47 research outputs found
Bright single photon emission from a quantum dot in a circular Bragg grating microcavity
Bright single photon emission from single quantum dots in suspended circular
Bragg grating microcavities is demonstrated. This geometry has been designed to
achieve efficient (> 50 %) single photon extraction into a near-Gaussian shaped
far-field pattern, modest (~10x) Purcell enhancement of the radiative rate, and
a spectral bandwidth of a few nanometers. Measurements of fabricated devices
show progress towards these goals, with collection efficiencies as high as ~10%
demonstrated with moderate spectral bandwidth and rate enhancement. Photon
correlation measurements are performed under above-bandgap excitation (pump
wavelength = 780 nm to 820 nm) and confirm the single photon character of the
collected emission. While the measured sources are all antibunched and
dominantly composed of single photons, the multi-photon probability varies
significantly. Devices exhibiting tradeoffs between collection efficiency,
Purcell enhancement, and multi-photon probability are explored and the results
are interpreted with the help of finite-difference time-domain simulations.
Below-bandgap excitation resonant with higher states of the quantum dot and/or
cavity (pump wavelength = 860 nm to 900 nm) shows a near-complete suppression
of multi-photon events and may circumvent some of the aforementioned tradeoffs.Comment: 11 pages, 12 figure
Multiple time scale blinking in InAs quantum dot single-photon sources
We use photon correlation measurements to study blinking in single,
epitaxially-grown self-assembled InAs quantum dots situated in circular Bragg
grating and microdisk cavities. The normalized second-order correlation
function g(2)(\tau) is studied across eleven orders of magnitude in time, and
shows signatures of blinking over timescales ranging from tens of nanoseconds
to tens of milliseconds. The g(2)(\tau) data is fit to a multi-level system
rate equation model that includes multiple non-radiating (dark) states, from
which radiative quantum yields significantly less than 1 are obtained. This
behavior is observed even in situations for which a direct histogramming
analysis of the emission time-trace data produces inconclusive results
Optomechanical transduction of an integrated silicon cantilever probe using a microdisk resonator
Sensitive transduction of the motion of a microscale cantilever is central to
many applications in mass, force, magnetic resonance, and displacement sensing.
Reducing cantilever size to nanoscale dimensions can improve the bandwidth and
sensitivity of techniques like atomic force microscopy, but current optical
transduction methods suffer when the cantilever is small compared to the
achievable spot size. Here, we demonstrate sensitive optical transduction in a
monolithic cavity-optomechanical system in which a sub-picogram silicon
cantilever with a sharp probe tip is separated from a microdisk optical
resonator by a nanoscale gap. High quality factor (Q ~ 10^5) microdisk optical
modes transduce the cantilever's MHz frequency thermally-driven vibrations with
a displacement sensitivity of ~ 4.4x10^-16 m\sqrt[2]{Hz} and bandwidth > 1 GHz,
and a dynamic range > 10^6 is estimated for a 1 s measurement.
Optically-induced stiffening due to the strong optomechanical interaction is
observed, and engineering of probe dynamics through cantilever design and
electrostatic actuation is illustrated
Nanoscale optical positioning of single quantum dots for bright and pure single-photon emission
Self-assembled, epitaxially grown InAs/GaAs quantum dots (QDs) are promising semiconductor quantum emitters that can be integrated on a chip for a variety of photonic quantum information science applications. However, self-assembled growth results in an essentially random in-plane spatial distribution of QDs, presenting a challenge in creating devices that exploit the strong interaction of single QDs with highly confined optical modes. Here, we present a photoluminescence imaging approach for locating single QDs with respect to alignment features with an average position uncertainty <30?nm (<10?nm when using a solid-immersion lens), which represents an enabling technology for the creation of optimized single QD devices. To that end, we create QD single-photon sources, based on a circular Bragg grating geometry, that simultaneously exhibit high collection efficiency (48%±5% into a 0.4 numerical aperture lens, close to the theoretically predicted value of 50%), low multiphoton probability (g(2)(0) <1%), and a significant Purcell enhancement factor (?3)