Showing papers on "Optical microcavity published in 2012"
TL;DR: In this article, a planar, optical microcavity was used to control the efficiency and spectral selection of photocurrent generation in the integrated graphene device, and a twenty-fold enhancement of the photocurrent was demonstrated.
Abstract: Graphene has extraordinary electronic and optical properties and holds great promise for applications in photonics and optoelectronics. Demonstrations including high-speed photodetectors, optical modulators, plasmonic devices, and ultrafast lasers have now been reported. More advanced device concepts would involve photonic elements such as cavities to control light–matter interaction in graphene. Here we report the first monolithic integration of a graphene transistor and a planar, optical microcavity. We find that the microcavity-induced optical confinement controls the efficiency and spectral selection of photocurrent generation in the integrated graphene device. A twenty-fold enhancement of photocurrent is demonstrated. The optical cavity also determines the spectral properties of the electrically excited thermal radiation of graphene. Most interestingly, we find that the cavity confinement modifies the electrical transport characteristics of the integrated graphene transistor. Our experimental approach opens up a route towards cavity-quantum electrodynamics on the nanometre scale with graphene as a current-carrying intra-cavity medium of atomic thickness.
349 citations
TL;DR: In this paper, spontaneous emission in organic electroluminescent devices is modeled by means of an approximate closed-form solution for the exciton rate equation, which yields the efficiency of conversion of electrical charges into molecular excited states.
Abstract: We examine spontaneous emission in organic electroluminescent devices and investigate the influence of the local photonic mode density on the emissive properties of molecular emitters. Spontaneous emission in organic electroluminescent devices is modeled by means of an approximate closed-form solution for the exciton rate equation, which yields the efficiency of conversion of electrical charges into molecular excited states. The exciton decay rate and the efficiency of conversion of molecular excitation into far-field radiated photons are described using a state-of-the-art classical electromagnetic formalism suitable to model multilayered organic light-emitting diodes (OLEDs). We present an in-depth analysis of the influence of optical microcavities and the corresponding resonant modes on the luminescent properties of organic molecules. Near-field coupling and coupling to metallic reflectors are demonstrated as the main effects responsible for environment-induced modifications of the rate and efficiency of spontaneous emission. The extent to which the excitonic decay rate is modified by the optical microcavity (Purcell effect) is shown to be strictly dependent on the intrinsic luminescence quantum yield of the molecular emitter. The modeling formalism is successfully validated against experimental results obtained on three series of small-molecule $p$-$i$-$n$ OLED samples, featuring phosphorescent or fluorescent molecular emitters, with a widely varying thickness of the optical microcavity. We demonstrate that, within its limits of validity, the theoretical treatment in this work provides a rigorous quantitative description of spontaneous emission in organic luminescent devices and allows for the identification of the factors determining the OLED internal and external quantum efficiencies.
251 citations
TL;DR: A regime with unusually large fluctuations of the condensate number is predicted for this system that is not observed in present atomic physics Bose-Einstein condensation experiments.
Abstract: We theoretically analyze the temperature behavior of paraxial light in thermal equilibrium with a dye-filled optical microcavity. At low temperatures the photon gas undergoes Bose-Einstein condensation, and the photon number in the cavity ground state becomes macroscopic with respect to the total photon number. Owing to a grand-canonical excitation exchange between the photon gas and the dye molecule reservoir, a regime with unusually large fluctuations of the condensate number is predicted for this system that is not observed in present atomic physics Bose-Einstein condensation experiments.
83 citations
TL;DR: In this article, a fiber-based, high-finesse optical microcavity was employed to detect the Brownian motion of a freely suspended carbon nanotube at room temperature under vacuum.
Abstract: Optical cavities with small mode volume are well-suited to detect the vibration of sub-wavelength sized objects. Here we employ a fiber-based, high-finesse optical microcavity to detect the Brownian motion of a freely suspended carbon nanotube at room temperature under vacuum. The optical detection resolves deflections of the oscillating tube down to 50pm/Hz^1/2. A full vibrational spectrum of the carbon nanotube is obtained and confirmed by characterization of the same device in a scanning electron microscope. Our work successfully extends the principles of high-sensitivity optomechanical detection to molecular scale nanomechanical systems.
71 citations
TL;DR: Simple numerical expressions to calculate the ultimate sensor resolution and detection limits were found, and the results compared to experiments in which the resonances of fluorescent-core microcapillaries responded to various sucrose concentrations in water.
Abstract: Many proposed microfluidic biosensor designs are based on the measurement of the resonances of an optical microcavity. Fluorescence-based resonators tend to be simpler and more robust than setups that use evanescent coupling from tuneable laser to probe the cavity. In all sensor designs the detection limits depend on the wavelength resolution of the detection system, which is a limitation of fluorescence-based devices. In this work, we explore the ultimate resolution and detection limits of refractometric microcavity sensor structures. Because many periodic modes are collected simultaneously from fluorescent resonators, standard Fourier methods can be best suited for rapid and precise analysis of the resonance shifts. Simple numerical expressions to calculate the ultimate sensor resolution and detection limits were found, and the results compared to experiments in which the resonances of fluorescent-core microcapillaries responded to various sucrose concentrations in water.
54 citations
TL;DR: In this paper, the authors demonstrate non-perturbative coupling between a single self-assembled InGaAs quantum dot and an external fiber-mirror based microcavity.
Abstract: We demonstrate non-perturbative coupling between a single self-assembled InGaAs quantum dot and an external fiber-mirror based microcavity. Our results extend the previous realizations of tunable microcavities while ensuring spatial and spectral overlap between the cavity-mode and the emitter by simultaneously allowing for deterministic charge control of the quantum dots. Using resonant spectroscopy, we show that the coupled quantum dot cavity system is at the onset of strong coupling, with a cooperativity parameter of 2. Our results constitute a milestone towards the realization of a high efficiency solid-state spin-photon interface.
53 citations
TL;DR: In this paper, the influence of the electron-phonon interaction on the decay dynamics of a quantum dot coupled to an optical microcavity was investigated using two different theoretical approaches: (i) a second-order expansion in the bare phonon coupling constant, and (ii) an expansion in a polaron-photon coupling constant.
Abstract: We investigate the influence of the electron-phonon interaction on the decay dynamics of a quantum dot coupled to an optical microcavity. We show that the electron-phonon interaction has important consequences on the dynamics, especially when the quantum dot and cavity are tuned out of resonance, in which case the phonons may add or remove energy leading to an effective nonresonant coupling between quantum dot and cavity. The system is investigated using two different theoretical approaches: (i) a second-order expansion in the bare phonon coupling constant, and (ii) an expansion in a polaron-photon coupling constant, arising from the polaron transformation which allows an accurate description at high temperatures. In the low-temperature regime, we find excellent agreement between the two approaches. An extensive study of the quantum dot decay dynamics is performed, where important parameter dependencies are covered. We find that in general the electron-phonon interaction gives rise to a greatly increased bandwidth of the coupling between quantum dot and cavity. At low temperature, an asymmetry in the quantum dot decay rate is observed, leading to a faster decay when the quantum dot has a larger energy than to the cavity. We explain this as due to the absence of phonon absorption processes. Furthermore, we derive approximate analytical expressions for the quantum dot decay rate, applicable when the cavity can be adiabatically eliminated. The expressions lead to a clear interpretation of the physics and emphasize the important role played by the effective phonon density, describing the availability of phonons for scattering, in quantum dot decay dynamics. Based on the analytical expressions, we present the parameter regimes where phonon effects are expected to be important. Also, we include all technical developments in appendixes.
52 citations
IBM1
TL;DR: In this article, the authors report a directly modulated 850nm VCSEL-based optical link operating at 55Gb/s, which is the highest modulation rate for VCSel-based link of any wavelength.
Abstract: We report a directly modulated 850nm VCSEL-based Optical link operating at 55Gb/s. This is the highest modulation rate for VCSEL-based link of any wavelength.
48 citations
TL;DR: Microcavity resonance is demonstrated in nanocrystal quantum dot fluorescence in a one-dimensional (1D) chiral photonic bandgap cholesteric-liquid crystal host under cw excitation, which has circular polarization due to microc Cavity chirality with 4.9 times intensity enhancement in comparison with polarization of the opposite handedness.
Abstract: Microcavity resonance is demonstrated in nanocrystal quantum dot fluorescence in a one-dimensional (1D) chiral photonic bandgap cholesteric-liquid crystal host under cw excitation. The resonance demonstrates coupling between quantum dot fluorescence and the cholesteric microcavity. Observed at a band edge of a photonic stop band, this resonance has circular polarization due to microcavity chirality with 4.9 times intensity enhancement in comparison with polarization of the opposite handedness. The circular-polarization dissymmetry factor ge of this resonance is ∼1.3. We also demonstrate photon antibunching of a single quantum dot in a similar glassy cholesteric microcavity. These results are important in cholesteric-laser research, in which so far only dyes were used, as well as for room-temperature single-photon source applications.
45 citations
TL;DR: In this article, a new form of induced transparency, called chaos-induced transparency, was demonstrated in a slightly deformed microcavity which supported both continuous chaotic modes and discrete regular modes with Q factors exceeding 3X?10^7.
Abstract: We demonstrate experimentally a new form of induced transparency, i.e., chaos-induced transparency, in a slightly deformed microcavity which support both continuous chaotic modes and discrete regular modes with Q factors exceeding 3X?10^7. When excited by a focused laser beam, the induced transparency in the transmission spectrum originates from the destructive interference of two parallel optical pathways: (i) directly refractive excitation of the chaotic modes, and (ii) excitation of the ultra-high-Q regular mode via chaos-assisted dynamical tunneling mechanism coupling back to the chaotic modes. By controlling the focal position of the laser beam, the induced transparency experiences a highly tunable Fano-like asymmetric lineshape. The experimental results are modeled by a quantum scattering theory and show excellent agreement. This chaos-induced transparency is accompanied by extremely steep normal dispersion, and may open up new possibilities a dramatic slow light behavior and a significant enhancement of nonlinear interactions.
44 citations
TL;DR: Selective control of the Q and transmission of an individual resonance of an optical microcavity is experimentally demonstrated by optically controlling its intracavity loss via inverse Raman scattering by analogous to Zeno effects observed in decoherence-driven atomic ensembles and two-level systems.
Abstract: We experimentally demonstrate selective control of the $Q$ and transmission of an individual resonance of an optical microcavity by optically controlling its intracavity loss via inverse Raman scattering. A strongly overcoupled resonance is brought into critical coupling with continuous tuning of the on-resonance transmission by $g9\text{ }\text{ }\mathrm{dB}$ and reduction of the intrinsic $Q$ factor by more than a factor of five. Adjacent resonances experience minimal disturbance and can be selectively controlled by tuning the control beam to the appropriate control resonance. These dynamics are analogous to Zeno effects observed in decoherence-driven atomic ensembles and two-level systems.
TL;DR: In this paper, a strain-controlled columnar quantum dot optical amplifiers (SC-CQDs) were proposed for the 1.5-μm wavelength band, which exhibited a high aspect ratio and had strain controlled side barriers for polarization-insensitive operation.
Abstract: A polarization-insensitive quantum dot semiconductor optical amplifiers (QD-SOAs) have been studied for use in future optical communication systems. A part of our work shows that the optical polarization property in QDs depends on both their aspect ratio and strain. To control these two parameters, we propose the use of strain-controlled columnar QDs (SC-CQDs), which exhibit a high aspect ratio and have strain-controlled side barriers for polarization-insensitive operation in the 1.5-μ m wavelength band. QD-SOAs with these optimized SC-CQDs demonstrated polarization-insensitive characteristics. They showed a gain of 8.0 dB with polarization dependence of the gain as low as 0.4 dB, -3-dB saturation output power of 18.5 dBm at a wavelength of 1550 nm, and error-free amplification at a bit rate of 40 Gbit/s.
TL;DR: In this paper, the optical nonlinearity present at very low optical power in a system consisting of a quantum dot strongly coupled to a cavity, and show that this system can be used for ultralow power and high-speed all-optical switching.
Abstract: We theoretically analyze the optical nonlinearity present at very low optical power in a system consisting of a quantum dot strongly coupled to a cavity, and show that this system can be used for ultralow power and high-speed all-optical switching. We also present numerical simulation results showing both the detailed temporal behavior of such switch and the time-integrated energy transmission through the cavity. We use two different approaches-a quantum optical one and a semiclassical one-to describe the system's behavior, and observe reasonable agreement between the outcomes of numerical simulations based on these two approaches.
TL;DR: In this paper, the lasing threshold for crystalline anthracene sandwiched within an optical microcavity consisting of two dielectric Bragg reflectors was found to decrease by an order of magnitude as temperature is reduced from 300 to 12 K while maintaining an energy dispersion characteristic of the cavity polariton across the entire temperature range studied.
Abstract: The lasing threshold for crystalline anthracene sandwiched within an optical microcavity consisting of two dielectric Bragg reflectors (DBRs) is found to decrease by an order of magnitude as temperature is reduced from 300 to 12 K while maintaining an energy dispersion characteristic of the cavity polariton across the entire temperature range studied. The linear temperature dependence differs from a conventional organic semiconductor laser that shows practically no variation in threshold over the same temperature range. The two-dimensional Bose-Einstein condensate (BEC) critical density and its relation to the polariton lasing threshold is considered in the thermodynamic limit along with other temperature-dependent processes that are used to explain our observations.
TL;DR: In this paper, the authors derived the maximum bandwidth of future VCSEL-based optical interconnects from the influence of device heating occurring in high-speed SVE arrays.
Abstract: Future high-performance computers require optical interconnects with aggregated Exa-Byte/s data transport. Densely packed arrays of vertical-cavity surface-emitting lasers (VCSELs) might present the only feasible technical solution. The high-speed properties of semiconductor lasers, however, are strongly affected by their operating temperature. Thermal crosstalk becomes dominant when densely packed arrays of high-speed VCSELs are required. In this paper, we derive the maximum bandwidth of future VCSEL-based optical interconnects from the influence of device heating occurring in high-speed VCSEL arrays. Furthermore, we estimate the scalability of this technology and address the challenges. From our calculations we obtain, that VCSEL arrays are scalable from a bandwidth density of 100 Gbps/mm2 with today's devices up to a technological limit of 15 Tbps/mm2.
TL;DR: In this paper, a planar two-dimensional organic photonic crystal microcavity laser was constructed using a tris(8-hydroxyquinolinato) aluminum doped with 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran.
Abstract: In this letter, we report the realization and characterization of a planar two-dimensional organic photonic crystal microcavity laser. The gain medium consists of a tris(8-hydroxyquinolinato) aluminum doped with 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran and is deposited on a lithographically patterned silicon nitride two dimensional photonic crystal H2 microcavity. The experimental results show a laser emission at 662 nm with a threshold of 9.7 μJ/cm2.
TL;DR: The spin selective coupling of the exciton state with cavity mode in a single quantum dot (QD)-micropillar cavity system is demonstrated, paving the way for the realization of future quantum light sources and the quantum information processing applications.
Abstract: We demonstrate the spin selective coupling of the exciton state with cavity mode in a single quantum dot (QD)–micropillar cavity system. By tuning an external magnetic field, each spin polarized exciton state can be selectively coupled with the cavity mode due to the Zeeman effect. A significant enhancement of spontaneous emission rate of each spin state is achieved, giving rise to a tunable circular polarization degree from −90% to 93%. A four-level rate equation model is developed, and it agrees well with our experimental data. In addition, the coupling between photon mode and each exciton spin state is also achieved by varying temperature, demonstrating the full manipulation over the spin states in the QD-cavity system. Our results pave the way for the realization of future quantum light sources and the quantum information processing applications.
TL;DR: In this article, a dynamic axial mode tuning method by means of near-field probe in a rolled-up optical microcavity is demonstrated by using the axial confinement model.
Abstract: We demonstrate a dynamic axial mode tuning method by means of near-field probe in a rolled-up optical microcavity. The spatially selective nature of the tuning has been explored through both the lateral and transversal probing processes. A series of perturbation calculations based on the axial confinement model are performed to prove and improve the understanding of experimental results.
TL;DR: Here, strong interaction between an optical microcavity and its image under external illumination is shown, using silicon nanospheres whose high refractive index makes well-defined optical resonances feasible and warrants a new kind of optical levitation that allows us to accurately manipulate small particles.
Abstract: Although science fiction literature and art portray extraordinary stories of people interacting with their images behind a mirror, we know that they are not real and belong to the realm of fantasy. However, it is well known that charges or magnets near a good electrical conductor experience real attractive or repulsive forces, respectively, originating in the interaction with their images. Here, we show strong interaction between an optical microcavity and its image under external illumination. Specifically, we use silicon nanospheres whose high refractive index makes well-defined optical resonances feasible. The strong interaction produces attractive and repulsive forces depending on incident wavelength, cavity-metal separation and resonance mode symmetry. These intense repulsive photonic forces warrant a new kind of optical levitation that allows us to accurately manipulate small particles, with important consequences for microscopy, optical sensing and control of light by light at the nanoscale.
TL;DR: In this paper, a polygonal silica toroidal microcavity was fabricated by using a combination of isotropic etching, anisotropic etching and laser reflow.
Abstract: We fabricated polygonal silica toroidal microcavities to achieve stable mechanical coupling with an evanescent coupler such as a tapered fiber. The polygonal cavity was fabricated by using a combination of isotropic etching, anisotropic etching and laser reflow. It offers both high and low coupling efficiencies with the cavity mode even when the coupler is in contact with the cavity, which offers the possibility of taking the device outside the laboratory. A numerical simulation showed that an octagonal silica toroidal microcavity had an optical quality factor of 8.8\times10^6.
TL;DR: In this paper, a hybrid plasmonic microcavity was proposed, which is composed of a silver nanoring and a silica toroidal nano-viscosity.
Abstract: We propose a novel hybrid plasmonic microcavity which is composed of a silver nanoring and a silica toroidal microcavity. The hybrid mode of the proposed hybrid plasmonic microcavity due to the coupling between the surface plasmon polaritons (SPPs) and the dielectric mode is demonstrated with a high quality factor (>1000) and an ultrasmall mode volume (∼0.8 μm3). This microcavity shows great potential in fundamental studies of nonlinear optics and cavity quantum electrodynamics (cQED) and applications in low-threshold plasmonic microlasers.
TL;DR: In this article, the frequency stability of an opto-mechanical oscillator based on resonant interaction of one mechanical, and two optical modes of the same optical microcavity was theoretically studied.
Abstract: We theoretically study the frequency stability of an opto-mechanical oscillator based on resonant interaction of one mechanical, and two optical modes of the same optical microcavity. A generalized expression for the phase noise of the oscillator is derived using Langevin formalism and compared to the phase noise of existing electronic oscillators.
TL;DR: In this paper, the nonlinear response of a silica toroid microcavity using coupledmode theory and a finite-element method was modeled, and a Kerr bistable memory with a memory holding time of 500 ns at an extremely low energy consumption was demonstrated.
Abstract: We model the nonlinear response of a silica toroid microcavity using coupled-mode theory
and a finite-element method, and successfully obtain Kerr bistable operation that does not suffer
from the thermo-optic effect by optimizing the fiber-cavity coupling. Our rigorous analysis reveals
the possibility of demonstrating a Kerr bistable memory with a memory holding time of 500 ns at
an extremely low energy consumption.
TL;DR: In this paper, the optical losses of ridge waveguide resonators are measured with passive and active techniques with the aim of implementing active plasmonic devices, and the effect of the proximity of the metal top contact to the laser active region is investigated.
Abstract: We performed an experimental study of tensile strain quantum wells for diode lasers operating at telecom wavelengths and in transverse magnetic polarization. The optical losses of ridge waveguide resonators are measured with passive and active techniques. The results are consistent with the theory and provide a useful material parameter database for this kind of devices. With the aim of implementing active plasmonic devices we studied the effect of the proximity of the metal top contact to the laser active region.
TL;DR: Optically pumped InGaN/GaN quantum well vertical-external-cavity surface-emitting laser emitting at 420nm has been realized in this paper, making integration of practical sized intracavity elements possible.
Abstract: Optically pumped InGaN/GaN quantum well vertical-external-cavity surface-emitting laser emitting at 420 nm has been realized. Lasing at external cavity lengths of up to 50 mm is demonstrated, making integration of practical sized intracavity elements possible. Spectral and beam profile measurements indicate best operation conditions in a semiconfocal cavity configuration. Lasing threshold of 20.9 W is achieved for a 49 mm long cavity with output beam quality parameter M2 not exceeding 1.1.
TL;DR: In this paper, the authors analytically show that inserting a driven, two-level system inside a microcavity can improve its optical properties, and they further predict that if the cavity is pumped through a resonant channel, optical absorptive or dispersive bistability can be combined with the population-oscillation induced steep material dispersion to obtain a strong quality-factor enhancement.
Abstract: We analytically show that inserting a driven, two-level system inside a microcavity can improve its optical properties. In this approach, the strong dispersion induced by a pump via population oscillations increases the cavity lifetime experienced by a slightly detuned probe. We further predict that if the cavity is pumped through a resonant channel, optical absorptive or dispersive bistability can be combined with the population-oscillation-induced steep material dispersion to obtain a strong quality-factor enhancement. Moreover, differential amplification coming from the nonlinear feature of the pump transfer function can be used to drastically increase the probe transmission beyond intrinsic characteristics of the resonator. The $Q$-factor enhancement and the differential amplification can be advantageously combined with a frequency pulling effect to stabilize or readjust the microcavity resonance frequency.
TL;DR: In this paper, the formation and superfluidity of polaritons in an optical microcavity formed by excitons embedded in gapped graphene embedded there and nano-light photons was predicted.
Abstract: We predict the formation and superfluidity of polaritons in an optical microcavity formed by excitons in gapped graphene embedded there and microcavity photons. The Rabi splitting related to the creation of an exciton in a graphene layer in the presence of the band gap is obtained. It is demonstrated that the Rabi splitting decreases when the energy gap increases, while the larger value of the dielectric constant of the microcavity gives a smaller value for the Rabi splitting. The analysis of collective excitations as well as the sound velocity is presented. We show that the superfluid density ${n}_{s}$ and temperature of the Kosterlitz-Thouless phase transition ${T}_{c}$ are decreasing functions of the energy gap.
TL;DR: In this paper, a self-assembled Cy5-conjugated lipid bilayer is formed on a spherical optical microcavity and the evanescent tail of the microsphere is used to excite the Cy5 dye molecules.
Abstract: Whispering gallery-mode optical microcavities have significantly impacted the field of label-free optical biodetection. By combining the evanescent field generated by the microcavity with biomimetic surface chemistries, it is possible to use the microcavities to study the fundamental photobleaching behavior of fluorescent molecules embedded in biomaterials. In this study, a self-assembled Cy5-conjugated lipid bilayer is formed on a spherical optical microcavity. The evanescent tail of the microsphere is used to excite the Cy5 dye molecules. Both the emission wavelength and the fluorescence intensity decrease of the Cy5-conjugated dye in the lipid bilayer are measured.
TL;DR: In this paper, an algorithm to simulate the optical response of these multilayers was developed, considering the optical properties of the individual layers and the results obtained by the simulation were experimentally verified; for this purpose different photonic structures were prepared, such as Bragg reflectors and microcavities.
TL;DR: In this paper, the effect of spontaneous emission on gain and lasing threshold of semiconductor microcavity lasers has not been discussed clearly, but it has been shown that gain in weakly coupled semiconductor cavities is a local phenomenon, which occurs due to stimulated emission induced by an electromagnetic excitation and remains unaffected by the cavity boundary conditions.
Abstract: The effect of enhanced rate of spontaneous emission on gain and lasing threshold of semiconductor microcavity lasers has not been discussed clearly. Some reports have suggested that the lasing threshold in microcavities could possibly be lowered due to the so-called Purcell effect. Here, we argue that gain in weakly coupled semiconductor cavities is a local phenomenon, which occurs due to stimulated emission induced by an electromagnetic excitation and remains unaffected by the cavity boundary conditions. Hence, the Purcell effect in microcavities filled uniformly with a gain medium should not lead to a reduction in the laser’s threshold pump density, provided radiative scattering is not the dominant relaxation mechanism in the excited state. A systematic experimental investigation of laser threshold in parallel-plate semiconductor microcavity terahertz quantum-cascade lasers of different dimensions was found to be in accordance with our arguments.