Inducing photonic transitions between discrete modes in a silicon optical microcavity

We show the existence of direct photonic transitions between modes of a silicon optical microcavity spaced apart in wavelength by over 8 nm. This is achieved by using ultrafast tuning of the refractive index of the cavity over a time interval that is comparable to the inverse of the frequency separation of modes. The demonstrated frequency mixing effect, i.e., the transitions between the modes, would enable on-chip silicon comb sources which can find wide applications in optical sensing, precise spectroscopy, and wavelength-division multiplexing for optical communications and interconnects.     

Direct measurement of the quality factor in a two-dimensional photonic-crystal microcavity

A new microcavity design is proposed and structures are realized with a two-dimensional photonic-crystal slab. The cavity consists of seven defect holes that encompass a hexagon and is designed to reduce vertical light leakage. From a direct transmission measurement, a Q value of 816+/-30 is achieved at lambda =1.55 mum . This high- Q cavity will permit the realistic realization of spontaneous-emission modification and on-off optical switches.     

Enhanced electro-optic response of a poled polymer in a reflective microcavity

We investigated the electro-optic (EO) response of a reflective planar microcavity with a poled polymer spacer using reflection ellipsometry. We designed and fabricated the microcavity to have an enhanced local field in the EO polymer spacer and evaluated the resulting enhancement in the voltage-induced phase difference between the s- and p-polarized components. The phase difference obtained was 56 times larger than that for the EO polymer alone. This enhancement is attributed to the polarization-dependent local field effect for oblique incidence.     

High-speed and broad optical bandwidth silicon modulator

A high-speed silicon modulator with broad optical bandwidth is proposed based on a symmetrically configured Mach–Zehnder interferometer.Careful phase bias control and traveling-wave design are used to improve the high-speed performance.Over a broadband wavelength range,high-speed operation up to 30 Gbit/s with a 4.5 dB–5.5 dB extinction ratio is experimentally demonstrated with a low driving voltage of 3 V.     

High-speed compact silicon digital optical switch with slot structure

A high-speed compact silicon digital optical switch (DOS) is proposed in this paper. The direct electro-optic effect is applied by filling electro-optic polymer in the void slot of the branches, which compensates the limitation of silicon itself. The crosstalk of about 35 dB and the insertion loss of 0.7 dB is obtained, the switching speed is less than 1 ps, and the whole device length can be shortened to 616 μm even using the basic mode-evolving principle and a simple Y-type structure. Analysis also shows that the device has good fabrication tolerance and wavelength independence over the C-band.     

Influence of optical confinement and excitonic absorption on strong coupling in a bulk GaN microcavity grown on silicon

We report the optical study of a lambda-thick GaN microcavity grown by molecular beam epitaxy on a silicon substrate. Angle-resolved reflectivity measurements evidence the strong coupling regime at room temperature on the half cavity (without the top mirror), but at low temperature, the high excitonic absorption quenches the optical cavity mode at the excitonic energies. On the whole microcavity, the improved quality factor leads to the observation of the polariton emission whatever the temperature. No bottleneck is observed at 70 K even at low pumping power and large negative detuning. The impact of the optical confinement and the excitonic absorption, studied through reflectivity measurements are accurately reproduced by the transfer-matrix formalism. The optimization of the design in this structure leads to a large Rabi splitting (52 meV) at room temperature.     

Vortices in the microcavity optical parametric oscillator

A theoretical treatment is presented for a novel from of optical vortex state, in a microcavity optical parametric oscillator (OPO). The state comprises a vortex/anti-vortex pair in the signal and idler beams, with a Gaussian pump. A numerical solution of the microcavity OPO equations shows that such a vortex can be stable.     

Visualizing the whispering gallery modes in a cylindrical optical microcavity

Whispering gallery modes in cylindrical integrated optics microcavities have, for what is to our knowledge the first time, been mapped with a photon scanning tunneling microscope. Optical images were obtained with a spatial resolution of 50 nm. By combination of information on the spatial optical distributions with wavelength-dependent measurements, an unexpectedly rich variety of intracavity phenomena, such as polarization conversion and interference of copropagating and counterpropagating modes, could be directly observed. A quantitative comparison of the experimental data with computer simulations results in a comprehensive understanding of the various whispering gallery modes inside the microcavity.     

一种新型光学微腔的理论分析

应用波动光学理论,分析了一种新型锥顶柱状光学微腔的本征模式,得到了谐振腔的谐振波长表达式.在谐振波长1550 nm附近进行了设计与仿真优化,优化结果显示新型谐振腔与传统平行腔相比,在腔长为4512.5 nm,直径为3134.4 nm时,其品质因数可以提高22.4%,达到了49928.5,同时谐振腔的有效模式体积减小了47.8%.     

Influence of the humidity conditions on the reflectivity spectrum of a porous silicon microcavity

We have designed and fabricated a porous silicon (PS) microcavity that shows a reflectivity resonance around 3 μm in between two spectral regions with high reflectivity values. The microcavity has been simulated following the photonic crystals formalism, which results in good agreement with the measured spectrum. The reflectivity spectrum of the microcavity has been analyzed under different humidity conditions. We demonstrate that the reflectivity resonance shifts to higher wavelengths and that the reflectivity decreases when the humidity increases. In addition, the reflectivity spectrum of the as-prepared device is recovered when the humidity returns to the initial laboratory conditions. Finally, the effect on the reflectivity spectrum of a condensed water layer at the surface of the microcavity is also analyzed.     

Sampling high-frequency signals using a poled-polymer asymmetric Fabry–Perot microcavity as an electro-optic probe tip

The sampling of high-frequency signals using poled electro-optic polymer films as electro-optic probe tips has been demonstrated for the first time. The electro-optic polymer, which was spin coated onto a high-reflectivity glass substrate, was corona poled; thus an asymmetric Fabry–Perot microcavity was formed, based on the difference between the polymer reflectivity and that of high-reflectivity glass. This converts phase modulation to amplitude modulation, so only one laser beam is needed in this system. The sampling technique has been analyzed by multiple reflection and index ellipsoid methods. A 1.2 GHz microwave signal propagating on a coplanar waveguide transmission line has been sampled, and a voltage sensitivity of about 0.5 mV/ was obtained. Received: 16 August 2001 / Revised version: 20 November 2001 / Published online: 14 March 2002     

Dynamics of four-wave mixing on excitons in a quantum optical microcavity

A theory of degenerate four-wave mixing in a semiconductor optical cavity with quantum wells is constructed. The nonlinear response of a microcavity can be four to five orders of magnitude stronger than that of an isolated quantum well. For P ² E-and P ³-type nonlinearities the damped diffracted signal oscillates with a period determined by the Rabi splitting. For a biexcitonic mechanism of nonlinearity, the signal contains damped overtones of the Rabi splitting and the biexciton binding energy. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 11, 749–754 (10 December 1996)     

Quantum theory of whispering gallery modes in a cylindrical optical microcavity

The quantum interpretation of whispering gallery modes in a cylindrical optical microcavity is presented in analogy with quantum mechanical theory. The formulas for the resonance shifts caused by a small change in correlative refractive index are derived. Then they are applied to two applications of the cylindrical microcavity to probe the change of surrounding medium and the nonlinear effect of cavity's surface.     

Spontaneous emission and energy transfer in the optical microcavity

Optical microcavities allow control over the interaction between light and matter, thus making them an important testing ground for basic optical physics. This review focuses on two of these interactions, spontaneous emission and energy transfer. Emphasis is placed on the underlying concepts, which are presented in the context of recent developments. Practical application of the microcavity concept to devices is now well underway and a discussion of these aspects forms an integral part of the review. This field is far from mature and though much has been accomplished, many questions in this area remain, some of which are identified and discussed.     

Highly efficient direct third-harmonic generation based on control of the electro-optic effect in quasi-periodic optical superlattices

We present a method for controlling the efficiency of direct third-harmonic generation in quasi-periodic optical superlattices by means of the electro-optic effect. The calculated results manifest that this method is extremely efficient for achieving high efficiency of direct third-harmonic generation in predesigned quasi-phase-matched coupled parametric processes and is feasible at any given fundamental intensity. In addition, we demonstrate that the electro-optic control approach is significantly better than the temperature-control method.     

Another model for a multiexcitonic quantum dot in an optical microcavity

Very recently, a multiexcitonic quantum dot in an optical microcavity have been theoretically studied [Herbert Vincka, Boris A. Rodriguez, and Augusto Gonzalez, Physica E, 2006, 35: 99–102]. However, due to the inevitable damping losses through the microcavity, in this work, we will present a more precise and sound model in the Lindblad form master equation to investigate the photonic properties of a single quantum dot (QD) in an optical microcavity system, in which the QD may confine the multiexcitons and be in resonant interaction with a single photonic mode of an optical microcavity. The excitation energies, and the properties of the emission photon from the QD microcavity are computed as functions of the exciton-photon coupling strength, detuning, and pump rate. We further compare our results with their results, and find that the calculated intensity of the emitted photon and the spectra crucially depend on the exciton-photon coupling strength g, the photon detuning, and the number of excitons in the QD. Finally, we will give a physical mechanism of the dressed-state picture for the strong coupling between the single mode of an optical microcavity and the QD emitters to explain the details of the emission photon spectra. Our study establishes useful guidelines for the experimental study of such multiexcitonic quantum dot in an optical microcavity system.      

Influence of two-photon absorption on bistable switching in a silicon photonic crystal microcavity

By employing a simplified nonlinear coupled mode theory, we discuss the influence of two-photon absorption (TPA) on the characteristics of bistable switching. It is revealed that the critical value of frequency detuning for bistability rises linearly with increasing TPA coefficient k (when k is less than 30), and eventually access to a saturated value. It is also found that TPA effect will be enhanced for a greater frequency detuning, especially when transmission reaches its peak value. As a result, the peak transmission will decrease monotonously with the increasing frequency detuning. Based on this simplified model, the TPA-induced temperature rise in microcavity is also estimated. The theoretical predictions show good agreement with the simultaneous results, as well as the proposed experimental phenomena.