Search

Near-infrared spectroscopy (NIR) is widely used today in applications ranging from monitoring industrial manufacturing processes to assessing the chemical composition and quality of products and materials. However, the challenge remains in reducing size and cost of these spectroscopic devices, while maintaining their sensitivity and robustness. The miniaturisation of spectral sensors is essential to expanding their application beyond dedicated stations in industrial settings and analytical labs, into the hands of non-specialists working on-site and eventually to consumers. The design of current portable NIR sensor systems is mostly inspired by conventional instruments that use gratings or interferometers. The drawback of these approaches is that they are complex to assemble and contain movable parts that are susceptible to shocks and mechanical vibrations.

Subwavelength sized on-chip coherent light sources are attractive for variety different applications, such as integrated optical interconnects [1] , super resolution imaging [2] and neuromorphic computing [3] . Practical demonstration of nanolasers brings a number of challenges, including the nanostructures sensitivity to the fabrication defects. High surface-to-volume ratio makes surface defects detrimental for lasing performance. To minimize the impact of non-radiative surface recombination, many surface passivation methods have been reported [4] . For InGaAs material, significant photoluminescence (PL) signal improvement has been observed for the combination of ammonium sulphide ((NH 4 ) 2 S) treatment and a thin SiO x layer coating deposited on the surface by plasma enhanced chemical vapour deposition (PECVD) [5] . Such passivation method may be promising for practical devices only if it is stable for high temperatures, since the fabrication of optoelectronic devices requires a number of high-temperature processes like rapid thermal annealing (RTA) for ohmic contacts formation. So far, the quality of the ammonium sulfide passivated surface has been shown to degrade upon annealing at temperatures above 300 °C [6] . In this work, we show photoluminescence performance improvement after ammonium sulphide and SiO x coating passivation and its stability in a subsequent high temperature treatment.

Displacement sensing at the nanoscale is required in many applications, including accelerometry, mass sensing and atomic force microscopy. Miniaturization of the sensing elements and integration of the read-out is key in achieving low cost, high resolution and high speed. Here, we present a novel integrated nano-opto-electro-mechanical device which potentially has subnanometer resolution for displacement sensing. The proposed device is a waveguide-coupled, micron-sized, double membrane photonic crystal cavity with integrated electro-optical read-out on a single chip.

A novel photon-number-resolving detector (PNRD) structure, based on an array of nanowire superconducting single photon detectors (SSPDs) connected in series, have recently been proposed. With this configuration, it is possible to scale to large photon numbers. In this framework, PNRDs capable of resolving up to four, eight and twelve photons at telecommunication wavelengths have been fabricated and tested. The photon-induced voltage signals from all the series elements are summed up into a single readout pulse with a height proportional to the detected photon number. Analysis of the linearity shows the potential of scaling to an even larger dynamic range. © 2014 AEIT.

We demonstrate the integration of a new and scalable photon-number-resolving detector (PNRD) based on a spatially multiplexed array of superconducting nanowire single photon detectors (SSPDs) connected in series. The waveguide photon number resolving detectors (WPNR) show a device quantum efficiency of 24% and can discriminate between 0-4 photons.

We present a quantum integrated photonics platform on GaAs including waveguide single-photon sources and detectors on the same chip.

We present a device for the spectral reconfiguration of a two-dimensional photonic crystal cavity (PCC) based on parallel semiconductor membranes. The mechanical motion of the slabs introduces a variation in the effective refractive index of the coupled waveguides where the photonic crystal is etched resulting in a shift of the free-space wavelength. Using an integrated electrostatic actuator we demonstrated independent tuning up to 15 nm with less than 6 V bias. We present the electromechanical control of a PCC mode in resonance to single quantum dot (QD) emission lines for the real-time compensation of the spectral mismatch due to the dots' inhomogeneity. We discuss the operation of the device at low temperatures (

Semiconductor nanolasers provide an attractive route towards high density photonic integrated circuits in low power applications such as optical interconnects. In this paper we present the concept of a waveguide-coupled nanolaser for integration in a CMOS compatible photonic platform. We exploit metallic and dielectric confinement to provide high quality factors exceeding 500 in a wavelength-scale cavity, that provides efficient cooling and cross-talk immunity due to the metal coverage. We present simulations detailing the design considerations for high quality factors and efficient waveguide coupling. Optical and electrical simulations predict room temperature operation at 1.55 μm with a threshold current of 120 μA and a differential quantum efficiency of 0.16. We also discuss briefly the challenges of fabricating these devices and integrating them in the photonic platform.

A plasmonic laser structure coupled to a dielectric waveguide is proposed and investigated by rigorous simulations. Modal characteristics, such as propagation loss and confinement factor were obtained for a wavelength of 1.55 µm. In addition, FDTD (Finite-Difference Time-Domain) simulations were used to calculate the reflectivity from the end facets of the laser structure and also to calculate the coupling between the laser and a dielectric waveguide. Simulations show that a threshold gain of 1796 cm-1 is required to compensate the total loss in a 200 nm wide and 50 µm long laser, which can be achievable at room temperature.

Time-resolved experiments are performed on single quantum dots in bulk material and photonic crystal diodes. These studies reveal that the cavity mode can be pumped by a broad emission originating from the presence of carriers in the wetting layer.

We report on the achievement of a continuously tunable photonic molecule from an homoatomic to an heteroatomic condition. A complete control of the local mode tuning of two nominally identical photonic crystal microcavities on slab is obtained by a combination of different techniques. Homoatomic molecules are obtained by compensating the photonic disorder up to the standard condition of zero detuning between identical modes of the two cavities. Heteroatomic molecules are then realized by a large tuning of one of the two cavities, producing the condition of zero detuning between two modes of different polarization and spatial distribution. Clear modes anticrossing and hybridization is observed.

InAs Columnar Quantum Dash (CQDash) structures on (100) InP for polarization insensitive semiconductor optical amplifiers have been realized. Photoluminescence and electroluminescence measurements confirm a strong relationship between the polarization degree of the emission and the orientation of the CQDashes. The polarization properties of the CQDash emission could thus be changed from predominantly transverse electric to transverse magnetic by adjusting the dash orientation relative to the light propagation axis.

The optical study of single quantum dashes located inside a 2.5D photonic crystal structure is performed. The enhancement of the emission is observed for quantum dash in resonance with a slow Bloch mode.

The coupling between single 1.3 μm InAs quantum dots (QDs) and photonic crystal nanocavities with quality factors Q up to 15000 is showed. In this condition the Purcell effect (increased spontaneous emission rate) is observed for the first time at these wavelengths. This result is an important step for the development of semiconductor based single photon sources at telecom wavelength, a fundamental need for application like quantum cryptography and quantum computing.

In this paper, we characterized the electro-optic coefficient and loss of multilayer InAs quantum dot laser structures at 1309 and 1515 nm. Quantum dot waveguides were grown by molecular beam epitaxy, where the active region is formed by three or five layers of self-assembled InAs QDs. Loss characterization were carried out by using a 1.3 μm light from a thermally tunable laser. Transmission through the device was recorded as a function of wavelength. Loss coefficient is found to be wavelength and bias voltage dependent.

We show coupling between single 1.3 μm InAs quantum dots (QDs) and photonic crystal nanocavities with quality factors up to 16 500. We demonstrate increased spontaneous emission rate for the first time in telecommunication wavelengths QDs.

Novel single-photon detectors based on NbN superconducting nanostructures promise orders-of-magnitude improvement over InGaAs APDs. We demonstrate this improved performance for the first time by measuring the g(2)(?) on single photon states produced by a quantum dot at telecom wavelength.

International audience; Round-Robin measurements on the linewidth enhancement factor are carried out in many laboratories participating to EU COST 288 Action. Up to 7 different techniques are applied to DFB, VCSELs, QCL, and QD lasers, and results are compared.

We have developed solid-state single-photon sources based on single InAs quantum dots emitting at 1300 nm. We report antibunching experiment and electroluminescence measurements, showing that our system can be used as an efficient single photon source under optical and electrical pumping.

This work has explored the relaxation oscillation dynamics in two-state quantum dot lasers. The device under investigation is a 3-stack, 2 mm long laser, whose spectrally-resolved light-current characteristics involve ground-state (GS) emission at 1.28 /spl mu/m and excited-state (ES) emission at 1.2 /spl mu/m. Results show good agreement between theory and experiment, which confirms the authors' understanding of the coupled GS-ES dynamics.

Wide-spectrum, high-power quantum dot superluminescent diodes emitting at 1.3 /spl mu/m are demonstrated. A new reproducible way of broadening the gain spectrum is proposed leading to 120 nm spectral bandwidth. L-I, spectra and degrees of coherence are presented.

Summary form only given. Among the most promising materials for 1300 nm emission applications are GaInNAs quantum wells (QWs) and InAs quantum dots (QDs). By directly comparing the radiative properties of identical structures comprising QDs and GaInNAs QWs, we evidence the fundamental differences between the two materials. From temperature-dependent photoluminescence (PL) experiments, we see a much stronger quenching of radiative efficiency for GaInNAs at room temperature (RT), which we attribute to a higher density of nonradiative defects related to N incorporation and low growth temperature. This is confirmed by the carrier lifetime values deduced from the time-resolved PL dynamics.

We compare several approaches to the fabrication of nanoscale quantum-dot LEDs for single-photon applications, including shadow-mask and oxide-confined structures. Strong carrier localization in the dots allows us to demonstrate efficient submicrometer-sized LEDs.

Summary form only given. Owing to their geometric advantage with respect to mass production, WDM VCSEL arrays have drawn attention as a low cost means of increasing data transmission rate for short haul communications. Recently, pie-shaped WDM VCSEL arrays were successfully fabricated by means of anodic etching followed by regrowth. In addition to this work, wavelength tuning of VCSEL emission has been demonstrated via postgrowth oxidation. In this paper, we present the results of applying postgrowth oxidation to the fabrication of mask-defined densely-packed WDM VCSEL arrays.

Summary form only given. Recent progress in wavelength tuning of InAs/InGaAs/GaAs self-assembled quantum dots (QDs) has shown that this system represents an adequate active material for 1.3 /spl mu/m lasers on gallium arsenide. Integration of 1.3 /spl mu/m QDs in a GaAs/AlGaAs vertical-cavity surface-emitting laser structure would allow the development of a low-cost laser module for 1.3 /spl mu/m fiber links. Embedding the QDs in a InGaAs quantum well (QW) has been proposed as an effective way to red-shift the emission wavelength to the 1.3 /spl mu/m region. In-plane lasers with low threshold current densities

We presents measurements of the intermixing-induced changes in second harmonic generation (SHG) efficiency of an asymmetric quantum well (AQW) superlattice waveguide after a patterned ion implantation. Determining the second order nonlinear optical susceptibility for SHG in intermixed AQWs provides useful information for WDM wavelength conversion, because the susceptibility for SHG is similar to the susceptibility for DFG when the signal and difference frequencies are almost equal, as is the case for WDM applications. Each AQW consists of a 2.7-nm GaAs well coupled to a 1.5-nm GaAs well through a 1.2-nm AlGaAs layer, and the coupled well pairs are separated by 16.0-nm AlGaAs barriers.

As a semiconductor with a centrosymmetric crystal structure, bulk GaAs is nonbirefringent and is therefore rarely used for nonlinear frequency conversion despite its attractive nonlinear coefficient. By building a multilayer system GaAs/oxidized AlAs (Alox), we have shown that high form birefringences can be obtained in the composite material. To obtain a birefringence sufficient for phase matching in frequency conversion, a high index contrast is required between the two materials in the multilayer stack, which can be obtained by the oxidation of AlAs. We show phase-matched frequency conversion processes using form birefringence in composite GaAs/Alox waveguides. We believe these experiments are the first experimental demonstration of Van der Ziel's proposal (1975) of using form birefringence for nonlinear phase matching.

Multiple-wavelength arrays of vertical-cavity lasers (VCLs) and detectors are important for wavelength-division-multiplexing systems. In-plane variation of the cavity resonant wavelength usually requires growth on patterned substrates or two successive growths and a complicated processing. It was recently observed that the lateral wet oxidation of an AlGaAs layer can result in partial vertical oxidation of an adjacent layer. We propose to use this combined lateral-vertical oxidation to change the optical thickness of a cavity after the epitaxial growth of both Bragg mirrors.

We demonstrate the first waveguide-coupled metal-cavity nanoLED in a III-V photonic membrane bonded to a silicon substrate, which operates at telecommunication wavelengths. The device works under electrical injection and was characterized through a grating coupler.