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中国物理学会期刊

9.1 dB HG10模压缩态光场的实验制备

CSTR: 32037.14.aps.74.20251109

Experimental generation of 9.1 dB HG10 mode squeezed light

CSTR: 32037.14.aps.74.20251109
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  • 高阶厄米高斯(HG)模压缩态光场作为一种量子光源, 在量子精密测量、量子成像等领域有重要的应用价值. HG模式量子态增强空间测量精度很大程度上取决于其压缩度. 然而, 利用光学参量振荡器产生高阶HG模压缩光的压缩度主要受泵浦功率限制. 本文理论分析并实验验证利用楔角非线性晶体构成的双共振光学参量振荡器, 在低泵浦功率条件下实现 \rm HG_10 模压缩态光场的实验制备. 通过调节光场经历楔角非线性晶体的长度和工作温度, 从而补偿 \rm HG_20 与 \rm HG_10 模式在腔内的Gouy 相位差和非线性晶体中不同频率光场引起的像散, 同时实现双共振条件和相位匹配要求. 实验结果表明仅需51 mW的 \rm HG_20 模式泵浦光操控光学参量振荡器产生9.1 dB的 \rm HG_10 模压缩态光场. 该量子技术解决了光学参量振荡器产生高阶横模量子态受泵浦功率限制的问题, 可用于制备高压缩度的高阶HG模压缩态光场, 为提高空间测量精度提供有效手段.

     

    The high-order Hermite-Gaussian (HG) mode squeezed light, as one of the important quantum sources, has significant application in quantum precision measurement and quantum imaging. The enhancement of spatial measurement precision largely depends on the squeezing level of high-order HG-mode quantum states. However, the squeezing level of high-order HG modes is primarily limited by the external pump power in the optical parametric oscillator (OPO) cavity. As is well known, the OPO with dual resonance for both squeezed light and pump light can lower external pump power. The generation of HG10 mode squeezed light differs from that of HG00 mode squeezed light, with an additional Gouy phase shift introduced between the HG20 pump mode and HG10 down-conversion mode within the OPO cavity. In this work, we conduct theoretical analysis and experimental generation of HG10 mode squeezed light at lower external pump power by using a doubly-resonant OPO based on a wedged periodically poled KTiOPO4 (PPKTP) crystal. By precisely controlling both the propagation length of the optical field and temperature in the wedged PPKTP crystal, we simultaneously compensate for the Gouy phase shift between the HG20 and HG10 modes and the astigmatism induced by the frequency-dependent refractive index. This configuration allows for dual resonance of the HG20 pump mode and the HG10 squeezed mode, while operating under the condition close to optimal phase matching. Increasing the reflectivity of the input coupler of OPO cavity enhances the intra-cavity circulating power of the pump light, thereby reducing the required external pump power. Here, the bow-tie-shaped OPO cavity consists of two plane mirrors and two concave mirrors with a curvature radius of 50 mm. The wedged PPKTP is placed in the smallest beam waist of the cavity. The mode converter is employed to generate high-purity HG20 pump mode with a measured purity of 98.0%. The mode-matching effciency of 93.0% is achieved between the high-purity HG20 pump mode and the OPO cavity. The homodyne visibility of the HG10 mode is 98.1%. We experimentally demonstrate the generation of 9.10 dB HG10 mode squeezed light by using a doubly-resonant OPO with only 51 mW of HG20 pump mode, and simultaneously achieve 9.20 dB of squeezing in the HG00 mode with 27 mW of HG00 pump mode. The inferred squeezing levels of both HG10 mode and HG00 mode squeezed light both reach up to 12.15 dB. The quantum technology has solved the pump power limitations in optical parametric oscillators, generating high-order HG mode states with high squeezing level and providing an effective method for enhancing spatial measurement precision.

     

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