Cao Bo, Hayama Kyohei, Suezawa Shun, Hisamitsu Mamoru, Tokuda Katsuhiko, Kurimura Sunao, Okamoto Ryo, Takeuchi Shigeki
Opt Express. 2023 Jul 3;31(14):23551-23562. doi: 10.1364/OE.488978.
Many optical quantum applications rely on broadband frequency correlated photon pair sources. We previously reported a scheme for collinear emission of high-efficiency and ultra-broadband photon pairs using chirped quasi-phase matching (QPM) periodically poled stoichiometric lithium tantalate (PPSLT) ridge waveguides. However, collinearly emitted photon pairs cannot be directly adopted for applications that are based on two-photon interference, such as quantum optical coherence tomography (QOCT). In this work, we developed a chirped QPM device with a slab waveguide structure. This device was designed to produce spatially separable (photon pair non-collinear emission) parametric fluorescence photon pairs with an ultra-broadband bandwidth in an extremely efficient manner. Using a non-chirped QPM slab waveguide, we observed a photon pair spectrum with a full-width-at-half-maximum (FWHM) bandwidth of 26 nm. When using a 3% chirped QPM slab waveguide, the FWHM bandwidth of the spectrum increased to 190 nm, and the base-to-base width is 308 nm. We also confirmed a generation efficiency of 2.4×10 pairs/(μW·s) using the non-chirped device, and a efficiency of 8×10 pairs/(μW·s) using the 3% chirped device under non-collinear emission conditions after single-mode fiber coupling. This is, to the best of our knowledge, the first report of frequency correlated photon pairs generation using slab waveguide device as a source. In addition, using slab waveguides as photon pair sources, we performed two-photon interference experiments with the non-chirped device and obtained a Hong-Ou-Mandel (HOM) dip with a FWHM of 7.7 μm and visibility of 98%. When using the 3% chirped device as photon pair source, the HOM measurement gave a 2 μm FWHM dip and 74% visibility.
许多光学量子应用都依赖于宽带频率相关光子对源。我们之前报道了一种利用啁啾准相位匹配（QPM）周期性极化化学计量比钽酸锂（PPSLT）脊形波导实现高效和超宽带光子对共线发射的方案。然而，共线发射的光子对不能直接用于基于双光子干涉的应用，如量子光学相干断层扫描（QOCT）。在这项工作中，我们开发了一种具有平板波导结构的啁啾QPM器件。该器件旨在以极高的效率产生具有超宽带宽的空间可分离（光子对非共线发射）参量荧光光子对。使用非啁啾QPM平板波导，我们观察到半高全宽（FWHM）带宽为26 nm的光子对光谱。当使用3%啁啾QPM平板波导时，光谱的FWHM带宽增加到190 nm，基到基宽度为308 nm。我们还证实，在单模光纤耦合后的非共线发射条件下，使用非啁啾器件时的产生效率为2.4×10对/（μW·s），使用3%啁啾器件时的效率为8×10对/（μW·s）。据我们所知，这是首次报道使用平板波导器件作为源产生频率相关光子对。此外，使用平板波导作为光子对源，我们用非啁啾器件进行了双光子干涉实验，获得了半高全宽为7.7 μm、可见度为98%的Hong-Ou-Mandel（HOM）凹陷。当使用3%啁啾器件作为光子对源时，HOM测量得到了2 μm半高全宽的凹陷和74%的可见度。
