arXiv subjects

Dirk Englund

Publications and source records attributed to Dirk Englund.

224 records · Page 13Linked to original sources

arXiv2007

Dynamics of Quantum Dot Photonic Crystal Lasers

Quantum dot photonic crystal membrane lasers were fabricated and the large signal modulation characteristics were studied. We find that the modulation characteristics of quantum dot lasers can be significantly improved using cavities with large spontaneous emission coupling factor. Our experiments show, and simulations confirm, that the modulation rate is limited by the rate of carrier capture into the dots to around 30GHz in our present system.

quant-ph↗

arXiv2006

Ultra Fast Nonlinear Optical Tuning of Photonic Crystal Cavities

We demonstrate fast (up to 20 GHz), low power (5 $μW$) modulation of photonic crystal (PC) cavities in GaAs containing InAs quantum dots. Rapid modulation through blue-shifting of the cavity resonance is achieved via free carrier injection by an above-band picosecond laser pulse. Slow tuning by several linewidths due to laser-induced heating is also demonstrated.

physics.optics↗

arXiv2006

Efficient Photonic Crystal Cavity-Waveguide Couplers

Coupling of photonic crystal (PC) linear three-hole defect cavities (L3) to PC waveguides is theoretically and experimentally investigated. The systems are designed to increase the overlap between the evanescent cavity field and the waveguide mode, and to operate in the linear dispersion region of the waveguide. Our simulations indicate increased coupling when the cavity is tilted by 60 degrees with respect to the waveguide axis, which we have also confirmed by experiments. We obtained up to 90% coupling efficiency into the waveguide.

physics.optics↗

arXiv2006

Generation and transfer of single photons on a photonic crystal chip

We present a basic building block of a quantum network consisting of a quantum dot coupled to a source cavity, which in turn is coupled to a target cavity via a waveguide. The single photon emission from the high-Q/V source cavity is characterized by a twelve-fold spontaneous emission (SE) rate enhancement that results in a SE coupling efficiency near 0.98 into the source cavity mode. Single photons are efficiently transferred into the target cavity through the waveguide, with a source/target field intensity ratio of 0.12 (up to 0.49 observed in other structures without coupled quantum dots). This system shows great promise as a building block of future on-chip quantum information processing systems.

quant-ph↗

arXiv2005

Generation and manipulation of nonclassical light using photonic crystals

Photonic crystal cavities can localize light into nanoscale volumes with high quality factors. This permits a strong interaction between light and matter, which is important for the construction of classical light sources with improved properties (e.g., low threshold lasers) and of nonclassical light sources (such as single and entangled photon sources) that are crucial pieces of hardware of quantum information processing systems. This article will review some of our recent experimental and theoretical results on the interaction between single quantum dots and photonic crystal cavity fields, and on the integration of multiple photonic crystal devices into functional circuits for quantum information processing.

quant-ph↗

arXiv2005

General Recipe for Designing Photonic Crystal Cavities

We describe a general recipe for designing high-quality factor (Q) photonic crystal cavities with small mode volumes. We first derive a simple expression for out-of-plane losses in terms of the k-space distribution of the cavity mode. Using this, we select a field that will result in a high Q. We then derive an analytical relation between the cavity field and the dielectric constant along a high symmetry direction, and use it to confine our desired mode. By employing this inverse problem approach, we are able to design photonic crystal cavities with Q > 4*10^6 and mode volumes V ~ (λ/n)^3. Our approach completely eliminates parameter space searches in photonic crystal cavity design, and allows rapid optimization of a large range of photonic crystal cavities. Finally, we study the limit of the out-of-plane cavity Q and mode volume ratio.

physics.optics↗

arXiv2005

Coupling of PbS Quantum Dots to Photonic Crystal Cavities at Room Temperature

We demonstrate the coupling of PbS quantum dot emission to photonic crystal cavities at room temperature. The cavities are defined in 33% Al, AlGaAs membranes on top of oxidized AlAs. Quantum dots were dissolved in Poly-methyl-methacrylate (PMMA) and spun on top of the cavities. Quantum dot emission is shown to map out the structure resonances, and may prove to be viable sources for room temperature cavity coupled single photon generation for quantum information processing applications. These results also indicate that such commercially available quantum dots can be used for passive structure characterization. The deposition technique is versatile and allows layers with different dot densities and emission wavelengths to be re-deposited on the same chip.

physics.optics↗

arXiv2005

Controlling the Spontaneous Emission Rate of Single Quantum Dots in a 2D Photonic Crystal

We observe large spontaneous emission rate modification of individual InAs Quantum Dots (QDs) in 2D a photonic crystal with a modified, high-Q single defect cavity. Compared to QDs in bulk semiconductor, QDs that are resonant with the cavity show an emission rate increase by up to a factor of 8. In contrast, off-resonant QDs indicate up to five-fold rate quenching as the local density of optical states (LDOS) is diminished in the photonic crystal. In both cases we demonstrate photon antibunching, showing that the structure represents an on-demand single photon source with pulse duration from 210 ps to 8 ns. We explain the suppression of QD emission rate using Finite Difference Time Domain (FDTD) simulations and find good agreement with experiment.

quant-ph↗