High-brightness all semiconductor laser at 1.57 µm for space-borne lidar measurements of atmospheric carbon dioxide: device design and analysis of requirements

The availability of suitable laser sources is one of the main challenges in future space missions for accurate measurement of atmospheric CO2. The main objective of the European project BRITESPACE is to demonstrate the feasibility of an all-semiconductor laser source to be used as a space-borne laser transmitter in an Integrated Path Differential Absorption (IPDA) lidar system. We present here the proposed transmitter and system architectures, the initial device design and the results of the simulations performed in order to estimate the source requirements in terms of power, beam quality, and spectral properties to achieve the required measurement accuracy. The laser transmitter is based on two InGaAsP/InP monolithic Master Oscillator Power Amplifiers (MOPAs), providing the ON and OFF wavelengths close to the selected absorption line around 1.57 µm. Each MOPA consists of a frequency stabilized Distributed Feedback (DFB) master oscillator, a modulator section, and a tapered semiconductor amplifier optimized to maximize the optical output power. The design of the space-compliant laser module includes the beam forming optics and the thermoelectric coolers.The proposed system replaces the conventional pulsed source with a modulated continuous wave source using the Random Modulation-Continuous Wave (RM-CW) approach, allowing the designed semiconductor MOPA to be applicable in such applications. The system requirements for obtaining a CO2 retrieval accuracy of 1 ppmv and a spatial resolution of less than 10 meters have been defined. Envelope estimated of the returns indicate that the average power needed is of a few watts and that the main noise source is the ambient noise

High brightness semiconductor lasers as transmitters for space lidar systems

High brightness semiconductor lasers are potential transmitters for future space lidar systems. In the framework of the European Project BRITESPACE, we propose an all-semiconductor laser source for an Integrated Path Differential Absorption lidar system for column-averaged measurements of atmospheric CO2 in future satellite missions. The complete system architecture has to be adapted to the particular emission properties of these devices using a Random Modulated Continuous Wave approach. We present the initial experimental results of the InGaAsP/InP monolithic Master Oscillator Power Amplifiers, providing the ON and OFF wavelengths close to the selected absorption line around 1572 nm

The H2020-SPACE-SIPHODIAS project: Space-grade optoelectronic interfaces for photonic digital and analogue very-high-throughput satellite payloads

The EU-SIPhoDiAS project deals with the development of critical photonic building blocks needed for high-performance and low size, weight, and power (SWaP) photonics-enabled Very High Throughput Satellites (VHTS). In this presentation, we report on the design and fabrication activities during the first year of the project concerning the targeted family of digital and microwave photonic components. This effort aims to demonstrate components of enhanced reliability at technology readiness level (TRL) 7. Specifically, with respect to microwave photonic links, we report: (i) the design of Ka and Q-bands analogue photodetectors that will be assembled in compact packages, allowing for very high bandwidth per unit area and (ii) on the design of compact V-band GaAs electro-optic modulator arrays, which use a folded-path optical configuration to manage all fiber interfaces packaged opposite direct in-line RF feeds for ease of board layouts and mass/size benefits. With respect to digital links, we report on the development of 100 Gb/s (4 x 25 Gb/s) digital optical transceiver sub-assemblies developed using flip-chip mounting of electronic and opto-parts on a high-reliability borosilicate substrate. The transceiver chipset developed specifically for this project refers to fully-custom 25 Gb/s radiation hard (RH) VCSEL driver and TIA ICs designed in IHP’s 130 nm SiGe BiCMOS Rad-Hard process

Root canal morphology of primary maxillary second molars:a micro-computed tomography analysis

Aim Successful endodontic treatment of primary teeth requires comprehensive knowledge and understanding of root canal morphology. The purpose of this study was to investigate the root canal configurations of primary maxillary second molars using micro-computed tomography. Methods Extracted human primary maxillary second molars (n = 57) were scanned using micro-computed tomography and reconstructed to produce three-dimensional models. Each root canal system was analysed qualitatively according to Vertucci's classification. Results 22.8% (n = 13) of the sample presented with the fusion of the disto-buccal and palatal roots; of these, Type V was the most prevalent classification. For teeth with three separate roots (n = 44), the most common root canal type was Type 1 for the palatal canal (100%) and disto-buccal canal (77.3%) and Type V for the mesio-buccal canal (36.4%). Overall, 7% (n = 4) of mesio-buccal canals were 'unclassifiable'. Conclusion The root canal systems of primary maxillary second molars were not only complex but had a range of configurations that may contribute to unfavourable clinical outcomes after endodontic treatment

LIDAR System based on a High Brightness Semiconductor Laser and Single Photon Counting Detection for Space -borne Atmospheric CO2 Monitoring

We theoretically investigate a dynamical regime, experimentally observed in monolithically integrated master oscillator power amplifiers emitting at 1.5 7 μm, consisting in large emission wavelength jumps of the device from the Bragg wavelength to that of the gain peak. Our analysis is based on numerical simulations by means of a travelling wave model that incorporates spatial effects such as spatial hole burning and coupled-cavity effects. Thermal effects are included by considering the optical response of the quantum well active medium within the quasi-equilibrium approximation at finite temperature, with a phenomenological description of the redshift of the gain peak and the changes in the background material refractive index by means of self- and cross-heating coefficients for both sections. We find that whereas the thermally-induced index changes are the responsible of the modal jumps between consecutive modes, the carrier-induced refractive index changes are the responsible of the jumps occurring between the Bragg wavelength and the gain peak

Phylogeography of the Patagonian otter Lontra provocax: adaptive divergence to marine habitat or signature of southern glacial refugia?

<p>Abstract</p> <p>Background</p> <p>A number of studies have described the extension of ice cover in western Patagonia during the Last Glacial Maximum, providing evidence of a complete cover of terrestrial habitat from 41°S to 56°S and two main refugia, one in south-eastern Tierra del Fuego and the other north of the Chiloé Island. However, recent evidence of high genetic diversity in Patagonian river species suggests the existence of aquatic refugia in this region. Here, we further test this hypothesis based on phylogeographic inferences from a semi-aquatic species that is a top predator of river and marine fauna, the huillín or Southern river otter (<it>Lontra provocax</it>).</p> <p>Results</p> <p>We examined mtDNA sequences of the control region, ND5 and Cytochrome-b (2151 bp in total) in 75 samples of <it>L. provocax </it>from 21 locations in river and marine habitats. Phylogenetic analysis illustrates two main divergent clades for <it>L. provocax </it>in continental freshwater habitat. A highly diverse clade was represented by haplotypes from the marine habitat of the Southern Fjords and Channels (SFC) region (43°38' to 53°08'S), whereas only one of these haplotypes was paraphyletic and associated with northern river haplotypes.</p> <p>Conclusions</p> <p>Our data support the hypothesis of the persistence of <it>L. provocax </it>in western Patagonia, south of the ice sheet limit, during last glacial maximum (41°S latitude). This limit also corresponds to a strong environmental change, which might have spurred <it>L. provocax </it>differentiation between the two environments.</p