Synthetic Aperture Radar (SAR) is a well-known technique for remote sensing applications with great advantages like uninterrupted imaging capabilities even at night or in presence of cloud cover. However, spaceborne SAR sensors face major challenges like cost and size, which are among the great barriers against their applicability for future constellations of low-Earth observation applications. SAR sensors are not compact and require large or medium-sized satellites weighting hundred kilograms or more, which cost hundreds million dollars. To solve these challenges, the recently started SPACEBEAM project, funded by the European Commission, aims at developing a novel SAR receiver approach, i.e., the Scan-on-Receive (SCORE), exploiting a hybrid integrated optical beamforming network (iOBFN) that also realizes the electro-photonic down-conversion of RF signals. The compactness and frequency flexibility of the proposed photonic solution complies with the requirements of future constellations of low-Earth orbit satellites in terms of size, weight, power consumption, and cost. A high-level representation of the SCORE SAR receiver module based on the multi-functional hybrid photonic integrated circuit (PIC), with 12 input RF channels and 3 output beam-formed IF channels, is shown in the submitted PDF document. For this design, we target the development of an X-band SCORE-SAR receiver having a swath width of 50 km (5 times wider than state-of-art spaceborne SAR systems), and enabling 1.5 m spatial resolution in both along-track and across-track directions. During the conference, we will present the design and specifications of the SCORE-SAR receiver at equipment level, where we aim at a hermetically packaged PIC that is also designed for space compliance. We target a flight-design for the RF front-end and control electronics, enabling the electro-photonic frequency down-conversion of the RF signals and the fast control of the PZT-driven iOBFN with <300 ns switching time.
In recent years there has been a rapidly increasing demand for CO2 sensors for applications in health monitoring, control of air quality and horticulture. Amongst the various approaches reported so far, the AlGaInSb quaternary alloy shows great promise for the development of compact Light Emitting Diodes (LEDs) as it offers bandgap Type-I alignments, which enable the design of effective multi-quantum well (MQW) active regions. In this paper we show a more than fourfold improvement in wall-plug efficiency by optimising both the strain in AlGaInSb MQW active regions and the fabrication process flow of LEDs emitting at 4.26 um.
In recent years there has been a rapidly increasing demand for energy-efficient and cost effective gas sensors. Of particular interest are CO2 sensors that can find numerous applications in health monitoring, control of air quality and horticulture. A major hurdle comes from the fact that the main CO2 absorption band lies above 4um, where very few cheap and compact sources are commercially available. Amongst the various approaches explored, the indium antimonide material system stands out as a very effective solution for the development of compact Light Emitting Diodes (LEDs). In particular, the quaternary compound AlGaInSb shows great promise as it offers a bandgap type-I alignment, which enables the design of effective multi-quantum well (MQW) active regions.
In this paper we show the great potential of LED structures with strained GaInSb MQWs and AlGaInSb barriers for the next generation of mid-IR emitters at 4.3 um. Different quantum well and barrier compositions were examined through k.p simulations to extract momentum matrix elements and energy levels. The simulations were also used to assess the impact of strain and quantum well width on the efficiency of the radiative transition and to optimise the profile of the carrier injection. Based on the theoretical analysis, a number of different epilayer structures were grown by molecular beam epitaxy and the performance of LEDs with varying geometries were compared. Results confirm that strained MQW structures suppress unwanted transitions by at least one order of magnitude and provide a substantial enhancement in the internal quantum efficiency of the LEDs.
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