The convergence of microelectronics and photonics on a single chip is one of the greatest challenges of present research. To make it happen, it is necessary to develop an entire novel class of optoelectronic devices exhibiting far beyond the state-of-the-art performance in term of compactness, speed and power efficiency. Silicon photonics enhanced with III-V semiconductors such as InP-based materials is the key technology to provide a platform able with all the necessary functionalities but it is only through the exploitation of nanophotonics concepts that disruptive performance can be reached.
During this presentation, we will show our latest results obtained on electrically powered InP-on-SOI photonic crystal devices. These results will concern first the demonstration of nanolaser diodes emitting at 1.55µm in a SOI waveguide with a wall-plug efficiency higher than 10%. The developed electrical injection scheme allows us, also, to conceive nano-amplifiers and electro-optical modulators which show promising features for their integration in a photonic circuit.
The development of energy-efficient ultra-compact nanolaser diodes integrated in a Silicon photonic platform is of paramount importance for the deployment of optical interconnects for intra-chip communications.
In this work, we present our results on InP-based electrically injected photonic crystal (PhC) nanolaser integrated on a SOI waveguide circuitry. The lasers emit at room temperature in a continuous wave regime at 1560nm and exhibit thresholds of 0.1mA at 1V. We measure more than 100μW of light coupled into the SOI waveguides giving a wall-plug efficiency greater than 10%.
The principle of the lasers relies on the use of a 1D PhC nanocavity made of InP-based materials positioned on top of a SOI waveguide to enable evanescent wave coupling. More in details, the laser cavity is a 650nm-wide rib waveguide drilled with a single row of equally sized holes (radius~100nm). The distance between the holes is varied to obtain Q-factors larger than 106 for a structure fully encapsulated in silica with material volume of the order of the cubic wavelength. Vertically, the InP heterostructure is a 450nm thick NIP junction embedding 5 strained InGaAsP quantum wells emitting at 1.53μm.
By smartly positioning the metallic contacts, this configuration enables the efficient electrical injection of electron-holes pairs within the cavity without inducing optical losses which led us to demonstrate the laser emission coupled ta a Si waveguide.
In this work we present the first experimental demonstration of a novel class of heterogeneously integrated III V-on-silicon microlasers. We first show that by coupling a silicon cavity to a III-V wire, the interaction between the propagating mode in the III-V wire and the cavity mode in the silicon resonator results in high, narrow band reflection back into the III-V waveguide, forming a so-called resonant mirror. By combining two such mirrors and providing optical gain in the III-V wire in between these 2 mirrors, laser operation can be realized. We simulate the reflectivity spectrum of such a resonant mirror using 3D FDTD and discuss the results. We also present experimental results of the very first optically pumped heterogeneously integrated resonant mirror laser. The fabricated device measures 55 μm by 2 μm and shows single mode laser emission with a side-mode suppression ratio of 37 dB.
HISTORIC aims to develop and test complex photonic integrated circuits containing a relatively large number
of digital photonic elements for use in e.g. all-optical packet switching. These photonic digital units are alloptical
flip-flops based on ultra compact laser diodes, such as microdisk lasers and photonic crystal lasers.
These lasers are fabricated making use of the heterogeneous integration of InP membranes on top of silicon
on insulator (SOI) passive optical circuits. The very small dimensions of the lasers are, at least for some
approaches, possible because of the high index contrast of the InP membranes and by making use of the
extreme accuracy of CMOS processing.
All-optical flip-flops based on heterogeneously integrated microdisk lasers with diameter of 7.5μm have
already been demonstrated. They operate with a CW power consumption of a few mW and can switch in 60ps
with switching energies as low as 1.8 fJ. Their operation as all-optical gate has also been demonstrated.
Work is also on-going to fabricate heterogeneously integrated photonic crystal lasers and all-optical flip-flops
based on such lasers. A lot of attention is given to the electrical pumping of the membrane InP-based photonic
crystal lasers and to the coupling to SOI wire waveguides. Optically pumped photonic crystal lasers coupled
to SOI wires have been demonstrated already.
The all-optical flip-flops and gates will be combined into more complex photonic integrated circuits,
implementing all-optical shift registers, D flip-flops, and other all-optical switching building blocks.
The possibility to integrate a large number of photonic digital units together, but also to integrate them with
compact passive optical routers such as AWGs, opens new perspectives for the design of integrated optical
processors or optical buffers. The project therefore also focuses on designing new architectures for such
optical processing or buffer chips.
We predict and experimentally observe the enhancement by three orders of magnitude of phase mismatched second and
third harmonic generation in a GaAs cavity at 650 and 433 nm, respectively, well above the absorption edge. Phase
locking between the pump and the harmonics changes the effective dispersion of the medium and inhibits absorption.
Despite hostile conditions the harmonics resonate inside the cavity and become amplified leading to relatively large
conversion efficiencies. Field localization thus plays a pivotal role despite the presence of absorption, and ushers in a
new class of semiconductor-based devices in the visible and UV ranges.
Temporal characteristics of band-edge photonic crystal are
precisely analyzed using a high-resolution up-conversion system. The
InGaAs/InP photonic crystal laser operates at room temperature at 1.55 μm
and turn on times ranging from 17ps to 30ps are measured.
We present continuous-wave laser operation at room temperature at 1.55 μm by optically pumping a photonic crystal
structure containing an InGaAs/InP quantum well active layer. The active layer is integrated onto a Silicon chip by
means of Au/In bonding technology. This metallic layer provides the reduction of heating by thermal dissipation into the
substrate, and increases the quality-factor by reducing the radiative losses.
We have investigated a three-dimensionally periodic (3D) photonic crystal structure based on an epitaxial periodic GaAs/Al0.93Ga0.07As multilayer structure that was designed for non-linear optical interactions. The 3D photonic crystal structure consisted of a two-dimensionally periodic planar photonic crystal hole pattern etched into the one-dimensionally periodic multilayer structure designed for a centre wavelength of λ = 1.6 μm. Numerical simulations on the 3D PhC structure have shown that it should exhibit slow group velocity modal features near the edge of the photonic bandgap.
We demonstrate multifunction operation in a 2D PC slab showing that the same structure may be used for lasing, frequency shifting and switching under appropriate stimulus. Our analytical model, based on a coupled modes nonlinear approach closely describes the main experimental features. The experimental results constitute a first step towards an active reconfiguration of photonic crystal all-optical circuits.