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Spectral sensing is an emerging field driven by the need for fast and non-invasive methods for the chemical analysis of materials in agri-food, healthcare, and industrial applications. We demonstrate a near-infrared spectral sensor, based on a scalable fabrication process and combining high responsivity, narrow linewidth, and low noise. The sensor consists of 16 resonant-cavity-enhanced photodetectors, each showing a unique spectral response consisting of narrow peaks. The spectral sensor thereby covers the wavelength range between 890 and 1650 nm, where organic materials show relevant spectral features from first and second overtones. For the fabrication of the detector arrays, we propose a simple and scalable fabrication approach that yields largely improved device characteristics with respect to the grey-scale electron-beam lithography process reported earlier. Through a series of five optical lithography steps, tuning layers of silicon nitride are deposited stepwise to obtain 16 different thicknesses and reduced surface roughness. With this novel fabrication approach, the obtained photodetectors achieve an average peak linewidth of 55 nm, a maximum peak responsivity of 0.3 A/W, and high suppression of the non-resonant background. We also demonstrate the impact of these improvements on the sensing performance for two relevant problems through an experiment and a set of simulations. With lateral dimensions of ∼1.4 × 1.4 mm2, the proposed photodetector array can be the key to robust, portable, and low-cost sensing instrumentation for on-site material analysis in various application fields.

Illicit-drug production, trafficking and seizures are on an all-time high. This consequently raises pressure on investigative authorities to provide rapid forensic results to assist law enforcement and legal processes in drug-related cases. Ideally, every police officer is equipped with a detector to reliably perform drug testing directly at the incident scene. Such a detector should preferably be small, portable, inexpensive and shock-resistant but should also provide sufficient selectivity to prevent erroneous identifications. This study explores the concept of on-site drugs-of-abuse detection using a 1.8 × 2.2 mm2 multipixel near-infrared (NIR) spectral sensor that potentially can be integrated into a smartphone. This integrated sensor, based on an InGaAs-on-silicon technology, exploits an array of resonant-cavity enhanced photodetectors without any moving parts. A 100% correct classification of 11 common illicit drugs, pharmaceuticals and adulterants was achieved by chemometric modelling of the response of 15 wavelength-specific pixels. The performance on actual forensic casework was investigated on 246 cocaine-suspected powders and 39 MDMA-suspected ecstasy tablets yielding an over 90% correct classification in both cases. These findings show that presumptive drug testing by miniaturized spectral sensors is a promising development ultimately paving the way for a fully integrated drug-sensor in mobile communication devices used by law enforcement.

The control of defect states is becoming a powerful approach to tune two-dimensional materials. Black phosphorus (BP) is a layered material that offers opportunities in infrared optoelectronics. Its band gap depends strongly on the number of layers and covers wavelengths from 720 to 4000 nm from monolayer to bulk, but only in discrete steps and suffering from poor photostability. Here, we demonstrate tunable and stable infrared emission from defect states in few-layer BP. First, we demonstrate a continuous blue shift of the main photoluminescence peak under laser exposure in air due to the creation of crystal defects during photo-oxidation. The tunable emission spectrum continuously bridges the discrete near-infrared energies of few-layer BP for a decreasing number of layers. Second, using plasma-enhanced encapsulation, we report the creation and protection of defects with peak emission energy between bilayer and trilayer BP. The emission is photostable and has an efficiency comparable to that of pristine layers while retaining the strong polarization anisotropy characteristic of BP. Our results put forward defect engineering in few-layer BP as a flexible strategy for stable and widely tunable infrared sources and detectors in integrated spectrometers and hyperspectral sensors.

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.

We propose a force sensor, with optical detection, based on a reconfigurable multicavity photonic molecule distributed over two parallel photonic crystal membranes. The system spectral behaviour is described with an analytical model based on coupled mode theory and validated by finite difference time domain simulations. The deformation of the upper photonic crystal membrane, due to a localized vertical force, is monitored by the relative spectral positions of the photonic molecule resonances. The proposed system can act both as force sensor, with pico-newton sensitivity, able to identify the position where the force is applied, and as torque sensor able to measure the torsion of the membrane along two perpendicular directions.

For decades, near-infrared (NIR) spectroscopy has been a valuable tool for material analysis in a variety of applications, ranging from industrial process monitoring to quality assessment. Traditional spectrometers are typically bulky, fragile and expensive, which makes them unsuitable for portable and in-field use. Thus, there is a growing interest for miniaturized, robust and low-cost NIR sensors. In this study, we demonstrate a handheld NIR spectral sensor module, based on a fully-integrated multipixel detector array, sensitive in the 850–1700 nm wavelength range. Differently from a spectrometer, the spectral sensor measures a limited number of NIR spectral bands. The capabilities of the spectral sensor module were evaluated alongside a commercially available portable spectrometer for two application cases: to quantify the moisture content in rice grains and to classify plastic types. Both devices achieved the two sensing tasks with comparable performance. Moisture quantification was achieved with a root mean square error (RMSE) prediction of 1.4% and 1.1% by the spectral sensor and spectrometer, respectively. Classification of the plastic type was achieved with a prediction accuracy on unknown samples of 100% and 96.4% by the spectral sensor and spectrometer, respectively. The results from this study are promising and demonstrate the potential for the compact NIR modules to be used in a variety of NIR sensing applications.

We investigated metal-organic vapor phase epitaxy grown (InGa)(AsSb)/GaAs/GaP Stranski–Krastanov quantum dots (QDs) with potential applications in QD-Flash memories by cross-sectional scanning tunneling microscopy (X-STM) and atom probe tomography (APT). The combination of X-STM and APT is a very powerful approach to study semiconductor heterostructures with atomic resolution, which provides detailed structural and compositional information on the system. The rather small QDs are found to be of truncated pyramid shape with a very small top facet and occur in our sample with a very high density of ∼4 × 1011 cm−2. APT experiments revealed that the QDs are GaAs rich with smaller amounts of In and Sb. Finite element (FE) simulations are performed using structural data from X-STM to calculate the lattice constant and the outward relaxation of the cleaved surface. The composition of the QDs is estimated by combining the results from X-STM and the FE simulations, yielding ∼InxGa1 − xAs1 − ySby, where x = 0.25–0.30 and y = 0.10–0.15. Noticeably, the reported composition is in good agreement with the experimental results obtained by APT, previous optical, electrical, and theoretical analysis carried out on this material system. This confirms that the InGaSb and GaAs layers involved in the QD formation have strongly intermixed. A detailed analysis of the QD capping layer shows the segregation of Sb and In from the QD layer, where both APT and X-STM show that the Sb mainly resides outside the QDs proving that Sb has mainly acted as a surfactant during the dot formation. Our structural and compositional analysis provides a valuable insight into this novel QD system and a path for further growth optimization to improve the storage time of the QD-Flash memory devices.

The original version of this Article contained an error in the Discussion, which incorrectly read ‘In summary, we have demonstrated an integrated optomechanical displacement sensor featuring 30 fm·Hz−1/2 imprecision’. The correct version states ‘45’ in place of ‘30’. This has been corrected in both the PDF and HTML versions of the Article.

Cross-sectional scanning tunneling microscopy (X-STM) was employed to characterize the InAs submono-layer quantum dots (SMLQDs) grown on top of a Si-doped GaAs(001) substrate in the presence of (2×4) andc(4×4) surface reconstructions. Multiple layers were grown under different conditions to study their effectson the formation, morphology, and local composition of the SMLQDs. The morphological and compositionalvariations in the SMLQDs were observed by both filled and empty-state imaging. A detailed analysis of indiumsegregation in the SMLQD layers was described by fitting the local indium-concentration profile with a standardsegregation model. We observed a strong influence of the arsenic flux over the indium incorporation andformation of the SMLQDs. We investigated the well-width fluctuations of the InGaAs quantum well in which theSMLQDs were formed. The well-width fluctuations were small compared to the more pronounced compositionfluctuations in all the layers. The lateral compositional variations lead to the formation of indium-rich clusterswhich can act as quantum dots and yield charge-carrier confinement.

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.

Recent theories proposed a deep revision of the well-known expression for the Purcell factor, with counterintuitive effects, such as complex modal volumes and non-Lorentzian local density of states. We experimentally demonstrate these predictions in tailored coupled cavities on photonic crystal slabs with relatively low optical losses. Near-field hyperspectral imaging of quantum dot photoluminescence is proved to be a direct tool for measuring the line shape of the local density of states. The experimental results clearly evidence non-Lorentzian character, in perfect agreement with numerical and theoretical predictions. Spatial maps with deep subwavelength resolution of the real and imaginary parts of the complex mode volumes are presented. The generality of these results is confirmed by an additional set of far-field and time-resolved experiments in cavities with larger modal volume and higher quality factors.

Hydrogenated amorphous silicon (a‐Si:H) is known for exhibiting light‐induced metastable properties that are reversible upon annealing. While these are commonly associated with the well‐known deleterious Staebler–Wronski effect in the field of thin‐film silicon solar cells, the associated changes in optical properties have not been well studied. Emerging reconfigurable photonic devices and applications can benefit from metastable optical properties where two states of the material are reversibly accessible without the need for continuous stimulation. The study demonstrates a light‐induced 0.3% increase of the metastable refractive index of a‐Si:H that is reversed upon annealing over several cycles using a highly sensitive Fabry–Perot interferometric technique. Utilizing this technique, a metastable optical switch based on a micro‐ring resonator is demonstrated with reversible distinct switching states separated by 0.3 nm between the light‐soaked and annealed states, a switching extinction exceeding 20 dB and an unchanged Q‐factor, suggesting no excess discernible optical loss. Furthermore, metastable strain changes in a‐Si:H‐based freestanding membrane structures are linked to the observed metastable optical properties and present a possible route to stable photonic devices. Our proof‐of‐concept demonstration showcases a‐Si:H‐based reconfigurable photonics that support multiple purpose photonic integrated circuits, reconfigurable metamaterials, and advanced optomechanical devices.

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.

The optical behavior of coupled systems, in which the breaking of parity and time-reversal symmetry occurs, is drawing increasing attention to address the physics of the exceptional point singularity, i.e., when the real and imaginary parts of the normal-mode eigenfrequencies coincide. At this stage, fascinating phenomena are predicted, including electromagnetic-induced transparency and phase transitions. To experimentally observe the exceptional points, the near-field coupling to waveguide proposed so far was proved to work only in peculiar cases. Here, we extend the interference detection scheme, which lies at the heart of the Fano lineshape, by introducing generalized Fano lineshapes as a signature of the exceptional point occurrence in resonant-scattering experiments. We investigate photonic molecules and necklace states in disordered media by means of a near-field hyperspectral mapping. Generalized Fano profiles in material science could extend the characterization of composite nanoresonators, semiconductor nanostructures, and plasmonic and metamaterial devices., Fano lineshapes are found in many photonic systems where discrete and extended spectra interfere. Here, the authors extend this description and introduce generalized Fano lineshapes to describe the results from hyperspectral mapping around an exceptional point in a coupled-cavity system.

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.

In this paper, compact optical subassemblies are demonstrated based on a novel silicon interposer, which is designed and fabricated in a wafer scale process. The interposer includes the design of optical and electrical connections. A low-cost fabrication method, wet etching, is used to define light inputs and outputs as well as create the required recesses in the interposer to embed the chips into the silicon wafer at the same time. Impedance matched traces, for the high speed signals of the CMOS and opto-electronic ICs, are designed using advanced design system software and transferred onto the interposer by photolithography and electro-plating, which are accomplished on the deeply etched topology. The whole process flow of the silicon interposer patterning is designed and demonstrated, and the challenges are discussed. After the process, the optoelectronic dies and their complimentary CMOS parts are flipped and bonded on the interposer in close proximity, and a mechanical optical interface (MOI) is mounted for light coupling. Both transmitter and receiver subassemblies provide 12 parallel optical interconnections, and are scaled down to an area measuring 6 by 8 mm. Signal integrity testing is performed on a probe station for 10 Gb/s data signal delivering clear eye patterns for all channels (in both Rx and Tx subassemblies). The performance is further characterized using bit error rate (BER) testing. Both transmitter and receiver assemblies outperform a reference SFP+, with receiver sensitivity of-10 dBm at a BER lower than 10-12 after compensating for the MOI insertion loss. Finally, we also test the assemblies for crosstalk and demonstrate that the current design has a maximal additional penalty lower than 0.2 and 0.8 dB for transmitter and receiver, respectively.

We measure the maximal distance at which two absorbed photons can jointly trigger a detection event in NbN nanowire superconducting single photon detector microbridges by comparing the one-photon and two-photon efficiencies of bridges of different overall lengths, from 0 to 400 nm. We find a length of 23 ± 2 nm. This value is in good agreement with the size of the quasiparticle cloud at the time of the detection event.Nanowire superconducting single photon detectors (SSPDs)1 are a crucial technology for a variety of applications.2 These devices consist of a thin superconducting film which detects photons when biased to a significant fraction of its critical current. Although details of the microscopic mechanism are still in dispute,3 the present understanding of this process in Niobium Nitride (NbN) SSPDs is as follows:4–13 after the absorption of a photon, a cloud of quasiparticles is created, which is known as a hotspot. This cloud diffuses, spreading out over some area of the wire. This causes the redistribution of bias current, which unbinds a vortex from the edge of the wire, if the applied bias current is such that the current for vortex entry is exceeded. The transition of a vortex across the wire creates a normal-state region, which grows under the influence of Joule heating from the bias current, leading to a voltage pulse and a detection event.14

Optical localization in strongly disordered photonic media is an attractive topic for proposing novel cavity-like structures. Light interference can produce random modes confined within small volumes, whose spatial distribution in the near-field is predicted to show hot spots at the nanoscale. However, these near-field speckles have not yet been experimentally investigated due to the lack of a high spatial resolution imaging techniques. Here, we study a system where the disorder is induced by random drilling air holes in a GaAs suspended membrane with internal InAs quantum dots. We perform deep-subwavelength near-field experiments in the telecom window to directly image the spatial distribution of the electric field intensity of disordered-induced localized optical modes. We retrieve the near-field speckle patterns that extend over few micrometers and show several single speckles of the order of λ/10 size. The results are compared with the numerical calculations and with the recent findings in the literature of disordered media. Notably, the hot spots of random modes are found in proximity of the air holes of the disordered system., This work was supported by the FET project FP7 618025 CARTOON. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM), which is financially supported by the Netherlands Organisation for Scientific Research (NWO), and it is also supported by the Dutch Technology Foundation STW, applied science division of NWO, the Technology Program of the Ministry of Economic Affairs under Project No. 10380. F.B. acknowledges funding from the Italian Ministry for Education, University and Research within the Futuro in Ricerca (FIRB) program (project DeLIGHTeD, Protocollo RBFR12RS1W).

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.

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 ceramics-based 100 Gbps optical transceiver engine is demonstrated. A ceramics-based interposer is fabricated using the multilayer thick film (MLTF) and photo-imageable thick film (PITF) technologies, which allow for multilayer metallization and ultra-fine resolution. The packaging method requires several flip-chip bonding steps using industry standard solder reflow and ultrasonic bonding processes. The assembled 4-channel optical engine performs error-free at 25.78 Gbps. Bit error rates (BER) and eye diagrams for all channels for both transmitter and receiver side are measured. Further, a crosstalk below 0.4 dB from adjacent channels is measured.

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.

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.

Through a single optical interface, a $250\ \mu m$ pitch two-dimensional $2\times 8$ -channel optical transceiver is integrated on a lithographically patterned silicon interposer, offering 200 Gb/s data input and output duplex within an area of $6\ mm\times 6\ mm$ .

In this paper, based on a wet etched silicon interposer, we propose a 2.5D assembly of two dimensional optical transceivers for 400 Gbps parallel optical interconnections. In this opto-electronic packaging, two dimensional optical matrix is formed as 250 μm in both the x -and y-directions by exploiting commercial opto-electronic arrays, and a compact optical interface is used to couple the light channels with fiber ribbons. Each quadrant of the optical matrix is connected with its CMOS IC part via impedance matched co-planner wave guides. The shortest traces between optics and CMOS ICs can be 300 μm, benefiting from flip-chip technology. The process flow of silicon interposer fabrication is illustrated. With flip-chip bonding, 25 Gbps 2D 16-channel receiver is assembled on the silicon interposer, and the sub-module, including the optical interface, is scaled down to 4 mm by 6 mm. In addition, the performance of this assembled module is fully characterized. Uniform and clear eye patterns are captured for all of the channels. Receiver sensitivities are also tested for all channels at 25.78 Gbps, 2 31-1 PRBS, with the variation less than 1.5 dB at error free operation.

In this paper, 4 pairs of commercial 12-channel electronic and photonic dies have been assembled on a patterned wet etched silicon interposer for a terabit/s class optical interconnect. In the scheme, the optical dies are flip-chip bonded to form a {4} \times {12} optical matrix with 250- \mu \text{m} pitch in both the {x} - and {y} -directions. A single compact optical connector, which is designed based on the commercial PRIZM MT ferrule, is employed to enable a single and direct connection of four fiber ribbons to all 48 channels. The alignment tolerance of the suggested optical connector is tested, and the best case loss is 1.0 dB. The electrical interface, for the connection of CMOS ICs and vertical-cavity surface-emitting laser dies, is designed and patterned on the silicon interposer. The process and assembly are also detailed. In performance testing, clear eye patterns for all the 48 channels are captured at 15 Gb/s with a pseudorandom bit stream 2 31 - 1 patterns. The bit error rate curves of all the channels are recorded at 10 Gb/s and show a receiver sensitivity spread of less than 2.1 dB across all 48 channels at 10 -12 level. In addition, crosstalk effects are also characterized, showing a negligible power penalty of less than 0.2 dB. The fully assembled module can offer for the first time 0.72 Tb/s optical data output, within an area of 1.32 cm 2 by using low cost processes and commercially available dies.

In this paper, we demonstrate a low-cost, 48-channel, high-speed, flexible printed circuit (FPC)-based interconnect packaging concept for on-board optical modules. Due to the good high-speed performance and low cost, the FPC board is used as the base carrier for both transmitter and receiver modules. The on-board transmitter and receiver are based on a commercial 1-mm-pitch ISI HoLi pin grid array connector. The size of each module is only 31.5 × 31.5 mm and offers a state-of-art bandwidth density of 0.483 Gb/s/mm 2 by using a compact design. Investigation of RF signal propagation on the FPC is carried out for design validation at 10 Gb/s and, in order to further explore the potential of the suggested platform, differential pairs are simulated up to 30 GHz. The low-cost packaging approach requires only several flip-chip bonding steps using industry-standard solder reflow and ultrasonic bonding processes. An 8 × 12 -channel optical straight lens connector is used to couple the light from the optics into two 48-fiber multi-fiber push on connectors with 8 × 12 -channel MT ferrules. The fully assembled transmitter and receiver are tested at 10 Gb/s demonstrating error-free operation with sensitivities comparable with those of commercial devices. Bit error rates for all 96 channels as well as representative eye diagrams at 10 Gb/s are reported.

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.

Ultracompact optical submodules for parallel optical interconnects are demonstrated based on a three-level silicon interposer, which is fabricated through a low-cost wet etching process. Using three steps of wet etching of silicon, a multilevel cavity is formed for embedding and flip-chipping optical and electrical dies, and opening optical through-silicon vias. In order to reduce thermal coupling between CMOS and GaAs dies, a 50- $\mu \text{m}$ thermal isolation air gap is formed between dies as a part of the assembly concept, and thermal simulations and experiments are carried to validate its effectiveness. Based on this 3-D packaging concept, compact 4 mm $\times6$ mm, 10-Gb/s 12-channel transmitter and receiver submodules are fully assembled and tested. Clear and uniform eye patterns for both modules are captured at 10 and 15 Gb/s for every channel. Bit error rate (BER) testing is also performed. Both transmitter and receiver submodules show uniform BER curves, with receiver sensitivity spreading less than 1 dB at a BER lower than 10−12. Also, crosstalk for both modules is tested, yielding only a 0.1- and 0.8-dB additional penalty for transmitter and receiver, respectively.

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.

With the help of a quantum simulator and Bayesian inference it is possible to determine the unknown Hamiltonian of a quantum system. An experiment demonstrates this using a photonic quantum simulator and a solid-state system. The efficient characterization of quantum systems1,2,3, the verification of the operations of quantum devices4,5,6 and the validation of underpinning physical models7,8,9, are central challenges for quantum technologies10,11,12 and fundamental physics13,14. The computational cost of such studies could be improved by machine learning enhanced by quantum simulators15,16. Here we interface two different quantum systems through a classical channel—a silicon-photonics quantum simulator and an electron spin in a diamond nitrogen–vacancy centre—and use the former to learn the Hamiltonian of the latter via Bayesian inference. We learn the salient Hamiltonian parameter with an uncertainty of approximately 10−5. Furthermore, an observed saturation in the learning algorithm suggests deficiencies in the underlying Hamiltonian model, which we exploit to further improve the model. We implement an interactive version of the protocol and experimentally show its ability to characterize the operation of the quantum photonic device.

Random dielectrics defines a class of non-absorbing materials where the index of refraction is randomly arranged in space. Whenever the transport mean free path is sufficiently small, light can be confined in modes with very small volume. Random photonic modes have been investigated for their basic physical insights, such as Anderson localization, and recently several applications have been envisioned in the field of renewable energies, telecommunications, and quantum electrodynamics. An advantage for optoelectronics and quantum source integration offered by random systems is their high density of photonic modes, which span a large range of spectral resonances and spatial distributions, thus increasing the probability to match randomly distributed emitters. Conversely, the main disadvantage is the lack of deterministic engineering of one or more of the many random photonic modes achieved. This issue is solved by demonstrating the capability to electrically and mechanically control the random modes at telecom wavelengths in a 2D double membrane system. Very large and reversible mode tuning (up to 50 nm), both toward shorter or longer wavelength, is obtained for random modes with modal volumes of the order of few tens of (λ/n)3 .

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.

A superconducting thin film with uniform properties is the key to realize nanowire superconducting single-photon detectors (SSPDs) with high performance and high yield. To investigate the uniformity of NbN films, we introduce and characterize simple detectors consisting of short nanowires with length ranging from 100nm to 15{\mu}m. Our nanowires, contrary to meander SSPDs, allow probing the homogeneity of NbN at the nanoscale. Experimental results, endorsed by a microscopic model, show the strongly inhomogeneous nature of NbN films on the sub-100nm scale., Comment: 10 pages, 4 figures

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. The efficient characterization and validation of the underlying model of a quantum physical system is a central challenge in the development of quantum devices and for our understanding of foundational quantum physics. However, the impossibility to efficiently predict the behaviour of complex quantum models on classical machines makes this challenge to be intractable to classical approaches. Quantum Hamiltonian Learning (QHL) [1, 2] combines the capabilities of quantum information processing and classical machine learning to allow the efficient characterisation of the model of quantum systems. In QHL the behaviour of a quantum Hamiltonian model is efficiently predicted by a quantum simulator, and the predictions are contrasted with the data obtained from the quantum system to infer the system Hamiltonian via Bayesian methods.

We present the experimental demonstration of quantum Hamiltonian learning. Using an integrated silicon-photonics quantum simulator with the classical machine learning technique, we successfully learn the Hamiltonian dynamics of a diamond nitrogen-vacancy center's electron ground-state spin.

We demonstrate a novel method to measure Nth-order (N=1,2,3,4) interferometric autocorrelation with high sensitivity and temporal resolution. It is based on the combination of linear absorption and nonlinear detection in a superconducting nanodetector, providing much higher efficiency than methods based on all-optical nonlinearities. Its temporal resolution is only limited by the quasiparticle energy relaxation time, which is directly measured to be in the 20 ps range for the NbN films used in this work. We present a general model of interferometric autocorrelation with these nonlinear detectors and discuss the comparison with other approaches and possible improvements. © 2013 American Physical Society.

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.

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.