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The low throughput of atomic force microscopy (AFM) is the main drawback in its large-scale deployment in industrial metrology. A promising solution would be based on the parallelization of the scanning probe system, allowing acquisition of the image by an array of probes operating simultaneously. A key step for reaching this goal relies on the miniaturization and integration of the sensing mechanism. Here, we demonstrate AFM imaging employing an on-chip displacement sensor, based on a photonic crystal cavity, combined with an integrated photodetector and coupled to an on-chip waveguide. This fully-integrated sensor allows high-sensitivity and high-resolution in a very small footprint and its readout is compatible with current commercial AFM systems.

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.

We have developed a near-infrared spectral sensor chip capable of classifying different materials and quantifying their composition. The core device consists of an array of pixels having distinct spectral responses covering the 900-1700 nm wavelength region. Each pixel consists of a resonant-enhanced photodetector comprising an absorbing layer and a tuning element embedded in a vertical cavity. The chip is based on a III-V/Silicon hybrid technology and enables easy customization of the wavelength response and high responsivity. Its robustness, small dimensions and single-shot operation make this sensor suitable for portable spectroscopic applications in the agro-food sector.

In this talk we will present recent process on the integration of nano-opto-electro-mechanical sensors with photonic circuits and optical read-out, showing a route towards fully-integrated optical sensing.

We present an efficient and flexible method to realize micro- and nano-optical structures on the tip of optical fibers. We demonstrate this approach for a fiber-tip sensor consisting of a photonic crystal (PhC) structure in a semiconductor membrane on the cleaved facet of a telecom fiber. The PhC structure is fabricated on a wafer by lithography and etching and then transferred to the fiber facet by a simple mechanical pickup process through an opening in the substrate, without the need for adhesives or a micromanipulator. Due to its reliability, scalability, and the use of wafer-scale fabrication methods, this process increases the possibilities for fiber-tip applications at the industrial level. With the fabricated fiber tip sensors, we demonstrate sensing of the refractive index and temperature, with resonance wavelength shifts of 120 nm/RIU and 95 pm/K, respectively.

We present a novel method to fabricate fiber-tip sensors. Using high-throughput semiconductor fabrication methods combined with a simple fiber-attachment scheme, we can mass-produce the sensors, preserving their surface unaltered. We experimentally demonstrate the sensor performance.

Optical read-out of motion is widely used in sensing applications. Recent developments in micro- and nano-optomechanical systems have given rise to on-chip mechanical sensing platforms, potentially leading to compact and integrated optical motion sensors. However, these systems typically exploit narrow spectral resonances and therefore require tuneable lasers with narrow linewidth and low spectral noise, which makes the integration of the read-out extremely challenging. Here, we report a step towards the practical application of nanomechanical sensors, by presenting a sensor with ultrawide (∼80 nm) optical bandwidth. It is based on a nanomechanical, three-dimensional directional coupler with integrated dual-channel waveguide photodiodes, and displays small displacement imprecision of only 45 fm/Hz1/2 as well as large dynamic range (>30 nm). The broad optical bandwidth releases the need for a tuneable laser and the on-chip photocurrent read-out replaces the external detector, opening the way to fully-integrated nanomechanical sensors., On-chip mechanical sensing platforms require tuneable lasers with narrow linewidth and low spectral noise, making read-out challenging. Here, the authors report a nanomechanical sensor with 80nm bandwidth, displacement imprecision of 45 fm/Hz1/2 as well as a dynamic range greater than 30 nm with integrated photodetectors.

Photonic integration in a micrometer-thick indium phosphide (InP) membrane on silicon (IMOS) offers intrinsic and high-performance optoelectronic functions together with high-index-contrast nanophotonic circuitries. Recently demonstrated devices have shown competitive performances, including high side-mode-suppression ratio (SMSR) lasers, ultrafast photodiodes, and significant improvement in critical dimensions. Applications of the IMOS devices and circuits in optical wireless, quantum photonics, and optical cross-connects have proven their performances and high potential.

Spectrometry is widely used for the characterization of materials, tissues, and gases, and the need for size and cost scaling is driving the development of mini and microspectrometers. While nanophotonic devices provide narrowband filtering that can be used for spectrometry, their practical application has been hampered by the difficulty of integrating tuning and read-out structures. Here, a nano-opto-electro-mechanical system is presented where the three functionalities of transduction, actuation, and detection are integrated, resulting in a high-resolution spectrometer with a micrometer-scale footprint. The system consists of an electromechanically tunable double-membrane photonic crystal cavity with an integrated quantum dot photodiode. Using this structure, we demonstrate a resonance modulation spectroscopy technique that provides subpicometer wavelength resolution. We show its application in the measurement of narrow gas absorption lines and in the interrogation of fiber Bragg gratings. We also explore its operation as displacement-to-photocurrent transducer, demonstrating optomechanical displacement sensing with integrated photocurrent read-out., Fully integratable spectrometers have trade-offs between size and resolution. Here, the authors present a nano-opto-electro-mechanical system where the functionalities of transduction, actuation and detection are fully integrated, resulting in an ultra-compact high-resolution spectrometer with a micrometer-scale footprint.

Nanoscale light sources using metal cavities have been proposed to enable high integration density, efficient operation at low energy per bit and ultra-fast modulation, which would make them attractive for future low-power optical interconnects. For this application, such devices are required to be efficient, waveguide-coupled and integrated on a silicon substrate. We demonstrate a metal-cavity light-emitting diode coupled to a waveguide on silicon. The cavity consists of a metal-coated III–V semiconductor nanopillar which funnels a large fraction of spontaneous emission into the fundamental mode of an InP waveguide bonded to a silicon wafer showing full compatibility with membrane-on-Si photonic integration platforms. The device was characterized through a grating coupler and shows on-chip external quantum efficiency in the 10−4–10−2 range at tens of microamp current injection levels, which greatly exceeds the performance of any waveguide-coupled nanoscale light source integrated on silicon in this current range. Furthermore, direct modulation experiments reveal sub-nanosecond electro-optical response with the potential for multi gigabit per second modulation speeds., Despite much progress, nanoscale light sources suitable for photonic integration are lacking. Here, the authors present a metal-cavity nanopillar LED on a silicon substrate working at telecommunications wavelengths, which demonstrates compatibility with membrane-on-Si photonic integration platforms.

We developed a high-throughput fabrication method of releasable photonic structures for lab-on-fiber technology. Fiber mounting is achieved without additional ma- chining and preserving the device surface. Our concept is demonstrated with sensing ex- periments.

Nanoscale light sources are being intensively investigated for their potential to enable low-energy, high-density optical communication and sensing systems. Both nano-light-emitting diodes (nanoLEDs) and nanolasers have been considered, based on advanced nanophotonic concepts such as photonic crystals and plasmonic structures, with dimensions well into the sub-micrometer domain. With decreasing dimensions, light-matter interaction becomes stronger, potentially leading to efficient and ultrafast radiative emission, both in the spontaneous and stimulated regime. These features have created wide expectations for the practical prospects of such nanoscale light sources, in particular for optical interconnects. In this article we examine the limits to the downscaling of LEDs and lasers, and ask ourselves which type of source is most suited to ultralow-power optical communications. Based on simple physical considerations on the scaling of spontaneous and stimulated emission rates for semiconductor active regions at room temperature, we analyze the speed and energy limits for nanoLEDs and nanolasers as a function of their size. The role of spontaneous emission enhancement (Purcell effect) in practical nanophotonic sources is also revisited. The main conclusion is that nanoLEDs reach a fundamental energy/speed limit for data rates exceeding a few Gb/s, whereas nanolasers with active dimensions in the range of few 100s nm may enable direct modulation rates larger than 40 Gb/s at power levels adequate for short-distance and low-energy optical interconnects., 13 pages, 8 figures

In this paper, an optical switch based on a microelectromechanical phase modulator is presented. Phase tuning is achieved by tuning the vertical gap between two vertically coupled waveguides through the application of a reverse bias on a p-i-n junction. An effective refractive index tuning Δneff of 0.03 and a phase shift of more than 3π rad at telecom wavelengths are measured with an on-chip Mach–Zehnder interferometer (MZI), with a phase-tuning length of only 140 μm. With a bias voltage of 5.1 V, a half-wave-voltage-length product (Vπ L) of 5.6 × 10−3 V·cm is achieved. Furthermore, optical crossbar switching in a MZI is demonstrated with a 15 dB extinction ratio using an actuation voltage of only 4.2 V. Our work provides a solution to on-chip, low-voltage phase modulation and optical switching. The switch is fabricated on an indium-phosphide membrane on a silicon substrate, which enables the integration with active components (e.g., amplifiers, lasers, and detectors) on a single chip.In this paper, an optical switch based on a microelectromechanical phase modulator is presented. Phase tuning is achieved by tuning the vertical gap between two vertically coupled waveguides through the application of a reverse bias on a p-i-n junction. An effective refractive index tuning Δneff of 0.03 and a phase shift of more than 3π rad at telecom wavelengths are measured with an on-chip Mach–Zehnder interferometer (MZI), with a phase-tuning length of only 140 μm. With a bias voltage of 5.1 V, a half-wave-voltage-length product (Vπ L) of 5.6 × 10−3 V·cm is achieved. Furthermore, optical crossbar switching in a MZI is demonstrated with a 15 dB extinction ratio using an actuation voltage of only 4.2 V. Our work provides a solution to on-chip, low-voltage phase modulation and optical switching. The switch is fabricated on an indium-phosphide membrane on a silicon substrate, which enables the integration with active components (e.g., amplifiers, lasers, and detectors) on a single chip.

A nano-opto-electro-mechanical transducer for displacement sensing is presented. It consists of a double-membrane photonic crystal cavity integrated with electro-optical read-out and on-chip light-delivery. The operation is demonstrated by atomic force microscope actuation and photocurrent sensing.

Quantum photonic integrated circuits (QPICs) on a GaAs platform allow the generation, manipulation, routing, and detection of non-classical states of light, which could pave the way for quantum information processing based on photons. In this article, the prototype of a multi-functional QPIC is presented together with our recent achievements in terms of nanofabrication and integration of each component of the circuit. Photons are generated by excited InAs quantum dots (QDs) and routed through ridge waveguides towards photonic crystal cavities acting as filters. The filters with a transmission of 20% and free spectral range ≥66 nm are able to select a single excitonic line out of the complex emission spectra of the QDs. The QD luminescence can be measured by on-chip superconducting single photon detectors made of niobium nitride (NbN) nanowires patterned on top of a suspended nanobeam, reaching a device quantum efficiency up to 28%. Moreover, two electrically independent detectors are integrated on top of the same nanobeam, resulting in a very compact autocorrelator for on-chip g(2)(τ) measurements.

The recent progress in integrated quantum optics has set the stage for the development of an integrated platform for quantum information processing with photons, with potential applications in quantum simulation. Among the different material platforms being investigated, direct-bandgap semiconductors and particularly gallium arsenide (GaAs) offer the widest range of functionalities, including single- and entangled-photon generation by radiative recombination, low-loss routing, electro-optic modulation and single-photon detection. This paper reviews the recent progress in the development of the key building blocks for GaAs quantum photonics and the perspectives for their full integration in a fully-functional and densely integrated quantum photonic circuit.

In this review, we report on the design, fabrication, and characterization of photonic crystal arrays, made of two and three coupled nanocavities. The properties of the cavity modes depend directly on the shape of the nanocavities and on their geometrical arrangement. A non-negligible role is also played by the possible disorder because of the fabrication processes. The experimental results on the spatial distribution of the cavity modes and their physical characteristics, like polarization and parity, are described and compared with the numerical simulations. Moreover, an innovative approach to deterministically couple the single emitters to the cavity modes is described. The possibility to image the mode spatial distribution, in single and coupled nanocavities, combined with the control of the emitter spatial position allows for a deterministic approach for the study of cavity quantum electrodynamics phenomena and for the development of new photonic-based applications., M.F. and A.P. acknowledge support by Sapienza Università di Roma under the “Ricerche Ateneo” Grants 2016 and 2017. F.B., M.F. and G.P. also acknowledge support and funding from the Italian Ministry for Education, University and Research within the Futuro in Ricerca (FIRB) program (project DeLIGHTeD, Prot. RBFR12RS1W). The work of F.B. was partially supported by Fondazione Ente Cassa di Risparmio di Firenze within the project PERBACCO (no. 2016.1084). A.P and M.F. have also received funding from the LazioInnova project “SINFONIA”, (Prot. n. 85-2017-15200)., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

Miniaturization of displacement sensors for nanoscale metrology is a key requirement in many applications such as accelerometry, mass sensing, and atomic force microscopy. While optics provides high resolution and bandwidth, integration of sensor readout is required to achieve low-cost, compact, and parallelizable devices. Here, we present a novel integrated opto-electro-mechanical device for displacement sensing that has sub-nanometer resolution. The proposed sensor is a micron-sized double-membrane photonic crystal cavity with integrated electro-optical readout, directly addressed via an on-chip waveguide. This sensor displays a noise floor down to 7 fm/Hz and is suitable for the realization of integrated arrays.

We experimentally demonstrate the control over the emission of quantum dots embedded in photonic molecules via mode field modulation. By locally changing the cavity frequencies we control, and even suppress, spontaneous emission.

Quantum dots (QDs) interacting with confined light fields in photonic crystal cavities represent a scalable light source for the generation of single photons and laser radiation in the solid-state platform. The complete control of light-matter interaction in these sources is needed to fully exploit their potential, but it has been challenging due to the small length scales involved. In this work, we experimentally demonstrate the control of the radiative interaction between InAs QDs and one mode of three coupled nanocavities. By non-locally moulding the mode field experienced by the QDs inside one of the cavities, we are able to deterministically tune, and even inhibit, the spontaneous emission into the mode. The presented method will enable the real-time switching of Rabi oscillations, the shaping of the temporal waveform of single photons, and the implementation of unexplored nanolaser modulation schemes.

Actively controlling the properties of localized optical modes is crucial for cavity quantum electrodynamics experiments. While several methods to tune the optical frequency have been demonstrated, the possibility of controlling the shape of the modes has scarcely been investigated. Yet an active manipulation of the mode pattern would allow direct control of the mode volume and the quality factor and therefore of the radiative processes. In this work, we propose and demonstrate a nano-optoelectromechanical device in which a mechanical displacement affects the spatial pattern of the electromagnetic field. The device is based on a double-membrane photonic crystal waveguide which, upon bending, creates a spatial modulation of the effective refractive index, resulting in an effective potential well or antiwell for the optical modes. The change in the field pattern drastically affects the optical losses: large modulations of the quality factors and dissipative coupling rates larger than 1 GHz/nm are predicted by calculations and confirmed by experiments. This concept opens new avenues in solid-state cavity quantum electrodynamics in which the field, instead of the frequency, is coupled to the mechanical motion.

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.

We report a systematic study of the In-assisted deoxidation (IAD) of epitaxial GaAs(100) substrates. Optimized IAD conditions resulting in a pit-free and smooth GaAs surface are found. Photoluminescence lines from single quantum dots (QDs) with linewidths in the range of 250–400 µeV are observed from low-density InAs QDs grown at a distance of 10 nm from a GaAs surface deoxidized under an optimized condition. Our study shows that IAD is very promising for application in the growth of nanostructures on patterned GaAs substrates.

In recent years, photon-number-resolving (PNR) detectors have attracted great interest, mainly because they can play a key role in diverse application fields. A PNR detector with a large dynamic range would represent an ideal photon detector, bringing the linear response of conventional analogue detectors down to the single-photon level. Several technologies, such as InGaAs single photon avalanche detectors (SPADs), arrays of silicon photomultipliers, InGaAs SPADs with self-differencing circuits and transition edge sensors have shown photon number resolving capability. Superconducting nanowires provide free-running single-photon sensitivity from visible to mid-infrared frequencies, low dark counts, excellent timing resolution (

Due to their deterministic nature and efficiency, devices based on quantum dots (QD) are currently replacing traditional single-photon sources in the most complex quantum optics experiments, such as boson sampling protocols. Embedding these emitters into photonic crystal (PhCs) cavities enables the creation of an array of Purcell-enhanced single photons required to build quantum photonic integrated circuits. So far scaling of the number of these cavity-emitters nodes on a single chip has been hampered by practical problems such as the lack of post-fabrication methods to control their relative detuning and the complexity involved with their optical excitation. Here, we present a tuneable single-photon source combining electrical injection and nano-opto-electromechanical cavity tuning. The device consists of a double-membrane electromechanically tuneable PhC structure. A vertical p-i-n junction, hosted in the top membrane, is exploited to inject current in the QD layer and demonstrate a tunable nano LED whose cavity wavelength can be reversibly varied over 15 nanometers by electromechanically varying the distance between membranes. Besides, electroluminescence from single QD lines coupled to PhC cavities is reported for the first time. The measurement of the second-order autocorrelation function from a cavity-enhanced line proves the anti-bunched character of the emitted light. Since electrical injection does not produce stray pump photons, it makes the integration with superconducting single-photon detectors much more feasible. The large-scale integration of such tuneable single-photon sources, passive optics and waveguide detectors may enable the implementation of fully-integrated boson sampling circuits able to manipulate tens of photons.

Disordered photonic materials can diffuse and localize light through random multiple scattering, offering opportunities to study mesoscopic phenomena, control light-matter interactions, and provide new strategies for photonic applications. Light transport in such media is governed by photonic modes characterized by resonances with finite spectral width and spatial extent. Considerable steps have been made recently towards control over the transport using wavefront shaping techniques. The selective engineering of individual modes, however, has been addressed only theoretically. Here, we experimentally demonstrate the possibility to engineer the confinement and the mutual interaction of modes in a two-dimensional disordered photonic structure. The strong light confinement is achieved at the fabrication stage by an optimization of the structure, and an accurate and local tuning of the mode resonance frequencies is achieved via post-fabrication processes. To show the versatility of our technique, we selectively control the detuning between overlapping localized modes and observe both frequency crossing and anti-crossing behaviours, thereby paving the way for the creation of open transmission channels in strongly scattering media.

Summary form only given. Pure and deterministic single-photon sources, obtained by coupling a semiconductor quantum dot (QD) to a photonic crystal (PhC) cavity, constitute a key component for quantum photonic integrated circuits (QPICs) [1]. These sources are commonly excited by a laser pump, which involves some practical limitations in scaling the number of integrated cavity-emitter nodes and is hardly compatible with on-chip single-photon detectors. Here, we present the first demonstration of electrical injection of single dot lines coupled to photonic crystal modes. The latter can be electrically re-configured to bring multiple cavity-emitters into energy resonance.

A single quantum dot deterministically coupled to a photonic crystal environment constitutes an indispensable elementary unit to both generate and manipulate single-photons in next-generation quantum photonic circuits. To date, the scaling of the number of these quantum nodes on a fully integrated chip has been prevented by the use of optical pumping strategies that require a bulky off-chip laser along with the lack of methods to control the energies of nano-cavities and emitters. Here, we concurrently overcome these limitations by demonstrating electrical injection of single excitonic lines within a nano-electro-mechanically tuneable photonic crystal cavity. When an electrically driven dot line is brought into resonance with a photonic crystal mode, its emission rate is enhanced. Anti-bunching experiments reveal the quantum nature of these on-demand sources emitting in the telecom range. These results represent an important step forward in the realization of integrated quantum optics experiments featuring multiple electrically triggered Purcell-enhanced single-photon sources embedded in a reconfigurable semiconductor architecture.

The III-V semiconductor InGaAs is a key material for photonics because it provides optical emission and absorption in the 1.55 μm telecommunication wavelength window. However, InGaAs suffers from pronounced nonradiative effects associated with its surface states, which affect the performance of nanophotonic devices for optical interconnects, namely nanolasers and nanodetectors. This work reports the strong suppression of surface recombination of undoped InGaAs/InP nanostructured semiconductor pillars using a combination of ammonium sulfide, (NH4)2S, chemical treatment and silicon oxide, SiOx, coating. An 80-fold enhancement in the photoluminescence (PL) intensity of submicrometer pillars at a wavelength of 1550 nm is observed as compared with the unpassivated nanopillars. The PL decay time of ∼0.3 μm wide square nanopillars is dramatically increased from ∼100 ps to ∼25 ns after sulfur treatment and SiOx coating. The extremely long lifetimes reported here, to our knowledge the highest reported to date for undoped InGaAs nanostructures, are associated with a record-low surface recombination velocity of ∼260 cm/s. We also conclusively show that the SiOx capping layer plays an active role in the passivation. These results are crucial for the future development of high-performance nanoscale optoelectronic devices for applications in energy-efficient data optical links, single-photon sensing, and photovoltaics.

Summary form only given. In this work, we report a remarkable suppression of the surface recombination rates in passivated III-V undoped InGaAs nanopillars on InP (inset of Fig. 1a). The surface passivation comprises ammonium sulfide, (NH4)2S, chemical treatment followed by encapsulation with a 50 nm layer of SiOx by plasma-enhanced chemical vapor deposition performed at 300°C. Before passivation, fabricated nanopillars with -300 nm lateral width, d, show a very poor photoluminescence (PL) emission (blue curve in Fig. 1a). The corresponding carrier dynamics, measured by time-correlated single-photon counting, Fig 1b, reveal an extremely short lifetime of ~130 ps, related to the well-known strong surface recombination velocity at InGaAs surfaces [3]. After the sulfur treatment followed by SiOx, we observe a substantial increase by almost two orders of magnitude of the PL intensity (red curve in Fig. 1a), while the carrier lifetime increases by more than two orders of magnitude to a value ~23 ns, red curve in Fig 1b. The estimated surface recombination velocity, S, decreases from about 2×104 cm/s in the untreated nanopillars down to around 260 cm/s (inset of Fig. 1b). To our knowledge, this is a record low value in undoped InGaAs semiconductors. Most importantly, our passivation studies reveal that the SiOx capping layer not only protects the pillars' sidewalls against oxidation, as reported in [5], but actively takes part in the passivation process, a result never previously reported.

We propose and theoretically investigate a new type of atom-phonon interaction in an optomechanical system. The interaction strength is controlled by the intensity of the intra-cavity optical field. We discuss relevant designs and possible applications.

We employed the contact forces induced by a near-field tip to tune and probe the optical resonances of a mechanically compliant photonic crystal molecule. Here, the pressure induced by the near-field tip is exploited to control the spectral proprieties of the coupled cavities in an ultrawide spectral range, demonstrating a reversible mode shift of $37.5\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$. Besides, by monitoring the coupling strength variation due to the vertical nanodeformation of the dielectric structure, distinct tip-sample interaction regimes have been unambiguously reconstructed with a nano-Newton sensitivity. These results demonstrate an optical method for mapping mechanical forces at the nanoscale with a lateral spatial resolution below 100 nm.

In this work we present the fabrication and the electro-optical characterization of a 24-pixel photon-number-resolving-detector, based on superconducting nanowires in a series configuration. In this configuration, the electrical responses of each firing pixel sum up into a single readout pulse whose height is proportional to the detected photon number. This device can resolve up to twenty-five distinct output levels corresponding to the detection of n = 0 - 24 photons. Due to its large dynamic range, high sensitivity, high speed and wide wavelength range, this device has potential for linear detection in the few tens of photons range.

Nanophotonic structures with narrow optical resonances, such as high-quality factor photonic crystal cavities, in principle enable spectral sensing with high resolution. This can also result in high-sensitivity displacement and/or acceleration sensing if a part of the cavity is compliant. However, the control of the resonance and its optical read-out are complex and usually not integrated with the sensing part. In this talk we will introduce a novel nano-opto-electromechanical system (NOEMS), where actuation, sensing and read-out are integrated in the same device. It consists of a double-membrane photonic crystal cavity, where the resonant wavelength is tuned by electrostatically controlling the separation between the membranes. The output current signal provides direct information about either the wavelength of the incident light or the cavity resonance. This nanophotonic sensing system can be employed to measure the spectrum of incident light, to determine the wavelength of a laser line with pm-range resolution, or equivalently to measure tiny displacements.

We investigate the transition from the photon-counting to the linear operation mode in a large-dynamic range photon-number-resolvingdetector (PNRD). A 24-pixel photon-number-resolving-detector, based on superconducting nanowires in a series configuration, has been fabricated and characterized. The voltage pulses, generated by the pixels, are summed up into a single readout pulse whose height is proportional to the detected photon number. The device can resolve up to twenty-five distinct output levels corresponding to the detection of n = 0-24 photons. Due to its large dynamic range, high sensitivity, high speed and wide wavelength range, this device has potential for linear detection in the few tens of photons range.We show its application in the detection of analog optical signals at frequencies up to few hundred MHz and investigate the limits related to the finite number of pixels and to the pixel's dead time.

A photonic crystal three missing holes nanocavity, having only a few modes, is coupled to a 60 missing holes long multimode cavity, both fabricated in the same InGaAsP membrane. The coupling was studied in detail by the photothermal tuning of the small cavity over about three free spectral ranges of the large cavity. Strong coupling effects, involving at least three large cavity modes simultaneously, were observed from level anticrossing data. The observations are excellently reproduced by a model of coupled Fabry Perot resonators.

We propose a novel photon number resolving detector structure with large dynamic range. It consists of the series connection of N superconducting nanowires, each connected in parallel to an integrated resistor. Photon absorption in a wire switches its current to the parallel resistor producing a voltage pulse and the sum of these voltages is measured at the output. The combination of this structure and a high input impedance preamplifier result in linear, high fidelity, and fast photon detection in the range from one to several tens of photons.

The insertion of a metal-coated tip on the surface of a photonic crystal microcavity is used for simultaneous near field imaging of electric and magnetic fields in photonic crystal nanocavities, via the radiative emission of embedded semiconductor quantum dots (QD). The photoluminescence intensity map directly gives the electric field distribution, to which the electric dipole of the QD is coupled. The magnetic field generates, via Faraday's law, a circular current in the apex of the metallized probe that can be schematized as a ring. The resulting magnetic perturbation of the photonic modes induces a blue shift, which can be used to map the magnetic field, within a single near-field scan. (C) 2011 Elsevier B.V. All rights reserved.

A method to avoid the stiction failure in nano-electro-opto-mechanical systems has been demonstrated by coating the system with an anti-stiction layer of Al2O3 grown by atomic layer deposition techniques. The device based on a double-membrane photonic crystal cavity can be reversibly operated from the pull-in back to its release status. This enables to electrically switch the wavelength of a mode over ~50 nm with a potential modulation frequency above 2 MHz. These results pave the way to reliable nano-mechanical sensors and optical switches.

The progress in nanofabrication has made possible the realization of optic nanodevices able to handle single photons and to exploit the quantum nature of single-photon states. In particular, quantum cryptography (or more precisely quantum key distribution, QKD) allows unconditionally secure exchange of cryptographic keys by the transmission of optical pulses each containing no more than one photon. Additionally, the coherent control of excitonic and photonic qubits is a major step forward in the field of solid-state cavity quantum electrodynamics, with potential applications in quantum computing. Here, we describe devices for realization of single photon generation and detection based on high resolution technologies and their physical properties. Particular attention will be devoted to the description of single-quantum dot sources based on photonic crystal microcavites optically and electrically driven: the electrically driven devices is an important result towards the realization of single photon source “on demand”. A new class of single photon detectors, based on superconducting nanowires, the superconducting single-photon detectors (SSPDs) are also introduced: the fabrication techniques and the design proposed to obtain large area coverage and photon number-resolving capability are described.

Using a pump-probe differential transmission experiment in heterodyne detection, we measured the refractive index dynamics at the ground-state excitonic transition in electrically pumped InAs/GaAs quantum-dot amplifiers emitting near 1.3 µm at room temperature. We compare three samples differing only in the level of p-doping, and interpret the measured index changes taking into account the gain dynamics in these devices. We find that in absorption, the excess hole density due to p-doping accelerates the recovery and reduces the refractive index change, since filling of the hole states by p-doping shifts the induced changes in the hole population toward high energy states. Conversely, in gain, the reduced electron reservoir in the excited states in p-doped devices results in slower gain recovery dynamics and in larger refractive index changes compared to undoped devices operating at the same modal gain. The linewidth enhancement factor inferred from these measurements shows that p-doping is effective in reducing this parameter mainly due to the larger differential gain in p-doped devices in the gain regime. © 2009 IEEE.

Optical-to-electrical conversion, which is the basis of the operation of optical detectors, can be linear or nonlinear. When high sensitivities are needed, single-photon detectors are used, which operate in a strongly nonlinear mode, their response being independent of the number of detected photons. However, photon-number-resolving detectors are needed, particularly in quantum optics, where n-photon states are routinely produced. In quantum communication and quantum information processing, the photon-numberre-solving functionality is key to many protocols, such as the implementation of quantum repeaters(1) and linear- optics quantum computing(2). A linear detector with single-photon sensitivity can also be used for measuring a temporal waveform at extremely low light levels, such as in long-distance optical communications, fluorescence spectroscopy and optical time-domain reflectometry. We demonstrate here a photon-number-resolving detector based on parallel superconducting nanowires and capable of counting up to four photons at telecommunication wavelengths, with an ultralow dark count rate and high counting frequency.

Electrical and optical characterization has been performed on several superconducting single photon detectors (SSPDs) consisting of meanders made of ultrathin NbN films. The NbN films, with thickness ranging from 150 nm to 3 nm, were deposited by dc magnetron sputtering on MgO substrates kept at temperature T = 400C. This deposition process carried out at low temperature opens the way of monolithic integration with other photonic devices. The superconducting properties of NbN films and the critical design parameters that affect the quantum efficiency (QE) have been optimized. In particular, by measuring the switching current distribution of each stripe of the meander the process uniformity has been studied. Optical measurements on the fabricated SSPDs showed a QE approximate to 20% at 4.2 K for photons with a wavelength of 1300 nm.

We unveil the role of bound-to-continuum photoexcitation of carriers as a relevant process that affects the performance of quantum dot (OD) lasers. We present the response of an InAs/InGaAs QD laser to a sub-band gap pump, showing an unexpected depletion of the emitted photons. We relate this observation with carrier photoexcitation through additional transmission and photocurrent measurements. We provide a theoretical support to the experimental data and highlight the important role of this process in the laser characteristics.

We demonstrate high-performance nanowire superconducting single photon detectors (SSPDs) on ultrathin NbN films grown at a temperature compatible with monolithic integration. NbN films ranging from 150nm to 3nm in thickness were deposited by dc magnetron sputtering on MgO substrates at 400C. The superconducting properties of NbN films were optimized studying the effects of deposition parameters on film properties. SSPDs were fabricated on high quality NbN films of different thickness (7 to 3nm) deposited under optimal conditions. Electrical and optical characterizations were performed on the SSPDs. The highest QE value measured at 4.2K is 20% at 1300nm.

Integrated quantum photonics offers three principal advantages over bulk optics—low loss, simplicity and scalability. Quantum photonic integrated circuits show promise for on-chip generation, manipulation and detection of tens of single photons for quantum information processing. For quantum photonic integration, gallium arsenide is one of the most promising material platforms as full integration of all active and passive circuit elements can be obtained.

Superconducting nanowire single photon detectors (SNSPDs) are the detectors of choice in quantum optics applications due to their leading performances. To exploit their performances, great care must be devoted to efficiently couple light from a single-mode fiber to their small area, ∼10 μm in size, at cryogenic temperature (∼3K). In addition, to further improve the SNSPDs functionality, implementing the photon number resolving capability, arrays of spatially multiplexed SNSPDs, must be realized. We will discuss our results obtained for these two approaches.

We investigated the passivation of III-V semiconductor nanostructures using wet-chemical ammonium sulfide treatment and SiOx encapsulation. We achieved an ultra-low surface recombination velocity value of ~530 cm/s enabling the future development of high-performance room-temperature nanolasers.

We use quantum detector tomography to investigate the detection mechanism in WSi nanowire superconducting single photon detectors (SSPDs). To this purpose, we fabricated a 250nm wide and 250nm long WSi nanowire and measured its response to impinging photons with wavelengths ranging from $\lambda$ = 900 nm to $\lambda$ = 1650 nm. Tomographic measurements show that the detector response depends on the total excitation energy only. Moreover, for energies Et > 0.8eV the current energy relation is linear, similar to what was observed in NbN nanowires, whereas the current-energy relation deviates from linear behaviour for total energies below 0.8eV.

Using a differential transmission pump-probe experiment in heterodyne detection, the ultrafast gain and refractive-index dynamics of the ground-state transition in InAs/GaAs quantum- dot amplifiers emitting near 1.3 mum at working condition, that is at room temperature and under electrical injection were measured. An ultrafast gain recovery on a subpicosecond time scale is observed at high electrical injection indicating fast carrier relaxation into the dot ground state, which is appealing for high-speed applications with these devices. Comparing p-doped and undoped devices of otherwise identical structure and operating at the same gain, a faster absorption recovery but a slower gain dynamics in p-doped amplifiers was observed. This finding should help in elucidating the role of p-doping in the design of QD-based devices with high-speed performances.