3 research outputs found
Nonmagnetic Quantum Emitters in Boron Nitride with Ultranarrow and Sideband-Free Emission Spectra
Hexagonal boron nitride
(hBN) is an emerging material in nanophotonics
and an attractive host for color centers for quantum photonic devices.
Here, we show that optical emission from individual quantum emitters
in hBN is spatially correlated with structural defects and can display
ultranarrow zero-phonon line width down to 45 μeV if spectral
diffusion is effectively eliminated by proper surface passivation.
We demonstrate that undesired emission into phonon sidebands is largely
absent for this type of emitter. In addition, magneto-optical characterization
reveals cycling optical transitions with an upper bound for the g-factor
of 0.2 ± 0.2. Spin-polarized density functional theory calculations
predict possible commensurate transitions between like-spin electron
states, which are in excellent agreement with the experimental nonmagnetic
defect center emission. Our results constitute a step toward the realization
of narrowband quantum light sources and the development of spin–photon
interfaces within 2D materials for future chip-scale quantum networks
Broadband Light Collection Efficiency Enhancement of Carbon Nanotube Excitons Coupled to Metallo-Dielectric Antenna Arrays
The realization of
on-chip quantum networks ideally requires lossless
interfaces between photons and solid-state quantum emitters. We propose
and demonstrate on-chip arrays of metallo-dielectric antennas (MDA)
that are tailored toward efficient and broadband light collection
from individual embedded carbon nanotube quantum emitters by trapping
air gaps on chip that form cavity modes. Scalable implementation is
realized by employing polymer layer dry-transfer techniques that avoid
solvent incompatibility issues, as well as a planar design that avoids
solid-immersion lenses. Cryogenic measurements demonstrate 7-fold
enhanced exciton intensity when compared to emitters located on bare
wafers, corresponding to a light collection efficiency (LCE) up to
92% in the best case (average LCE of 69%) into a narrow output cone
of ±15° that enables a priori fiber-to-chip butt coupling.
The demonstrated MDA arrays are directly compatible with other quantum
systems, particularly 2D materials, toward enabling efficient on-chip
quantum light sources or spin-photon interfaces requiring unity light
collection, both at cryogenic or room temperature
Low-Temperature Single Carbon Nanotube Spectroscopy of sp<sup>3</sup> Quantum Defects
Aiming
to unravel the relationship between chemical configuration
and electronic structure of sp<sup>3</sup> defects of aryl-functionalized
(6,5) single-walled carbon nanotubes (SWCNTs), we perform low-temperature
single nanotube photoluminescence (PL) spectroscopy studies and correlate
our observations with quantum chemistry simulations. We observe sharp
emission peaks from individual defect sites that are spread over an
extremely broad, 1000–1350 nm, spectral range. Our simulations
allow us to attribute this spectral diversity to the occurrence of
six chemically and energetically distinct defect states resulting
from topological variation in the chemical binding configuration of
the monovalent aryl groups. Both PL emission efficiency and spectral
line width of the defect states are strongly influenced by the local
dielectric environment. Wrapping the SWCNT with a polyfluorene polymer
provides the best isolation from the environment and yields the brightest
emission with near-resolution limited spectral line width of 270 μeV,
as well as spectrally resolved emission wings associated with localized
acoustic phonons. Pump-dependent studies further revealed that the
defect states are capable of emitting single, sharp, isolated PL peaks
over 3 orders of magnitude increase in pump power, a key characteristic
of two-level systems and an important prerequisite for single-photon
emission with high purity. These findings point to the tremendous
potential of sp<sup>3</sup> defects in development of room temperature
quantum light sources capable of operating at telecommunication wavelengths
as the emission of the defect states can readily be extended to this
range <i>via</i> use of larger diameter SWCNTs