Widely Tunable Single-Photon Source from a Carbon Nanotube in the Purcell Regime

Abstract

Single-Wall Carbon Nanotubes (SWNTs) are among the very few candidates for single-photon sources operating in the telecom bands since they exhibit large photon antibunching up to room temperature [1][2][3][4][5]. However, coupling a nanotube to a photonic structure is highly challenging because of the random location and emission wavelength in the growth process [6][7][8][9]. Here, we demonstrate the realization of a widely tunable single-photon source by using a carbon nanotube inserted in an original repositionable fiber micro-cavity: we fully characterize the emitter in the free-space and subsequently form the cavity around the nanotube. This brings an invaluable insight into the emergence of quantum electrodynamical effects. We observe an efficient funneling of the emission into the cavity mode with a strong sub-Poissonian statistics together with an up to 6-fold Purcell enhancement factor. By exploiting the cavity feeding effect on the phonon wings, we locked the single-photon emission at the cavity frequency over a 4 THz-wide band while keeping the mode width below 80 GHz. This paves the way to multiplexing and multiple qubit coupling.Coupling a carbon nanotube to a photonic resonator in a reliable way is highly desirable both for technological developments in view of quantum cryptography or quantum computation and for academical studies since nanotubes behave like an original nano-emitter showing an hybrid 1D-0D electronic behavior [10]. In addition, the low-cost, the high integrability and the possible electrical excitation of nanotubes [11] are attractive assets in such perspectives. However, due to the lack of control of the current growth or deposition processes, current attempts rely on random spectral and spatial matching between a resonator (micro-discs [12] or photonic crystals [13]) and randomly deposited nanotubes, leading to a very limited fabrication yield. This constrain becomes especially stringent when a high coupling between the emitter and the cavity is sought, which requires narrow spectral features.In this work, we propose an original approach where the nanotube is fully characterized in free-space by regular low-temperature micro-photoluminescence (micro-PL) spectroscopy and where a micro-cavity is subsequently formed around the emitter by approaching a concave dielectric mirror micro-engineered at the apex of an optical fiber. This geometry brings an unprecedented flexibility giving a built-in spectral and spatial matching, together with excellent quality factors and mode volumes [14]. Individual carbon nanotubes embedded in a polystyrene matrix were coupled to the cavity resulting in a strong brightening of the nanotube of more than an order of magnitude, bringing evidence for the relevance of exploiting cavity quantum electrodynamical (CQED) effects to enhance the photonic properties of carbon nanotubes. By means of time-resolved measurements we were able to investigate directly the cavityenhanced emission rate and found a corresponding Purcell factor F p of up to 5. In the same tim...

Exploiting One-Dimensional Exciton–Phonon Coupling for Tunable and Efficient Single-Photon Generation with a Carbon Nanotube

“…In the present case η represents the effective quantum yield of the ZPL which includes the Debye-Waller factor. It is obtained from saturation measurements in pulsed excitation [5]. As expected, the Purcell factors we deduce from this method follow a 1/V law ( Fig.…”

“…The experimental setup was described in Ref. [5]. In brief, PFO coated CoMoCat nanotubes embedded in a 120 nm thick layer of polystyrene [18] are deposited on a flat dielectric mirror.…”

“…2 (c)). Note that the full scanning window ( 20 meV) corresponds to a relative change in the cavity length of 1.4% and thus to a change in the mode volume of about 2%, which is negligible (see SI in [5]).…”

Spectral tuning of optical coupling between air-mode nanobeam cavities and individual carbon nanotubes

“…1,[8][9][10][11] The spectral overlap of the emission with the cavity is an important factor in determining these effects, and the overlap can be changed by preparing samples with different cavity lengths for coupling to ensembles of CNTs. 12 Sophisticated fiber microcavities enable in-situ tunable coupling to individual CNTs, 6 but it still remains a challenge to perform postfabrication tuning for on-chip cavities.…”

Quantum dot-like excitonic behavior in individual single walled-carbon nanotubes

“…Experimental observation of single CNT PL is challenging due to the low fluorescence yield and a strong structural (chirality) dependence of their optical properties6. Recently, the signatures of quantum light from individual CNTs were demonstrated789, attributed to the localization of excitons which form quantum dot-like (QD-like) states10. The existence of QD-like states has been observed in single CNT electronic transport measurements11 and near field optical spectroscopy12.…”