Two-photon Excited Fluorescence of Nitrogen-Vacancy Centers in Proton-Irradiated Type Ib Diamond

Abstract

Two-photon fluorescence spectroscopy of negatively charged nitrogen-vacancy [(N-V)-] centers in type Ib diamond single crystals have been studied with a picosecond (7.5 ps) mode-locked Nd:YVO(4) laser operating at 1064 nm. The (N-V)- centers were produced by radiation damage of diamond using a 3 MeV proton beam, followed by thermal annealing at 800 degrees C. Prior to the irradiation treatment, infrared spectroscopy of the C-N vibrational modes at 1344 cm(-1) suggested a nitrogen content of 109 +/- 10 ppm. Irradiation and annealing of the specimen led to the emergence of a new absorption band peaking at approximately 560 nm. From a measurement of the integrated absorption intensity of the sharp zero-phonon line (637 nm) at liquid nitrogen temperature, we determined a (N-V)- density of (4.5 +/- 1.1) x 10(18) centers/cm3 (or 25 +/- 6 ppm) for the substrate irradiated at a dose of 1 x 1016) H(+)/cm(2). Such a high defect density allowed us to observe two-photon excited fluorescence and measure the corresponding fluorescence decay time. No significant difference in the spectral feature and fluorescence lifetime was observed between one-photon and two-photon excitations. Assuming that the fluorescence quantum yields are the same for both processes, a two-photon absorption cross section of sigma(TPA) = (0.45 +/- 0.23) x 10(-50) cm(4).s/photon at 1064 nm was determined for the (N-V)- center based on its one-photon absorption cross section of sigma(OPA) = (3.1 +/- 0.8) x 10(-17) cm2 at 532 nm. The material is highly photostable and shows no sign of photobleaching even under continuous two-photon excitation at a peak power density of 3 GW/cm(2) for 5 min.

Physical principles for scalable neural recording

“…Due to Pauli exclusion, use of this technique requires an indicator with unpaired electrons. These can be found in nitrogen vacancy diamond nano-crystals (Horowitz et al, 2012) (nano-diamonds), which are also sensitive to voltage (Dolde et al, 2011) and to magnetic fields (Hall et al, 2012), and are amenable to optical control and fluorescent readout of the spin state [although the 2P cross-section of the ( N − V ) − center appears to be relatively low (Wee et al, 2007)].…”

Vertical distribution of nitrogen-vacancy centers in diamond formed by ion implantation and annealing

“…It has been well established that NV centers can be created by ion implantation or irradiation followed by annealing 26,27,28,29,30,31 . Ion implantation is used to create damage (carbon vacancies) in the diamond lattice, and it can also be used to introduce nitrogen impurities 20,32,33,34 .…”

Nanometre-scale thermometry in a living cell

“…The large dynamic range of our quantum thermometer and it’s intrinsic robustness may also allow for the direct microscopic monitoring and control of chemical reactions 20 . Moreover, combining our technique with two-photon microscopy 28, 29 may enable in vivo identification of local tumor activity by mapping atypical thermogenesis at the single-cell level 30 . Finally the combination of thermoablative therapy with our temperature sensor constitutes a potent tool for the selective identification and killing of malignant cells without damaging surrounding tissue 7, 8 .…”