Generation Of Single Photons Based On Color Centers In Diamond And Investigation On Its Fluorescence Dynamics

Quantum optics achieved huge development since the invention of laser. People grew more and more interest on the interaction between lights and matter, and so is our knowledge of the nature of lights and matter. In recent years, scientists demonstrated various conjectures about the quantum mechanics, basing on the achievement of single photon sources in experiments. Therefore, researches on single photon sources became one of the hottest fields in the world. While, single photon sources based on the combination of diamond defects and crystal vacancies (also called color centers) attracted scientists all around the world because its holder-diamond is transparent to visible light, hardest material ever known, resistant to acid and alkali, and usually they emits photons stably and their electronic levels are easy to manipulate. Significant experiments were conducted and thus benefit important applications such as quantum cryptography, bio-imaging, sensitive probes at nanoscale, quantum computation and so on. The main purpose of researches in this paper is to study optical properties of single photon sources based on color centers in diamond and the dynamics of fluorescence from color centers in diamond. The results of the investigations would benefit for generation of more applicable single photons with high repetition rate and narrow linewidth, and further benefit for applications in quantum cryptography, probing at nanoscale and so on, and provide important references for the exploration on frequency conversion of single photons and high level manipulation of single photons. The main research content are as the following.1. A new method of fabricating negatively charged nitrogen vacancy (NV-) color centers by illumination of femtosecond laser was achieved. We used an ultrafast femtosecond laser filaments to generate electron beam, which then sputtered on the surface of our Ib diamond sample leading to the fabrication of single NV- centers, multiple NV- centers and NV" ensembles with high density. The fabrication of these three forms of NV- centers can be controlled by changing the femtosecond laser illumination time. Single NV- centers show a clear sharp narrow zero-phonon line, and its fluorescence photons showed good "unitary" (i.e, antibunching effect).2. A new triggered single photon source with high repetition rate and narrow linewidth based on a negatively charged single silicon vacancy (SiV-) color center in diamond was developed. Since excitation state lifetime of SiV- center is quite short～1-2 ns and 70% of SiV- fluorescence is concentrated at its ZPL, single SiV- color centers could become one of the most appealing single photon source. We started with building a fiber-based picosecond pulsed laser with repetition rate as high as 30 MHz to achieve high-frequency pulsed-excitation of a single SiV- center. Then a confocal microscopy was built to achieve collection efficiency as high as we could. A bandpath filter (centered at 740 nm, band width～10 nm) with superb performance to get only the SiV-ZPL. The experimental result demonstrated that a new type of triggered single photon source with high repetition rate and narrow linewidth was successfully built. This research will benefit for quantum cryptography which bases on triggered single photon source for quantum key distribution, and for investigations on fluorescence dynamics of SiV- centers. It can further promote studies on generation and manipulation of single photons.3. Fluorescence dynamics of a polarization-switching single SiV- center was investigated thoroughly with a series of experiments. Under excitation of low-power 532 nm laser, the SiV- showed stable fluorescence intensity, spectrum, normal polarization contrast and good "unitary". While laser power increases, another polarization generates. With a detailed study on its polarization properties, this research revealed several important fluorescence dynamics of this polarization-switching single SiV-. The experiment results provide important evidence for more specific study on electronic structure and optical properties of SiV- center, and would also benefit for achieving more applicable single photon source with higher performance.