Efficient Coupling of an Ensemble of Nitrogen Vacancy Center to the Mode of a High-Q, Si₃N₄ Photonic Crystal Cavity

Abstract

Integrated nanophotonics is an emerging field with high potential for quantum technology applications such as quantum sensing or quantum networks. A desired photonics platform is Si 3 N 4 due to lowphoton loss and well-established fabrication techniques. However, quantum optics applications are not yet established. Here, we investigate an approach toward Si 3 N 4 -based quantum photonics utilizing a crossed waveguide, pump−probe design. The platform enables efficient, on-chip excitation, strong background suppression, and at the same time, efficient coupling to the mode of a high-Q photonic crystal cavity. The freestanding photonic crystal cavities reach high Q-factors up to 47 × 10 3 . To test our platform, we positioned an ensemble of negatively charged nitrogen vacancy centers located in a nanodiamond within the interaction zone of the photonic crystal cavity. We quantify the efficiency of the coupling with the β λ -factor reaching values as large as 0.71. We further demonstrate on-chip excitation of the quantum emitter with strong suppression (∼20 dB) of the background fluorescence. Our results unfold the potential to utilize negatively charged nitrogen vacancy centers in nanodiamonds and Si 3 N 4 platforms as an efficient, on-chip spin-photon interface in quantum photonics experiments.

Superconducting nanowire single-photon detectors integrated with tantalum pentoxide waveguides

“…We anticipate that the wide-band transparency of Ta 2 O 5 35 can be exploited for implementing integrated quantum photonics experiments in the visible wavelength range with further improvements in detection efficiency, such as longer plateaus of saturated internal OCDE, because the sensitivity of SNSPDs increases for shorter wavelengths 64 . The visible wavelength range is of particular relevance for future integrated quantum photonic applications exploiting single-photon generation from waveguide-coupled quantum emitters 65 – 67 , which will tremendously benefit from the low intrinsic autofluorescence 40 , 41 and absorption 39 of the tantalum pentoxide material system. Other attractive possibilities for quantum light generation in nanophotonic Ta 2 O 5 devices arise from the material’s strong optical nonlinearity and small thermo-optic coefficient, which can be exploited for spontaneous four wave mixing 42 , 45 , 46 alongside integrated SNSPDs.…”

Integrated Magnetometry Platform with Stackable Waveguide-Assisted Detection Channels for Sensing Arrays

“…The combination with atomic-force microscopy has revolutionized scanning-probe magnetometry [9,10] with applications in material science and life sciences. Advanced photonics could further improve the performance in terms of losses, signal-to-noise and operation speed [11,12] and includes integration into optical fibers [13,14], diamond nanopillar arrays [15,16] and integrated photonics [17][18][19]. The latter enables, in addition, the realization of compact devices.…”

Swing-up of quantum emitter population using detuned pulses

“…Deterministically preparing the excited state of a quantum emitter is a key to many applications in quantum information technology, since the subsequent decay of the excited state yields a single-photon [1][2][3]. Prominent examples for quantum emitters are semiconductor quantum dots [4][5][6][7][8][9][10], strain potentials and defects in monolayers of atomically thin semiconductors [11][12][13], defect centers in diamond [14][15][16][17][18] or in hexagonal boron nitride [19][20][21]. The deterministic preparation relies on the direct excitation of the quantum emitter excited state by an external laser pulse.…”