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Frontiers in Optics

A monolithic, doubly-resonant parametric down-conversion source for Caesium Raman memories

Benjamin Brecht, O. Lazo-Arjona, K. T. Kaczmarek, T. Parker, Raimund Ricken, Viktor Quiring, Christof Eigner, Kai-Hong Luo, Harald Herrmann, Christine Silberhorn, Ian A. Walmsley

Published Jan 1, 2017• 0 citations
Publisher

Abstract

We demonstrate a monolithic, doubly-resonant parametric down-conversion source in periodically poled lithium niobate waveguide that is compatible with Caesium quantum memories. Our source generates signal and idler photons with wavelengths of 852.4 nm and 1601 nm, allowing for storage of the signal and low-loss fibre transmission of the idler. The photons exhibit spectral bandwidths of ∆νs ≈ 230 MHz and ∆νi ≈ 300 MHz, respectively. We find an effective mode number of K = 1.25(27) which demonstrates single mode emission, and a high spectral brightness of ∼ 1.8 · 104 pairs/(s mW MHz).

DOI
10.1364/fio.2017.jw4a.3

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Quantum Science and Technology•May 8, 2018•36 citations
We demonstrate a monolithic, doubly-resonant parametric down-conversion source in periodically poled lithium niobate waveguide that is compatible with Caesium quantum memories. Our source generates signal and idler photons with wavelengths of 852.4 nm and 1601 nm, allowing for storage of the signal and low-loss fibre transmission of the idler. The photons exhibit spectral bandwidths of ∆νs ≈ 230 MHz and ∆νi ≈ 300 MHz, respectively. We find an effective mode number of K = 1.25(27) which demonstrates single mode emission, and a high spectral brightness of ∼ 1.8 · 104 pairs/(s mW MHz).
We report on an integrated non-degenerate narrowband photon pair source produced at 890 nm and 1320nm via type II parametric down-conversion in a periodically poled waveguide with high-reflective dielectric mirrors deposited on the waveguide end faces. The conversion spectrum consists of three clusters and only 3 to 4 longitudinal modes with about 150 MHz bandwidth in each cluster. The high conversion efficiency in the waveguide, together with the spectral clustering in the double resonator, leads to a high brightness of 3×103 3\times10^3~3×103 pairs/(s⋅\cdot⋅mW⋅\cdot⋅MHz). The compact and rugged monolithic design makes the source a versatile device for various applications in quantum communication.
In this paper, we present a compact source of narrow-band energy–time-entangled photon pairs in the telecom regime based on a Ti-indiffused periodically poled lithium niobate (PPLN) waveguide resonator, i.e. a waveguide with end-face dielectric multi-layer mirrors. This is a monolithic doubly resonant optical parametric oscillator (OPO) far below threshold, which generates photon pairs by spontaneous parametric down-conversion (SPDC) at around 1560 nm with a 117 MHz (0.91 pm)-bandwidth. A coherence time of 2.7 ns is estimated by a time correlation measurement and a high quality of the entangled states is confirmed by a Bell-type experiment. Since highly coherent energy–time-entangled photon pairs in the telecom regime are suitable for long distance transmission and manipulation, this source is well suited to the requirements of quantum communication.
In this paper, we present a compact source of narrow-band energy–time-entangled photon pairs in the telecom regime based on a Ti-indiffused periodically poled lithium niobate (PPLN) waveguide resonator, i.e. a waveguide with end-face dielectric multi-layer mirrors. This is a monolithic doubly resonant optical parametric oscillator (OPO) far below threshold, which generates photon pairs by spontaneous parametric down-conversion (SPDC) at around 1560 nm with a 117 MHz (0.91 pm)-bandwidth. A coherence time of 2.7 ns is estimated by a time correlation measurement and a high quality of the entangled states is confirmed by a Bell-type experiment. Since highly coherent energy–time-entangled photon pairs in the telecom regime are suitable for long distance transmission and manipulation, this source is well suited to the requirements of quantum communication.
The practical prospect of quantum communication and information processing relies on sophisticated single-photon pairs, which feature a controllable waveform, narrow spectrum, excellent purity, fiber compatibility, and miniaturized design. For practical realizations, stable, miniaturized, low-cost devices are required. Sources with one or some of the above characteristics have already been demonstrated, but it is quite challenging to obtain a source with all of the described characteristics simultaneously. Here we report on an integrated single-longitudinal-mode, non-degenerate, narrowband photon pair source that exhibits all the requirements needed for quantum applications. The device is composed of a periodically poled, Ti-indiffused, lithium niobate waveguide with high reflective dielectric mirror coatings deposited on the waveguide end-faces. Photon pairs with wavelengths around 890 and 1320 nm are generated via type II phase-matched parametric down-conversion (PDC). Clustering in this dispersive cavity restricts the whole conversion spectrum to one single-longitudinal mode in a single cluster, yielding a narrow bandwidth of only 60 MHz. The high conversion efficiency in the waveguide, together with the spectral clustering in the doubly resonant waveguide, leads to a high brightness of pairs/(s mW MHz). This source exhibits prominent single-longitudinal-mode purity and remarkable temporal shaping capability. In particular, due to temporal broadening, we can observe that the coherence time of the two-photon component of the PDC state is actually longer than that of the single-photon states. The miniaturized monolithic design enables this source to have various fiber communication applications.
Lithium niobate is one of the most widely used platforms for generating photon pairs, usually called signal and idler, via parametric down-conversion (PDC). Here we characterize a commercially available type-II periodically-poled lithium niobate waveguide (PPLN-WG) with highly reflecting end-facets forming a resonator at the PDC wavelengths. We measure conventional key figures of merit of our PDC source, including the coincidence-to-accidentals ratio (CAR), Klyshko efficiencies, and the temporal profile of signal and idler. Furthermore, by independently measuring the optical path length difference of signal and idler, we additionally extract the phasematching bandwidth, the group delay, and the resonators cluster spacing [1]. These results provide a comprehensive performance assessment of the device and support its use in quantum optics and integrated photonics applications. [1] Kazmaier and Laiho, Phys. Scr. 100, 081502 (2025).
Abstract We demonstrate an ultrabright, narrow-band and frequency-tunable photon-pair source based on cavity-enhanced spontaneous parametric down conversion (SPDC) which is compatible with atomic transition of rubidium D 2 -line (780 nm) or cesium D 2 -line (852 nm). With the pump beam alternating between a high and a low power phase, the output is switching between the optical parametric oscillator (OPO) and photon-pair generation mode. We utilize the OPO output light to lock the cavity length to maintain the double resonances of signal and idler, as well as to lock the signal frequency to cesium atomic transition. With a type-II phase matching and a double-passed pump scheme such that the cluster frequency spacing is larger than the SPDC bandwidth, the photon-pair output is in a nearly single-mode operation as confirmed by a scanning Fabry–Perot interferometer with its output detected by a photomultiplier. The achieved generation and detection rates are 7.24 × 10 5 and 6142 s −1 mW −1 , respectively. The correlation time of the photon pair is 21.6(2.2) ns, corresponding to a bandwidth of 2 π × 6.6(6) MHz. The spectral brightness is 1.06 × 10 5 s −1 mW −1 MHz −1 . This is a relatively high value under a single-mode operation with the cavity-SPDC scheme. The generated single photons can be readily used in experiments related to atomic quantum memories.