We demonstrate that symmetry breaking opens a new degree of freedom to tailor energy-momentum dispersion in photonic crystals. Using a general theoretical framework in two illustrative practical ...structures, we show that breaking symmetry enables an on-demand tuning of the local density of states of the same photonic band from zero (Dirac cone dispersion) to infinity (flatband dispersion), as well as any constant density over an adjustable spectral range. As a proof of concept, we demonstrate experimentally the transformation of the very same photonic band from a conventional quadratic shape to a Dirac dispersion, a flatband dispersion, and a multivalley one. This transition is achieved by finely tuning the vertical symmetry breaking of the photonic structures. Our results provide an unprecedented degree of freedom for optical dispersion engineering in planar integrated photonic devices.
Two-dimensional (2-D) compact photonic crystal reflectors on suspended InP membranes were studied under normal incidence. We report the first experimental demonstration of 2-D broadband reflectors ...(experimental stopband superior to 200 nm, theoretical stopband of 350 nm). They are based on the coupling of free space waves with two slow Bloch modes of the crystal. Moreover, they present a very strong sensitivity of the polarization dependence, when modifying their geometry. A compact (50×50 μm 2 ) demonstrator was realized and characterized, behaving either as a broadband reflector or as a broadband transmitter, depending on the polarization of the incident wave. Experimental results are in good agreement with numerical simulations.
Vertical Fabry Perot cavities (VFPC) have been extensively studied, especially for the realization of vertical-cavity surface emitting lasers (VCSELs). They are traditionally composed of two ...Distributed Bragg Reflectors (DBR) which reflectivity has to be sufficient in order to obtain highly resonant cavity, which is particularly necessary for laser emission in VCSELs. As a consequence, DBRs consist generally in very thick layer stacks. In this paper, we demonstrate the smallest conceivable high Q vertical Fabry-Perot cavity, using ultra-thin and highly-efficient photonic crystal slab mirrors instead of conventional DBRs, which enable moreover a control of the polarization.
2D photonic crystal (2DPC) structures consisting in 2D silicon nanopillar arrays in silica are investigated. The main motivation of this work lies in that 2D rod arrays should be easily combined with ...refractive structures (e. g. micro-wire waveguides), unlike 2DPC consisting in hole lattices. Such an association is expected to lead to both new functionalities and larger scale integration. In this paper, we study the loss mechanism for non degenerated Bloch modes located at Gamma-point in a 2DPC slab constituted by a square lattice of silicon rods in silica. For such modes, we show that the quality factor is mainly governed by the lateral losses. To further inhibit the lateral losses, a photonic heterostructure is used. 3D FDTD calculations show that quality factors of 4000 are achieved. To reduce the vertical losses, the 2DPC heterostructure is associated with a vertical Bragg mirror, thus resulting in very high quality factors (>40000).
The authors report a compact and highly selective tunable filter using a Fabry-Perot resonator combining a bottom micromachined 3-pair-InP/air-gap Bragg reflector with a top photonic crystal slab ...mirror. It is based on the coupling between radiated vertical cavity modes and waveguided modes of the photonic crystal. The full-width at half maximum (FWHM) of the resonance, as measured by microreflectivity experiments, is close to 1.5nm (around 1.55 microm). The presence of the photonic crystal slab mirror results in a very compact resonator, with a limited number of layers. The demonstrator was tuned over a 20nm range for a 4V tuning voltage, the FWHM being kept below 2.5nm. Bending of membranes is a critical issue, and better results (FWHM=0.5nm) should be obtained on the same structure if this technological point is fixed.
A new approach is proposed to realize an optical link for intrachip optical interconnects. This link includes III-V compound-based laser sources and photodetectors, and silicon-on-insulator-based ...strip waveguides. The heterogeneous integration of an InP-based microdisk laser with a silicon waveguide using SiO/sub 2/-SiO/sub 2/ molecular bonding and nanofabrication procedures is emphasized. The technological procedure is described and first experimental results show that, with an adequate configuration, 35% of light could be coupled from the optically pumped microlaser to the waveguide, as a result of the vertical evanescent coupling.
We propose to use a localized Γ-point slow Bloch mode in a 2D-Photonic Crystal (PC) membrane to realize an efficient surface emitting source. This device can be used as a quantum photonic device, ...e.g. a single photon source. The physical mechanisms to increase the Q/V factor and to improve the directivity of the PC microcavity rely on a fine tuning of the geometry in the three directions of space. The PC lateral mirrors are first engineered in order to optimize photons confinement. Then, the effect of a Bragg mirror below the 2DPC membrane is investigated in terms of out-of-plane leakages and far field emission pattern. This photonic heterostructure allows for a strong lateral confinement of photons, with a modal volume of a few (λ/n)3 and a Purcell factor up to 80, as calculated by two different numerical methods. We finally discuss the efficiency of the single photon source for different collection set-up.
It is emphasized that two‐dimensional photonic crystals (2D PC) have not only a great potential for the development of 2D nanophotonics in the inplane waveguided configuration, but that they may also ...open the way to other brilliant developments, with an extension to out‐of‐plane operation, along a 2.5D nanophotonics approach. In this 2.5D approach, a 1D–2D high index contrast lateral structuration is combined with a 1D high index contrast vertical structuration, using multilayer membrane stacks including 1D–2D photonic crystal membranes, thus resulting in so‐called 2.5D PC. As a specific illustration of recent achievements along this approach, new families of VCSEL structures are presented.
Two‐dimensional photonic crystals (2D PC) have a great potential for the development of 2D nanophotonics in the inplane waveguided configuration, and may also open the way to other brilliant developments, with an extension to out‐of‐plane operation, along a 2.5D nanophotonics approach. In this 2.5D approach, a 1D–2D high index contrast lateral structuration is combined with a 1D high index contrast vertical structuration, using multilayer membrane stacks, thus resulting in so‐called 2.5D PC. As a specific illustration of recent achievements along this approach, new families of VCSEL structures are presented.
A study of vertical coupling conditions between microdisk based resonators and waveguides is presented using an analytical model. The coupling efficiency optimization is investigated and compared to ...3D FDTD computations. We also demonstrate that coupling losses can be exploited to favor high quality factor modes in circular resonators. In addition, we propose to modify the shape of the coupled waveguide to enhance mode selectivity and obtain a very compact structure with mode hoping capacities. Lower thresholds and modulation are also expected.
We report on a tuneable dual-wavelength micro-resonator with a resonant photonic crystal membrane (PCM) inserted in a vertical Fabry-Perot (FP) cavity. Strong optical coupling between both resonators ...leads to dual-wavelength resonances. Their energy difference, determined by the overlap of both modes, can be tuned using micro-opto-electro-mechanical systems. Variations in spectral and field overlaps are considered separately with a phenomenological matrix method through, respectively, the FP cavity thickness and the PCM position change. This approach is compared with 2-D finite-difference time-domain simulations in the second case. Periodic evolution of both modes is observed with unsymmetrical amplitude, unlike with the model cause of its approximations.
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