Fabrication of Sawfish photonic crystal cavities in bulk diamond

• Main Authors: Pregnolato, Tommaso, Stucki, Marco E, Bopp, Julian M, Hoeven, Maarten H. v. d, Gokhale, Alok, Krüger, Olaf, Schröder, Tim
• Format: Journal Article
• Language: English
• Published: 14-11-2023
• Subjects: Physics - Applied Physics; Physics - Optics; Physics - Quantum Physics
• DOI: 10.48550/arxiv.2311.03618

Color centers in diamond are quantum systems with optically active
spin-states that show long coherence times and are therefore a promising
candidate for the development of efficient spin-photon interfaces. However,
only a small portion of the emitted photons is generated by the coherent
optical transition of the zero-phonon line (ZPL), which limits the overall
performance of the system. Embedding these emitters in photonic crystal
cavities improves the coupling to the ZPL photons and increases their emission
rate. Here, we demonstrate the fabrication process of "Sawfish" cavities, a
design recently proposed that has the experimentally-realistic potential to
simultaneously enhance the emission rate by a factor of 46 and couple photons
into a single-mode fiber with an efficiency of 88%. The presented process
allows for the fabrication of fully suspended devices with a total length of
20.5 $\mu$m and features size as small as 40 nm. The optical characterization
shows fundamental mode resonances that follow the behavior expected from the
corresponding design parameters and quality (Q) factors as high as 3825.
Finally, we investigate the effects of nanofabrication on the devices and show
that, despite a noticeable erosion of the fine features, the measured cavity
resonances deviate by only 0.9 (1.2)% from the corresponding simulated values.
This proves that the Sawfish design is robust against fabrication
imperfections, which makes it an attractive choice for the development of
quantum photonic networks.