Surface plasmon enhanced light-emitting diode

A method for enhancing the emission properties of light-emitting diodes, by coupling to surface plasmons, is analyzed both theoretically and experimentally. The analyzed structure consists of a semiconductor emitter layer thinner than λ/2 sandwiched between two metal films. If a periodic pattern is defined in the top semitransparent metal layer by lithography, it is possible to efficiently couple out the light emitted from the semiconductor and to simultaneously enhance the spontaneous emission rate. For the analyzed designs, we theoretically estimate extraction efficiencies as high as 37% and Purcell factors of up to 4.5. We have experimentally measured photoluminescence intensities of up to 46 times higher in fabricated structures compared to unprocessed wafers. The increased light emission is due to an increase in the efficiency and an increase in the pumping intensity resulting from trapping of pump photons within the microcavity

Optimal pulse to generate non-classical photon states via photon blockade

The single photon character of nonclassical states of light that can be generated using photon blockade is analyzed for time domain operation. We show that improved single photon statistics (single photon around 85% with a multi-photon of 8%) can be obtained by adequately choosing the parameters (mainly amplitude and pulse-duration) of the driving laser pulses. An alternative method, where the system is driven via a continuous wave laser and the frequency of the dipole is controlled (e.g. electrically) at very fast timescales is presented. We also show that this non-classical state performs better than a weak coherent pulse, when applied to BB84 quantum cryptography protocol

Finite-difference time-domain calculation of the spontaneous-emission coupling factor in optical microcavities

We present a general method for the β factor calculation in optical microcavities. The analysis is based on the classical model for atomic transitions in a semiconductor active medium. The finite-difference time-domain method is used to evolve the electromagnetic fields of the system and calculate the total radiated energy, as well as the energy radiated into the mode of interest. We analyze the microdisk laser and compare our result with the previous theoretical and experimental analyses. We also calculate the β factor of the microcavity based on a two-dimensional (2-D) photonic crystal in an optically thin dielectric slab. From the β calculations, we are able to estimate the coupling to radiation modes in both the microdisk and the 2-D photonic crystal cavity, thereby showing the effectiveness of the photonic crystal in suppressing in-plane radiation modes

Theoretical and Experimental Investigation of Efficient Photonic Crystal Cavity-Waveguide Couplers

Coupling of photonic crystal (PC) linear three-hole defect cavities to PC waveguides is theoretically and experimentally investigated. An improved coupling is obtained by tilting the cavity axis by 60° with respect to the waveguide direction

Methods for controlling positions of guided modes of photonic-crystal waveguides

We analyze different methods for controlling positions of guided modes of planar photonic-crystal waveguides. Methods based both on rearrangements of holes in the photonic-crystal lattice and on changes of hole sizes are presented. The ability to tune frequencies of guided modes within a frequency bandgap is necessary to achieve efficient guiding of light within a waveguide, as well as to match frequencies of eigenmodes of different photonic-crystal-based devices for the purpose of good coupling between them. We observe and explain the appearance of acceptor-type modes in donor-type waveguides

Generation of nonclassical states of light via photon blockade in optical nanocavities

The generation of nonclassical states of light via photon blockade with time-modulated input is analyzed. We show that improved single-photon statistics can be obtained by adequately choosing the parameters of the driving laser pulses. An alternative method, where the system is driven via a continuous-wave laser and the frequency of the dipole is controlled (e.g., electrically) at very fast time scales is presented

Engineering anti-bunching via photon blockade in photonic crystal cavity-quantum dot systems

Methods to improve single photon generation via photon-blockade in a photonic-crystal cavity with a strongly coupled quantum-dot are presented. With realistic system parameters, significant improvement in second-order-auto-correlation g^2 (0) (from 0.93 to 0.79) is achieved

Polarization control and sensing with two-dimensional coupled photonic crystal microcavity arrays

We have experimentally studied polarization properties of the two-dimensional coupled photonic crystal microcavity arrays, and observed a strong polarization dependence of the transmission and reflection of light from the structures - the effects that can be employed in building miniaturized polarizing optical components. Moreover, by combining these properties with a strong sensitivity of the coupled bands on the surrounding refractive index, we have demonstrated a detection of small refractive index changes in the environment, which is useful for construction of bio-chemical sensors.Comment: 8 pages text and 4 figures on 4 pages. Submitted for publication on 07/14/0

High quality two-dimensional photonic crystal slab cavities

We have fabricated and characterized donor-mode nanocavities formed by a single defect cavity defined within a two-dimensional photonic crystal slab. Quantum dots emitting in the 1.1-1.3 micron range were used as luminescence sources, and a design using fractional edge dislocations was used to demonstrate well-confined dipole modes with high quality factors. By applying the fractional dislocation geometry, the measured quality factor could be increased to values as high as 2800. This compares with typical quality factors of around 1500 measured from more conventional shallow donor mode cavities with larger mode volumes

Optimization of Q factor in optical nanocavities based on free-standing membranes

We express the quality factor of a mode in terms of the Fourier transforms of its field components, and prove that the reduction in radiation loss can be achieved by suppressing the mode's wave-vector components within the light cone. Although this is intuitively clear, our analytical proof gives us insight into how to achieve the Q factor optimization, without the mode delocalization. We focus on the dipole defect mode in free standing membrane and achieve Q > 10^4, while preserving the mode volume of the order of one half of cubic wavelength in material. The derived expressions and conclusions can be used in optimization of Q factor for any type of defect in planar photonic crystals