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Femtosecond time-resolved photoluminescence spectroscopy is used to study the dynamics of optical emission from poly(p-phenylenevinylene) at 77 K over an energy range of 2.19–2.37 eV. All of the decay curves in this energy range can be described by the summation of two exponential functions. Analysis of the spectral dependence of the time constants extracted from these fits indicates that the transient photoluminescence at any given wavelength is due in general to the superposition of three transitions emanating from a single set of inhomogeneously broadened excitons. The three distinct transitions correspond to processes in which two, one, or zero phonons are excited in the host polymer during the emission event. By separating out these three contributions, it is determined that the effective lifetime of the inhomogeneously broadened excitons increases monotonically from 980 fs at 280 meV above the peak in the density of states (DOS), to 114 ps near the peak in the DOS.

The realization of an integrated diamond photonic platform, based on a thin single crystal diamond film on top of a silicon dioxide/silicon substrate, is reported. Using this approach, we demonstrate high-quality factor single crystal diamond race-track resonators, operating at near-infrared wavelengths (1550 nm). The devices are integrated with low-loss diamond waveguides terminated with polymer pads (spot size converters) to facilitate in- (out-) coupling of light from (to) an optical fiber. Optical characterization of these resonators reveal quality factors as high as ∼250 000 and overall insertion losses as low as 1 dB/facet. Scattering induced mode splitting as well as signatures of nonlinear effects such as optical bistability are observed at an input pump power of ∼100 mW in the waveguides.

We report a new approach for realizing a flexible photonic crystal (PC) cavity that enables wide-range tuning of its resonance frequency. Our PC cavity consists of a regular array of silicon nanowires embedded in a polydimethylsiloxane (PDMS) matrix and exhibits a cavity resonance in the telecommunication band that can be reversibly tuned over 60 nm via mechanical stretching-a record for two-dimensional (2D) PC structures. These mechanically reconfigurable devices could find potential applications in integrated photonics, sensing in biological systems, and smart materials.

Diamond is a unique material with exceptional physical and chemical properties that offers potential for the realization of high-performance devices with novel functionalities. For example diamond's high refractive index, transparency over wide wavelength range, and large Raman gain are of interest for the implementation of novel photonic devices. Recently, atom-like impurities in diamond emerged as an exceptional system for quantum information processing, quantum sensing and quantum networks. For these and other applications, it is essential to develop an integrated nanophotonic platform based on diamond. Here, we report on the realization of such an integrated diamond photonic platform, diamond on insulator (DOI), consisting of a thin single crystal diamond film on top of an insulating silicon dioxide/silicon substrate. Using this approach, we demonstrate diamond ring resonators that operate in a wide wavelength range, including the visible (630nm) and near-infrared (1,550nm). Finally, we demonstrate an integrated, on-chip quantum nanophotonic network, consisting of ring resonators coupled to low loss waveguides with grating couplers, that enables the generation and efficient routing of single photons at room temperature., This paper has been withdrawn to change the outline of the paper

Si3N4 is an excellent material for applications of nanophotonics at visible wavelengths due to its wide bandgap and moderately large refractive index (n $\approx$ 2.0). We present the fabrication and characterization of Si3N4 photonic crystal nanobeam cavities for coupling to diamond nanocrystals and Nitrogen-Vacancy centers in a cavity QED system. Confocal micro-photoluminescence analysis of the nanobeam cavities demonstrates quality factors up to Q ~ 55,000, which is limited by the resolution of our spectrometer. We also demonstrate coarse tuning of cavity resonances across the 600-700nm range by lithographically scaling the size of fabricated devices. This is an order of magnitude improvement over previous SiNx cavities at this important wavelength range.

High-index-contrast, wavelength scale texture in thin semiconductor membranes can be used to resonantly enhance a variety of nonlinear optical processes. Several experimental demonstrations in III-V, and silicon membranes incorporating PbSe nanocrystals will be described.

Much recent effort has focused on coupling individual quantum emitters to optical microcavities in order to produce single photons on demand, enable single-photon optical switching, and implement functional nodes of a quantum network. Techniques to control the bandwidth and frequency of the outgoing single photons are of practical importance, allowing direct emission into telecommunications wavelengths and "hybrid" quantum networks incorporating different emitters. Here, we describe an integrated approach involving a quantum emitter coupled to a nonlinear optical resonator, in which the emission wavelength and pulse shape are controlled using the intra-cavity nonlinearity. Our scheme is general in nature, and demonstrates how the photonic environment of a quantum emitter can be tailored to determine the emission properties. As specific examples, we discuss a high Q-factor, TE-TM double-mode photonic crystal cavity design that allows for direct generation of single photons at telecom wavelengths (1425 nm) starting from an InAs/GaAs quantum dot with a 950 nm transition wavelength, and a scheme for direct optical coupling between such a quantum dot and a diamond nitrogen-vacancy center at 637 nm.

We report the use of plasmonic and photonic nanoarray to achieve light management in thin film solar cells. Theoretical and experimental data will be presented.

We propose a scheme for efficient cavity-enhanced nonlinear THz generation via difference-frequency generation (DFG) processes using a triply resonant system based on photonic crystal cavities. We show that high nonlinear overlap can be achieved by coupling a THz cavity to a doubly-resonant, dual-polarization near-infrared (e.g. telecom band) photonic-crystal nanobeam cavity, allowing the mixing of three mutually orthogonal fundamental cavity modes through a chi(2) nonlinearity. We demonstrate through coupled-mode theory that complete depletion of the pump frequency - i.e., quantum-limited conversion - is possible in an experimentally feasible geometry, with the operating output power at the point of optimal total conversion efficiency adjustable by varying the mode quality (Q) factors.

We demonstrate tunable frequency-converted light mediated by a chi-(2) nonlinear photonic crystal nanocavity. The wavelength-scale InP-based cavity supports two closely-spaced localized modes near 1550 nm which are resonantly excited by a 130 fs laser pulse. The cavity is simultaneously irradiated with a non-resonant probe beam, giving rise to rich second-order scattering spectra reflecting nonlinear mixing of the different resonant and non-resonant components. In particular, we highlight the radiation at the sum frequencies of the probe beam and the respective cavity modes. This would be a useful, minimally-invasive monitor of the joint occupancy state of multiple cavities in an integrated optical circuit., 4 pages, 4 figures

We present a design and a top-down fabrication method for realizing diamond nanowires in both bulk single crystal and polycrystalline diamond. Numerical modeling was used to study coupling between a Nitrogen Vacancy (NV) color center and optical modes of a nanowire, and to find an optimal range of nanowire diameters that allows for large collection efficiency of emitted photons. Inductively coupled plasma (ICP) reactive ion etching (RIE) with oxygen is used to fabricate the nanowires. Drop-casted nanoparticles (including $\mathrm{Au}$, $\mathrm{SiO_{2}}$ and $\mathrm{Al_2O_3}$) as well as electron beam lithography defined spin-on glass and evaporated $\mathrm{Au}$ have been used as an etch mask. We found $\mathrm{Al_2O_3}$ nanoparticles to be the most etch resistant. At the same time FOx e-beam resist (spin-on glass) proved to be a suitable etch mask for fabrication of ordered arrays of diamond nanowires. We were able to obtain nanowires with near vertical sidewalls in both polycrystalline and single crystal diamond. The heights and diameters of the polycrystalline nanowires presented in this paper are $\unit[\approx1]{\mu m}$ and $\unit[120-340]{nm}$, respectively, having a $\unit[200]{nm/min}$ etch rate. In the case of single crystal diamond (types Ib and IIa) nanowires the height and diameter for different diamonds and masks shown in this paper were $\unit[1-2.4]{\mu m}$ and $\unit[120-490]{nm}$ with etch rates between $\unit[190-240]{nm/min}$., Comment: 11 pages, 26 figures, submitted to Diamond and related Materials; http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TWV-4Y7MM1M-1&_user=10&_coverDate=01%2F25%2F2010&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6dc58b30f4773a710c667306fc541cca

A photonic crystal nanocavity with a Quality (Q) factor of 1.4 x 10(6), a mode volume of 0.78(lambda/n)(3), and an operating wavelength of 637 nm is designed in a silicon nitride (SiN(x)) ridge waveguide with refractive index of 2.0. The effect on the cavity Q factor and mode volume of single diamond nanocrystals of various sizes and locations embedded in the center and on top of the nanocavity is simulated, demonstrating that Q > 1 x 10(6) is achievable for realistic parameters. An analysis of the figures of merit for cavity quantum electrodynamics reveals that strong coupling between an embedded diamond nitrogen-vacancy center and the cavity mode is achievable for a range of cavity dimensions.

An ultrafast pump-probe experiment is performed on wavelength-scale, silicon-based, optical microcavities that confine light in three dimensions with resonant wavelengths near 1.5 mum, and lifetimes on the order of 20 ps. A below-bandgap probe pulse tuned to overlap the cavity resonant frequency is used to inject electromagnetic energy into the cavity, and an above-bandgap pump pulse is used to generate free carriers in the silicon, thus altering the real and imaginary components of the cavity's refractive index, and hence its resonant frequency and lifetime. When the pump pulse injects a carrier density of ~ 5 x10(17) cm(-3) before the resonant probe pulse strikes the sample, the emitted radiation from the cavity is blue-shifted by 16 times the bare cavity linewidth, and the new linewidth is 3.5 times wider than the original. When the pump pulse injects carriers, and thus suddenly perturbs the cavity properties after the probe pulse has injected energy into the cavity, we show that the emitted radiation is not simply a superposition of Lorentzians centred at the initial and perturbed cavity frequencies. Under these conditions, a simple model and the experimental results show that the power spectrum of radiation emitted by the stored electromagnetic energy when the cavity frequency is perturbed during ring-down consists of a series of coherent oscillations between the original and perturbed cavity frequencies, accompanied by a gradual decrease and broadening of the original cavity line, and the emergence of the new cavity resonance. The modified cavity lifetime is shown to have a significant impact on the evolution of the emission as a function of the pump-probe delay.

We demonstrate photonic crystal nanobeam cavities that support both TE- and TM-polarized modes, each with a Quality factor greater than one million and a mode volume on the order of the cubic wavelength. We show that these orthogonally polarized modes have a tunable frequency separation and a high nonlinear spatial overlap. We expect these cavities to have a variety of applications in resonance-enhanced nonlinear optics., 4 pages, 4 figures

We describe the design, fabrication, and spectroscopy of coupled, high Quality (Q) factor silicon nanobeam photonic crystal cavities. We show that the single nanobeam cavity modes are coupled into even and odd superposition modes, and we simulate the frequency and Q factor as a function of nanobeam spacing, demonstrating that a differential wavelength shift of 70 nm between the two modes is possible while maintaining Q factors greater than 10^6. For both on-substrate and free-standing nanobeams, we experimentally monitor the response of the even mode as the gap is varied, and measure Q factors as high as 200,000., 4 pages, 3 figures

We develop a theoretical framework for second-order nonlinear difference frequency generation in triply resonant wavelength-scale cavities, demonstrating stable CW conversion with quantum-limited efficiency. We propose a scheme for efficient THz generation based on this framework.

Wavelength-scale and high-Q photonic crystal resonators made in various materials (Si, Si3N4, III-Vs), as well as their application in novel single-photon sources and nonlinear wavelength conversion at single-photon level, will be discussed.

Using a tapered photonic crysal cavity approach we designed cavities with theoretical Quality factors Q=2 × 107 and measured experimental Q= 7.5 × 105. Non-linear broadening of the cavity resonance has also been observed.

We theoretically demonstrate high fidelity frequency conversion of a photon generated by a dipole-like emitter in a double mode nonlinear cavity irradiated by a classical field, and propose a realistic photonic crystal nanocavity implementation.

We for the first time present designs of high-Q photonic crystal nanocavities in the cases previously rendered “impossible”, including an ultra-high Q dual-polarized nanocavities, high Q/V cavities based on low-index materials, and high-Q air-band-mode cavities.

Superconducting oscillators have been successfully used for quantum control and readout devices in conjunction with superconducting qubits. Also, squeezed states can improve the accuracy of measurements to subquantum, or at least subthermal, levels. Here, we show theoretically how to produce squeezed states of microwave radiation in a superconducting oscillator with tunable parameters. Its resonance frequency can be changed by controlling an rf SQUID inductively coupled to the oscillator. By repeatedly shifting the resonance frequency between any two values, it is possible to produce squeezed and subthermal states of the electromagnetic field in the (0.1--10) GHz range, even when the relative frequency change is small. We propose experimental protocols for the verification of squeezed state generation, and for their use to improve the readout fidelity when such oscillators serve as quantum transducers.

In order to improve the efficiency of quantum emitters, in particular nitrogen-vacancy (NV) color centers in diamond nanocrystals (NCs), it is important to enhance their photon production rate as well as the collection efficiency of the emitted photons. This can be achieved by embedding the emitters within optical cavities. Here we describe the design and fabrication of 1-D photonic crystal nanocavities in an air-bridge silicon nitride (SiNx) structure. In spite of the low index of silicon nitride (n˜2), we were able to design optical nanocavities with Quality factors as high as Q˜1 × 106. These nanocavities were designed to operate near 637 nm in order to strongly enhance the zero-phonon line (ZPL) emission of an NV center in a diamond NC while suppressing the in-plane emission into the phonon side-band. Simulation results show that a NV center placed near the top of the cavity would experience a reduction of radiative lifetime from ˜15ns to ˜2ps (Purcell factor ˜7000), thus significantly improving the photon production rate. Experimental results show a cavity resonance at ˜630nm, with a linewidth corresponding to Q˜1250, limited by the spectrometer resolution. The presented work is an important step towards the realization of diamond-based single photon devices, including switches.

The second harmonic radiation emitted into the top half space from three dimensionally localized modes of L3 defect cavities in InP-based planar photonic crystals is studied using both CW and pulsed excitation. The far field harmonic radiation patterns observed from modes with resonant wavelengths ~ 1550 nm, excited by a tunable CW laser with less than 1 mW power, reveal strong local field enhancement (> 1000 X). A detailed comparison with FDTD modeling allows us to conclude that the bulk InP second order susceptibility tensor dominates the second order response of these microcavities. When a broadband, sub picoseconds source is used to simultaneously excite two of the microcavity modes, the harmonic spectrum in general consists of three contributions, the second harmonic from each of the excited modes, and a third peak due to the second order (sum frequency) mixing of the two modes. By using short and long pulse excitation simultaneously, we demonstrate how the emission frequency due to sum frequency processes can be used to continuously tune the harmonic emission frequency dependent on the occupation of various cavity modes.

A high Q mode in a silicon planar photonic crystal microcavity is dynamically perturbed by injection of free carriers, and modelled by a damped harmonic oscillator which undergoes an instantaneous frequency and lifetime shift.

The far-field second-order radiation pattern from a wavelength-scale, InP-based photonic crystal microcavity that confines light in three dimensions is measured when excited on resonance by $300\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{W}$ of continuous-wave power from a laser diode. The measurements are accurately simulated using the finite-difference time-domain method, showing that both absorption and scattering play significant roles in determining the pattern of the radiation. The results show that the bulk second-order nonlinear susceptibility mediates the nonlinear process. In a separate set of experiments, a short-pulse laser is used to simultaneously populate two distinct modes of a similar microcavity. The detected second-order spectra show features due to the second harmonic generated by each mode, as well as the sum-frequency generation due to nonlinear intermode mixing. The key phenomena that determine the second-order response of these fundamentally small optical cavities are identified.

Polarization-resolved second-harmonic spectra are obtained from the resonant modes of a two-dimensional planar photonic crystal microcavity patterned in a free-standing InP slab. The photonic crystal microcavity is comprised of a single missing-hole defect in a hexagonal photonic crystal host formed with elliptically-shaped holes. The cavity supports two orthogonally-polarized resonant modes split by 60 wavenumbers. Sum-frequency data are reported from the nonlinear interaction of the two coherently excited modes, and the polarization dependence is explained in terms of the nonlinear susceptibility tensor of the host InP., Comment: 7 pages, 8 Postscript figures, to be presented at Photonics West Jan. 25

Sum frequency data are reported from the nonlinear interaction of two coherently excited resonant modes of a two-dimensional planar photonic crystal microcavity patterned in a free-standing InP slab.

The resonant modes of two-dimensional planar photonic crystal microcavities patterned in a free-standing InP slab are probed in a novel fashion using a long working distance microscope objective to obtain cross-polarized resonant scattering and second-harmonic spectra. We show that these techniques can be used to do rapid effective assays of large arrays of microcavities that do not necessarily contain resonant light-emitting layers. The techniques are demonstrated using microcavities comprised of single missing-hole defects in hexagonal photonic crystal hosts formed with elliptically shaped holes. These cavities typically support two orthogonally polarized resonant modes, and the resonant scattering and harmonic spectra are well fitted using a coherent sum of Lorentzian functions. The well-defined coherence between the two resonant features is explained in terms of a microscopic harmonic oscillator model. The relative merits of these techniques are quantitatively compared with the more commonly used cavi...

We experimentally demonstrate high quality factor dual-polarized photonic crystal nanobeam cavities. The free-standing nanobeams are fabricated in a 500 nm thick silicon layer, and are probed using both tapered optical fiber and free-space resonant scattering set-ups. We measure Q factors greater than 104 for both transverse magnetic (TM) and transverse electric modes, and observe fiber transmission drops as large as 1−T=0.8 at the TM mode resonances.

We present dynamically reconfigurable photonic crystal nanobeam cavities, operating at ~1550 nm, that can be continuously and reversibly tuned over a 9.5 nm wavelength range. The devices are formed by two coupled nanobeam cavities, and the tuning is achieved by varying the lateral gap between the nanobeams. An electrostatic force, obtained by applying bias voltages directly to the nanobeams, is used to control the spacing between the nanobeams, which in turn results in tuning of the cavity resonance. The observed tuning trends were confirmed through simulations that modeled the electrostatic actuation as well as the optical resonances in our reconfigurable geometries.

We present a comprehensive study of second-order nonlinear difference frequency generation in triply resonant cavities using a theoretical framework based on coupled-mode theory. We show that optimal quantum-limited conversion efficiency can be achieved at any pump power when the powers at the pump and idler frequencies satisfy a critical relationship. We demonstrate the existence of a broad parameter range in which all triply-resonant DFG processes exhibit monostable conversion. We also demonstrate the existence of a geometry-dependent bistable region., Comment: 10 pages, 3 figures

We investigate the design, fabrication and experimental characterization of high Quality factor photonic crystal nanobeam cavities in silicon. Using a five-hole tapered 1D photonic crystal mirror and precise control of the cavity length, we designed cavities with theoretical Quality factors as high as 14 million. By detecting the cross-polarized resonantly scattered light from a normally incident laser beam, we measure a Quality factor of nearly 750,000. The effect of cavity size on mode frequency and Quality factor was simulated and then verified experimentally., Comment: 3 pages, 4 figures, submitted to APL. One change: added 1 author to version v1

The unidirectional coupling of a microcavity mode to a ridge waveguide in a slab photonic crystal structure was investigated for the first time. Experimental observation of the coupling efficiency for the signal coupled out of the structure is in good agreement with the result of three-dimensional finite-difference time-domain simulations. The coupling efficiency of the cavity mode to the output channel is ∼60%.

We present a fabrication method for diamond based resonators. Optical characterization of a diamond ring resonator on quartz substrate reveals cavity modes both in the telecom and the visible wavelength regime having with Q-factors ∼8000.

Wavelength-scale and high-Q photonic crystal nanobeam resonators, made in Si, III–Vs, and Si 3 N 4 , and their applications in reconfigurable photonics, optoelectronics, biochemical sensing and quantum information processing are presented.