Characterization of the wavelength-dependent coupling function from nitrogen-vacancy fluorescence into surface plasmon polaritons

The nitrogen-vacancy (NV) centers in diamond have gained the attention of an increasing number of research groups due to their property to emit single photons at room temperature, and have become attractive candidates for... [ view full abstract ]

The nitrogen-vacancy (NV) centers in diamond have gained the attention of an increasing number of research groups due to their property to emit single photons at room temperature, and have become attractive candidates for quantum information processing. The NV centers can be implanted on diamond nanoparticles (NDs), enabling the possibility to couple the emitted light into nanostructured optical systems, e.g. in plasmonic devices. In this work, we have centered our attention in the characterization of the wavelength-dependent coupling of the fluorescence of NV centers in NDs into surface plasmon polaritons (SPPs). The sample consists of NDs (r = 50 nm) with multiple NV centers (~ 400) that are spin coated over a 70-nm-thick gold thin film and characterized using leakage-radiation microscopy (LRM) and spectroscopy (LRS), in both the image and Fourier plane [Fig. 1]. The LRM setup allows one to observe the image and intensity distribution of the SPPs that are being excited when pumping the NDs with a 532 nm Nd:YAG laser, while the LRS setup permits to measure the spectra and lifetime of the SPPs coupled from the emitted fluorescence in the Fourier plane. We use the capabilities of leakage-radiation setup to discriminate the coupled, from the uncoupled fluorescence, using filters in the Fourier plane, in order to obtain the wavelength-dependent coupling function. The results showed significant changes in the spectra and a reduction of the lifetime when the coupled fluorescence is compared to the back-scattered fluorescence of the NDs.