We designed, fabricated, and measured superconducting nanowire single-photon detectors (SSPDs) with low filling factor which achieve high system detection efficiency (SDE) and counting rate simultaneously. Numerical simulation reveals that high optical absorptance is possible in SSPDs even for low filing factor by tuning the device design. The SDEs of fabricated 18-50% filling factor SSPDs were measured systematically, and all SSPDs showed high SDEs of 61-80% and the lowest 18% filling factor SSPD achieved a high SDE of 69%.
We designed, fabricated, and measured superconducting nanowire single-photon detectors (SSPDs) with low filling factor which achieve high system detection efficiency (SDE) and counting rate simultaneously. Numerical simulation reveals that high optical absorptance is possible in SSPDs even for low filing factor by tuning the device design. The SDEs of fabricated 18-50% filling factor SSPDs were measured systematically, and all SSPDs showed high SDEs of 61-80% and the lowest 18% filling factor SSPD achieved a high SDE of 69%.
We designed a low-filling-factor and polarization-sensitive superconducting nanowire single photon detector (SNSPD), which can achieve a high absorption efficiency and counting rate simultaneously. Numerical simulations show that high absorption efficiency can be achieved by low-filling-factor SNSPDs with a silicon slot and silver reflector. The absorptance of the NbN nanowire for a transverse magnetic (TM) wave at the wavelength of 1550 nm can be 84.4% when the filling factor is only 16.5%, and the corresponding polarization extinction ratio (PER) is 562.9; the absorptance of the NbN nanowire for a transverse electric (TE) wave can be 67.0% when the filling factor is only 11.7%, and the PER is 7.4.
We present a numerical simulation of the optical absorptance for the superconducting nanowire single-photon detectors (SNSPDs or SSPDs) designed with various layouts by using finite-element analysis software. The simulation results reveal that the electric field concentrated in the superconducting nanowire is enhanced by reducing the filling factor, and the degree of the enhancement becomes larger for thicker nanowires. Due to the large enhancement of the electric field in the nanowire with a double-side cavity structure, the high optical absorptance can be achieved even for the low-filling-factor layout by tuning the device design, which leads to the realization of SSPDs with high system detection efficiency and high counting rate.
We propose a superconducting nanowire single photon detector (SNSPD) that can work efficiently at two target wavelengths and has a significant improvement in the counting rate due to the low-filling-factor nanowires in the silicon slots and the silver reflector. Numerical simulations show that the absorption efficiency can be over 90% at a single wavelength, whether the incident light wavelength is 1550 nm or 1064 nm, and over 80% when the SNSPD is designed to work at both wavelengths. In addition, the reset time is about 24% of the conventional SNSPDs. Our work presents a design for fabricating faster, larger-area, and multispectral SNSPDs with a high efficiency, which can be applied in applications such as quantum optics communication and multiwavelength sensing.
Implementations of quantum information require single-photon detectors (SPDs) with high detection efficiency (DE) at a wavelength of 940 nm, which is a challenge for the available semiconducting SPDs. Superconducting nanowire SPDs (SNSPDs) are capable of detecting visible and near-infrared single photons with high DE. However, these detection capabilities place stringent design requirements on the cavity and nanowire geometry structures. We design, fabricate, and measure SNSPDs with high DE optimized for the 940-nm wavelength. The NbN SNSPDs were fabricated on 1-D photonic crystals for high optical absorptance. By tuning the filling factor of the nanowire through numerical simulations and experiments, we were able to obtain an SNSPD (7 nm thick, 125 nm width, and 0.57 filling factor, as well as active area of18∗18μm) with a saturated system DE of 83.6$\pm3.7\pm$0.02. To our best knowledge, this is the highest value reported for NbN SNSPDs at 940-nm wavelength. The availability of an SNSPD with high system DE at 940 nm may have a profound impact in the field of photonic quantum technologies, such as multiphoton entanglement.
Ever since superconducting nanowire single-photon detectors (SNSPDs or SSPDs) were demonstrated, they have attracted a considerable attention due to the detectors’ promising performance that includes high detection efficiency (DE), low dark count rate (DCR), broadband sensitivity, and low timing jitter. The system detection efficiency (SDE) has been improved to be over 90% with a wavelength of 1550 nm in a fiber-coupled system by embedding the SNSPD in optical cavities. However, the implementation of optical cavity usually reduces the bandwidth of SNSPDs. As a result, there are some recent works on increasing the bandwidth of SNSPD. Furthermore, the size of the active area of meandered nanowires has to be compatible with the core size of an optical fiber such that good optical coupling can be achieved; this setup requires a long nanowire with a large kinetic inductance, thus resulting in a small counting rate and a large timing jitter, particularly for multi-mode fiber-coupled devices. Nevertheless, a particularly impressive waveguide-coupled SNSPD has been developed in recent years. By placing an SNSPD atop an optical waveguide that has been fabricated on various substrate materials, photons propagating in the waveguide have been found to be evanescently absorbed by nanowires that are only a few tens of microns long. The on-chip DE of this device has been estimated to be over 90%, thus indicating that it has both high absorptance and high intrinsic DE. If the waveguide and the nanowire are correctly dimensioned, the absorptance of this device can reach over 90% for a wavelength range of more than 700 nm. Furthermore, the length of the nanowire is shorter than that of the fiber-coupled SNSPD, thus leading to a higher count rate and lower timing jitter (~18 ps). However, unsatisfactory coupling losses between the optical fiber and the waveguide in such devices can decrease its SDE (~10%), thus limiting its applicability to quantum photonic integrated circuits (QPIC). Recently, we proposed a type of SNSPD that was coupled with microfibers (MFs), and simulations for this SNSPD indicated that its absorption would be as high as 90%. Microfibers and nanofibers, tapered adiabatically from standard fibers, with diameters close to or smaller than the wavelength of the guided light were demonstrated to have low transmittance losses by Tong et al. in 2003. MFs have been shown to have many interesting properties, such as strong evanescent fields, tight optical confinement, wideband abilities, and small masses; these properties are appealing for applications such as optical sensing and coupling. MFs also provide seamless connections with high transmittance from standard fibers; therefore, MF-coupled SNSPDs can achieve both high SDEs and wideband compatibility. We proposed and demonstrated the MF-coupled SNSPDs successfully. The simulation results indicate that with optimal device structure, the optical absorption with efficiency < 90% can be realized over a wavelength range of 350 nm to 2150 nm. The fabricated MF-coupled SNSPD, shows unparalleled broadband system detection efficiencies (SDEs) of more than 50% from 630 nm to 1500 nm. The SDEs reach 66% at 785 nm and 45% at 1550 nm. These results pave the way for ultra-broadband weak light detection with quantum-limit sensitivity.
Superconducting nanowires enable the operation of outstanding single-photon detectors, which are required particularly for quantum information and weak-light measurement applications. However, the trade-off between detection speed and efficiency, which is related to the filling factors of superconducting nanowires, is still a challenge. Here, we propose a fast, efficient single-photon detector fabricated by integrating ultralow-filling-factor meandered superconducting nanowires atop a photonic crystal (PhC) resonator. This unique structure enables a fast photon response due to the low kinetic inductance of the short nanowires and ensures efficient photon absorption due to the resonant effect of the PhC structure. The proposed detector has a filling factor of only ∼12% while maintaining a high maximum absorption in our simulation of 90%. The fabricated device exhibits a maximum system detection efficiency of 60%, a maximum count rate of ∼80 MHz, and a recovery time of only ∼12 ns, which is three times faster than that of the conventional meandered structure at the same sensing diameter (18 μm). This work helps advance the movement toward high-efficiency, high-speed single-photon detectors and promotes their future application in quantum communication and imaging.