arXiv subjects

Sihao Wang

Publications and source records attributed to Sihao Wang.

24 records · Page 2Linked to original sources

arXiv2019

Lithium-Niobate-on-Insulator Waveguide-Integrated Superconducting Nanowire Single-Photon Detectors

We demonstrate waveguide-integrated superconducting nanowire single-photon detectors on thin-film lithium niobate (LN). Using a 250 um-long NbN superconducting nanowire lithographically defined on top of a 125 um-long LN nanowaveguide, on-chip detection efficiency of 46% is realized with simultaneous high performance in dark count rate and timing jitter. As LN possesses high second-order nonlinear \c{hi}(2) and electro-optic properties, an efficient single-photon detector on thin-film LN opens up the possibility to construct small scale fully-integrated quantum photonic chip which includes single-photon sources, filters, tunable quantum gates and detectors.

physics.app-ph↗

arXiv2019

Incorporation of erbium ions into thin-film lithium niobate integrated photonics

As an active material with favorable linear and nonlinear optical properties, thin-film lithium niobate has demonstrated its potential in integrated photonics. Integration with rare-earth ions, which are promising candidates for quantum memories and transducers, will enrich the system with new applications in quantum information processing. Here, we investigate the optical properties at 1.5 micron wavelengths of rare-earth ions (Er$^{3+}$) implanted in thin-film lithium niobate waveguides and micro-ring resonators. Optical quality factors near a million after post annealing show that ion implantation damage can be successfully repaired. The transition linewidth and fluorescence lifetime of erbium ions are characterized, revealing values comparable to bulk-doped crystals. The ion-cavity coupling is observed through a Purcell enhanced fluorescence, from which a Purcell factor of ~3.8 is extracted. This platform is compatible with top-down lithography processes and leads to a scalable path for controlling spin-photon interfaces in photonic circuits.

physics.optics↗

arXiv2019

Superconducting nanowire single-photon detectors fabricated from atomic-layer-deposited NbN

High-quality ultra-thin films of niobium nitride (NbN) are developed by plasma-enhanced atomic layer deposition (PEALD) technique. Superconducting nanowire single-photon detectors (SNSPDs) patterned from this material exhibit high switching currents and saturated internal efficiencies over a broad bias range at 1550 nm telecommunication wavelength. Statistical analyses on hundreds of fabricated devices show near-unity throughput yield due to exceptional homogeneity of the films. The ALD-NbN material represents an ideal superconducting material for fabricating large single-photon detector arrays combining high efficiency, low jitter, low dark counts.

physics.app-ph↗

arXiv2019

Broadband on-chip single-photon spectrometer

Single-photon counters are single-pixel binary devices that click upon the absorption of a photon but obscure its spectral information, whereas resolving the colour of detected photons has been in critical demand for frontier astronomical observation, spectroscopic imaging and wavelength division multiplexed quantum communications. Current implementations of single-photon spectrometers either consist of bulky wavelength-scanning components or have limited detection channels, preventing parallel detection of broadband single photons with high spectral resolutions. Here, we present the first broadband chip-scale single-photon spectrometer covering both visible and infrared wavebands spanning from 600nm to 2000nm. The spectrometer integrates an on-chip dispersive echelle grating with a single-element propagating superconducting nanowire detector of ultraslow-velocity for mapping the dispersed photons with high spatial resolutions. The demonstrated on-chip single-photon spectrometer features small device footprint, high robustness with no moving parts and meanwhile offers more than 200 equivalent wavelength detection channels with further scalability.

physics.app-ph↗

arXiv2018

Superconducting cavity electro-optics: a platform for coherent photon conversion between superconducting and photonic circuits

Leveraging the quantum information processing ability of superconducting circuits and long-distance distribution ability of optical photons promises the realization of complex and large-scale quantum networks. In such a scheme, a coherent and efficient quantum transducer between superconducting and photonic circuits is critical. However, such quantum transducer is still challenging since the use of intermediate excitations in current schemes introduces extra noise and limits bandwidth. Here we realize direct and coherent transduction between superconducting and photonic circuits based on triple-resonance electro-optics principle, with integrated devices incorporating both superconducting and optical cavities on the same chip. Electromagnetically induced transparency is observed, indicating the coherent interaction between microwave and optical photons. Internal conversion efficiency of 25.9\pm0.3\% has been achieved, with 2.05\pm0.04\% total efficiency. Superconducting cavity electro-optics offers broad transduction bandwidth and high scalability, and represents a significant step towards the integrated hybrid quantum circuits and distributed quantum computation.

physics.optics↗

arXiv2012

Optical conductivity study of screening of many-body effects in graphene interfaces

Theoretical studies have shown that electron-electron (e-e) and electron-hole (e-h) interactions play important roles in many observed quantum properties of graphene making this an ideal system to study many body effects. In this report we show that spectroscopic ellipsometry can enable us to measure this interactions quantitatively. We present spectroscopic data in two extreme systems of graphene on quartz (GOQ), an insulator, and graphene on copper (GOC), a metal which show that for GOQ, both e-e and e-h interactions dominate while for GOC e-h interactions are screened. The data further enables the estimation of the strength of the many body interaction through the effective fine structure constant, $α_{g}^{*}$. The $α_{g}^{*}$ for GOQ indicates a strong correlation with an almost energy independent value of about 1.37. In contrast, $α_{g}^{*}$ value of GOC is photon energy dependent, is almost two orders of magnitude lower at low energies indicating very weak correlation.

cond-mat.mes-hall↗