33 research outputs found
Efficient continuous-wave nonlinear frequency conversion in high-Q Gallium Nitride photonic crystal cavities on Silicon
We report on nonlinear frequency conversion from the telecom range via second
harmonic generation (SHG) and third harmonic generation (THG) in suspended
gallium nitride slab photonic crystal (PhC) cavities on silicon, under
continuous-wave resonant excitation. Optimized two-dimensional PhC cavities
with augmented far-field coupling have been characterized with quality factors
as high as 4.4, approaching the computed theoretical values. The
strong enhancement in light confinement has enabled efficient SHG, achieving
normalized conversion efficiency of 2.4 , as well as
simultaneous THG. SHG emission power of up to 0.74 nW has been detected without
saturation. The results herein validate the suitability of gallium nitride for
integrated nonlinear optical processing.Comment: 5 pages, 5 figure
Bright Room-Temperature Single Photon Emission from Defects in Gallium Nitride
Single photon emitters play a central role in many photonic quantum
technologies. A promising class of single photon emitters consists of atomic
color centers in wide-bandgap crystals, such as diamond silicon carbide and
hexagonal boron nitride. However, it is currently not possible to grow these
materials as sub-micron thick films on low-refractive index substrates, which
is necessary for mature photonic integrated circuit technologies. Hence, there
is great interest in identifying quantum emitters in technologically mature
semiconductors that are compatible with suitable heteroepitaxies. Here, we
demonstrate robust single photon emitters based on defects in gallium nitride
(GaN), the most established and well understood semiconductor that can emit
light over the entire visible spectrum. We show that the emitters have
excellent photophysical properties including a brightness in excess of 500x10^3
counts/s. We further show that the emitters can be found in a variety of GaN
wafers, thus offering reliable and scalable platform for further technological
development. We propose a theoretical model to explain the origin of these
emitters based on cubic inclusions in hexagonal gallium nitride. Our results
constitute a feasible path to scalable, integrated on-chip quantum technologies
based on GaN
Gallium nitride L3 photonic crystal cavities with an average quality factor of 16,900 in the near infrared
Photonic crystal point-defect cavities were fabricated in a GaN free-standing
photonic crystal slab. The cavities are based on the popular L3 design, which
was optimized using an automated process based on a genetic algorithm, in order
to maximize the quality factor. Optical characterization of several individual
cavity replicas resulted in an average unloaded quality factor Q = 16,900 at
the resonant wavelength {\lambda} {\mu}m, with a maximal measured Q
value of 22,500. The statistics of both the quality factor and the resonant
wavelength are well explained by first-principles simulations including
fabrication disorder and background optical absorption.Comment: 3 figure
Doubly resonant second-harmonic generation of a vortex beam from a bound state in the continuum
Second harmonic generation in nonlinear materials can be greatly enhanced by
realizing doubly-resonant cavities with high quality factors. However,
fulfilling such doubly resonant condition in photonic crystal (PhC) cavities is
a long-standing challenge, because of the difficulty in engineering photonic
bandgaps around both frequencies. Here, by implementing a second-harmonic bound
state in the continuum (BIC) and confining it with a heterostructure design, we
show the first doubly-resonant PhC slab cavity with W
conversion efficiency under continuous wave excitation. We also report the
confirmation of highly normal-direction concentrated far-field emission pattern
with radial polarization at the second harmonic frequency. These results
represent a solid verification of previous theoretical predictions and a
cornerstone achievement, not only for nonlinear frequency conversion but also
for vortex beam generation and prospective nonclassical sources of radiation.Comment: revtex4-2, 7 pages, 5 figures, conference CLE