Mechanical photoluminescence excitation spectra of a strongly driven spin-mechanical system

We report experimental studies of a driven spin-mechanical system, in which a nitrogen vacancy (NV) center couples to out-of-plane vibrations of a diamond cantilever through the excited-state deformation potential. Photoluminescence excitation studies show that in the unresolved sideband regime and under strong resonant mechanical driving, the excitation spectra of a NV optical transition feature two spectrally sharp peaks, corresponding to the two turning points of the oscillating cantilever. In the limit that the strain-induced frequency separation between the two peaks far exceeds the NV zero-phonon linewidth, the spectral position of the individual peak becomes sensitive to minute detuning between the mechanical resonance and the external driving force. For a fixed optical excitation frequency near the NV transition, NV fluorescence as a function of mechanical detuning features resonances with a linewidth that can be orders of magnitude smaller than the intrinsic linewidth of the mechanical mode. This enhanced sensitivity to mechanical detuning can potentially provide an effective mechanism for mechanical sensing, for example, mass sensing via measurements of induced changes in the mechanical oscillator frequency

Diamond nanomechanical resonators protected by a phononic band gap

We report the design, fabrication, and characterization of diamond cantilevers attached to a phononic square lattice. We show that the robust protection of mechanical modes by phononic band gaps leads to a three-orders-of-magnitude increase in mechanical Q-factors, with the Q-factors exceeding 10^6 at frequencies as high as 100 MHz. Temperature dependent studies indicate that the Q-factors obtained at a few K are still limited by the materials loss. The high-Q diamond nanomechanical resonators provide a promising hybrid quantum system for spin-mechanics studies

An experimental study of the indentation behaviour of Al foam

The indentation response of a closed-cell Al foam under the flat-end cylindrical indenter was experimentally investigated. The effects of indenter sizes, relative density of Al foam and boundary condition on the mechanical and energy absorption characteristics of indentation were also investigated. Experimental results show that the indentation load-displacement response obtained using the flat-end cylindrical indenter is similar to that observed under uniaxial compression. Crosssectional views of the indented specimens show that the deformation is confined only to the region directly under the indenter with very little lateral spread, and that the indentation deformation of Al foam is non-uniform. The tear energy and energy absorbing efficiency of Al foam is not related with the indenter diameter and relative density of Al foam. By increasing the indenter diameter or decreasing relative density, the indentation hardness is linearly decreased, but the energy absorbing capability linearly increases with an increase in indenter diameter or an increase in relative density. At a certain indentation depth range, the difference between rigid foundation and the indentation response of Al foam under simply supported conditions can be ignored