Philippe Regreny

Electrically pumped InP-based microdisk lasers integrated with a nanophotonic silicon-on-insulator waveguide circuit

A compact, electrically driven light source integrated on silicon is a key component for large-scale integration of electronic and photonic integrated circuits. Here we demonstrate electrically injected continuous-wave lasing in InP-based microdisk lasers coupled to a sub-micron silicon wire waveguide, fabricated through heterogeneous integration of InP on silicon-on-insulator (SOI). The InP-based microdisk has a diameter of 7.5 mum and a thickness of 1 mum. A tunnel junction was incorporated to efficiently contact the p-side of the pn-junction. The laser emits at 1.6 mum, with a threshold current as low as 0.5 mA under continuous-wave operation at room temperature, and a threshold voltage of 1.65 V. The SOI-coupled laser slope efficiency was estimated to be 30 muW/mA, with a maximum unidirectional output power of 10 muW.

III-V/Si photonics by die-to-wafer bonding

Photonic integrated circuits offer the potential of realizing low-cost, compact optical functions. Silicon-on-insulator (SOI) is a promising material platform for this photonic integration, as one can rely on the massive electronics processing infrastructure to process the optical components. However, the integration of a Si laser is hampered by its indirect bandgap. Here, we present the integration of a direct bandgap III-V epitaxial layer on top of the SOI waveguide layer by means of a die-to-wafer bonding process in order to realize near-infrared laser emission on and coupled to SOI.

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.

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.

Nanophotonic Devices for Optical Interconnect

We review recent progress in nanophotonic devices for compact optical interconnect networks. We focus on microdisk-laser-based transmitters and discuss improved design and advanced functionality including all-optical wavelength conversion and flip-flops. Next we discuss the fabrication uniformity of the passive routing circuits and their thermal tuning. Finally, we discuss the performance of a wavelength selective detector.

Heterogeneous integration of electrically driven microdisk based laser sources for optical interconnects and photonic ICs

A new approach for an electrically driven microlaser based on a microdisk transferred onto Silicon is proposed. The structure is based on a quaternary InGaAsP p-i-n junction including three InAsP quantum wells, on a thin membrane transferred onto silicon by molecular bonding. A p++/n++ tunnel junction is used as the p-type contact. The technological procedure is described and first experimental results show a laser emission in pulsed regime at room temperature, with a threshold current near 1.5 mA.

Monolithic integration of InP based heterostructures on silicon using crystalline Gd2O3 buffers

A new approach of monolithic integration of InP based heterostructures on silicon is proposed, based on the plastic compliant behavior of the InP/Gd2O3(111) heterointerface. When grown on a crystalline Gd2O3/Si(111) buffer, InP takes its bulk lattice parameter as soon as the growth begins, allowing the monolithic growth of good quality InAsP/InP heterostructures on Si, as attested by room-temperature photoluminescence experiments.

Improved design of an InP-based microdisk laser heterogeneously integrated with SOI

Microdisk lasers heterogeneously Integrated with SOI are promising sources for photonic Integrated circuits based on silicon. The microdisk lasers are only a few micrometers In size and they allow for wafer scale fabrication. We have demonstrated a new design of an electrically Injected microdisk laser bonded on SOI with a considerable Improvement of the performance. We observed threshold currents as low as 350 μΑ and output power up to 120 μW for a 7.5 μm microdisk diameter under continuous-wave operation. Compared to previous results this comes down to a 30% reduction of the threshold current and a maximum output power which is increased by more than a factor of 10.

Spontaneous compliance of the InP∕SrTiO3 heterointerface

The lattice mismatch between a growing layer and its substrate is a major limitation for heteroepitaxy. Finding solutions to overcome this limitation has given rise to many researches that have up to now not come out any satisfying solution. Here we demonstrate the compliant behavior of the InP∕SrTiO3 (STO) heterointerface. InP islands grown on STO substrates and STO/Si crystalline layers are defect-free, oriented with respect to STO, and have their InP bulk lattice parameter. This contrasts with plastic relaxation mechanisms observed for III-V, Si, or Ge mismatched heterostructures. Compliance occurs spontaneously during the growth and does not require any substrate patterning.

Thermal Characterization of Electrically Injected Thin-Film InGaAsP Microdisk Lasers on Si

We have performed a numerical and experimental analysis of the thermal behavior of electrically injected microdisk lasers that are defined in an InGaAsP-based thin film bonded on top of a silicon wafer. Both the turn-on as well as the pulsed-regime temperature evolution in the lasing region was simulated using the finite-element method. The simulation results are in good agreement with experimental data, which was extracted from the broadening of the time-averaged emission spectra. Lasing at room temperature was only possible in pulsed regime due to the high thermal resistance (10 K/mW). Some strategies to decrease the thermal resistance of the microdisk lasers are proposed and discussed.