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Study for the development of a cavity enhanced single photon source

Elisa Da Ros

Published Dec 1, 2014• 0 citations
OpenAlex

Abstract

The nitrogen-vacancy defect in diamond (NV centre) is a leading candidate for solid-state implementations of quantum information technologies. Among other useful properties, it is a bright source of single photons. It is difficult, though, to collect the emitted photons in a single spatial and spectral mode which is often needed for quantum information applications. One way to improve the single-mode collection efficiency is to embed an NV centre in a high-finesse cavity. The coupling of the NV centre dipole to the cavity mode gives rise to the Purcell enhancement -- an increase of the emission into the cavity's spectral and spatial mode. The goal of this project will be to develop a fibre-based microcavity and to use it for the observation of enhanced single-photon emission from a diamond nanocrystal. It will involve a wide range of experimental techniques, for example basic optics (particularly Gaussian beam propagation), CO2 laser ablation, surface analysis by optical and atomic force microscopes, interferometry, photon counting, etc. There will also be a certain amount of data analysis, simulations and theoretical calculations.

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A room temperature single photon source, cavity coupling of single solid-state defects to open-access microcavitie

Sanmi Adekanye

Room temperature solid-state emitters provide a promising source of single photons for use in quantum technologies. The emitters studied in this thesis are the nitrogen-vacancy (NV) centre in diamond, and defects in two-dimensional hexagonal boron nitride (hBN). In this thesis, I present investigations into the coupling of these defects to open-access microcavities at room temperature. The optical microcavity serves to confine the electric field down to mode volumes on the order of λ3, increasing the spontaneous emission rate of these emitters and channelling this emission into well defined cavity modes. The general properties of both emitters will be presented, including examples of single photon emission, emission spectra, saturation behaviour and photo-stability. A few examples highlighting the long-term photo-stability of the NV centre under pulsed excitation will be displayed. This will highlight the suitability of the NV centre for a practical device. Following the preparation and characterisation of each emitter, single photon emission into the cavity modes is verified, reaching single photon purities greater than 97%. Enhancements in the spectral density of photons were observed for both the NV centre (~25×) and defect in hBN (~3×), along with decreases in the excited state lifetimes. While the NV centre provides a stable source of single photons, the cavity enhancement is limited by its broad emission spectrum. Defects in hBN present near-ideal optical properties in the absence of the cavity, and were expected to deliver superior results within the cavity. However, the poor photo-stability of these defects did not allow complete characterisation of the cavity coupled emission. FDTD simulations were combined with changes in the excited state lifetime to infer the quantum efficiency of these defects. The results of this thesis form the foundation for the realisation of a robust room temperature single photon source.

•Jan 1, 2019•0 citations

Cavity enhancement of a Nitrogen-Vacancy-based single photon source

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The optically active Nitrogen-Vacancy (NV) defect in diamond holds substantial promise as a potential single photon source for quantum cryptography. Here we report enhanced spectral properties of an NV centre through a high-quality single-moded cavity coupled to an optical fibre. We use the secure bit rate of the BB84 quantum key distribution protocol as our figure of merit to demonstrate the significant improvements from employing state of the art cavities.

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Coupling nitrogen-vacancy centers in diamond to fiber-based Fabry-Pérot microcavities

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This thesis investigates the coupling of the fluorescence of nitrogen-vacancy (NV) centers in diamond to tunable optical microresonators at ambient conditions, in particular in the regime of Purcell enhancement. We use fiber-based, open-access Fabry-Pérot cavities optimized for high finesse and ultra-small mode volume. Different regimes of cavity enhancement are studied that are complementary to each other: A first experiment relies on a high-finesse cavity with dielectric mirrors. The scaling laws of Purcell enhancement are explicitly demonstrated by a large-range variation of both the cavity mode volume (V = 16 − 600 µm^3 ) and the quality factor (Q = 6 · 10^3 − 2 · 10^6). We detect an enhancement of the emission spectral density by up to a factor of 300. The full potential of this resonator can be exploited with emitters having a linewidth which is narrower than the resonance linewidth of the cavity. This concept holds promise for the implementation of wavelength-tunable, narrow-band single-photon sources as well as the generation of indistinguishable single-photons at ambient conditions. However, for broad-band emitters like the NV center at room temperature, the emission lifetime is not affected noticeably in this configuration. In order to directly observe lifetime changes and Purcell-enhanced single-photon emission, we manufacture fiber-based cavities with silver-coated mirrors having ultra-small mode volumes, as small as V = 1.0 λ^3 = 0.34 µm^3. We demonstrate cavity-enhanced fluorescence imaging, which allows to locate and analyze several single NV centers with one cavity. The Purcell effect is evidenced by an enhanced fluorescence collection of up to 1.6 · 10^6 photons per second from single-NV centers and a tunable variation of the emission lifetime corresponding to an effective Purcell factor of up to 2. We furthermore investigate a benefcial regime of optical confinement where the Fabry-Pérot cavity mode is combined with additional mode confinement by the diamond nanocrystal itself, enabling sub-λ^3 mode volumes. We perform simulations that predict effective Purcell factors of up to 11 for NV centers and of up to 63 for silicon-vacancy centers, revealing a great potential for bright single-photon sources and effcient spin readout at ambient conditions.

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The coupling of Nitrogen-Vacancy centres in diamond to tunable open-microcavities

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The Nitrogen-Vacancy (NV) centre in diamond possesses an optical read out of its spin state and shows great promise for applications in solid state quantum technologies. Its broad phonon assisted emission spectrum, with only 4% of emission from the zero-phonon line, is a major drawback to this. The optical microcavity will be essential in efficiently interfacing these centres with photonic networks. Here we present investigations into the coupling of NV centres in nanodiamond to tunable open-microcavities, both at room temperature and at cryogenic temperatures. These structures will be shown to achieve good photon confinement, with mode volumes down to 5λ3. Room temperature studies on ensembles of NVs will illustrate the tunable spectral and spatial overlap between the emitter and the cavity mode. It will be shown that small enhancements are possible in this regime. After the preparation and characterisation of single emitters, low temperature coupling to the narrowed zero-phonon line will be the central theme of this thesis. Single photon emission into the cavity mode is verified. We observe the enhancement of the light-matter interaction in this regime, by a 39% increase in the emission rate when cavity-coupled, with the dependence on mode volume also demonstrated. These results are important for the realisation of a spin-photon interface in scalable quantum networks.

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Purcell-Enhanced Single-Photon Emission from Nitrogen-Vacancy Centers Coupled to a Tunable Microcavity

Hanno Kaupp, Thomas Hümmer, Matthias Mader +7 more

Solid-state quantum emitters such as the N-$V$ center in diamond have applications ranging from single-photon sources to quantum sensors, with some quantum properties preserved even under ambient conditions. A central challenge is to access these quantum properties efficiently, by catching as much emitted light as possible. In this study a tunable optical microcavity, with a mode volume as small as one wavelength cubed, is used to enhance spontaneous emission of single N-$V$ centers in diamond, via the Purcell effect. This allows the authors to extract large amounts of light from several individually addressable emitters, and to control their spontaneous-emission rate.

arXiv:1606.00167•Physical Review Applied•Nov 22, 2016•117 citations

The coupling of Nitrogen-Vacancy centres in diamond to tunable open-microcavities

Sam Johnson

The Nitrogen-Vacancy (NV) centre in diamond possesses an optical read out of its spin state and shows great promise for applications in solid state quantum technologies. Its broad phonon assisted emission spectrum, with only 4p of emission from the zero-phonon line, is a major drawback to this. The optical microcavity will be essential in efficiently interfacing these centres with photonic networks. Here we present investigations into the coupling of NV centres in nanodiamond to tunable open-microcavities, both at room temperature and at cryogenic temperatures. These structures will be shown to achieve good photon confinement, with mode volumes down to 5λ3. Room temperature studies on ensembles of NVs will illustrate the tunable spectral and spatial overlap between the emitter and the cavity mode. It will be shown that small enhancements are possible in this regime. After the preparation and characterisation of single emitters, low temperature coupling to the narrowed zero-phonon line will be the central theme of this thesis. Single photon emission into the cavity mode is verified. We observe the enhancement of the light-matter interaction in this regime, by a 39p increase in the emission rate when cavity-coupled, with the dependence on mode volume also demonstrated. These results are important for the realisation of a spin-photon interface in scalable quantum networks.

•Jan 1, 2015•0 citations
The nitrogen-vacancy defect in diamond (NV centre) is a leading candidate for solid-state implementations of quantum information technologies. Among other useful properties, it is a bright source of single photons. It is difficult, though, to collect the emitted photons in a single spatial and spectral mode which is often needed for quantum information applications. One way to improve the single-mode collection efficiency is to embed an NV centre in a high-finesse cavity. The coupling of the NV centre dipole to the cavity mode gives rise to the Purcell enhancement -- an increase of the emission into the cavity's spectral and spatial mode.
The goal of this project will be to develop a fibre-based microcavity and to use it for the observation of enhanced single-photon emission from a diamond nanocrystal. It will involve a wide range of experimental techniques, for example basic optics (particularly Gaussian beam propagation), CO2 laser ablation, surface analysis by optical and atomic force microscopes, interferometry, photon counting, etc. There will also be a certain amount of data analysis, simulations and theoretical calculations.
Room temperature solid-state emitters provide a promising source of single photons for use in quantum technologies. The emitters studied in this thesis are the nitrogen-vacancy (NV) centre in diamond, and defects in two-dimensional hexagonal boron nitride (hBN). In this thesis, I present investigations into the coupling of these defects to open-access microcavities at room temperature. The optical microcavity serves to confine the electric field down to mode volumes on the order of λ3, increasing the spontaneous emission rate of these emitters and channelling this emission into well defined cavity modes. The general properties of both emitters will be presented, including examples of single photon emission, emission spectra, saturation behaviour and photo-stability. A few examples highlighting the long-term photo-stability of the NV centre under pulsed excitation will be displayed. This will highlight the suitability of the NV centre for a practical device. Following the preparation and characterisation of each emitter, single photon emission into the cavity modes is verified, reaching single photon purities greater than 97%. Enhancements in the spectral density of photons were observed for both the NV centre (~25×) and defect in hBN (~3×), along with decreases in the excited state lifetimes. While the NV centre provides a stable source of single photons, the cavity enhancement is limited by its broad emission spectrum. Defects in hBN present near-ideal optical properties in the absence of the cavity, and were expected to deliver superior results within the cavity. However, the poor photo-stability of these defects did not allow complete characterisation of the cavity coupled emission. FDTD simulations were combined with changes in the excited state lifetime to infer the quantum efficiency of these defects. The results of this thesis form the foundation for the realisation of a robust room temperature single photon source.
This thesis investigates the coupling of the fluorescence of nitrogen-vacancy (NV) centers in diamond to tunable optical microresonators at ambient conditions, in particular in the regime of Purcell enhancement. We use fiber-based, open-access Fabry-Pérot cavities optimized for high finesse and ultra-small mode volume. Different regimes of cavity enhancement are studied that are complementary to each other: A first experiment relies on a high-finesse cavity with dielectric mirrors. The scaling laws of Purcell enhancement are explicitly demonstrated by a large-range variation of both the cavity mode volume (V = 16 − 600 µm^3 ) and the quality factor (Q = 6 · 10^3 − 2 · 10^6). We detect an enhancement of the emission spectral density by up to a factor of 300. The full potential of this resonator can be exploited with emitters having a linewidth which is narrower than the resonance linewidth of the cavity. This concept holds promise for the implementation of wavelength-tunable, narrow-band single-photon sources as well as the generation of indistinguishable single-photons at ambient conditions. However, for broad-band emitters like the NV center at room temperature, the emission lifetime is not affected noticeably in this configuration. In order to directly observe lifetime changes and Purcell-enhanced single-photon emission, we manufacture fiber-based cavities with silver-coated mirrors having ultra-small mode volumes, as small as V = 1.0 λ^3 = 0.34 µm^3. We demonstrate cavity-enhanced fluorescence imaging, which allows to locate and analyze several single NV centers with one cavity. The Purcell effect is evidenced by an enhanced fluorescence collection of up to 1.6 · 10^6 photons per second from single-NV centers and a tunable variation of the emission lifetime corresponding to an effective Purcell factor of up to 2. We furthermore investigate a benefcial regime of optical confinement where the Fabry-Pérot cavity mode is combined with additional mode confinement by the diamond nanocrystal itself, enabling sub-λ^3 mode volumes. We perform simulations that predict effective Purcell factors of up to 11 for NV centers and of up to 63 for silicon-vacancy centers, revealing a great potential for bright single-photon sources and effcient spin readout at ambient conditions.
The Nitrogen-Vacancy (NV) centre in diamond possesses an optical read out of its spin state and shows great promise for applications in solid state quantum technologies. Its broad phonon assisted emission spectrum, with only 4% of emission from the zero-phonon line, is a major drawback to this. The optical microcavity will be essential in efficiently interfacing these centres with photonic networks. Here we present investigations into the coupling of NV centres in nanodiamond to tunable open-microcavities, both at room temperature and at cryogenic temperatures. These structures will be shown to achieve good photon confinement, with mode volumes down to 5λ3. Room temperature studies on ensembles of NVs will illustrate the tunable spectral and spatial overlap between the emitter and the cavity mode. It will be shown that small enhancements are possible in this regime. After the preparation and characterisation of single emitters, low temperature coupling to the narrowed zero-phonon line will be the central theme of this thesis. Single photon emission into the cavity mode is verified. We observe the enhancement of the light-matter interaction in this regime, by a 39% increase in the emission rate when cavity-coupled, with the dependence on mode volume also demonstrated. These results are important for the realisation of a spin-photon interface in scalable quantum networks.
Solid-state quantum emitters such as the N-VVV center in diamond have applications ranging from single-photon sources to quantum sensors, with some quantum properties preserved even under ambient conditions. A central challenge is to access these quantum properties efficiently, by catching as much emitted light as possible. In this study a tunable optical microcavity, with a mode volume as small as one wavelength cubed, is used to enhance spontaneous emission of single N-VVV centers in diamond, via the Purcell effect. This allows the authors to extract large amounts of light from several individually addressable emitters, and to control their spontaneous-emission rate.
The Nitrogen-Vacancy (NV) centre in diamond possesses an optical read out of its spin state and shows great promise for applications in solid state quantum technologies. Its broad phonon assisted emission spectrum, with only 4p of emission from the zero-phonon line, is a major drawback to this. The optical microcavity will be essential in efficiently interfacing these centres with photonic networks. Here we present investigations into the coupling of NV centres in nanodiamond to tunable open-microcavities, both at room temperature and at cryogenic temperatures. These structures will be shown to achieve good photon confinement, with mode volumes down to 5λ3. Room temperature studies on ensembles of NVs will illustrate the tunable spectral and spatial overlap between the emitter and the cavity mode. It will be shown that small enhancements are possible in this regime. After the preparation and characterisation of single emitters, low temperature coupling to the narrowed zero-phonon line will be the central theme of this thesis. Single photon emission into the cavity mode is verified. We observe the enhancement of the light-matter interaction in this regime, by a 39p increase in the emission rate when cavity-coupled, with the dependence on mode volume also demonstrated. These results are important for the realisation of a spin-photon interface in scalable quantum networks.