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

Abstract

We demonstrate control over optical coupling between air-suspended carbon nanotubes and air-mode nanobeam cavities by spectral tuning. Taking advantage of the large dielectric screening effects caused by adsorbed molecules, laser heating is used to blueshift the nanotube photoluminescence. Significant increase of the cavity peak is observed when the nanotube emission is brought into resonance, and the spontaneous emission enhancement is estimated from the photoluminescence spectra. We find that the enhancement shows good correlation to the spectral overlap of the nanotube emission and the cavity peak. Our technique offers a convenient method for controlling the optical coupling of air-suspended nanotubes to photonic structures.

Near-unity radiative quantum efficiency of excitons in carbon nanotubes

“…These tubes are known to exhibit high PL yields, indicative of their pristine nature [24]. To modify the radiative decay rates by the Purcell effect, the air-suspended tubes are coupled to silicon photonic crystal nanobeam cavities [14,17] as shown in Fig. 1a.…”

“…Electricallygated pn-junction devices can be constructed from nanotubes with diameters significantly smaller than the wavelength, where extremely efficient photocurrent generation [7,8] and excitonic electroluminescence [9,10] have been demonstrated. Unique exciton physics can be exploited to generate telecom band single photons at room temperature [11][12][13], and the compatibility of nanotube emitters with silicon photonics [14][15][16][17][18][19] offers opportunities in integrated quantum optics [20]. The device performance is again limited by the radiative quantum efficiency, but uncertainty of absorption cross section and sensitivity to nanotube quality have made quantitative characterization difficult.…”

Integration of Semiconducting Carbon Nanotubes Within a Silicon Photonic Molecule

“…By using Poly-9, 9-di-n-octyl-fluorenyk-2,7-diyl (PFO), a mixture of s-SWNTs with two main chiralities (8,6), and (8,7) was selected, emitting light near the 1200 nm and 1300 nm wavelengths, respectively. The CNT-PFO matrix serves as a robust low refractive index (∼1.6) cladding material for integrated silicon photonic devices, providing s-SWNTs emitters in the cavity vicinity without PL spectrum detuning typically observed in single nanotube experiments at low power photon excitation [21], [22]. A thick PFO-CNT layer (≥500 nm) was deposited by drop casting the solution on top of the fabricated silicon cavity structures.…”

Quantum emission assisted by energy landscape modification in pentacene-decorated carbon nanotubes

“…An additional approach that can possibly control the exciton diffusion and induce strong photon antibunching is the noncovalent functionalization of CNTs by intentional molecular adsorption. Because of the atomically thin nature of CNTs, excitons in air-suspended CNTs are highly sensitive to the dielectric environment, and adsorbed molecules can cause a significant reduction in the excitonic energies [52][53][54][55][56][57][58][59][60][61]. Meanwhile, the excellent optical properties of the CNTs can be preserved because noncovalent functionalization is less perturbative, and the molecular coverage can be effectively controlled by different adsorption conditions or heating-induced molecular desorption [53,54,57,60].…”