  Magnetic resonance with ensembles of electron spins is nowadays performed in
frequency ranges up to 240 GHz and in corresponding magnetic fields of up to 10
T. However, experiments with single electron and nuclear spins so far only
reach into frequency ranges of several 10 GHz, where existing coplanar
waveguide structures for microwave (MW) delivery are compatible with single
spin readout techniques (e.g. electrical or optical readout). Here, we explore
the frequency range up to 90 GHz, respectively magnetic fields of up to
$\approx 3\,$T for single spin magnetic resonance in conjunction with optical
spin readout. To this end, we develop MW resonators with optical single spin
access. In our case, rectangular E-band waveguides guarantee low-loss supply of
microwaves to the resonators. Three dimensional cavities, as well as coplanar
waveguide resonators enhance MW fields by spatial and spectral confinement with
a MW efficiency of $1.36\,\mathrm{mT/\sqrt{W}}$. We utilize single NV centers
as hosts for optically accessible spins, and show, that their properties
regarding optical spin readout known from smaller fields (<0.65 T) are retained
up to fields of 3 T. In addition, we demonstrate coherent control of single
nuclear spins under these conditions. Furthermore, our results extend the
applicable magnetic field range of a single spin magnetic field sensor.
Regarding spin based quantum registers, high fields lead to a purer product
basis of electron and nuclear spins, which promises improved spin lifetimes.
For example, during continuous single-shot readout the $^{14}$N nuclear spin
shows second-long longitudinal relaxation times.
