In this work, we report InGaAs based photodiodes integrating liquid crystal (LC) microcells resonant microcavity on their surface. The LC microcavities monolithically integrated on the photodiodes act as a wavelength selective filter for the device. Photodetection measurements performed with a tunable laser operating in the telecom S and C bands demonstrated a wavelength sweep for the photodiode from 1480 nm to 1560 nm limited by the tuning range of the laser. This spectral window is covered with a LC driving voltage of 7V only, corresponding to extremely low power consumption. The average sensitivity over the whole spectral range is 0.4 A/W, slightly lower than 0.6 A/W for similar photodiodes that do not integrate such a LC tunable filter. The quality of the filter integrated onto the surfaces of the photodiodes is constant over a large tuning range (70 nm), showing a FWHM of 1.5 nm.
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 paper, we report the investigation of two-dimensional organic photonic crystal microcavity laser (2D OPCM). The
gain medium consists of an Alq3:DCJTB layer deposited on a planar Si<sub>3</sub>N4 photonic crystal microcavity. Both H2 and
L3 photonic crystal cavities are studied in terms of quality factor and the resonance wavelength by 3D FDTD
simulations. The structures are characterized under optical pumping by using a Nd:YAG frequency-tripled laser emitting
at 355 nm with a repetition frequency of 10 Hz and a pulse duration of 6 ns. A laser peak at 652 nm is observed for both
cavities with lasing thresholds of 0.014 nJ and 0.017 nJ for the H2 and the L3 cavities, respectively.
III-Nitride semiconductors are promising nonlinear materials for optical wavelength conversion. However second
harmonic generation in bulk GaN is weak because GaN is strongly dispersive. We show that appropriate photonic crystal
patterning in GaN helps to overcome dispersion and provides quasi-phase matching conditions, resulting in substantially
increased conversion efficiency obtained in a flexible manner. Enhancement factors of more than five orders of
magnitude can be achieved. Use of photonic crystals makes it possible to reduce the effective observation volume,
thereby opening new opportunities such as the study of single-molecule dynamics, even in high concentration solutions.
We have demonstrated sharp enhancement of the fluorescence of single molecules immobilized on the surface of a GaN
photonic crysta,l when the molecules are excited via the resonant second harmonic generation process.
Mode-locked vertical-extended-cavity-surface emitting lasers (ML-VECSEL) are promising candidates for the
generation of stable short pulses at multi-GHz rate. However, the poor thermal behavior of quaternary InP-based
semiconductor compounds often limits the performance of ML-VECSELs operating at 1.55 μm. In this work, we report
on a specific approach using downward heat sinking to optimize the heat dissipation out of the active region. VECSEL
chips with a low thermal resistance are fabricated using a hybrid metal-metamorphic GaAs/AlAs mirror and bonding to a
highly thermally conductive host substrate. We show that superior performance can be obtained with a CVD diamond
substrate, while electroplated copper host substrate can afford a flexible and low cost alternate approach for moderate
(~100 mW) output power. The VECSEL chip assembled with a 1.55μm fast InGaAs(Sb)N/GaAsN semiconductor
saturable absorber mirror (SESAM) produces nearly Fourier transform-limited mode-locked pulses at ~ 2 GHz repetition
frequency, and the RF linewidth of the free running laser is measured to be less than 1000 Hz. When the resonance and
group delay dispersion of the SESAM microcavity are tuned by selective etching of specific top phase layers, the modelocked
pulse width is reduced from several picoseconds to less than 1 ps.
In high finesse semiconductor microcavities containing quantum wells, photons emitted by the quantum well excitons
can oscillate long enough inside the cavity to be reabsorbed reemitted again and so forth. The system enters the so-called
strong coupling regime, with the formation of entangled exciton-photon eigenstates, named cavity polaritons, which
governs all the physics of the system. After an introduction to cavity polaritons, we will review in this paper some of
their original physical properties and discuss their potential in terms of new photonic devices. In a first part, we will
show how polaritons can massively occupy a single quantum state, thus acquiring spatial and temporal coherence
reflected in the emitted light. Such polariton laser could provide a low threshold source of coherent light. Then the
properties of polariton diodes will be addressed and in particular we will describe a new optical bistability based on the
control of the light matter coupling via the intra cavity electric field.
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 report on the design, fabrication, and characterization of InP-based 1.55 &mgr;m wavelength large diameter (50 &mgr;m)
electrically-pumped vertical external cavity surface emitting lasers (EP-VECSELs). The hybrid device consists of a half
vertical cavity surface emitting laser (1/2-VCSEL) structure assembled with a concave dielectric external mirror. The 1/2-
VCSEL is monolithically grown on InP substrate and includes a semiconductor Bragg mirror and a tunnel junction for
electrical injection. Buried (BTJ) and ion implanted (ITJ) tunnel junction electrical confinement schemes are compared
in terms of their thermal and electrical characteristics. Lower thermal resistance values are measured for BJT, but
reduced current crowding effects and uniform current injection are evidenced for ITJ. Using the ITJ technique, we
demonstrate Room-Temperature (RT) continuous-wave (CW) single transverse mode laser operation from 50-&mgr;m
diameter EP-VECSEL devices. We show that the experimental laser optical output versus injected current (L-I) curves
are well-reproduced by a simple analytical thermal model, consistent with the thermal resistance measurements
performed on the 1/2-VCSEL structure. Our results indicate that thermal heating is the main mechanism limiting the
maximum CW output power of 50-&mgr;m diameter VECSELs, rather than current injection inhomogeneity.
We aim to explore the nanostructuring potential of a highly focused pencil of ions. We show that focused ion beam technology (FIB) is capable of overcoming some basic limitations of current nanofabrication techniques and allowing innovative patterning schemes for nanoscience. In this work, we first detail the very high resolution FIB instrument developed specifically to meet nanofabrication requirements. Then we introduce and illustrate some new patterning schemes for next-generation FIB processing. These patterning schemes are: 1. nanoengraving of membranes as a template for nanopores and nanomask fabrication; 2. local defect injection for magnetic thin film direct patterning; 3. function of graphite substrates to prepare 2-D organized arrays of clusters; and 5. selective epitaxy of III-V semiconductors on FIB patterned surfaces. Finally, we show that FIB patterning allows "bottom-up" or "organization" processes.
InP-based micro-opto-electro-mechanical systems (MOEMS) for the long wavelength range (1.3 and 1.55 μm) have been extensively investigated during the last years. The fabrication of ultra-thin and hence ultra-flexible structures that can be actuated electrostatically was limited by residual strain within the structural layers. Highly flexible membranes are necessary if the tuning voltage is to be kept below 10 V and a wide tuning range is required. Adapting the metal-organic vapor phase epitaxial growth conditions, the residual strain was significantly reduced, allowing the fabrication of InP membranes as thin as 30 nm. Tunable micro-cavities (L<sub>cavity</sub>=0.5 λ, λ=1.55 μm) with a InP membrane thickness of only 123 nm show an optical tunability of up to 30.5 nm/V<sup>2</sup> and a maximum tuning range of more than 160 nm. When reducing the thickness to 123 nm (which corresponds to λ/4) a significant deformation of the membranes was observed that has to be taken into account for the fabrication of MOEMS since additional losses are created. A highly selective, widely tunable filter for dense wavelength division multiplexing systems (WDM) was fabricated and exhibits a selectivity of < 0.4 nm throughout the entire tuning range of 48 nm.
We report on the combination of the well established 1.55 micrometers monolithic VCSEL's concept with the Micro-Opto-Electro- Mechanical System (MOEMS) technological breakthrough in order to develop a novel tunable laser device for wavelength division multiplexing optical systems. Technological issures are presented for fabricating surface micromachined InP-based tunable VCSELs.