Timothy Karle

Hybrid III-V semiconductor/silicon nanolaser

Heterogeneous integration of III-V compound semiconductors on Silicon on Insulator is one the key technology for next-generation on-chip optical interconnects. In this context, the use of photonic crystals lasers represents a disruptive solution in terms of footprint, activation energy and ultrafast response. In this work, we propose and fabricate very compact laser sources integrated with a passive silicon waveguide circuitry. Using a subjacent Silicon-On-Insulator waveguide, the emitted light from a photonic crystal based cavity laser is efficiently captured. We study experimentally the evanescent wave coupling responsible for the funneling of the emitted light into the silicon waveguide mode as a function of the hybrid structure parameters, showing that 90% of coupling efficiency is possible.

Heterogeneous integration and precise alignment of InP-based photonic crystal lasers to complementary metal-oxide semiconductor fabricated silicon-on-insulator wire waveguides

The integration of two-dimensional III-V InP-based photonic crystal and silicon wire waveguides is achieved through an accurate alignment of the two optical levels using mix-and-match deep ultraviolet (DUV)/electron beam lithography. The adhesively bonded structures exhibit an enhancement of light emission at frequencies where low group velocity modes of the photonic crystal line defect waveguides occur. Pulsed laser operation is obtained from these modes at room temperature under optical pumping. The laser light is coupled out of the Si waveguide via grating couplers directly to single mode fiber.

Continuous-wave operation of photonic band-edge laser near 1.55 μm on silicon wafer

We report on the continuous-wave operation of a band edge laser at room temperature near 1.55 μm in an InGaAs/InP photonic crystal. A flat dispersion band-edge photonic mode is used for surface normal operation. The photonic crystal slab is integrated onto a Silicon chip by means of Au/In bonding technology, which combines two advantages, efficient heat sinking and broad band reflectivity.

Thermo-optical dynamics in an optically pumped Photonic Crystal nano-cavity

Linear and non-linear thermo-optical dynamical regimes were investigated in a photonic crystal cavity. First, we have measured the thermal relaxation time in an InP-based nano-cavity with quantum dots in the presence of optical pumping. The experimental method presented here allows one to obtain the dynamics of temperature in a nanocavity based on reflectivity measurements of a cw probe beam coupled through an adiabatically tapered fiber. Characteristic times of 1.0+/-0.2 micros and 0.9+/-0.2 micros for the heating and the cooling processes were obtained. Finally, thermal dynamics were also investigated in a thermo-optical bistable regime. Switch-on/off times of 2 micros and 4 micros respectively were measured, which could be explained in terms of a simple non-linear dynamical representation.

Optimizing H1 cavities for the generation of entangled photon pairs

We report on the theoretical investigation of photonic crystal cavities etched on a suspended membrane for the generation of polarization entangled photon pairs using the biexciton cascade in a single quantum dot. The implementation of the spontaneous emission enhancement effect increases the entanglement visibility, while the concomitant preferential funneling of the emission in the cavity mode increases the collection of both entangled photons. We demonstrate and quantify that standard cavity designs present a polarization-dependent emission diagram, detrimental to entanglement. The optimization of H1 cavities allows us to obtain both high collection efficiencies and polarization-independent emission, while keeping the high Purcell factors necessary for high-quality entangled photon sources.

Hybrid InP-based photonic crystal lasers on silicon on insulator wires

We report on InP-based photonic crystal lasers operating at 1.585 μm at room temperature, integrated with and evanescently coupled to silicon on insulator (SOI) waveguides. By optically pumping at 1.18 μm through the SOI wires, pulsed laser emission from line defect photonic crystal waveguides accurately aligned (<30 nm) to the silicon circuitry is demonstrated.

Dynamics of band-edge photonic crystal lasers

Band-edge photonic crystal lasers were fabricated and their temporal characteristics were minutely analyzed using a high resolution up-conversion system. The InGaAs/InP photonic crystal laser operates at room temperature at 1.55 microm with turn on time ranging from 17ps to 30ps.

Radiation patterns from coupled photonic crystal nanocavities

We report on far field measurements on two coupled photonic crystal nanocavities. The distinct features of the antisymmetric modes (minima of intensity at zero-emission angles) allow us to demonstrate a π-phase difference between the cavity fields, a clear signature of evanescent coupling. Good agreement between experimental results and simulated radiation patterns has been found.

III–V photonic crystal lasers heterogeneously bonded to Silicon-On-Insulator waveguides

We report on the fabrication of InP-based 2D photonic crystal lasers operating around λ = 1.55 µm at room temperature, integrated with and evanescently coupled to Silicon-On-Insulator waveguides. Pulsed laser operation is obtained from a line defect photonic crystal waveguide accurately aligned (≪ 30 nm) on top the SOI circuitry. This active-passive integration is demonstrated using an adhesive bonding technique. Lasing action is demonstrated for several low group velocity modes of the photonic crystal defect waveguide.

Thermal improvement of InP wire photonic crystal laser on silicon by addition of Diamond Nanoparticles in polymer bonding layer

Diamond Nanoparticles are added to BCB polymer in order to increase the thermal dissipation of InP-based photonic crystal cavity laser bonded on silicon. Optical measurement are performed to evaluate the enhancement of the heat sinking with nanoparticles density.