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International audience; We present CW operation of a tunable InP based Vertical Cavity Surface Emitting Laser, integrating a liquid crystal (LC) micro-cell. In comparison with previous work, a larger 33 nm (vs 23 nm) tuning and stable operation are obtained, according to major improvements presented in this paper.

International audience; An InP-based Vertical-Cavity Surface-Emitting 1 Laser (VCSEL) with a liquid crystal (LC) microcell monolithically integrated on its surface for spectral tuning is investigated. Unlike tunable VCSELs integrating a movable membrane, here the physical length of the cavity remains unchanged and only the voltage applied on the LC ensures a refractive index modification for a particular polarization emitted by the VCSEL. This tunable VCSEL operates in CW at room temperature and exhibits more than 23 nm wavelength tuning around 1.55 µm at a maximum applied voltage of 20 V. The measured laser threshold around 6.5 mW is still comparable to VCSEL without LC microcell, a clear indication that the optical losses related to the LC are very low. On the other hand, for this first optically pumped device, the lasing characteristics suggest that the LC birefringence is lower than expected. To assess this hypothesis, thermo-optical simulations have been conducted.

By exploiting one-dimensional photonic crystal nanocavities, an ultra-compact indium phosphide-on-silicon laser diode with low current threshold, high wall-plug efficiency and high integrability is demonstrated. The most-awaited convergence of microelectronics and photonics promises to bring about a revolution for on-chip data communications and processing1. Among all the optoelectronic devices to be developed, power-efficient nanolaser diodes able to be integrated densely with silicon photonics and electronics are essential to convert electrical data into the optical domain. Here, we report a demonstration of ultracompact laser diodes based on one-dimensional (1D) photonic crystal (PhC) nanocavities2,3,4 made in InP nanoribs heterogeneously integrated on a silicon-waveguide circuitry. The specific nanorib design enables an efficient electrical injection of carriers in the nanocavity without spoiling its optical properties. Room-temperature continuous-wave (CW) single-mode operation is obtained with a low current threshold of 100 µA. Laser emission at 1.56 µm in the silicon waveguides is obtained with wall-plug efficiencies greater than 10%. This result opens up exciting avenues for constructing optical networks at the submillimetre scale for on-chip interconnects and signal processing.

International audience; Photonic devices with wavelength tuning capabilities are investigated with the use of liquid crystal microcells monolithically integrated onto the surfaces of photodiodes or VCSEL fabricated on InP based materials. For these two devices, we demonstrated that the detected or emitted wavelength can be selected on a tuning range of more than 70 nm in the case of the photodiode, and of more than 20 nm in the case of VCSEL.

We have realized a dual-frequency vertical external cavity surface emitting laser (VECSEL) at 1.5 μm. Laser emission of two orthogonally polarized cavity modes is obtained by inserting a birefringent crystal into the VECSEL cavity. We have examined the influence of the different intracavity elements on the laser emission. It is shown that optimizing the free spectral range and the bandwidth of the intracavity Fabry–Perot etalon is of practical importance to achieve a stable single longitudinal laser emission for each of the two orthogonal polarizations. The optimization of the output power has also been investigated, and it is concluded that up to 50 mW output power can be expected in dual-frequency operation by adjusting the reflectivity of the output coupling mirror of the VECSEL cavity. The influence of different parameters on the stability of the dual-frequency emission has been studied. It is concluded that mechanical vibrations are the main cause of radio-frequency (RF) signal instability in our free-running VECSEL cavity. The design of a compact or mono-block cavity may allow meeting the stability requirements for optical fiber sensors based on Brillouin scattering.

International audience; 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.

A simple technology is demonstrated for the wafer-scale fabrication of liquid-crystal (LC) microcells that can be integrated in active optoelectronic devices. Fabrication of 1.55- $\mu \text{m}$ tunable Fabry–Perot optical micro-filter arrays is achieved owing to the insertion of a single nanoimprinted polymer grating dedicated to LC alignment and to the soft thermal transfer of a dry thick resist film between two highly reflective mirrors. The filter exhibits a spectral tuning range of 102 nm with only 18 V applied, as well as negligible internal loss, which makes it suitable for being inserted in a laser cavity. This constitutes a key step toward the large-scale integration of widely tunable photonic devices such as vertical-cavity surface-emitting lasers using LC technology.

In this work, wurtzite BAlN layers with boron composition as high as 12% were successfully grown by MOVPE. The growth was performed at 650 °C and then annealed at 1020 °C. Low temperature growth was used in order to alleviate B-rich phase poisoning under high TEB/III ratio. The growth was performed by continuous epitaxy as well as by flow-modulate epitaxy. BAlN single layers with clearly defined X-ray diffraction peaks were achieved on AlN templates which are appropriate substrates for deep UV devices, as well as on GaN templates to facilitate distinguishing of the XRD peak of BAlN from the substrate peak. The layer demonstrated columnar crystalline features and inherited wurtzite structure from substrates. Cross-section STEM image (bright field) of 75 nm thick BAlN layers containing 12% boron taken along the [11−2 0] zone axis. Zone A is lattice-oriented along c-axis and zone B has columnar structure; (b) higher magnification image for the top part of the layer; (c) higher magnification image for the film/substrate interface.

We demonstrate a novel class of compact and power efficient optoelectronic devices integrated on SOI photonic circuit based on InP photonic crystals nanocavities. In particular, results on electrically injected hybrid nanolasers will be shown.

We report on the optimization of 2D planar photonic crystal (PhC) SiN x microcavities for the fabrication of surface-emitting thin-film organic micro-lasers with a low lasing threshold (~10 μJ/cm 2 ). Modified H2 and L3 PhC-microcavity geometries are designed in order to achieve quality factors Q in the range of 1000–2000 with a good matching of the cavity mode spectral position with the emission range of the organic layer. 3D-Finite Difference Time Domain (3D-FDTD) simulations show that the etch depth in the SiO 2 buffer layer has to be optimized in order to maintain the Q > 1000 , depending on the thickness of the organic layer to be evaporated onto the SiN x /SiO 2 PhC pattern. 3D-FDTD simulations also show that the optical microcavity properties are robust against typical variations of the dimensions occurring in the technological process. The PhC microcavities are designed and fabricated to be used with tris(8-hydroxyquinolinato)aluminum ( Alq3 ) doped with 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran ( DCJTB ) as the gain material.

This paper reviews and discusses recent developments in passively mode-locked vertical external cavity surface emitting lasers (ML-VECSELs) for short pulse generation at 1.55 μm. After comparing ML-VECSELs to other options for short pulse generation, we reviewed the results of ML-VECSELs operating at telecommunication wavelength and point out the challenges in achieving sub-picosecond operation from a ML-VECSEL at 1.55 μm. We described our recent work in the VECSELs and semiconductor saturable absorber mirrors (SESAMs), their structure design, optimization and characterization, with the goal of moving the pulse width from picosecond to sub-picosecond.

The wet oxidation from the mesa sidewalls of AlGaAs/GaAs epitaxial structures is investigated in details. In addition to the intended lateral oxidation of the Al-rich buried layer, we observe a parasitic vertical oxidation of the adjacent layers of lower Al content. This vertical oxidation produces a rough interface between the oxidized and non-oxidized materials and reduces the effective thickness of the adjacent layers. This detrimental phenomenon is drastically reduced when the adjacent layer is replaced by a GaAs/AlAs superlattice (SL). In this case, a sharp interface between the Al-Ga-oxide and the SL is obtained after the oxidation process. Further experiments point out the critical role of hydrogen in the oxidation process of low Al content alloys. Hydrogen atoms produced during the oxidation of the Al-rich layer are proposed to be responsible for the vertical oxidation of the adjacent layers. We devise that the SL interfaces are favorable to reduce the diffusion of the reactants in the vertical direction.

We aim at realizing an optically-pumped, dual-frequency VECSEL at telecom wavelength (1.5 µm) with a frequency difference in the radio-frequency (RF) range (around 11 GHz), to be used in a sensor unit based on Brillouin scattering in optical fibers. Laser emission of two orthogonally-polarized cavity modes with a controlled frequency difference is obtained by inserting a birefringent crystal in the VECSEL cavity. We have examined the influence of the different intra-cavity elements on the laser emission. It is shown that optimizing the free spectral range and the bandwidth of the intra-cavity Fabry-Perot etalon is of practical importance to achieve a stable single longitudinal laser emission for each of the two orthogonal polarizations. The optimization of the output power has also been investigated and it is concluded that up to 100 mW output power can be expected by adjusting the reflectivity of the output coupling mirror of the VECSEL cavity. The achievement of a highly-stable frequency difference is crucial for sensing applications. For this reason the influence of different parameters on the stability of the dual-frequency emission have been studied. It is concluded that mechanical vibrations are the main cause of the RF signal instability in our free-running VECSEL cavity. The design of a compact or mono-block cavity may allow to meet the stability requirements for our sensors.

Electrically driven CW operation of energy-efficient ultra-compact InP-based nanolasers in a Silicon photonic platform is demonstrated. The nanolaser diode is single mode and emits at 1560 nm with SMSR grater than 20dB. The threshold is low, around 0.1mA at 1 V and the emitted power in the SOI waveguide is of the order of 0.1mW giving a wall-plug efficiency higher than 10 percents.

An electroplated copper substrate was evaluated for heat dissipation in 1.55-μ.m optically pumped vertical extended cavity surface emitting lasers (OP-VECSELs). It is a cost-effective and flexible solution compared with the previously proposed chemical vapor deposition diamond substrate assembled by metallic bonding. Continuous-wave (CW) lasing operation was demonstrated from a device (with copper electroplated substrate) under optical pumping with pump spot diameter of 100 μm and a maximum output power of 260 mW at 0°C; heatsink temperature was achieved. Room-temperature CW operation with an output power of 75 mW and an external quantum efficiency of 35% was achieved in an optimized plane-concave cavity. The thermal resistance and the maximum output power of VECSEL chips assembled with bonded bulk copper and electroplated copper substrates were measured and compared. A value of ~50 K/W was estimated for both devices, and a similar rollover point was observed, which indicates that the electroplated copper solution leads to similar thermal properties as a bonded bulk copper substrate.

Lasing in a ZnO planar microcavity is reported under optical excitation up to room temperature. The cavity presents a quality factor of 450 and the simultaneous presence of two cavity modes with different interference orders. The transition from the strong coupling to the weak coupling regime is observed at lasing threshold. The gain mechanism below T = 240 K is attributed to excitons, according to the observation of a specific gain transition within the strong coupling regime. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

GaN structures have been grown by selective area growth (SAG) in an atmospheric hydride vapour phase epitaxy (HVPE) reactor on c-plane sapphire and metal organic vapour phase epitaxy (MOVPE) grown GaN/c-plane sapphire substrates. The substrates were patterned in two perpendicular crystallographic directions 〈1 1 −2 0〉 and 〈1 −1 0 0〉. The growth morphologies of the GaN stripes were systematically investigated by scanning electron microscopy (SEM). A complete cartography of GaN SAG was established, after varying the growth temperature and the V/III ratio on both types of substrate. The cartography permits to fix the appropriate parameters for growing GaN quasi-substrates or GaN nano-structures with controlled morphology.

We have realized several one-dimensional (1D) microcavities, containing self-assembled perovskite layers, emitting in the ultraviolet (UV) range (around 3.5 eV), working in the strong-coupling regime at room temperature. Procedures to increase the quality factor of the microcavities have been explored. Two different technologies have to be combined: the soft technologies related to the organic materials and polymers and the technologies which are more specific to inorganic materials, such as electron-beam evaporation and sputtering, used in particular to deposit dielectric mirrors.

We report on the thermal design and the characterization of InP-based 1.55 μm wavelength large diameter (∼100 μm) optically pumped vertical external cavity surface emitting lasers (OP-VECSELs). The device is thermally optimized for high power ( > 70 mW) room-temperature (RT) continuous-wave (CW) single-mode operation. Efficient bottom heat dissipation in the 1/2-VCSEL chip is obtained thanks to the use of a hybrid metal– metamorphic GaAs/AlAs mirror integrated to the InP-based active region, and to subsequent soldering on a SiC substrate. A single-mode output power of 77mW is obtained under CW-RT laser operation, limited by the pump power. Moreover thermal simulations and characterizations of the 1/2-VCSEL chip show that even higher power could be obtained at higher pumping levels, using a CVD diamond substrate.

International audience; The achievement of a 1.51 µm InAs/InP(311)B quantum dot (QD) single-mode Fabry–Perot laser operating under continuous wave at room temperature is reported. A threshold current of 80 mA associated with a 0.12 W/A external efficiency is reported for as-cleaved device at room temperature. The maximum output power, the gain peak wavelength at threshold and the full width at half maximum of the spectral gain are 5 mW, 1512 nm and 60 nm, respectively. Although these performances must be improved in the future, these results constitute to our knowledge the state-of-the-art on InP(3 1 1)B substrate. These results are of great interest since QD-based lasers are expected to play a major role in the next generation telecommunication networks as low-cost devices.

International audience; We report on the design, fabrication, and characterization of InP-based 1.55 μm wavelength large diameter (50 μm) 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-μm 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-μm diameter VECSELs, rather than current injection inhomogeneity.

The polariton condensation phase diagram is compared in GaN and ZnO microcavities grown on mesa-patterned silicon substrate. Owing to a common platform, these microcavities share similar photonic properties with large quality factors and low photonic disorder, which makes it possible to determine the optimal spot diameter and to realize a thorough phase diagram study. Both systems have been investigated under the same experimental conditions. The experimental results and the subsequent analysis reveal clearly that longitudinal optical phonons have no influence in the thermodynamic region of the condensation phase diagram, while they allow a strong (slight) decrease of the polariton lasing threshold in the trade-off zone (kinetic region). Phase diagrams are compared with numerical simulations using Boltzmann equations, and are in satisfactory agreement. A lower polariton lasing threshold has been measured at low temperature in the ZnO microcavity, as is expected due to a larger Rabi splitting. This study highlights polariton relaxation mechanisms and their importance in polariton lasing.

Light-matter coupling in a cavity results in a ladder of states with splittings determined by the coupling strength. We observe the higher ladder rungs in a semiconductor microcavity using multiquantum coherent optical photocurrent spectroscopy.

We report on the first room temperature (RT) laser operation at 1.04 μm from strained InGaAs/GaAs quantum well structures grown by metalorganic chemical vapour deposition and monolithically integrated on Si using a 6° offcut Ge/GeSi/Si virtual substrate (VS) realised by low energy-plasma enhanced chemical vapour deposition. Similar threshold current density from identical control laser diodes grown on bulk germanium substrates demonstrates the potential of Ge/GeSi/Si-VS for the monolithic integration of long wavelength GaAs-based lasers on Si. A way to reduce the crack density is also proposed to improve the laser characteristics.

International audience; We report room temperature (20 °C) continuous-wave operation of 1.55 μm vertical-external-cavity surface-emitting lasers. The optically pumped monolithic InP-based structure, grown by metal–organic chemical vapor deposition, includes a InP/InGaAsP Bragg reflector, and an active region with strain compensated quantum wells. Output power up to 4 mW is obtained at 0 °C. The thermal impedance of the structure is deduced from the experimental data.

We report on the design, fabrication and characteristics of both hybrid and monolithic micro-electro-mechanically wavelength tunable 1.55 μm InP-based Vertical-Cavity Surface-Emitting Laser (VCSEL) structures. Photo-pumped tunable VCSELs are successfully realized using both configurations, and a design for electrically pumped tunable VCSEL is presented. To cite this article: I. Sagnes et al., C. R. Physique 4 (2003).

Single-mode diode lasers on an InP(001) substrate have been developed using InAs/In0.53Ga0.47As quantum dash (Qdash) active regions and etched lateral Bragg gratings. The lasers have been designed to operate at wavelengths near 2 μm and exhibit a threshold current of 65 mA for a 600 μm long cavity, and a room temperature continuous wave output power per facet >5 mW. Using our novel growth approach based on the low ternary In0.53Ga0.47As barriers, we also demonstrate ridge-waveguide lasers emitting up to 2.1 μm and underline the possibilities for further pushing the emission wavelength out towards longer wavelengths with this material system. By introducing experimentally the concept of high-duty-cycle lateral Bragg gratings, a side mode suppression ratio of >37 dB has been achieved, owing to an appreciably increased grating coupling coefficient of κ ∼ 40 cm−1. These laterally coupled distributed feedback (LC-DFB) lasers combine the advantage of high and well-controlled coupling coefficients achieved in conventional DFB lasers, with the regrowth-free fabrication process of lateral gratings, and exhibit substantially lower optical losses compared to the conventional metal-based LC-DFB lasers.

We describe a compact, ultralow noise, and high-power semiconductor laser implemented in a high performances wideband externally modulated optical link. The laser is based on a vertical external cavity surface emitting laser (VECSEL) designed for high-power and low-noise operation. Thanks to a specific design of the gain chip, the half-VCSEL, based on a metamorphic Bragg mirror and a report on a copper substrate, an optical power of 110 mW is obtained at 1.55 μm in the single frequency regime. For low-noise operation, the laser cavity is designed for free-relaxation-oscillations operation, i.e., in the so-called class-A regime. The Class-A VECSEL exhibits a relative intensity noise below −170 dB/Hz over a wide frequency bandwidth, from 300 MHz to 40 GHz, except at the laser free spectral range (20.4 GHz). In the low-frequency range, the laser noise, mainly due to transfer of pump noise to laser noise, goes from −110 dB/Hz at 1 kHz down to −158 dB/Hz at 10 MHz. Two externally modulated optical links are implemented and compared in terms of the RF gain and the noise figure. The first optical link is based on the ultralow noise class-A VECSEL and the second one is based on a low noise class-B DFB laser. Thanks to the outstanding noise properties of the designed VECSEL, the VECSEL-based optical link outperforms the DFB-based one, in particular for frequencies larger than 20 GHz.

International audience; Five-period AlN/BAlN heterostructure containing boron as high as 11% has been successfully grown by MOVPE. Good periodicity of two alternative layers has been observed by both SIMS profile and Z-contrast HAADF-STEM images. The BAlN layers demonstrate columnar polycrystalline feature. The BAlN layers exhibit an emission peak by CL and absorption edge in transmission spectra at around 260 nm. The results enable the development of BAlGaN based multi-layered heterostructure for UV and deep UV applications.

Fabrication of high Q-factor InP-based Photonic Crystal nanobeam cavities is demonstrated by improving ICP etching. We measure Q-factors as high as ~130,000 for passive cavities by integrating them on to SOI wire waveguides. Nanolasers exhibiting low lasing threshold are then obtained using this technology.

We present results on InAs/InP quantum dash based broad area and ridge-waveguide lasers with emission wavelength up to 2 um. In addition a simulation-based design for laterally coupled DFB/DBR lasers is discussed, and the optimization of the processing steps for the realization of this design is presented. The design is fully compatible with readily available processing techniques and enables sufficiently high coupling coefficients for the realization of a tunable laterally coupled DBR (LC-DBR) laser, without the need of employing any regrowth steps over corrugated substrates, used for conventional DBR lasers.

We report class-A dual-frequency oscillation at 1.55 μm in a vertical external cavity surface emitting laser with more than 100 mW optical power. The two orthogonal linear polarizations of different frequencies oscillate simultaneously as their nonlinear coupling is reduced below unity by spatially separating them inside the active medium. The spectral behavior of the radio frequency beatnote obtained by optically mixing two polarizations and the phase noise of the beatnote have been explored for different coupling strengths between the lasing modes.

The MOVPE growth of (InGa)(NAs)/GaAs structures with room temperature photoluminescence (RTPL) in 1–1.59 μm range is presented. Infinite threshold current densities of 0.095, 1.22 and 2.3 kA/cm 2 at 1.18, 1.22 and 1.24 μm emission wavelengths, for the In 0.35 Ga 0.65 N y As 1− y /GaAs quantum well (QW) laser diodes with 0%, 0.4% and 0.5% of nitrogen, respectively, were obtained. Characteristic temperature ( T 0 ) values of 82, 117 and 102 K were determined for as-cleaved lasers in the 20–80°C temperature range.

Selective planar regrowth of high resistivity (as high as 10 9 Ω cm) Fe-doped semi-insulating InP epitaxial layers has been studied to fabricate current confining layers for buried heterostructure lasers. The epitaxial layers were grown on patterned, nonplanar heterostructure mesa by low-pressure organometallic vapor phase epitaxy (LP-MOVPE) with tertiarybutylphosphine (TBP), trimethylindium (TMI) and iron dicyclopentadienyle (Fe(C 5 H 5 ) 2 ) as the reactant gases. The shape of the growth around masked mesas without any overhang of the mask has been studied as a function of both the growth conditions and the mesa height. Finally, an optimization of the growth conditions has been performed to planarize ridges as high as 2 μm, the layer quality being characterized by SEM.

We report on an extensive experimental study of the barrier strain influence on the high-speed properties of compressively strained quaternary (InGaAsP) multiquantum-well (MQW) lasers emitting at 1.55 /spl mu/m. In the design of strained MQW laser structure emitting at 1.55 /spl mu/m, the main effect of varying the barrier strain amount is to modify the effective well/barrier height for both electrons and holes. In this paper, it is shown experimentally from MQW structures with different barrier strain values, that a strong decrease of the nonlinear gain coefficient can be obtained when the barrier strain is reduced, leading to quantum-well (QW) laser structures with a damping coefficient (called the K-factor) as low as 0.18 ns, i.e., theoretical damping limited bandwidth as high as 50 GHz. This result appears to be qualitatively well explained by a substantial reduction of the carrier capture time to escape time ratio, due to an increase of the well/barrier offset in the conduction and valence bands.

We describe a compact, ultra-low noise and high-power laser implemented in a wideband externally-modulated optical link. The laser is based on a Vertical External Cavity Surface Emitting Laser designed for free-relaxation-oscillations operation, i.e. in the so-called class-A regime. Thanks to a specific design of the 1/2-VCSEL, a metamorphic Bragg mirror and a report on a copper substrate, an optical power of 110 mW is obtained at 1.55μm in the single frequency regime. The Class-A VECSEL exhibits a relative intensity noise below -170 dB/Hz over a wide frequency bandwidth, from 300 MHz to 40 GHz, except at the laser free spectral range (20.4 GHz). A VECSEL-based optical link and a low RIN Class-B DFB-laser-based optical link are implemented and compared in terms of gain and noise factor. Thanks to its flat and ultra-low noise over a wide frequency bandwidth, the VECSEL outperforms the DFB laser, in particular for frequencies larger than 30 GHz.

We present a design of an atom interferometer using thermal atoms trapped on a chip. We point-out that such an interferometer requires highly symmetrical potentials, and we propose a splitter based on microwave potentials with two coplanar waveguides to achieve this goal.

International audience; We report on the realization of monolithic optical microcavities using a single wall carbon nanotubes doped polymer as active material. Thanks to the control of the polymer thickness, a ne control of the cavity mode energy is achieved, which allows to tune it in exact resonance with a speci c chiral species emission line. The quality factor of the lled cavity mode (Q = 40) allows to selectively extract the luminescence of the (7,5) chiral species. Finally, angle resolved experiments show the tunability of the emission energy within a 150 meV range.

International audience; We report exciton-polariton condensation in a new family of fully hybrid ZnO based microcavity demonstrating the best-quality ZnO material available (a bulk substrate), a large quality factor (~4000) and large Rabi splittings (~240 meV). Condensation is achieved between 4 and 300 K and for excitonic fractions ranging between 17% and 96 %, which corresponds to a tuning of the exciton-polariton mass, lifetime and interaction constant by one order of magnitude. We demonstrate mode switching between polariton branches allowing, just by controlling the pumping power, to tune the photonic fraction by a factor 4.

The spectro-temporal behavior of actively mode-locked fiber-external-cavity DFB lasers at 1.55 /spl mu/m is analyzed in detail. Experiments are performed with multiquantum-well InGaAsP lasers of different lengths and different phase-amplitude coupling factors. Transform-limited picosecond pulses are generated with pulsewidth adjustable over half a decade by changing the RF conditions and the device length. As in the case of conventional laser diodes with external grating, the smallest time-bandwidth products are obtained for modulation frequencies to the high-frequency side of the mode-locking band. This result is presently described in terms of chirp compensation by the DFB cavity dispersion. An analytical expression of the pulse compressibility is established from a steady-state mode-locking equation including refractive index variations and cavity dispersion effects. Gain parameters entering the expression are separately evaluated from standard rate equations. A good agreement is found between experimental and theoretical results.

We have optimized the structure of InGaAlAs multiple quantum-well electroabsorption modulators for all-optical signal processing. As wavelength conversion is a key function for all-optical telecommunication network, we have based our optimization upon the main parameters of this function, namely, polarization insensitivity, exciton saturation, and photogenerated carrier sweep-out time. Four samples have been studied with different well tensile strain and barrier height. We find low polarization dependence over a range of applied bias. Less than 10-ps absorption-saturation recovery time at lower biases and smaller saturation power than in the literature are reported.

SiO2/SiNx and SiO2/HfO2 distributed Bragg reflectors for the ultra-violet (λ = 360 nm–380 nm) are compared through their structural and optical properties. The SiO2/HfO2 system exhibits a lower interface roughness, higher reflectance, larger stop band, and lower penetration depth than SiO2/SiNx. A cavity quality factor of 3700 at about 360 nm is measured on a passive SiO2/HfO2-based planar microcavity. Compared with values obtained in the literature for the near UV range, the latter is rather large. Micro-reflectance measurements have been performed on a series of passive microcavities with increasing cavity thickness to determine the residual absorption in the SiO2 and HfO2 layers. Absorption coefficients of 30 (k = 0.86 × 10−4) and 160 cm−1 (k = 4.59 × 10−4) near λ ∼ 360 nm have been extracted for SiO2 and HfO2, respectively. Transfer-matrix simulations taking into account the residual absorption show that microcavity quality factors up to 8000 can be expected at 360–380 nm with this material system. Su...

High-quality (Q) factor indium phosphide (InP)-based 1D photonic crystal nanobeam cavities are fabricated on silicon on insulator waveguides. Through the optimization of the fabrication process, the intrinsic Q factor of these fully encapsulated nanocavities is demonstrated to attain values higher than 100,000. Experimental and numerical investigations are carried out on the impact, on the Q factor, of the strength of the evanescent wave coupling between the cavity and the waveguide. We reveal that this coupling can result in a modification of the electromagnetic field distribution in the resonant mode, which gives rise up to a factor 4 reduction in the intrinsic Q factor for the structures under study.

GaInNAsSb quantum wells grown by molecular-beam epitaxy on GaAs substrates were investigated. Intricate incorporation mechanisms of the constituents in this quinary alloy were seen. In highly strained indium-rich alloys, antimony incorporation is strongly reduced, and a beneficial surfactant effect is observed. Due to this effect, high structural quality is preserved even for an uncompensated 2.67% strained multiquantum-well structure. Narrow luminescence linewidth (35 meV) could be achieved near 1.55 μm wavelength with these quantum wells. Laser emission is demonstrated at 1.50 μm with threshold current density of 3.5 kA/cm2.

We report on the fabrication of a perovskite-based ((C6H5C2H4 - NH3)2 PbI4) planar microcavity with a technique of a top dielectric mirror's migration in liquid, avoiding the degradation of the perovskite material. This approach allows for increasing the cavity Q-factor, without degrading the fragile molecular material. Strong coupling of the perovskite exciton to both the cavity mode and the first Bragg mode is evidenced from angle-resolved reflectivity and microphotoluminescence measurements at room temperature; an efficient relaxation toward the minimum of the main polariton branch is observed. The measured quality factor is significantly increased compared to previous reports where a top metallic mirror was used, showing the decisive advantage of the present fabrication technique toward the achievement of stimulated effects and polariton lasing with perovskite materials.

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 3 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.

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.

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.

We present a simple model which allows us to predict the spectral behaviour of gain-switched Fabry-Perot (F-P) laser diodes submitted to a weak quasi-monochromatic cw (or pulsed) injection signal. Different experiments are reported for illustration, some of them being new. The model describes the competition between the injection-driven field and the spontaneousnoise driven field during pulse build-up. The relative amplitudes of the two fields are evaluated at the gains-witching time as well as the spectral content of the injection-driven field. Different types of modal selection are found depending on the injection conditions. In the case of cw injection, there is a wide range of injection frequencies leading to single-mode emission, but two-mode lasing is also predicted for lasers exhibiting strong intrinsic chirp. These results are confirmed in experiments carried out on a 1.5 μm Fabry-Perot laser driven by different cw dfb injection lasers. In the case of pulsed injection, the laser behaviours are similar but the model also shows the influence of the pulsed-injection arrival time on the mode selection process. This is experimentally illustrated in the case of a pulsed 1.3 μm laser operated in self-injection, the injected signal resulting from a weak spectrally-filtered optical feedback.

We realize a Fabry-Perot hybrid microcavity containing an association of a ZnO thin layer and of a layer of the two-dimensional layered perovskite 5-methyl-2-furanmethanamonium lead bromide (MFMPB). From angle-resolved reflectivity experiments performed at low temperature of 5 K, we show that this hybrid cavity works in the strong-coupling regime and that the lower, middle, and upper polariton branches are observed. We show that the middle polariton branch (MPB) contains a significant component of the cavity photon and both of the two exciton species.