reflected from deep tissue structures. The successful implementation of the OPA enables a robust and sensitive detection method that offers the potential to replace PMTs in imaging applications within the NIR spectral range.
我们提出了一种基于光学参量放大的检测方法，用于放大和检测近红外（NIR）光学成像信号。采用周期性极化铌酸锂晶体作为光学参量放大器（OPA），它为光学参量放大过程提供了优异的准相位匹配条件。在1465nm处的弱反射成像信号由OPA以高达92dB的高增益进行放大，并且放大后的光信号在环境光条件下用低成本光电探测器进行检测。如此高的增益在5MHz检测带宽下导致检测限为23pW，这明显低于近红外光电倍增管（PMT）的理论值。通过利用OPA的优势，显微镜或成像所需的入射功率降低了40 - 60dB。OPA的高成像增益还通过选择性检测从深部组织结构反射的微弱信号，显著提高了成像穿透深度。OPA的成功实现使得一种强大且灵敏的检测方法成为可能，该方法有潜力在近红外光谱范围内的成像应用中取代PMT。
