We experimentally demonstrate a high-spectral-purity photon source by designing a dual-Mach–Zehnder-interferometer-coupled silicon ring resonator, wherein the linewidths of pump and signal (idler) resonances can be engineered independently. A high spectral purity of
95
%
±
1.5
%
is obtained via a time-integrated
g
(
2
)
correlation measurement, which exceeds the theoretical 93% bound of a traditional ring’s spontaneous four-wave-mixing photon source. This source also possesses high performance in other metrics including a measured coincidence of 9599 pairs/s and a preparation heralding efficiency of 52.4% at a relatively low pump power of 61 µW as well as high drop-to-through suppression of 20.2 dB. By overcoming the trade-off between spectral purity and brightness in the post-filtering way, such a method guarantees bright pure photons and will pave the way for development of on-chip quantum information processing with improved operation fidelity and efficiency.
Optical vector network analyzers (OVNAs) based on optical single-sideband (OSSB) modulation are of great interest thanks to the potentially high measurement resolution. However, the measurement accuracy of the OSSBbased OVNA is limited by the high-order sidebands in the OSSB signal. To study the influence of the high-order optical sidebands in OSSB signals on the measurement accuracy, an analytical model is established to present the expression of the measurement error and a numerical simulation is performed. For the OSSB-based OVNA implemented by a 90-deg electrical hybrid coupler and a dual-drive modulator, when the −1st order sideband is fully suppressed by the OSSB modulation, the existence of the 2nd-order sideband severely degrades the resolution of the measurement, while the −3rd and −2nd order sidebands place a restriction on the dynamic range of the measurement. In addition, these sidebands also introduce evident measurement errors to the phase response. The study may provide a good guidance in designing the high performance OVNA.
Single photons and photon pairs are typically generated by spontaneous parametric down conversion or quantum dots; however, spontaneous four-wave mixing (SFWM) in silicon microring resonators [1] is also an appealing source of entangled photons, offering a strong cavity-enhanced nonlinear interactions while maintaining features, such as compact, simple to fabricate, and allowing for thermal tuning. However, silicon ring-resonators usually suffer from a trade-off between providing a high pair generation rate (PGR) and high extraction efficiency. To achieve high PGR, devices are generally operated with the signal and idler photons in the undercoupling regime and pump photons at the critical coupling point, while high extraction rates require the converted photons to be overcoupled. Therefore, the optimal conditions for achieving maximal output photon pair flux are critical coupling for the pump photons and overcoupling for the converted photons [2,3]. However, it is not easy to approach such optimal coupling conditions with traditional single-bus waveguide-coupled resonators and double-bus resonators because they do not allow the coupling conditions for the pump and converted photons to be controlled independently.Herein, we propose to use dual asymmetric Mach-Zehnder *Corresponding authors (YueChan Kong,
Top-illuminated PIN photodetectors (PDs) are widely utilized in telecommunication systems, and more efforts have been focused on optimizing the optical responsibility and bandwidth for high-speed and capacity applications. In this work, we develop an integrated top-illuminated InP/InGaAs PIN PD with a back reflector by using a microtransfer printing (µ-TP) process. An improved µ-TP process, where the tether of silicon nitride instead of photoresist, is selected to support an underetched III-V device on an InP substrate before transfer. According to theoretical simulations and experimental measurements, the seamless integration of the PD with a back reflector through µ-TP process makes full use of the 2nd or even multiple reflecting light in the absorption layer to optimize the maximum responsibility. The integrated device with a 5 µm square p-mesa possesses a high optical responsibility of 0.78 A/W and 3 dB bandwidth of 54 GHz using a 500 nm i-InGaAs absorption layer. The present approach for top-illuminated PIN PDs demonstrates an advanced route in which a thin intrinsic layer is available for application in high-performance systems.
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