  Photonic structures in diamond are key to most of its application in quantum
technology. Here, we demonstrate tapered nano-waveguides structured directly
onto the diamond substrate hosting shallow-implanted nitrogen vacancy (NV)
centers. By optimization based on simulations and precise experimental control
of the geometry of these pillar-shaped nano-waveguides, we achieve a net photon
flux up to ~ $1.7 \cdot 10^6 /s$. This presents the brightest monolithic bulk
diamond structure based on single NV centers so far. We observe no impact on
excited state lifetime and electronic spin dephasing time ($T_2$) due to the
nanofabrication process. Possessing such high brightness with low background in
addition to preserved spin quality, this geometry can improve the current
nanomagnetometry sensitivity ~ 5 times. In addition, it facilitates a wide
range of diamond defects-based magnetometry applications. As a demonstration,
we measure the temperature dependency of $T_1$ relaxation time of a single
shallow NV center electronic spin. We observe the two-phonon Raman process to
be negligible in comparison to the dominant two-phonon Orbach process.
