Polarization CARS microscopy of diamond needles

Abstract

We employed polarization-sensitive nonlinear optical microscopy to assess crystallinity of diamond microneedles. In the experiment, we mapped the coherent anti-Stokes Raman spectroscopy (CARS) signal in the vicinity of 1332 cm−1 diamond Raman peak over the needle length and demonstrated that the third-order nonlinear optical susceptibility remains the same at both micrometer-sized base and the nanoscale thin apex of the needle. This indicated the single-crystal nature of the diamond needle and allowed us to describe the results of the polarization CARS measurements in terms of the third-order nonlinear susceptibility of diamond. High crystallinity of the needle was also confirmed by measuring the linewidth of the zero-phonon line of the silicon-vacancy centers in diamond.