GaN-on-Silicon nanowire technology is promising for several display applications. Since one of the microLED display major challenges is to drastically reduce the cost, the possibility to downsize the microLED is paramount. Aledia has developed a nanowire microLED technology on large Si wafers which keeps the same blue emission efficiency for ⪅2μm size devices containing only 1 NW as for larger devices containing up to few hundreds of NWs. A RGB integrated pixel relying on this technology is presented where quantum dots are used for green and red color conversion. Another nanowire microLED concept for AR/MR applications is also presented where light emission directivity and pixel size downsizing are mandatory.
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
silicon photonics.
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
[1]) 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.
The on-coming photonic layer of CMOS integrated circuits needs efficient light sources to treat and transmit the flow of
data. We develop new configurations of III-V/Si vertical cavity lasers coupled to silicon optical waveguides using
mirror/coupler based on photonic crystals. These devices can be fabricated using fully CMOS-compatible technological
steps. Using this approach, the optical gain is provided by the III-V material, while all the remaining part of the optical
cavity is in silicon. The output coupling to the sub-µm waveguides of the CMOS optical layer can then be inherently
optimised since the laser mirror/coupler and the Si output waveguides will be realised together during the same
fabrication step.
It has been demonstrated that photonic crystals membrane can act as very efficient reflectors (PCM-mirrors) for vertical
microresonators. In this communication, the design of a vertical cavity microlaser based on these PCM-mirrors will
be presented. We will show that high Q-factors (>10000) along with strong vertical and lateral confinements can be
achieved. As a first demonstration, experimental results on silicon PhC-mirrors and associated vertical cavities will be
discussed, showing Q factors larger than 2000. Finally, theoretical results on the coupling between such cavities and a
silicon micro-waveguide will be presented.
We report on the epitaxy of vertically aligned ZnO nanowires (NWs), the collective integration technology of these
nanowires and their optical and electrical characterizations. ZnO based nanowires are grown mainly on sapphire
substrates by metal-organic vapour phase epitaxy (MOVPE). Photoluminescence spectra at 4 K exhibit strong excitonic
peaks at around 380 nm without green luminescence band, showing the low deep radiative defect density. Technological
processes have been developed both for mineral and organic integrations of the as-grown nanowires. Photoconducting
properties in the UV-visible range have been investigated through collective electrical contacts. The electrical transport
properties of vertically integrated single nanowires have also been investigated by current sensing AFM measurements.
A comparison of the PL spectra at 300 K of the as-grown and integrated nanowires has shown no significant impact of
the integration process on the crystal quality of the nanowires.
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 [1])
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.
F. Levy, Y. Desieres, P. Ferret, S. Fichet, S. Gidon, P. Gilet, P. Noel, I.-C. Robin, E. Romain-Latu, M. Rosina, R. Songmuang, G. Feuillet, B. Daudin, A. Chelnokov
LEDs based on semiconductor nanowires are a promising alternative to the standard planar devices to achieve low cost high yield manufacturing for the general lighting applications. The expected advantages of such structures are a high crystalline quality of the heterostructures, compliance with a large range of substrates and light extraction enhancement. We report here on the present status of our research work concerning the electromagnetic simulation of nanowire emission, the epitaxy of near-UV semiconductor vertically aligned nanowires, the collective integration technology of these nanowires and their characterizations.
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
applications.
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 [10], using either molecular beam epitaxy (MBE) or metalorganic vapor phase
epitaxy (MOVPE).
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.
In the context of optical interconnection applications, we report on results obtained on strained InGaAs quantum well Vertical Cavity Surface Emitting Lasers (VCSELs). Our devices are top p-type DBR oxide-confined VCSEL, grown by metalorganic vapour-phase epitaxy (MOVPE). These lasers exhibit low threshold currents and deliver up to 1.77 mW in continuous wave operation at room temperature. Fundamental mode continuous-wave lasing at wavelengths beyond 1300 nm at room temperature is reached for a 4 μm oxide diameter VCSEL. The particular design of the active layer based on a large detuning between the gain maximum and the cavity resonance gives our devices a very specific thermal and modal behaviour. Therefore, we study the spectral and spatial distributions of the transverse modes by near field scanning optical microscopy using a micropolymer tip at the end of an optical fibre.
We report results on strained InGaAs quantum well Vertical Cavity Surface Emitting Lasers (VCSELs) for optical interconnection applications. The structure was grown by metalorganic vapour-phase epitaxy (MOVPE) and processed as top p-type DBR oxide-confined device. Our VCSELs exhibit low threshold currents and deliver up to 1.77 mW in continuous wave operation at room temperature. Fundamental mode continuous-wave lasing at wavelengths beyond 1300 nm is demonstrated at room temperature. The thermal behaviour of our devices is explained through the threshold current-temperature characteristics. Furthermore, the effective index model is used to understand the modal behaviour.
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