arXiv subjects

Paul E. Barclay

Publications and source records attributed to Paul E. Barclay.

At least 73 records · Page 4Linked to original sources

arXiv2010

Resonant enhancement of the zero-phonon emission from a color center in a diamond cavity

We demonstrate coupling of the zero-phonon line of individual nitrogen-vacancy centers and the modes of microring resonators fabricated in single-crystal diamond. A zero-phonon line enhancement exceeding ten-fold is estimated from lifetime measurements at cryogenic temperatures. The devices are fabricated using standard semiconductor techniques and off-the-shelf materials, thus enabling integrated diamond photonics.

quant-ph↗

arXiv2009

Observation of the dynamic Jahn-Teller effect in the excited states of nitrogen-vacancy centers in diamond

The optical transition linewidth and emission polarization of single nitrogen-vacancy (NV) centers are measured from 5 K to room temperature. Inter-excited state population relaxation is shown to broaden the zero-phonon line and both the relaxation and linewidth are found to follow a T^5 dependence for T up to 100 K. This dependence indicates that the dynamic Jahn-Teller effect is the dominant dephasing mechanism for the NV optical transitions at low temperatures.

cond-mat.mtrl-sci↗

arXiv2009

On the indistinguishability of Raman photons

We provide a theoretical framework to study the effect of dephasing on the quantum indistinguishability of single photons emitted from a coherently driven cavity QED $Λ$-system. We show that with a large excited-state detuning, the photon indistinguishability can be drastically improved provided that the fluctuation rate of the noise source affecting the excited state is fast compared with the photon emission rate. In some cases a spectral filter is required to realize this improvement, but the cost in efficiency can be made small.

quant-ph↗

arXiv2009

Chip-based microcavities coupled to NV centers in single crystal diamond

Optical coupling of nitrogen vacancy centers in single-crystal diamond to an on-chip microcavity is demonstrated. The microcavity is fabricated from a hybrid gallium phosphide and diamond material system, and supports whispering gallery mode resonances with spectrometer resolution limited Q > 25000.

quant-ph↗

arXiv2009

Hybrid photonic crystal cavity and waveguide for coupling to diamond NV-centers

A design for an ultra-high Q photonic crystal nanocavity engineered to interact with nitrogen-vacancy (NV) centers located near the surface of a single crystal diamond sample is presented. The structure is based upon a nanowire photonic crystal geometry, and consists of a patterned high refractive index membrane, such as gallium phosphide (GaP), supported by a diamond substrate. The nanocavity supports a mode with quality factor Q > 1.5 million and mode volume V < 0.52 (λ/n_\text{GaP})^3, and promises to allow Purcell enhanced collection of spontaneous emission from an NV located more than 50 nm below the diamond surface. The nanowire photonic crystal waveguide can be used to efficiently couple light into and out of the cavity, or as an efficient broadband collector of NV phonon sideband emission. The proposed structures can be fabricated using existing materials and processing techniques.

quant-ph↗

arXiv2009

Vertical distribution of nitrogen-vacancy centers in diamond formed by ion implantation and annealing

Etching experiments were performed that reveal the vertical distribution of optically active nitrogen-vacancy (NV) centers in diamond created in close proximity to a surface through ion implantation and annealing. The NV distribution depends strongly on the native nitrogen concentration, and spectral measurements of the neutral and negatively-charged NV peaks give evidence for electron depletion effects in lower-nitrogen material. The results are important for potential quantum information and magnetometer devices where NV centers must be created in close proximity to a surface for coupling to optical structures.

cond-mat.mes-hall↗

arXiv2008

Coherent interference effects in a nano-assembled optical cavity-QED system

Diamond nanocrystals containing NV color centers are positioned with 100-nanometer-scale accuracy in the near-field of a high-Q SiO2 microdisk cavity using a fiber taper. The cavity modified nanocrystal photoluminescence is studied, with Fano-like quantum interference features observed in the far-field emission spectrum. A quantum optical model of the system is proposed, from which the NV- zero phonon line coherent coupling rate to the microdisk is estimated to be 28 MHz for a nearly optimally placed nanocrystal.

quant-ph↗

arXiv2006

Integration of fiber coupled high-Q silicon nitride microdisks with atom chips

Micron scale silicon nitride (SiN_x) microdisk optical resonators are demonstrated with Q = 3.6 x 10^6 and an effective mode volume of 15 (λ/ n)^3 at near visible wavelengths. A hydrofluoric acid wet etch provides sensitive tuning of the microdisk resonances, and robust mounting of a fiber taper provides efficient fiber optic coupling to the microdisks while allowing unfettered optical access for laser cooling and trapping of atoms. Measurements indicate that cesium adsorption on the SiN_x surfaces significantly red-detunes the microdisk resonances. A technique for parallel integration of multiple (10) microdisks with a single fiber taper is also demonstrated.

quant-ph↗

arXiv2004

Optical loss and lasing characteristics of high-quality-factor AlGaAs microdisk resonators with embedded quantum dots

Optical characterization of AlGaAs microdisk resonant cavities with a quantum dot active region is presented. Direct passive measurement of the optical loss within AlGaAs microdisk resonant structures embedded with InAs/InGaAs dots-in-a-well (DWELL) is performed using an optical-fiber-based probing technique at a wavelength (lambda~1400 nm) that is red-detuned from the dot emission wavelength (lambda~1200 nm). Measurements in the 1400 nm wavelength band on microdisks of diameter D = 4.5 microns show that these structures support modes with cold-cavity quality factors as high as 360,000. DWELL-containing microdisks are then studied through optical pumping at room temperature. Pulsed lasing at lambda ~ 1200 nm is seen for cavities containing a single layer of InAs dots, with threshold values of ~ 17 microWatts, approaching the estimated material transparency level. Room-temperature continuous wave operation is also observed.

quant-ph↗

arXiv2004

Nonlinear absorption and dispersion in fiber-taper-coupled silicon photonic crystal microresonators

A technique is demonstrated which efficiently transfers light between a tapered standard single-mode optical fiber and a high-Q, ultra-small mode volume, silicon photonic crystal resonant cavity. Cavity mode quality factors of 47000 are measured, and a total fiber-to-cavity coupling efficiency of 44% is demonstrated. Using this efficient cavity input and output channel, the steady-state nonlinear absorption and dispersion of the photonic crystal cavity is studied. Optical bistability is observed for fiber input powers as low as 250 μW, corresponding to a dropped power of 100 μW and 3 fJ of stored cavity energy. A high-density effective free-carrier lifetime for these silicon photonic crystal resonators of 0.5 ns is also estimated from power dependent loss and dispersion measurements.

physics.optics↗

arXiv2004

An optical fiber-based probe for photonic crystal microcavities

We review a novel method for characterizing both the spectral and spatial properties of resonant cavities within two-dimensional photonic crystals (PCs). An optical fiber taper serves as an external waveguide probe whose micron-scale field is used to source and couple light from the cavity modes, which appear as resonant features in the taper's wavelength-dependent transmission spectrum when it is placed within the cavity's near field. Studying the linewidth and depth of these resonances as a function of the taper's position with respect to the resonator produces quantitative measurements of the quality factor Q and modal volume Veff of the resonant cavity modes. Polarization information about the cavity modes can be obtained by studying their depths of coupling when the cavity is probed along different axes by the taper. This fiber-based technique has been used to measure Q ~ 40,000 and Veff ~ 0.9 cubic wavelengths in a graded square lattice PC microcavity fabricated in silicon. The speed and versatility of this fiber-based probe is highlighted, and a discussion of its applicability to other wavelength-scale resonant elements is given.

physics.optics↗

arXiv2004

Rayleigh scattering, mode coupling, and optical loss in silicon microdisks

High refractive index contrast optical microdisk resonators fabricated from silicon-on-insulator wafers are studied using an external silica fiber taper waveguide as a wafer-scale optical probe. Measurements performed in the 1500 nm wavelength band show that these silicon microdisks can support whispering-gallery modes with quality factors as high as 5.2 x 10^5, limited by Rayleigh scattering from fabrication induced surface roughness. Microdisks with radii as small as 2.5 microns are studied, with measured quality factors as high as 4.7 x 10^5 for an optical mode volume of 5.3 cubic wavelengths in the material.

physics.optics↗

arXiv2004

Experimental demonstration of fiber-accessible metal nanoparticle plasmon waveguides for planar energy guiding and sensing

Experimental evidence of mode-selective evanescent power coupling at telecommunication frequencies with efficiencies up to 75 % from a tapered optical fiber to a carefully designed metal nanoparticle plasmon waveguide is presented. The waveguide consists of a two-dimensional square lattice of lithographically defined Au nanoparticles on an optically thin silicon membrane. The dispersion and attenuation properties of the waveguide are analyzed using the fiber taper. The high efficiency of power transfer into these waveguides solves the coupling problem between conventional optics and plasmonic devices and could lead to the development of highly efficient plasmonic sensors and optical switches.

physics.optics↗

arXiv2004

Optical fiber coupling to planar photonic crystal microcavities

A technique is demonstrated which efficiently transfers light between a tapered standard single-mode optical fiber and a resonant mode of a high-Q photonic crystal cavity with mode volume less than a cubic wavelength in size. Cavity mode quality factors of 4.7 x 10^4 are measured, and a total fiber-to-cavity coupling efficiency of 44% is demonstrated.

physics.optics↗

arXiv2003

A low-loss fiber accessible plasmon photonic crystal waveguide for planar energy guiding and sensing

A metal nanoparticle plasmon waveguide for electromagnetic energy transport utilizing dispersion engineering to dramatically increase lateral energy confinement via a two-dimensional pattern of Au dots on an optically thin Si membrane is described. Using finite-difference time-domain simulations and coupled-mode theory, we show that phase-matched evanescent excitation from conventional fiber tapers is possible with efficiencies > 90 % for realistic geometries. Energy loss in this waveguide is mainly due to material absorption, allowing for 1/e energy decay distances of about 2 mm for excitation at telecommunication frequencies. This concept can be extended to the visible regime and promises applications in optical energy guiding, optical sensing, and switching.

physics.optics↗

arXiv2003

Fabrication-tolerant high quality factor photonic crystal microcavities

A two-dimensional photonic crystal microcavity design supporting a wavelength-scale volume resonant mode with a calculated quality factor (Q) insensitive to deviations in the cavity geometry at the level of Q~2x10^4 is presented. The robustness of the cavity design is confirmed by optical fiber-based measurements of passive cavities fabricated in silicon. For microcavities operating in the lambda = 1500 nm wavelength band, quality factors between 1.3-4.0x10^4 are measured for significant variations in cavity geometry and for resonant mode normalized frequencies shifted by as much as 10% of the nominal value.

physics.optics↗

arXiv2003

Efficient input and output fiber coupling to a photonic crystal waveguide

The efficiency of evanescent coupling between a silica optical fiber taper and a silicon photonic crystal waveguide is studied. A high reflectivity mirror on the end of the photonic crystal waveguide is used to recollect, in the backwards propagating fiber mode, the optical power that is initially coupled into the photonic crystal waveguide. An outcoupled power in the backward propagating fiber mode of 88% of the input power is measured, corresponding to a lower bound on the coupler efficiency of 94%.

physics.optics↗

arXiv2003

Optical-fiber based measurement of an ultra-small volume high-Q photonic crystal microcavity

A two-dimensional photonic crystal semiconductor microcavity with a quality factor Q ~ 40,000 and a modal volume Veff ~ 0.9 cubic wavelengths is demonstrated. A micron-scale optical fiber taper is used as a means to probe both the spectral and spatial properties of the cavity modes, allowing not only measurement of modal loss, but also the ability to ascertain the in-plane localization of the cavity modes. This simultaneous demonstration of high-Q and ultra-small Veff in an optical microcavity is of potential interest in quantum optics, nonlinear optics, and optoelectronics. In particular, the measured Q and Veff values could enable strong coupling to both atomic and quantum dot systems in cavity quantum electrodynamics.

quant-ph↗