article published Jatin Kumar author Aleksa Krstić author Sina Saravi author Frank Setzpfandt author 975 department <jats:p>We investigated the spectral properties of squeezed light generated via parametric down-conversion in the high-gain regime, considering both unapodized and apodized dispersion-engineered waveguides. The gain-dependent evolution of these states is examined starting from the low-gain regime, which includes both highly correlated and nearly uncorrelated cases. For the unapodized configuration, our simulated results show a monotonic increase in spectral purity with gain, whereas for some of the apodized configuration, they exhibit a nonmonotonic dependence, initially decreasing and then recovering at higher gain. By combining Schmidt-mode analysis with a group-velocity-based interpretation, we explain why different dispersion conditions exhibit distinct gain-dependent behavior, specifically that rapid purification occurs when the pump group velocity lies between those of the signal and idler. Our study shows that the evolution of spectral purity is governed primarily by the underlying dispersion of the waveguide. These results demonstrate that dispersion engineering and parametric gain can be jointly exploited to tailor the spectral-mode structure of squeezed-light sources, enabling their optimization for a broad range of quantum applications.</jats:p> American Physical Society (APS)2026 eng 2469-9926 2469-993410.1103/2hth-yy33 1142 Kumar, Jatin, et al. “Toward Spectral Engineering of Squeezed Light in High-Gain Parametric down-Conversion.” <i>Physical Review A</i>, vol. 114, no. 2, 023706, American Physical Society (APS), 2026, doi:<a href="https://doi.org/10.1103/2hth-yy33">10.1103/2hth-yy33</a>. Kumar J, Krstić A, Saravi S, Setzpfandt F. Toward spectral engineering of squeezed light in high-gain parametric down-conversion. <i>Physical Review A</i>. 2026;114(2). doi:<a href="https://doi.org/10.1103/2hth-yy33">10.1103/2hth-yy33</a> @article{Kumar_Krstić_Saravi_Setzpfandt_2026, title={Toward spectral engineering of squeezed light in high-gain parametric down-conversion}, volume={114}, DOI={<a href="https://doi.org/10.1103/2hth-yy33">10.1103/2hth-yy33</a>}, number={2023706}, journal={Physical Review A}, publisher={American Physical Society (APS)}, author={Kumar, Jatin and Krstić, Aleksa and Saravi, Sina and Setzpfandt, Frank}, year={2026} } Kumar, J., Krstić, A., Saravi, S., &#38; Setzpfandt, F. (2026). Toward spectral engineering of squeezed light in high-gain parametric down-conversion. <i>Physical Review A</i>, <i>114</i>(2), Article 023706. <a href="https://doi.org/10.1103/2hth-yy33">https://doi.org/10.1103/2hth-yy33</a> J. Kumar, A. Krstić, S. Saravi, and F. Setzpfandt, “Toward spectral engineering of squeezed light in high-gain parametric down-conversion,” <i>Physical Review A</i>, vol. 114, no. 2, Art. no. 023706, 2026, doi: <a href="https://doi.org/10.1103/2hth-yy33">10.1103/2hth-yy33</a>. J. Kumar, A. Krstić, S. Saravi, F. Setzpfandt, Physical Review A 114 (2026). Kumar, Jatin, Aleksa Krstić, Sina Saravi, and Frank Setzpfandt. “Toward Spectral Engineering of Squeezed Light in High-Gain Parametric down-Conversion.” <i>Physical Review A</i> 114, no. 2 (2026). <a href="https://doi.org/10.1103/2hth-yy33">https://doi.org/10.1103/2hth-yy33</a>. 671332026-09-12T10:08:24Z2026-09-12T10:10:11Z