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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.

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.

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.

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.

III-V semiconductors such as InP are highly efficient light absorbers for photoelectrochemical (PEC) water splitting devices. Yet, their cathodic stability is limited due to photocorrosion and the measured photocurrents do not necessarily originate from H2 evolution only. We evaluated the PEC stability and activation of model p-InP(100) photocathodes upon photoelectrochemical passivation (i.e. repeated surface oxidation/reduction). The electrode was subjected to a sequence of linear potential scans with or without intermittent passivation steps (repeated passivation and continuous reduction, respectively). The evolution of H2 and PH3 gases was monitored by online electrochemical mass spectrometry (OLEMS) and the Faradaic efficiencies of these processes were determined. Repeated passivation led to an increase of the photocurrent in 0.5 M H2SO4, while continuous reduction did not affect the photocurrent of p-InP(100). Neither H2 nor PH3 formation increased to the same extent as the photocurrent during the repeated passivation treatment. Surface analysis of the spent electrodes revealed substantial roughening of the electrode surface by repeated passivation, while continuous reduction left the surface unaltered. On the other hand, photocathodic conditioning performed in 0.5 M HCl led to the expected correlation between photocurrent increase and H2 formation. Ultimately, the H2 evolution rates of the photoelectrodes in H2SO4 and HCl are comparable. The much higher photocurrent in H2SO4 is due to competing side-reactions. The results emphasize the need for a detailed evaluation of the Faradaic efficiencies of all the involved processes using a chemical-specific technique like OLEMS. Photo-OLEMS can be beneficial in the study of photoelectrochemical reactions enabling the instantaneous detection of small amounts of reaction by-products.

An integrated semiconductor spectral sensor is demonstrated. It is based on an array of resonant- cavity-enhanced photodetectors covering the short-wavelength infrared region. Its robustness and small footprint make this device suitable for on-site spectral sensing applications.

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.

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.

The solar energy conversion efficiency of photoelectrochemical (PEC) devices is usually limited by poor interface energetics, limiting the onset potential, and light reflection losses. Here, a three-pronged approach to obtain excellent performance of an InP-based photoelectrode for water reduction is presented. First, a buried p-n+ junction is fabricated, which shifts the valence band edge favorably with respect to the hydrogen redox potential. Photoelectron spectroscopy substantiates that the shift of the surface photovoltage is mainly determined by the buried junction. Second, a periodic array of InP nanopillars is created at the surface of the photoelectrode to substantially reduce the optical reflection losses. This device displays an unprecedented photocathodic power-saved efficiency of 15.8% for single junction water reduction. Third, a thin TiO2 protection layer significantly increases the stability of the InP-based photoelectrode. Careful design of the interface energetics based on surface photovoltage spectroscopy allows obtaining a PEC cell with stable record performance in water reduction. The efficiency of photoelectrochemical (PEC) water splitting devices is usually limited by interface energetics mismatch between the semiconductor and the electrolyte and insufficient light absorption. The highest photocathodic power-saved efficiency of 15.8% reported so far for single junction PEC water reduction is obtained through interface energetics design and photon management of an InP-based photoelectrode.

We demonstrate an efficiency enhancement of an InP nanowire (NW) axial p-n junction solar cell by cleaning the NW surface. NW arrays were grown with in situ HCl etching on an InP substrate patterned by nanoimprint lithography, and the NWs surfaces were cleaned after growth by piranha etching. We find that the postgrowth piranha etching is critical for obtaining a good solar cell performance. With this procedure, a high diode rectification factor of 10(7) is obtained at ±1 V. The resulting NW solar cell exhibits an open-circuit voltage (Voc) of 0.73 V, a short-circuit current density (Jsc) of 21 mA/cm(2), and a fill factor (FF) of 0.73 at 1 sun. This yields a power conversion efficiency of up to 11.1% at 1 sun and 10.3% at 12 suns.

InAs quantum dots (QDs) are grown on planar InP (1 0 0) by metalorganic vapor-phase epitaxy (MOVPE) with a thin GaAs interlayer beneath the QDs. The QDs’ structural and optical properties are investigated when varying the GaAs interlayer thickness, growth temperature, and group V/III ratio and related to As/P exchange, the goal being to obtain high-quality QDs with emission wavelength around 1.55 μm.

For the first time a detailed study of hybrid mode-locking in two- section InAs/InP quantum dot Fabry-Pérot-type lasers is presented. The output pulses have a typical upchirp of approximately 8 ps/nm, leading to very elongated pulses. The mechanism leading to this typical pulse shape and the phase noise is investigated by detailed radio-frequency and optical spectral studies as well as time-domain studies. The pulse shaping mechanism in these lasers is found to be fundamentally different than the mechanism observed in conventional mode-locked laser diodes, based on quantum well gain or bulk material. ©2009 Optical Society of America.

An ultrasmall (10 μm length) polarization converter in InP membrane is fabricated and characterized. The device relies on the beating between the two eigenmodes of chemically etched triangular waveguides. Measurements show a very high polarization conversion efficiency of99% with insertion losses of-1.2 dB at a wavelength of 1.53 μm. Furthermore, our design is found to be broadband and tolerant to dimension variations.

Photonic integrated circuits (PICs) are considered as the way to make photonic systems or subsystems cheap and ubiquitous. PICs still are several orders of magnitude more expensive than their microelectronic counterparts, which has restricted their application to a few niche markets. Recently, a novel approach in photonic integration is emerging which will reduce the R&D and prototyping costs and the throughput time of PICs by more than an order of magnitude. It will bring the application of PICs that integrate complex and advanced photonic functionality on a single chip within reach for a large number of small and larger companies and initiate a breakthrough in the application of Photonic ICs. The paper explains the concept of generic photonic integration technology using the technology developed by the COBRA research institute of TU Eindhoven as an example, and it describes the current status and prospects of generic InP-based integration technology

Wavelength-tunable InAs quantum dots (QDs) embedded in lattice-matched InGaAsP on InP(100) substrates are grown by metalorganic vapor-phase epitaxy (MOVPE). As/P exchange, which causes a QD size and an emission wavelength that are very large, is suppressed by decreasing the QD growth temperature and V–III flow ratio. As/P exchange, QD size and emission wavelength are then reproducibly controlled by the thickness of ultrathin [0–2 monolayers (ML)] GaAs interlayers underneath the QDs. Submonolayer GaAs coverages result in a shape transition from QDs to quantum dashes for a low V–III flow ratio. It is the combination of reduced growth temperature and V–III flow ratio with the insertion of GaAs interlayers of greater than 1 ML thickness which allows the tuning of the emission wavelength of QDs at room temperature in the 1.55 µm wavelength range. Temperature-dependent photoluminescence (PL) measurements reveal the excellent optical properties of the QDs. Widely stacked QD layers are reproduced with identical PL emission to increase the active volume while closely stacked QD layers reveal a systematic PL redshift and linewidth reduction due to vertical electronic coupling, which is proven by the fact that the linear polarization of the cleaved-side PL changes from in-plane to isotropic. Ridge-waveguide laser diodes with stacked QD layers for their active regions exhibit threshold currents at room temperature in continuous-wave mode that are among the lowest threshold currents achieved for InAs/InP QD lasers operating in the 1.55 µm wavelength range.

InAs quantum dots (QDs) are grown on InP (1 0 0) substrates by metalorganic vapor-phase epitaxy and the optical quality depending on the InP capping procedure is evaluated. The thickness of the low-temperature (Low-T) InP cap layer directly on the QDs is crucial for the QD photoluminescence (PL) peak wavelength and efficiency when followed by high-temperature capping. With increase of the Low-T cap layer thickness, the PL peak redshifts and the efficiency increases up to a thickness of 8 nm after which the PL peak wavelength stays constant and the efficiency strongly decreases. This behavior is attributed to the balance between stability of the QDs and defect diffusion toward the QDs.

We report on the shape and polarization control of site-controlled multiple and single InAs quantum dots (QDs) on InP pyramids grown by selective-area metal-organic vapor phase epitaxy. With increasing growth temperature the QDs elongate causing strong linear polarization of the photoluminescence. With reduced pyramid base/pyramid top area/QD number, the degree of polarization decreases, attributed to the symmetric pyramid top, reaching zero for single QDs grown at lower temperature. This control of linear polarization is important for entangled photon sources operating in the 1.55 µm wavelength region.

Position-controlled InAs quantum dots (QDs) are integrated into planar InP structures by employing selective area growth of InP pyramids and regrowth by metalorganic vapor-phase epitaxy. A smooth surface morphology is obtained at elevated regrowth temperature due to suppression of three-dimensional growth on the pyramids. The height differences are less than 30 nm after nominal 700 nm InP regrowth at 640¿°C. Most important, the integrated QDs maintain good optical quality after regrowth for the realization of integrated nanophotonic devices and circuits operating at telecom wavelengths.

In recent years, several on-chip MEMS switches on silicon photonics have been reported [1, 2]. These switches require tens of volts for the actuation, which is challenging for their application in photonic integrated circuits. In this abstract we present an on-chip MEMS Mach-Zehnder Interferometer, which presents a switching voltage of 4.4V with an extinction ratio above 15dB within a bandwidth of 34nm in the C-band. While the design can be implemented on different platforms as well, we use a InP membrane on a silicon substrate by an adhesive bonding technique [3], which provides the possibility to integrate our device with active components (amplifiers, lasers, detectors) on a single chip.

We present a spectral sensor based on an integrated array of resonant-cavity-enhanced photodetectors operating in the near-infrared. Prediction models are built directly using the 15 photodetector responses, without the need for spectral reconstruction.