The interaction of a single quantum emitter with its environment is a central
theme in quantum optics. When placed in highly confined optical fields, such as
those created in optical cavities or plasmonic structures, the optical
properties of the emitter can change drastically. In particular, photonic
crystal (PC) cavities show high quality factors combined with an extremely
small mode volume. Efficiently coupling a single quantum emitter to a PC cavity
is challenging because of the required positioning accuracy. Here, we
demonstrate deterministic coupling of single Nitrogen-Vacancy (NV) centers to
high-quality gallium phosphide PC cavities, by deterministically positioning
their 50 nm-sized host nanocrystals into the cavity mode maximum with
few-nanometer accuracy. The coupling results in a 25-fold enhancement of NV
center emission at the cavity wavelength. With this technique, the NV center
photoluminescence spectrum can be reshaped allowing for efficient generation of
coherent photons, providing new opportunities for quantum science.Comment: 13 pages, 4 figure

Bouwmeester, D.

Hagemeier, J.

Hanson, R.

Heeres, E. C.

Kim, H.

Oosterkamp, T. H.

Petroff, P. M.

Pfaff, W.

Thon, S. M.

van der Sar, T.

English

arXiv

Sar, T. van der

Heeres, E.C.

Thon, S.M.

Petroff, P.M.

Oosterkamp, T.H.

Leiden University Scholary Publications

Deterministic nanoassembly of a coupled quantum emitter–photonic crystal cavitysystemT. van der Sar, J. Hagemeier, W. Pfaff, E. C. Heeres, S. M. Thon, H. Kim, P. M. Petroff, T. H. Oosterkamp, D.Bouwmeester, and R. HansonCitation: Appl. Phys. Lett. 98, 193103 (2011);View online: https://doi.org/10.1063/1.3571437View Table of Contents: http://aip.scitation.org/toc/apl/98/19Published by the American Institute of PhysicsArticles you may be interested inIndependent tuning of quantum dots in a photonic crystal cavityApplied Physics Letters 95, 243107 (2009); 10.1063/1.3275002Strong coupling through optical positioning of a quantum dot in a photonic crystal cavityApplied Physics Letters 94, 111115 (2009); 10.1063/1.3103885Independent electrical tuning of separated quantum dots in coupled photonic crystal cavitiesApplied Physics Letters 99, 161102 (2011); 10.1063/1.3651491Tuning micropillar cavity birefringence by laser induced surface defectsApplied Physics Letters 95, 251104 (2009); 10.1063/1.3276550Permanent tuning of quantum dot transitions to degenerate microcavity resonancesApplied Physics Letters 98, 121111 (2011); 10.1063/1.3569587Fiber-connectorized micropillar cavitiesApplied Physics Letters 97, 131113 (2010); 10.1063/1.3493187Deterministic nanoassembly of a coupled quantum emitter–photoniccrystal cavity systemT. van der Sar,1,a J. Hagemeier,2 W. Pfaff,1 E. C. Heeres,3 S. M. Thon,2 H. Kim,2,bP. M. Petroff,4 T. H. Oosterkamp,3 D. Bouwmeester,2,3 and R. Hanson11Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft,The Netherlands2Department of Physics, University of California–Santa Barbara, Santa Barbara, California 93106, USA3Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands4Department of Materials, University of California–Santa Barbara, Santa Barbara, California 93106, USAand Department of ECE, University of California–Santa Barbara, Santa Barbara, California 93106 USAReceived 9 November 2010; accepted 3 March 2011; published online 9 May 2011Controlling the interaction of a single quantum emitter with its environment is a key challenge inquantum optics. Here, we demonstrate deterministic coupling of single nitrogen-vacancy NVcenters to high-quality photonic crystal cavities. We preselect single NV centers and position their50-nm-sized host nanocrystals into the mode maximum of photonic crystal S1 cavities withfew-nanometer accuracy. The coupling results in a strong enhancement of NV center emission at thecavity wavelength. © 2011 American Institute of Physics. doi:10.1063/1.3571437Spontaneous light emission can be controlled by enhanc-ing or suppressing the vacuum fluctuations of the electro-magnetic field at the location of the light source.1 Whenplaced into highly confined optical fields, such as thosecreated in optical cavities or plasmonic structures, the opti-cal properties of single quantum emitters can changedrastically.2–5 In particular, photonic crystal PC cavitiesshow high quality factors combined with an extremely smallmode volume.6 It is challenging however to efficientlycouple single photon sources to a PC cavity because theemitter has to be positioned in the localized optical mode,which is confined to an extremely small volume with a sizeof about a wavelength.7–9Nitrogen-vacancy NV centers in diamond are promis-ing candidates for application as solid state quantumbits.10–12 Long distance entanglement between NV centersenabling quantum repeater protocols may be achieved bytwo-photon quantum interference,13,14 but is hindered by theNV centers’ weak coherent photon emission rate. Being ableto control and reshape the emission spectrum of a single NVcenter is therefore not only of fundamental interest but couldalso have potential applications in solid state quantum infor-mation processing.15Fabrication of high-quality PC cavities in diamondwould be a natural way to control the emission properties ofembedded NV centers but this is challenging because of thedifficulties in growing and etching diamond single-crystalthin films.16,17 An alternative, hybrid approach is to positiona diamond nanocrystal with a single NV center near a PCcavity of a different material.18–21 Because of the small sizeof such a crystal, the NV center can be placed in the highlyconfined optical mode where coupling can be efficient.Here, we demonstrate the deterministic nanoassembly ofcoupled single NV center–PC cavity systems by positioning50 nm sized diamond nanocrystals into gallium phosphideS1 cavities located on a different chip. The S1 cavity offersunique advantages over the well-studied L3 cavity.19,20Whereas in the L3 cavity the mode maximum is confinedwithin the dielectric material, the mode maximum of the S1cavity is localized in the air holes surrounding the cavity,making it accessible for coupling to external emitters. We areable to pick up and place a preselected diamond nanocrystalexactly into the mode maximum of a PC cavity, due to theversatility of our nanopositioning method. The coupling of asingle NV center to a PC cavity is evidenced by a Purcell-enhanced spontaneous emission rate at the cavity resonancefrequency.Our samples were grown by molecular beam epitaxy ona 100 gallium phosphide GaP wafer, with a 1 m sacri-ficial layer of Al0.75Ga0.25P, and a 120 nm GaP membranelayer. PC cavities were defined by e-beam lithography, fol-lowed by inductively coupled plasma etching to transfer theresist pattern into the substrate. An HF chemical wet etchselectively undercuts the sacrificial layer, leaving a free-standing membrane. Structure parameters were optimized us-ing finite-difference-time-domain simulations. The lowestenergy mode of these cavities generally has the highest qual-ity factor, up to 3800 for S1 cavities, to our knowledge thehighest reported value for a S1 PC cavity at these wave-lengths.We assemble a coupled single NV center–PC cavity sys-tem by nanopositioning a diamond nanocrystal into an airhole surrounding the cavity,22 where the S1 cavity has itsmaximum field intensity Fig. 1a. First, a home-built con-focal microscope is used to locate and identify single NVcenters on a chip that contains a sparse dispersion of dia-mond nanocrystals. We then select NV centers that do notshow switching from the negatively charged state to the neu-tral state.23 By accurately measuring the position of a candi-date NV center with respect to a gold marker fabricatedusing electron beam lithography, we can identify the hostnanocrystal inside a scanning electron microscope SEMFig. 1b. This SEM contains a home-built nanomanipula-tor with a sharp tungsten tip that is mounted on a piezoelec-tric stage with subnanometer positioning accuracy.24 Withthis tip we can pick up a nanocrystal Fig. 1c, and positionaElectronic mail: t.vandersar@tudelft.nl.bPresent address: Department of ECE, IREAP, University of Maryland, Col-lege Park, Maryland 20742, USA.APPLIED PHYSICS LETTERS 98, 193103 20110003-6951/2011/9819/193103/3/$30.00 © 2011 American Institute of Physics98, 193103-1it in an arbitrary new location on a different chip. Here, weposition a nanocrystal that contains a single NV center intothe hole of an S1 cavity Fig. 1d.25When an NV center is successfully coupled to the cavity,it will show an enhanced spontaneous emission rate at thecavity wavelength by means of the Purcell effect.1 Comparedto the spectrum of the NV center before positioning, thespectrum of the coupled system shows a sharp Fano-shapedresonance at the cavity frequency Fig. 2a.26–28To verify that the spectrum originates from a single NVcenter we perform a second-order autocorrelation measure-ment on photon detection times. After correcting for back-ground luminescence caused by substrate photoluminescencePL, we find an antibunching dip below 0.5 Fig. 2b.29,30The presence of a single NV center is also confirmed by thelevel of the observed PL. This in agreement with our previ-ous studies22 where we found that single NV centers are notaffected by the nanopositioning.To verify that the NV center is coupled to the cavity, wemeasure the spectrum of the NV center in the cavity middlepanel Fig. 2a as a function of optical excitation power. Byfitting this data, inset middle panel Fig. 2a, we obtain theamplitude of the cavity resonance and the zero phonon lineZPL as a function of optical excitation power Fig. 2c. Inaddition to a linear component caused by background lumi-nescence coupling to the cavity, we observe the same satu-ration behavior for the cavity resonance as for the NV cen-ter’s zero-phonon line. This in contrast to the purely linearincrease in background luminescence measured in cavitieswithout NV centers data not shown. We conclude that thecavity is being fed by single photons from the NV center, asthe finite optical lifetime of the NV center puts an upper limiton the photon emission rate.25The Purcell enhancement of the emission at the cavitywavelength can be estimated from the spectrum and the rela-tive detection efficiencies of cavity emission and NV centeremission. After subtracting the linear background contribu-tion from the spectrum in Fig. 2a middle panel, we findthat coupling to the cavity has increased the relative intensityof detected NV emission at the cavity wavelength by a factor4. This underestimates the actual Purcell enhancement be-cause far-field detection of light emitted by an S1 cavity isrelatively inefficient due to a large mode mismatch betweenthe cavity and detection channel.31 By comparing the detec-tion efficiency of S1 cavity emission obtained by calculatingits far-field emission profile following the method describedin Ref. 32 to the detection efficiency of directly detected NVcenter emission, we estimate the actual Purcell enhancementto be 25. For comparison, the calculated Purcell enhance-ment for an optimally oriented NV center is 100. By addingefficient on-chip PC outcoupling structures or by optimizingthe far-field emission profile of the cavity,33,34 the detectionefficiency can be increased, allowing the full cavity-enhanced emission to be exploited.In conclusion, we have demonstrated the coupling ofsingle NV centers to S1 PC cavities by positioning 50-nm-sized diamond nanocrystals exactly into the cavity modemaximum. By preselecting nanocrystals with single NV cen-ters that have rare but highly desirable optical propertiessuch as a lifetime limited linewidth,35 our method could be0 0.5 1(b)(c) (d)250 nm500 μm500 nm 200 nm2 μm2 μm250 nm(a)250 nmFIG. 1. Color online Nanoassembling a coupled single NV center–PCcavity system. a Top view and cross section through the center of an S1cavity showing the simulated intensity profile of the lowest energy mode. bSEM overview of the nanopositioning process. From the chip with nano-crystals below the dashed line, a nanocrystal that contains a single NVcenter is located using reference markers lower inset, and subsequentlypicked up using a sharp tip and transferred to a chip containing PCs abovethe dashed line. Top inset: close up of an S1 cavity. c SEM picture of ananocrystal on the tip. d SEM picture showing a single NV containingnanocrystal that has been positioned into a hole of an S1 cavity. In b–d,shades were added to the tip, the gold marker and the nanocrystals forclarity.637 644CP reflectionuncoupled PLcoupled PL102030620 640 660 680 700Countrate(1/s/nmbin)Intensity(a.u.)306090Wavelength (nm)Intensity(norm.)0 100 2000.00.51.0g2(τ)Delay time, τ (ns)(a) (b)(c)0 1 2 3012Power (mW)zero phonon linecavityQ=1.6x103FanoamplitudeFull bandwidthZPLamplitude200300#ofcoincidencesFIG. 2. Color online Characterization of a coupled NV center–cavity sys-tem. a Top panel: PL spectrum of a NV center before it was positioned intothe nearest air hole of a S1 cavity see Fig. 1d. Excitation: 300 W at532 nm. Middle panel: Spectrum of the coupled NV center–cavity system. AFano resonance is observed at the cavity frequency close to the zero phononline. Inset: Close up of the ZPL and the cavity line. The red line is a fit usinga linear background plus a Gaussian and a Fano lineshape to model theshape of the ZPL and cavity line respectively. Excitation: 500 W at 568nm 568 nm laser light induces less background PL than 532 nm. Bottompanel: CP reflection measurement showing the cavity resonance. All mea-surements were done at room temperature. b Measurement of the second-order auto-correlation function g2 of emission within a 615–700 nmbandwidth. Left axis: number of coincidences. Right axis: g2, correctedfor background contribution estimated from APD signals measured next tothe NV center indicated by the dashed line Ref. 30. Excitation: 300 Wat 568 nm c Power dependence of the ZPL and Fano amplitude obtainedby a fit as in Fig. 2a, and of the integrated spectrum. Solid lines are fitswith y=yP / P+ Psat+aP, where P is the excitation power, and y, Psat,and a are fit parameters. From the fit of the ZPL amplitude, which weassume to contain no background contribution a=0, we extract Psat=770 W. The other curves were fit using this value. All curves are nor-malized to their respective y, so that the difference with the ZPL curveindicates the relative background contribution.193103-2 van der Sar et al. Appl. Phys. Lett. 98, 193103 2011applied to reshape the NV center spectrum for a more effi-cient emission of coherent photons. We envision that nanoas-sembled, coupled NV center–cavity systems could serve asbuilding blocks for quantum optical engineering, potentiallyleading to the first observation of entanglement between dis-tant NV centers.This work is supported by Stichting voor FundamenteelOnderzoek der Materie FOM, the Nederlandse Organisatievoor Wetenschappelijk Onderzoek NWO, and the EUSOLID program. T.H.O. acknowledges support from Tech-nologiestichting STW and from an ERC Starting Grant. D.B.acknowledges support from NSF Grant No. 0901886 andMarie Curie Grant No. EXT-CT-2006-042580. J.H. acknowl-edges support from a U.S. Department of EducationGAANN grant.1L. Mandel and E. 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Deterministic nanoassembly of a coupled quantum emitter-photonic crystal cavity system

NARCIS 

T. van der Sar

J. Hagemeier

W. Pfaff

E. C. Heeres

S. M. Thon

H. Kim

P. M. Petroff

T. H. Oosterkamp

D. Bouwmeester

R. Hanson

Crossref

Applied Physics Letters

Deterministic nanoassembly of a coupled quantum emitter–photonic crystal cavity system

Controlling the interaction of a single quantum emitter with its environment is a key challenge in quantum optics. Here, we demonstrate deterministic coupling of single nitrogen-vacancy (NV) centers to high-quality photonic crystal cavities. We preselect single NV centers and position their 50-nm-sized host nanocrystals into the mode maximum of photonic crystal S1 cavities with few-nanometer accuracy. The coupling results in a strong enhancement of NV center emission at the cavity wavelength.QN/Quantum NanoscienceApplied Science

Van der Sar, T. (author)

Hagemeier, J. (author)

Pfaff, W. (author)

Heeres, E.C. (author)

Thon, S.M. (author)

Kim, H. (author)

Petroff, P.M. (author)

Oosterkamp, T.H. (author)

Bouwmeester, D. (author)

Hanson, R. (author)

TU Delft Repository

Controlling the interaction of a single quantum emitter with its environment is a key challenge in quantum optics. Here, we demonstrate deterministic coupling of single nitrogen-vacancy (NV) centers to high-quality photonic crystal cavities. We preselect single NV centers and position their 50-nm-sized host nanocrystals into the mode maximum of photonic crystal S1 cavities with few-nanometer accuracy. The coupling results in a strong enhancement of NV center emission at the cavity wavelength

Van der Sar, T.

Deterministic nano-assembly of a coupled quantum emitter - photonic
  crystal cavity system

Deterministic nano-assembly of a coupled quantum emitter - photonic crystal cavity system

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Leiden University Scholary Publications

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Crossref

TU Delft Repository

NARCIS