arXiv subjects

Dirk Bouwmeester

Publications and source records attributed to Dirk Bouwmeester.

54 records · Page 3Linked to original sources

arXiv2012

Far-field emission profiles from L3 photonic crystal cavity modes

We experimentally characterize the spatial far-field emission profiles for the two lowest confined modes of a photonic crystal cavity of the L3 type, finding a good agreement with FDTD simulations. We then link the far-field profiles to relevant features of the cavity mode near-fields, using a simple Fabry-Perot resonator model. The effect of disorder on far-field cavity profiles is clarified through comparison between experiments and simulations. These results can be useful for emission engineering from active centers embedded in the cavity.

cond-mat.mes-hall↗

arXiv2012

Macroscopic superpositions via nested interferometry: finite temperature and decoherence considerations

Recently there has been much interest in optomechanical devices for the production of macroscopic quantum states. Here we focus on a proposed scheme for achieving macroscopic superpositions via nested interferometry. We consider the effects of finite temperature on the superposition produced. We also investigate in detail the scheme's feasibility for probing various novel decoherence mechanisms.

quant-ph↗

arXiv2012

Dynamic modulation of photonic crystal nanocavities using gigahertz acoustic phonons

Photonic crystal membranes (PCM) provide a versatile planar platform for on-chip implementations of photonic quantum circuits. One prominent quantum element is a coupled system consisting of a nanocavity and a single quantum dot (QD) which forms a fundamental building block for elaborate quantum information networks and a cavity quantum electrodynamic (cQED) system controlled by single photons. So far no fast tuning mechanism is available to achieve control within the system coherence time. Here we demonstrate dynamic tuning by monochromatic coherent acoustic phonons formed by a surface acoustic wave (SAW) with frequencies exceeding 1.7 gigahertz, one order of magnitude faster than alternative approaches. We resolve a periodic modulation of the optical mode exceeding eight times its linewidth, preserving both the spatial mode profile and a high quality factor. Since PCMs confine photonic and phononic excitations, coupling optical to acoustic frequencies, our technique opens ways towards coherent acoustic control of optomechanical crystals.

cond-mat.mes-hall↗

arXiv2012

Optomechanical superpositions via nested interferometry

We present a scheme for achieving macroscopic quantum superpositions in optomechanical systems by using single photon postselection and detecting them with nested interferometers. This method relieves many of the challenges associated with previous optical schemes for measuring macroscopic superpositions, and only requires the devices to be in the weak coupling regime. It requires only small improvements on currently achievable device parameters, and allows observation of decoherence on a timescale unconstrained by the system's optical decay time. Prospects for observing novel decoherence mechanisms are discussed.

quant-ph↗

arXiv2011

Independent electrical tuning of separated quantum dots in coupled photonic crystal cavities

Systems of photonic crystal cavities coupled to quantum dots are a promising architecture for quantum networking and quantum simulators. The ability to independently tune the frequencies of laterally separated quantum dots is a crucial component of such a scheme. Here, we demonstrate independent tuning of laterally separated quantum dots in photonic crystal cavities coupled by in-plane waveguides by implanting lines of protons which serve to electrically isolate different sections of a diode structure.

cond-mat.mes-hall↗

arXiv2011

Strain-tuning of quantum dot optical transitions via laser-induced surface defects

We discuss the fine-tuning of the optical properties of self-assembled quantum dots by the strain perturbation introduced by laser-induced surface defects. We show experimentally that the quantum dot transition red-shifts, independently of the actual position of the defect, and that such frequency shift is about a factor five larger than the corresponding shift of a micropillar cavity mode resonance. We present a simple model that accounts for these experimental findings.

cond-mat.mes-hall↗

arXiv2011

Permanent tuning of quantum dot transitions to degenerate microcavity resonances

We demonstrate a technique for achieving spectral resonance between a polarization-degenerate micropillar cavity mode and an embedded quantum dot transition. Our approach is based on a combination of isotropic and anisotropic tensile strain effected by laser-induced surface defects, thereby providing permanent tuning. Such a technique is a prerequisite for the implementation of scalable quantum information schemes based on solid-state cavity quantum electrodynamics.

physics.optics↗

arXiv2010

CNOT and Bell-state analysis in the weak-coupling cavity QED regime

We propose an interface between the spin of a photon and the spin of an electron confined in a quantum dot embedded in a microcavity operating in the weak coupling regime. This interface, based on spin selective photon reflection from the cavity, can be used to construct a CNOT gate, a multi-photon entangler and a photonic Bell-state analyzer. Finally, we analyze experimental feasibility, concluding that the schemes can be implemented with current technology.

quant-ph↗

arXiv2009

Tuning micropillar cavity birefringence by laser induced surface defects

We demonstrate a technique to tune the optical properties of micropillar cavities by creating small defects on the sample surface near the cavity region with an intense focused laser beam. Such defects modify strain in the structure, changing the birefringence in a controllable way. We apply the technique to make the fundamental cavity mode polarization-degenerate and to fine tune the overall mode frequencies, as needed for applications in quantum information science.

physics.optics↗

arXiv2006

Optimal Generation of Pulsed Entangled Photon Pairs

We experimentally investigate a double-pass parametric down-conversion scheme for producing pulsed, polarization-entangled photon pairs with high visibility. The amplitudes for creating photon pairs on each pass interfere to compensate for distinguishing characteristics that normally degrade two-photon visibility. The result is a high-flux source of polarization-entangled photon pulses that does not require spectral filtering. We observe quantum interference visibility of over 95% without the use of spectral filters for 200 femtosecond pulses, and up to 98.1% with 5 nm bandwidth filters.

quant-ph↗

arXiv2006

Strong coupling between single photons in semiconductor microcavities

We discuss the observability of strong coupling between single photons in semiconductor microcavities coupled by a chi(2) nonlinearity. We present two schemes and analyze the feasibility of their practical implementation in three systems: photonic crystal defects, micropillars and microdisks, fabricated out of GaAs. We show that if a weak coherent state is used to enhance the chi(2) interaction, the strong coupling regime between two modes at different frequencies occupied by a single photon is within reach of current technology. The unstimulated strong coupling of a single photon and a photon pair is very challenging and will require an improvement in mirocavity quality factors of 2-4 orders of magnitude to be observable.

quant-ph↗

arXiv2006

Validation of Lasing in Active Nanocavities

An unambiguous proof of lasing in an active nanocavity with ultrahigh spontaneous emission coupling factor (beta = 0.65) is presented. To distinguish the subtle lasing threshold features from possible material-related phenomena, such as saturable absorption in the gain medium, a series of active nanocavities with different values of beta have been designed to systematically approach the high-beta device. The demonstration of the lasing threshold is obtained through the observation of the transition from thermal to coherent light photon statistics that is well understood and identified in the beta << 1 lasing regime. The systematic investigation allows a more definitive validation of the onset of lasing in these active nanocavities.

physics.optics↗

arXiv2005

Frequency control of photonic crystal membrane resonators by mono-layer deposition

We study the response of GaAs photonic crystal membrane resonators to thin film deposition. Slow spectral shifts of the cavity mode of several nanometers are observed at low temperatures, caused by cryo-gettering of background molecules. Heating the membrane resets the drift and shielding will prevent drift altogether. In order to explore the drift as a tool to detect surface layers, or to intentionally shift the cavity resonance frequency, we studied the effect of self-assembled monolayers of polypeptide molecules attached to the membranes. The 2 nm thick monolayers lead to a discrete step in the resonance frequency and partially passivate the surface.

cond-mat.mtrl-sci↗

arXiv2005

Photon statistics from coupled quantum dots

We present an optical study of closely-spaced self-assembled InAs/GaAs quantum dots. The energy spectrum and correlations between photons subsequently emitted from a single pair provide not only clear evidence of coupling between the quantum dots but also insight into the coupling mechanism. Our results are in agreement with recent theories predicting that tunneling is largely suppressed between nonidentical quantum dots and that the interaction is instead dominated by dipole-dipole coupling and phonon-assisted energy transfer processes.

cond-mat.other↗

arXiv2005

Bloch theory of entangled photon generation in non-linear photonic crystals

We present a quantum mechanical description of parametric down-conversion and phase-matching of Bloch-waves in non-linear photonic crystals. We discuss the theory in one-dimensional Bragg structures giving a recipe for calculating the down-converted emission strength and direction. We exemplify the discussion by making explicit analytical predictions for the emission amplitude and direction from a one-dimensional structure that consists of alternating layers of Al0.4Ga0.6As and Air. We show that the emission is suitable for the extraction of polarization-entangled photons.

quant-ph↗

arXiv2004

Ultrafast Optical Response of a High-Reflectivity GaAs/AlAs Bragg Mirror

The ultrafast response of a high-reflectivity GaAs/AlAs Bragg mirror to optical pumping is investigated for all-optical switching applications. Both Kerr and free carrier nonlinearities are induced with 100 fs, 780 nm pulses with a fluence of 0.64 kJ/m^2 and 0.8 kJ/m^2. The absolute transmission of the mirror at 931 nm increases by a factor of 27 from 0.0024% to 0.065% on a picosecond timescale. These results demonstrate the potential for a high-reflectivity ultrafast switchable mirror for quantum optics and optical communication applications. A design is proposed for a structure to be pumped below the bandgaps of the semiconductor mirror materials. Theoretical calculations on this structure show switching ratios up to 2200 corresponding to switching from 0.017% to 37.4% transmission.

cond-mat.mtrl-sci↗

arXiv2004

Realisation of Hardy's Thought Experiment

We present an experimental realisation of Hardy's thought experiment [Phys. Rev. Lett. {\bf 68}, 2981 (1992)], using photons. The experiment consists of a pair of Mach-Zehnder interferometers that interact through photon bunching at a beam splitter. A striking contradiction is created between the predictions of quantum mechanics and local hidden variable based theories. The contradiction relies on non-maximally entangled position states of two particles.

quant-ph↗

arXiv2004

Non-linear photonic crystals as a source of entangled photons

Non-linear photonic crystals can be used to provide phase-matching for frequency conversion in optically isotropic materials. The phase-matching mechanism proposed here is a combination of form birefringence and phase velocity dispersion in a periodic structure. Since the phase-matching relies on the geometry of the photonic crystal, it becomes possible to use highly non-linear materials. This is illustrated considering a one-dimensional periodic Al$_{0.4}$Ga$_{0.6}$As / air structure for the generation of 1.5 $μ$m light. We show that phase-matching conditions used in schemes to create entangled photon pairs can be achieved in photonic crystals.

quant-ph↗