Resonant cascaded nonlinearity (RCN) induced by optical parametric amplification (OPA) in a chirped quasi-phase-matching chip can be applied to control the group velocity of ultrafast lasers. However, the group delay produced in a single-stage OPA is limited to the pulse duration, and its sign cannot be altered. In this study, we propose a tandem RCN configuration with multiple OPA stages that can produce large-magnitude and sign-controllable group delays. The group delay produced in the multi-stage configuration is shown to be a linear superposition of each single-stage group delay. By virtue of the byproduct idler in the OPA process, the signal-group delay can be altered from positive to negative (and vice versa) with the same chip structure and pump condition. In the numerical simulation with two OPA stages, both a positive and negative group delay of six-fold pulse duration were achieved for 100-fs pulses at 1550 nm. A much larger group delay can be achieved by increasing the number of OPA stages.

中文翻译：

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通过串联共振级联非线性来进行大幅度，符号可控的超快群速度控制

optical准相位匹配芯片中由光参量放大（OPA）引起的共振级联非线性（RCN）可用于控制超快激光器的群速度。但是，在单级OPA中产生的群延迟限于脉冲持续时间，并且其符号不能改变。在这项研究中，我们提出了具有多个OPA阶段的串联RCN配置，可以产生大幅度和符号可控的群时延。在多级配置中产生的组延迟显示为每个单级组延迟的线性叠加。借助OPA工艺中的副产品惰轮，可以在相同的芯片结构和泵浦条件下将信号组延迟从正改变为负（反之亦然）。在两个OPA阶段的数值模拟中，对于1550 nm处的100 fs脉冲，正负群延迟均为6倍脉冲持续时间。通过增加OPA级数，可以实现更大的群延迟。