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Fabrication of oriented NV center arrays in diamond via femtosecond laser writing and reorientation

Kai Klink, Andrew Raj Kirkpatrick, Yukihiro Tadokoro, Jonas Nils Becker, Shannon Singer Nicley

TL;DR

The paper tackles the orientation randomness of $NV^{-}$ centers produced by ultrafast laser writing and its impact on vector magnetometry. The authors present an all-optical femtosecond laser annealing process that dissociates and reforms centers to achieve orientation along a chosen crystallographic axis, integrated with in situ polarization-based feedback. They demonstrate deterministic orientation control on both $(100)$ and $(111)$ diamonds, including a single reoriented center and a compact 9-site array. The technique promises enhanced magnetometry sensitivity and photon collection efficiency, enabling scalable orientation-controlled $NV^{-}$ devices for quantum sensing.

Abstract

Nitrogen-vacancy (NV) centers in diamond are widely recognized as highly promising solid-state quantum sensors due to their long room temperature coherence times and atomic-scale size, which enable exceptional sensitivity and nanoscale spatial resolution under ambient conditions. Ultrafast laser writing has demonstrated the deterministic spatial control of individual NV$^-$ centers, however, the resulting random orientation of the defect axis limits the magnetic field sensitivity and signal contrast. Here, we present an all-optical approach for reorienting laser-written NV$^-$ centers to lie along a specific crystallographic axis using femtosecond laser annealing. This technique enables the creation of spatially ordered NV$^-$ arrays with uniform orientation, for enhancing performance for quantum magnetometry. We achieve deterministic alignment along the optical axis in both (100)- and (111)-oriented diamond substrates, paving the way for scalable, high-performance quantum devices based on orientation-controlled NV$^-$ centers.

Fabrication of oriented NV center arrays in diamond via femtosecond laser writing and reorientation

TL;DR

The paper tackles the orientation randomness of centers produced by ultrafast laser writing and its impact on vector magnetometry. The authors present an all-optical femtosecond laser annealing process that dissociates and reforms centers to achieve orientation along a chosen crystallographic axis, integrated with in situ polarization-based feedback. They demonstrate deterministic orientation control on both and diamonds, including a single reoriented center and a compact 9-site array. The technique promises enhanced magnetometry sensitivity and photon collection efficiency, enabling scalable orientation-controlled devices for quantum sensing.

Abstract

Nitrogen-vacancy (NV) centers in diamond are widely recognized as highly promising solid-state quantum sensors due to their long room temperature coherence times and atomic-scale size, which enable exceptional sensitivity and nanoscale spatial resolution under ambient conditions. Ultrafast laser writing has demonstrated the deterministic spatial control of individual NV centers, however, the resulting random orientation of the defect axis limits the magnetic field sensitivity and signal contrast. Here, we present an all-optical approach for reorienting laser-written NV centers to lie along a specific crystallographic axis using femtosecond laser annealing. This technique enables the creation of spatially ordered NV arrays with uniform orientation, for enhancing performance for quantum magnetometry. We achieve deterministic alignment along the optical axis in both (100)- and (111)-oriented diamond substrates, paving the way for scalable, high-performance quantum devices based on orientation-controlled NV centers.

Paper Structure

This paper contains 3 sections, 3 figures.

Table of Contents

  1. Introduction
  2. Methods
  3. Results and Discussion

Figures (3)

  • Figure 1: Schematic diagram of the ultrafast laser fabrication system with in situ confocal microscope. Ultrafast 515 nm laser pulses (light green) are produced by a Yb:KYW laser and are corrected for aberrations using a spatial light modulator. The beam-scanning confocal fluorescence microscope excites with a 532 nm CW laser (dark green) and collects fluorescence (red) from the NV$^-$ center onto a single photon detector. Both the writing system and the microscope share a common objective lens onto the sample, which is illuminated in transmission for widefield microscopy onto a CMOS camera.
  • Figure 2: (a) Fluorescence trace of an NV$^-$ center during reorientation in (100)-orientated diamond. Initially an NV$^-$ center is created along either of the, polarization degenerate, $[111]$ or $[1\bar{1}\bar{1}]$ directions, as shown by the red-shaded polarization map. The diffusion pulse train is active between 1.8 and 3.9 s on the fluorescence trace. After some fluctuation in the measured fluorescence during diffusion, the NV$^-$ orientation is probed resulting in the blue-shaded polarization map. This demonstrates a NV$^-$ orientation change between the polarization degenerate orientations of $[\bar{1}\bar{1}1]/[\bar{1}1\bar{1}]\rightarrow[111]/[1\bar{1}\bar{1}]$. The fluorescence is confirmed to be from a single NV$^-$ by (b) Second-order photon autocorrelation measurement and (c) Room temperature fluorescence spectrum.
  • Figure 3: (a) Confocal fluorescence image of laser written array of 9 NV$^-$ centers aligned parallel to the optical axis in (111)-oriented diamond. (b) Initial polarization maps of the NV$^-$ centers before reorientation, demonstrating random orientation. (c) Polarization maps for each NV$^-$ center in the array after reorientation to the optical axis, which identify all the NV$^-$ centers as being aligned along the optical axis in (111)-oriented diamond.