In this communication, we report on the design, fabrication, and testing of Silicon Nitride on Insulator (SiNOI) and Aluminum-Gallium-Arsenide (AlGaAs) on silicon-on-insulator (SOI) nonlinear photonic circuits for continuum generation in Silicon (Si) photonics. As recently demonstrated, the generation of frequency continua and supercontinua can be used to overcome the intrinsic limitations of nowadays silicon photonics notably concerning the heterogeneous integration of III-V on SOI lasers for datacom and telecom applications. By using the Kerr nonlinearity of monolithic silicon nitride and heterointegrated GaAs-based alloys on SOI, the generation of tens or even hundreds of new optical frequencies can be obtained in dispersion tailored waveguides, thus providing an all-optical alternative to the heterointegration of hundreds of standalone III-V on Si lasers. In our work, we present paths to energy-efficient continua generation on silicon photonics circuits. Notably, we demonstrate spectral broadening covering the full C-band via Kerrbased self-phase modulation in SiNOI nanowires featuring full process compatibility with Si photonic devices. Moreover, AlGaAs waveguides are heterointegrated on SOI in order to dramatically reduce (x1/10) thresholds in optical parametric oscillation and in the power required for supercontinuum generation under pulsed pumping. The manufacturing techniques allowing the monolithic co-integration of nonlinear functionalities on existing CMOS-compatible Si photonics for both active and passive components will be shown. Experimental evidence based on self-phase modulation show SiNOI and AlGaAs nanowires capable of generating wide-spanning frequency continua in the C-Band. This will pave the way for low-threshold power-efficient Kerr-based comb- and continuum- sources featuring compatibility with Si photonic integrated circuits (Si-PICs).
We review recent theoretical and experimental work on InP membrane microdisk lasers heterogeneously integrated on SOI and coupled to a Si bus waveguide. After a general introduction on the fabrication and the operation principles, we will describe various improvements in the fabrication technology. This includes improvements in the yield of the bonding of the InP die on the SOI die and in the controllability of the bonding layer thickness, as well as an optimization of the alignment of the microdisk with respect to the silicon waveguide and some proposals for better heat sinking and loss reduction. Improvement in the alignment and the bonding has led to interesting results on the uniformity in device characteristics. In a second part, unidirectional behaviour and reflection sensitivity will be briefly discussed. Theoretical, numerical and experimental results will be shown about the unidirectional behavior and it will be explained how unidirectional microdisk lasers can be a lot less sensitive to external reflections than other lasers. We will also show how such lasers can be used as optical signal regenerators that can work with low optical input powers and that have small power consumption. We will end with a description of demonstrations of optical interconnects based on heterogeneously integrated microdisk lasers and heterogeneously integrated photodetectors. Optical interconnects on chip have been demonstrated at 10 Gb/s. An epitaxial layer stack that contains both the laser and the detector structure has been used for this purpose.
We report on hybrid Si/III-V lasers with adiabatic coupling. The proposed architectures, based on adiabatic mode
transformers, allow laser mode to experience maximal gain available in the III-V region while maintaining a high
coupling efficiency (>95%) to Si-waveguides. Hybrid Fabry-Pérot laser and integrated racetrack laser, photodetector and
waveguide-to-fiber surface grating coupler are presented.
Vertical-cavity surface-emitting lasers (VCSELs) using hybrid III-V / Si microcavities and based on
double photonic crystal reflectors for the heterogeneous integration on complementary metal-oxidesilicon
(CMOS) are presented. The latest achievements in optical mode engineering and technological
processing are shown and discussed.
For about ten years, we have been developing InP on Si devices under different projects focusing first on
μlasers then on semicompact lasers. For aiming the integration on a CMOS circuit and for thermal issue, we relied
on SiO<sub>2</sub> direct bonding of InP unpatterned materials. After the chemical removal of the InP substrate, the
heterostructures lie on top of silicon waveguides of an SOI wafer with a separation of about 100nm. Different
lasers or photodetectors have been achieved for off-chip optical communication and for intra-chip optical
communication within an optical network. For high performance computing with high speed communication
between cores, we developed InP microdisk lasers that are coupled to silicon waveguide and produced 100μW of
optical power and that can be directly modulated up to 5G at different wavelengths. The optical network is based
on wavelength selective circuits with ring resonators. InGaAs photodetectors are evanescently coupled to the
silicon waveguide with an efficiency of 0.8A/W. The fabrication has been demonstrated at 200mm wafer scale in
a microelectronics clean room for CMOS compatibility. For off-chip communication, silicon on InP evanescent
laser have been realized with an innovative design where the cavity is defined in silicon and the gain localized in
the QW of bonded InP hererostructure. The investigated devices operate at continuous wave regime with room
temperature threshold current below 100 mA, the side mode suppression ratio is as high as 20dB, and the fibercoupled
output power is ~7mW. Direct modulation can be achieved with already 6G operation.
We report the first Silicon/III-V evanescent laser based on adiabatic mode transformers. The hybrid structure is formed
by two vertically superimposed waveguides separated by a 100nm-thick SiO<sub>2</sub> layer. The top waveguide, fabricated in an
InP/InGaAsP-based heterostructure, serves to provide optical gain, and the bottom Si-waveguides system, which
supports all optical functions, is constituted by two tapered rib-waveguides (mode transformers), two distributed Bragg
reflectors (DBR), and a surface-grating coupler. The supermode of this hybrid structure is controlled by an appropriate
design of the tapers located at the edges of the gain region. In the middle part of the devices, almost all the field resides
in the III-V waveguide so that the optical mode experiences maximal gain, while in regions near the III-V facets, mode
transformers ensure an efficient transfer of the power flow towards Si-waveguides. The investigated device operates
under quasi-continuous wave regime. The room temperature threshold current is 100 mA, the side mode suppression
ratio is as high as 20dB, and the fiber-coupled output power is ~7mW.
In this article, we report our results on 980nm high-index-contrast subwavelength grating (HCG) VCSELs for optical
interconnection applications. In our structure, a thin undoped HCG layer replaces a thick p-type Bragg mirror. The HCG
mirror can feasibly achieve polarization-selective reflectivities close to 100%. The investigated structure consists of a
HCG mirror with an underneath λ/4-thick oxide gap, four p-type GaAlAs/GaAs pairs for current spreading, three
InGaAs/GaAs quantum wells, and an n-type GaAlAs/GaAs Bragg mirror. The HCG structure was defined by e-beam
lithography and dry etching. The current oxide aperture and the oxide gap underneath the HCG were simultaneously
formed by the selective wet oxidation process. Compared to air-gap high contrast grating mirrors demonstrated
elsewhere, our grating mirrors are particular since they are supported by thinner λ/4 aluminium oxide layer, and thus are
mechanically robust and thinner than usual designs. Sub-milliamp threshold currents and single-transverse-mode
operation was obtained. A hero device exhibited maximum singlemode output power of more than 4 mW at room
temperature and 1 mw at 70°C, which are the highest values ever reported from the HCG structures. These results build a
bridge between a standard VCSEL and a hybrid laser on silicon, making them of potential use for the realization of
In this article, we report on long wavelength (1.27 μm) single-mode micro-structured photonic crystal strained InGaAs
quantum wells VCSELs for optical interconnection applications. Single fundamental mode room-temperature
continuous-wave lasing operation was demonstrated for devices designed and processed with different two-dimensional
etched patterns. The conventional epitaxial structure was grown by Metal-Organic Vapor Phase Epitaxy (MOVPE) and
contains fully doped GaAs/AlGaAs DBRs, one oxidation layer and three strained InGaAs quantum wells. The holes were
etched half-way through the top-mirror following various designs (triangular and square lattices) and with varying hole's
diameters and pitches.
We obtained up to 1.7 mW optical output power and more than 30 dB Side-Mode Suppression Ratio (SMSR) at
room temperature and in continuous wave operation. Systematic static electrical, optical and spectral characterization
was performed on wafer using an automated probe station. Numerical modeling using the MIT Photonic-Bands (MPB
) package of the transverse modal behaviors in the photonic crystal was performed using the plane wave method in
order to understand the index-guiding effects of the chosen patterns, and to further optimize the design structures for
mode selection at the given wavelength.
FTTH networks require implementing a diplexer at each user termination. According to most of the standards, this
diplexer detects a download signal beam at 1.49μm and emits an upload signal beam at 1.31μm on the same single
mode fibre. Both signals exhibit datarate speed below 2.5Gbps. Today, most of the diplexers are obtained by actively
aligning a set of individual optoelectronic components and
micro-optics. However, new manufacturing solutions
satisfying very low cost and mass production capability requirements of this market would help to speed the massive
spreading of this technology. In this paper, we present an original packaging design to manufacture Diplexer Optical
Sub-Assembly for FTTH application. A dual photodiode is stacked over a VCSEL and detects both the download
signal beam at 1.49μm passing through the laser and one part of the upload signal beam at 1.31μm for monitoring.
To satisfy this approach, an innovative VCSEL has been designed to have a very high transmission at 1.49μm. All
these components are mounted on a very small circuit board on glass including also integrated circuits such as
transimpedance amplifier. So, the device combines advanced optoelectronic components and highly integrated
Multi-Chip-Module on glass approach using collective wafer-level assembling technologies. For the single mode
fibre optical coupling, active and passive alignment solutions are considered.
We use a vector field model to analyze the third-harmonic generation (THG) emission patterns for isolated objects
illuminated by a Gaussian beam. Simulations and experiments indicate that THG from biological (dielectric) structures is
essentially forward-directed, as opposed to e.g. THG from gold particles. We then address the issue of epidetecting
forward-emitted light backscattered in a turbid medium. We use Monte Carlo simulations and measurements to analyze
the effect of tissue properties (absorption, scattering), and of the geometry of the collecting optics. This analysis provides
guidelines for optimizing epidetection in coherent nonlinear microscopy.
An erratum is attached.
In this article, we present our results on long wavelength (1.1 μm) single-mode micro-structured photonic crystal
strained InGaAs quantum wells VCSELs for optical interconnection applications. Single fundamental mode roomtemperature
continuous-wave lasing operation was demonstrated for devices designed and processed with a number of
different two-dimensional etched patterns. The conventional epitaxial structure was grown by Molecular Beam Epitaxy
(MBE) and contains fully doped GaAs/AlGaAs DBRs, one oxidation layer and three strained InGaAs quantum wells.
The holes were etched half-way through the top-mirror following various designs (triangular and square lattices) and
with varying hole's diameters and pitches.
At room temperature and in continuous wave operation, micro-structured 50 µm diameter mesa VCSELs with
10 μm oxidation aperture exhibited more than 1 mW optical power, 2 to 5 mA threshold currents and more than 30 dB
side mode suppression ratio at a wavelength of 1090 nm. These structures show slight power reduction but similar
electrical performances than unstructured devices. Systematic static electrical, optical and spectral characterization was
performed on wafer using an automated probe station. Numerical modeling using the MIT Photonic-Bands (MPB )
package of the transverse modal behaviors in the photonic crystal was performed using the plane wave method in order
to understand the index-guiding effects of the chosen patterns, and to further optimize the design structures for mode
selection at extended wavelength range.
In this article, we report our results on 1.3&mgr;m VCSELs for optical interconnection applications. Room
temperature continuous-wave lasing operation is demonstrated for top emitting oxide-confined devices with three
different active materials, highly strained InGaAs/GaAs(A) and GaInNAs/GaAs (B) multiple quantum wells (MQW) or
InAs/GaAs (C) quantum dots (QD). Conventional epitaxial structures grown respectively by Metal Organic Vapour
Phase Epitaxy (MOVPE), Molecular Beam Epitaxy (MBE) and MBE, contain fully doped GaAs/AlGaAs DBRs. All
three epilayers are processed in the same way. Current and optical confinement are realized by selective wet oxidation.
Circular apertures from 2 (micron)m to 16 (micron)m diameters are defined.
At room temperature and in continuous wave operation, all three systems exhibit lasing operation at
wavelengths above 1 275nm and reached 1 300nm for material (A). Typical threshold currents are in the range [1-
10]mA and are strongly dependent firstly on oxide diameter and secondly on temperature. Room temperature cw
maximum output power corresponds respectively to 1.77mW, 0.5mW and 0.6mW. By increasing driving current,
multimode operation occurs at different level depending on the oxide diameter. In case (A), non conventional modal
behaviors will be presented and explained by the presence of specific oxide modes.
Thermal behaviors of the different devices have been compared. In case (A) and (C) we obtain a negative T0.
We will conclude on the different active materials in terms of performances with respect to 1300nm VCSEL
In the field of datacom, 10 Gbit/s sources with a good coupling in monomode silica fibers, whose
dispersion minimum occurs at 1.3 μm, are required. Vertical Cavity Surface Emitting Lasers (VCSELs)
emitting at 1.3 μm are key components in this field thanks to their compactness, their ability of being
operated at high frequencies, their low threshold current and their low beam divergence. Such devices
emitting in this wavelength range have been demonstrated using different materials such as strained
GaInAs/GaAs quantum wells [1-3], GaInNAs/GaAs quantum wells [4-7], InAs/GaAs quantum dots [8,
9], and antimonides , using either molecular beam epitaxy (MBE) or metalorganic vapor phase
In the emerging field of photonics on CMOS, there is a need to bond efficient III-V laser sources on SOI wafers. These components should operate at small voltage and current, have a small footprint, and be
efficiently couple to Si waveguides, these latter being transparent above 1.1 μm. Since these
requirements resemble VCSEL properties, the development of VCSEL emitting above 1.1 μm could
therefore benefit to future new sources for photonics on silicon applications.
In this context we developed GaAs-based VCSELs emitting in the 1.1 μm - 1.3 μm range with
GaInAs/GaAs or GaInNAs/GaAs quantum wells (QWs) as the active materials.