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arXiv:1404.0593 · Physical Review A

Highly efficient generation of single-mode photon pairs from a crystalline whispering-gallery-mode resonator source

Michael Förtsch, Gerhard Schunk, Josef Urban Fürst, Dmitry Strekalov, Thomas Gerrits, Martin J. Stevens, Florian Sedlmeir, Harald G. L. Schwefel, Sae Woo Nam, Gerd Leuchs, Christoph Marquardt

Published Feb 11, 2015• 52 citations
arXivHTMLPDF

Abstract

We report a highly efficient source of narrow-band photon pairs based on parametric down-conversion in a crystalline whispering-gallery-mode resonator. Remarkably, each photon of a pair is detected in a single spatial and temporal mode, as witnessed by Glauber's autocorrelation function. We explore the phase-matching conditions in spherical geometries, and determine the requirements for single-mode operation. Understanding these conditions has allowed us to experimentally demonstrate a single-mode pair-detection efficiency of $1.13\ifmmode\times\else\texttimes\fi{}{10}^{6}$ pairs/s per mW pump power per 26.8 MHz bandwidth.

DOI
10.1103/physreva.91.023812

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Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text M. Förtsch, G. Schunk, J. Fürst, F. Sedlmeir, D. Strekalov, H. G. L. Schwefel, T. Gerrits, M. J. Stevens, S. W. Nam, G. Leuchs, and C. Marquardt, "Highly efficient generation of narrow-band single-mode photon pairs from a whispering gallery mode resonator," in CLEO: 2014, OSA Technical Digest (online) (Optica Publishing Group, 2014), paper FW3A.6. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

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Optical parametric down-conversion has proven to be a valuable source of nonclassical light. The process is inherently able to produce twin-beam correlations along with individual intensity squeezing of either parametric beam, when pumped far above threshold. Here, we present for the first time the direct observation of intensity squeezing of -1.2 dB of each of the individual parametric beams in parametric down-conversion by use of a high quality whispering-gallery-mode disk resonator. In addition, we observed twin-beam quantum correlations of -2.7 dB with this cavity. Such resonators feature strong optical confinement and offer tunable coupling to an external optical field. This work exemplifies the potential of crystalline whispering-gallery-mode resonators for the generation of quantum light. The simplicity of this device makes the application of quantum light in various fields highly feasible.

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We report a highly efficient source of narrow-band photon pairs based on parametric down-conversion in a crystalline whispering-gallery-mode resonator. Remarkably, each photon of a pair is detected in a single spatial and temporal mode, as witnessed by Glauber's autocorrelation function. We explore the phase-matching conditions in spherical geometries, and determine the requirements for single-mode operation. Understanding these conditions has allowed us to experimentally demonstrate a single-mode pair-detection efficiency of 1.13\ifmmode×\else\texttimes\fi1061.13\ifmmode\times\else\texttimes\fi{}{10}^{6}1.13\ifmmode×\else\texttimes\fi106 pairs/s per mW pump power per 26.8 MHz bandwidth.
Cavity-enhanced spontaneous parametric down-conversion is capable of efficient generation of single photons with suitable spectral properties for interfacing with the atoms. However, beside the remarkable progress of this technique, multimode longitudinal emission remains a major drawback. Here, we demonstrate a bright source of single photons that overcomes this limitation by a novel mode-selection technique based on the introduction of an additional birefringent element to the cavity. This enables us to tune the double resonance condition independent of the phase matching and thus to achieve single-mode operation without mode filters. Our source emits single-frequency-mode photons at 852 nm, which is compatible to the Cs D2 line, with a bandwidth of 10.9 MHz and a detected photon-pair rate of 2.5 kHz at 10 mW of pump power, while maintaining g(2)(0) = 0.13. The efficiency of our source is further underlined by detecting a four-photon rate of 0.28 Hz at 20 mW of pump power. These detected rates correspond to a photon-pair generation rate of 47.5 Hz, and a four-photon generation rate of 37 Hz. Such photon generation rates open up a variety of new applications reaching from hybrid light-matter interactions to optical quantum information tasks based on long temporal coherence.
Single-photon sources play a crucial role in quantum information processing. Among the various methods for generating single photons, spontaneous parametric down-conversion (SPDC) is one of the most widely used. Numerous studies have demonstrated the implementation of SPDC sources across different platforms. Among these, crystalline whispering-gallery-mode resonators (WGMRs) represent an intriguing platform for realizing SPDC-based sources. WGMR-based SPDC sources have been shown to be capable of efficiently interacting with alkali atoms due to the narrow and tunable emission bandwidths. Moreover, they operate with relatively low pump power, which is advantageous for large-scale integration and power-constrained applications. In this work, we further demonstrate the versatility of WGMR-based SPDC sources through three key experiments. First, we generate polarization-entangled photon pairs using an interferometric scheme, achieving a Clauser–Horne–Shimony–Holt (CHSH) inequality parameter of 𝑆 =2.54 ±0.06, violating the classical bound by over eight standard deviations. Second, we observe Hong–Ou–Mandel interference with visibilities of 74 ±5% and 76 ±4% for photons from one and two independent WGMRs, respectively, using an in-coupled pump power as low as 50 nW. Finally, we demonstrate photon--ion interaction between a WGMR-generated photon and a ¹⁴⁷Yb⁺ ion with a success probability of 8%. These results highlight the potential of WGMR-based SPDC sources for scalable quantum networks and hybrid quantum systems.
Quantum repeaters rely on an interfacing of flying qubits with quantum memories. The most common implementations include a narrowband single photon matched in bandwidth and central frequency to an atomic system. Previously, we demonstrated the compatibility of our versatile source of heralded single photons, which is based on parametric down-conversion in a triply-resonant whispering-gallery mode resonator, with alkaline transitions [Schunk et al., Optica 2, 773 (2015)]. In this paper, we analyze our source in terms of phase matching, available wavelength-tuning mechanisms, and applications to narrow-band atomic systems. We resonantly address the D1 transitions of cesium and rubidium with this optical parametric oscillator pumped above its oscillation threshold. Below threshold, the efficient coupling of single photons to atomic transitions heralded by single telecom-band photons is demonstrated. Finally, we present an accurate analytical description of our observations. Providing the demonstrated flexibility in connecting various atomic transitions with telecom wavelengths, we show a promising approach to realize an essential building block for quantum repeaters.
Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text M. Förtsch, G. Schunk, J. Fürst, F. Sedlmeir, D. Strekalov, H. G. L. Schwefel, T. Gerrits, M. J. Stevens, S. W. Nam, G. Leuchs, and C. Marquardt, "Highly efficient generation of narrow-band single-mode photon pairs from a whispering gallery mode resonator," in CLEO: 2014, OSA Technical Digest (online) (Optica Publishing Group, 2014), paper FW3A.6. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article
Optical parametric down-conversion has proven to be a valuable source of nonclassical light. The process is inherently able to produce twin-beam correlations along with individual intensity squeezing of either parametric beam, when pumped far above threshold. Here, we present for the first time the direct observation of intensity squeezing of -1.2 dB of each of the individual parametric beams in parametric down-conversion by use of a high quality whispering-gallery-mode disk resonator. In addition, we observed twin-beam quantum correlations of -2.7 dB with this cavity. Such resonators feature strong optical confinement and offer tunable coupling to an external optical field. This work exemplifies the potential of crystalline whispering-gallery-mode resonators for the generation of quantum light. The simplicity of this device makes the application of quantum light in various fields highly feasible.