C. Seassal

InP-based two-dimensional photonic crystal on silicon: In-plane Bloch mode laser

Defectless two-dimensional photonic crystal structures have been fabricated by drilling holes in a thin multi-quantum-well InP-based heterostructure transferred onto a silicon host wafer. Extremely low group velocity modes, which correspond to the predicted photonic valence band edge, have been observed for different filling factors. Under pulsed optical pumping, room temperature laser operation around 1.5 μm has been achieved on these structures with a threshold in the milliwatt range.

Seventy-fold enhancement of light extraction from a defectless photonic crystal made on silicon-on-insulator

Very high photoluminescence extraction is observed from defectless two-dimensional photonic crystals etched in the upper 200-nm-thick silicon layer of a silicon-on-insulator (SOI) substrate. Predicted very low group velocity modes near the Γ point of the band structure lying above the light line are used to extract light from the photonic crystal slab into the free space. It is found that light is extracted on a 80-nm-wide band along directions near to the perpendicular to the slab, with an extraction enhancement up to 70 compared to an unpatterned SOI.

Group velocity and propagation losses measurement in a single-line photonic-crystal waveguide on InP membranes

Single-line photonic-crystal waveguides are investigated. Photoluminescence experiments and three-dimensional calculation are performed and allow a clear identification of the guided modes. The propagation properties of the latter (group velocity, losses) are extracted from photoluminescence spectra obtained on closed waveguides which act as linear cavities.

A Compact SOI-Integrated Multiwavelength Laser Source Based on Cascaded InP Microdisks

We report on the performance of a compact multi- wavelength laser (MWL) source heterogeneously integrated with and coupled to a silicon-on-insulator (SOI) waveguide circuit. The MWL consists of four InP-based microdisk lasers, coupled to a common SOI wire waveguide. The microdisk lasers operate in continuous-wave regime at room temperature, with a threshold current around 0.9 mA and a waveguide-coupled slope efficiency of up to 8 muW/mA, for a microdisk diameter of 7.5 mum. The output spectrum contains four laser peaks uniformly distributed within the free-spectral range of a single microdisk. While thermal crosstalk is negligible, laser peak output powers vary up to 8 dB for equal microdisk drive currents, as a result of loss due to coupling with higher order modes supported by the 1-mum-thick microdisks. This nonuniformity could be eliminated by reducing the microdisk thickness.

Highly selective and widely tunable 1.55-μm InP/air-gap micromachined Fabry-Perot filter for optical communications

The authors report, for the first time, a highly selective and widely tunable optical filter at 1.55 /spl mu/m using a Fabry-Perot resonator with micromachined InP/air-gap distributed Bragg reflectors. The minimum resonance full-width at half-maximum (FWHM), as measured by microreflectivity experiments, is close to 0.4 mm (around 1.55 /spl mu/m) and is compatible with wavelength-division multiplexing specifications of optical telecommunications. The tuning range is 62 nm for a tuning voltage of 14 V. The FWHM is kept below 1 nm over a 40 nm tuning range.

Switching devices with spatial and spectral resolution combining photonic crystal and MOEMS structures

One- and two-dimensional photonic crystal slabs have numerous applications in integrated optics. Unfortunately, due to their finite height, their in-plane guided modes can suffer outcoupling losses. Although considered as detrimental in the context of the development of photonic integrated circuits, it turns that the coupling of waveguided modes to radiative modes can be usefully exploited for the manipulation of photons in free space. It is shown in this paper that interaction of radiative and guided modes through a photonic crystal, especially under conditions where the latter correspond to extrema of the dispersion characteristics of the photonic crystal, results in resonance phenomena, which can be used practically for the development of new classes of devices, e.g., combining photonic crystal and microoptoelectromechanical systems structures.

Surface-emitting microlaser combining two-dimensional photonic crystal membrane and vertical Bragg mirror

We report on the design and fabrication of heterogeneous and compact surface-emitting microlasers, optically pumped and operating at 1.5μm at room-temperature. A very low threshold, below 15μW, is achieved. The devices consists of a top two-dimensional InP photonic crystal slab, including four InAsP quantum wells, a SiO2 bonding layer, and a bottom high index contrast Si∕SiO2 Bragg mirror deposited on a Si wafer. The graphitelike photonic crystal lattice is tailored for vertical emission. We theoretically and experimentally demonstrate that the Bragg reflector can strongly enhance the quality factor of the photonic crystal resonant mode, leading to a drastic decrease of the lasing threshold.

Heterogeneous integration of microdisk lasers on silicon strip waveguides for optical interconnects

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.

Triangular and hexagonal high Q-factor 2-D photonic bandgap cavities on III-V suspended membranes

We demonstrate InP-based triangular and hexagonal two-dimensional (2-D) planar photonic bandgap (PGB) crystal-based microcavities, positioned on a suspended membrane. Photoluminescence spectra of the structure clearly show well-resolved cavity modes, whose structure depends on the cavity shape. Q factors from 200 up to at least 900 are derived.

Two-dimensional hexagonal-shaped microcavities formed in a two-dimensional photonic crystal on an InP membrane

We present simulation and experimental results on hexagonal-shaped microcavities formed in two-dimensional (2D) photonic crystals (PC’s). The PC structures, realized with InP-based materials, are studied in two configurations : Air-suspended membranes (A type) and membranes supported by silica (S type). The optical properties of these microcavities are analyzed through photoluminescence experiments. Plane-wave expansion method calculations provide simulation results that are consistent with experimental data. The influence on spectral properties of various parameters, such as cavity size or air filling factor (f), is thoroughly analyzed, and their effect on resonator loss mechanisms is extracted, to give guidance for further PC laser improvement, e.g., threshold reduction.