Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Frequency-definite photon pairs from a Lithium Niobate waveguide resonator

Stefan Kazmaier, Kaisa Laiho

Published Sep 1, 2026• 0 citations
OpenAlex

Abstract

Quantum light sources that will be embedded in future quantum networks like for example in long distance communication need to fulfil a versatile range of requirements. Most importantly, low propagation losses and a good time synchronization between the remote nodes are required. Additional constrains will be provided by other hardware components like the quantum memories that so far exist only for narrow spectral bandwidths. We present here a pulsed quantum light source based on parametric down-conversion in a periodically-poled Lithium Niobate waveguide (PPLN-WG) resonator. The end facets of the PPLN-WG are coated with a high reflection coating forming a Fabry-Perot Resonator (FPR). Our source works at the well-established telecommunication C-Band and produces in pulsed operation photon pairs with a 2GHz bandwidth. Here, we present a thorough investigation of the FPR, its bandwidth, the group indices of the PPLN-WG, as well as the temporal pulse shapes of the photon pairs paving our way towards the generation of the time-bin entanglement.

Related papers

Waveguide-based OPO source of entangled photon pairs

Enrico Pomarico, Bruno Sanguinetti, Nicolas Gisin +5 more

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.

arXiv:0909.1208•New Journal of Physics•Nov 24, 2009•81 citations

Time-Bin Properties of Photon Pairs from a 2GHz Waveguide Resonator

Stefan Kazmaier, Kaisa Laiho

We produce degenerate photon pairs called signal and idler via parametric down-conversion (PDC) in a Fabry-Pérot waveguide resonator having close to a 2GHz bandwidth in the telecom C-band. Our PDC source is based on a type-II periodically-poled Lithium Niobate waveguide with high-reflecting end facets forming the resonator. We measure the strength of the photon-pair correlation between signal and idler after selecting a single resonator mode from the multimode PDC emission. Thereafter, we investigate their sub-nanosecond long pulse shapes, in other words the time bins, with standard photon counting. We find that the time-bin durations vary significantly from each other, which can be predicted by the different optical losses of the cross-polarized signal and idler. Further, we simulate the temporal properties of signal and idler via the Fourier transform of their joint spectral characteristics. Our results deliver empiric insight about the time bins of photon pairs and are relevant for driving future quantum networks at the edge to narrow bandwidths but nevertheless in the pulsed regime.

quant-pharXiv:2610.09545•Oct 8, 2026•0 citations

Spectro-Temporal Study of Photon Pairs from a Lithium Niobate Waveguide Resonator

Stefan Kazmaier, Kaisa Laiho

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).

•Mar 2, 2026•0 citations

Waveguide-based OPO source of entangled photon pairs

Enrico Pomarico, Bruno Sanguinetti, Nicolas Gisin +5 more

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.

•Jan 1, 2009•50 citations

Generation and quantum characterization of miniaturized frequency entangled source in telecommunication band based on type-II periodically poled lithium niobate waveguide

Yue Zhang, Hou Fei-Yan, Tao Liu +3 more

The frequency entangled photon pairs generated by spontaneous parametric down-conversion (SPDC) possess wide applications in quantum optics and relevant fields.To facilitate the practical quantum information technologies,particularly in optical fiber links,a frequency entangled source at telecommunication wavelength with features of compactness,portability,high efficiency and miniaturization is highly desired.In this paper,we report the experimental generation of a miniaturized frequency entangled source in telecommunication band from a 10 mm-long type-Ⅱ periodically poled lithium niobate (PPLN) waveguide pumped by a 780 nm distributed Bragg reflector (DBR) laser diode.The frequency entangled photon pairs generated by SPDC possess wide applications in quantum optics and relevant fields.When the DBR laser diode is driven by a current of 170 mA at a temperature controlled to 20℃,the output power is measured to be 70.4 mW with a central wavelength of 780.585 nm.Under this pump,the orthogonally-polarized photon pairs are generated and output from the PPLN waveguide.After filtering out the remaining pump by three high-performance long-pass filters mounted on an adjustable U-type fiber bench,the photon-pair generation rate,spectral and temporal properties of the generated frequency entangled source are measured.The results show that the generation rate of the photon pairs,after being corrected for the detection efficiencies of the single photon detectors and the optical losses,is achieved to be 1.86×107 s-1 at a pump power of 44.9 mW (coupled into the waveguide).Optimizing the working temperature of the waveguide and fixing it at 46.5℃,the frequency degeneracy of the SPDC generated photon pairs is realized.Based on the coincidence measurement setup together with two infrared spectrometers,the spectra of the signal and idler photons are obtained with their center wavelengths of 1561.43 nm and 1561.45 nm,and their 3-dB bandwidths of 3.62 nm and 3.60 nm respectively.The joint spectrum of the photon pair is observed,showing a joint spectrum bandwidth of 3.18 nm.The degree of frequency entanglement is quantified to be 1.13 according to the bandwidth ratio between the single photon spectrum and the joint spectrum.Furthermore,based on the Hong-Ou-Mandel (HOM) interferometric coincidence measurement setup,a visibility of about 96.1% is observed,which indicates the very good frequency indistinguishibility of the down-converted biphotons.The measured 3-dB width of the HOM dip is 1.47 ps and shows good agreement with the measured single-photon spectral bandwidth.The experimental results lay a solid foundation for developing portable,miniaturized frequency entangled sources at telecommunication band for the further applications in quantum information areas,such as quantum time synchronization.

Acta Physica Sinica•Jan 1, 2018•4 citations

Generation of time-bin entangled photon pairs by cascaded second-order nonlinearity in a single periodically poled LiNbO_3 waveguide

Myrtille O. J. Y. Hunault, Hiroki Takesue, Osamu Tadanaga +2 more

Entangled photon pairs are one of the most important resources for the development of quantum communication technologies. In order to produce pulsed photon pairs in the telecommunication band from 1.5 mum pump light, most of the previous experiments used two successive periodically poled lithium niobate (PPLN) waveguides. We report what we believe to be a new method using cascaded second-order nonlinearity in a single PPLN waveguide to produce high-purity time-bin entangled photon pairs. We confirmed the generation of entanglement through a two-photon interference experiment showing a coincidence fringe with a visibility of up to 97%.

Optics Letters•Apr 15, 2010•59 citations
Quantum light sources that will be embedded in future quantum networks like for example in long distance communication need to fulfil a versatile range of requirements. Most importantly, low propagation losses and a good time synchronization between the remote nodes are required. Additional constrains will be provided by other hardware components like the quantum memories that so far exist only for narrow spectral bandwidths. We present here a pulsed quantum light source based on parametric down-conversion in a periodically-poled Lithium Niobate waveguide (PPLN-WG) resonator. The end facets of the PPLN-WG are coated with a high reflection coating forming a Fabry-Perot Resonator (FPR). Our source works at the well-established telecommunication C-Band and produces in pulsed operation photon pairs with a 2GHz bandwidth. Here, we present a thorough investigation of the FPR, its bandwidth, the group indices of the PPLN-WG, as well as the temporal pulse shapes of the photon pairs paving our way towards the generation of the time-bin entanglement.
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.
We produce degenerate photon pairs called signal and idler via parametric down-conversion (PDC) in a Fabry-Pérot waveguide resonator having close to a 2GHz bandwidth in the telecom C-band. Our PDC source is based on a type-II periodically-poled Lithium Niobate waveguide with high-reflecting end facets forming the resonator. We measure the strength of the photon-pair correlation between signal and idler after selecting a single resonator mode from the multimode PDC emission. Thereafter, we investigate their sub-nanosecond long pulse shapes, in other words the time bins, with standard photon counting. We find that the time-bin durations vary significantly from each other, which can be predicted by the different optical losses of the cross-polarized signal and idler. Further, we simulate the temporal properties of signal and idler via the Fourier transform of their joint spectral characteristics. Our results deliver empiric insight about the time bins of photon pairs and are relevant for driving future quantum networks at the edge to narrow bandwidths but nevertheless in the pulsed regime.
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).
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 frequency entangled photon pairs generated by spontaneous parametric down-conversion (SPDC) possess wide applications in quantum optics and relevant fields.To facilitate the practical quantum information technologies,particularly in optical fiber links,a frequency entangled source at telecommunication wavelength with features of compactness,portability,high efficiency and miniaturization is highly desired.In this paper,we report the experimental generation of a miniaturized frequency entangled source in telecommunication band from a 10 mm-long type-Ⅱ periodically poled lithium niobate (PPLN) waveguide pumped by a 780 nm distributed Bragg reflector (DBR) laser diode.The frequency entangled photon pairs generated by SPDC possess wide applications in quantum optics and relevant fields.When the DBR laser diode is driven by a current of 170 mA at a temperature controlled to 20℃,the output power is measured to be 70.4 mW with a central wavelength of 780.585 nm.Under this pump,the orthogonally-polarized photon pairs are generated and output from the PPLN waveguide.After filtering out the remaining pump by three high-performance long-pass filters mounted on an adjustable U-type fiber bench,the photon-pair generation rate,spectral and temporal properties of the generated frequency entangled source are measured.The results show that the generation rate of the photon pairs,after being corrected for the detection efficiencies of the single photon detectors and the optical losses,is achieved to be 1.86×107 s-1 at a pump power of 44.9 mW (coupled into the waveguide).Optimizing the working temperature of the waveguide and fixing it at 46.5℃,the frequency degeneracy of the SPDC generated photon pairs is realized.Based on the coincidence measurement setup together with two infrared spectrometers,the spectra of the signal and idler photons are obtained with their center wavelengths of 1561.43 nm and 1561.45 nm,and their 3-dB bandwidths of 3.62 nm and 3.60 nm respectively.The joint spectrum of the photon pair is observed,showing a joint spectrum bandwidth of 3.18 nm.The degree of frequency entanglement is quantified to be 1.13 according to the bandwidth ratio between the single photon spectrum and the joint spectrum.Furthermore,based on the Hong-Ou-Mandel (HOM) interferometric coincidence measurement setup,a visibility of about 96.1% is observed,which indicates the very good frequency indistinguishibility of the down-converted biphotons.The measured 3-dB width of the HOM dip is 1.47 ps and shows good agreement with the measured single-photon spectral bandwidth.The experimental results lay a solid foundation for developing portable,miniaturized frequency entangled sources at telecommunication band for the further applications in quantum information areas,such as quantum time synchronization.
Entangled photon pairs are one of the most important resources for the development of quantum communication technologies. In order to produce pulsed photon pairs in the telecommunication band from 1.5 mum pump light, most of the previous experiments used two successive periodically poled lithium niobate (PPLN) waveguides. We report what we believe to be a new method using cascaded second-order nonlinearity in a single PPLN waveguide to produce high-purity time-bin entangled photon pairs. We confirmed the generation of entanglement through a two-photon interference experiment showing a coincidence fringe with a visibility of up to 97%.