BRITESPACE

High Brightness Semiconductor Laser Sources for Space Applications in Earth Observation

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 Obiettivo del progetto (Objective)

'The availability of suitable laser sources is one of the key issues for the development of active optical instruments in future earth observation missions. The main objective of this project is to demonstrate the feasibility of a semiconductor based laser source to be used as a laser transmitter in a Differential- Absorption LIDAR (DIAL) system for the observation and monitoring of greenhouse gases in the atmosphere. The basic building block of the project is a monolithic Master Oscillator Power Amplifier (MOPA) consisting of a frequency stabilized Distributed Feedback (DFB) Master Oscillator (MO) and a multi-section tapered semiconductor Power Amplifier (PA). The required on-, off-line laser wavelengths will be generated in the DFB section and amplified and modulated in the PA section. The device will be fabricated, mounted in a module with the beam forming optics and completed with the stabilization and control electronics. The entire laser source will be designed so that it can be used as the transmitter unit of a Random Modulated CW LIDAR system enabling measurements of the atmospheric CO2 concentration by Integrated-Path Differential-Absorption (IPDA) LIDAR with no signal ambiguity over a distance of 30 km and accuracy in distance determination better than 10 m. As a proof of concept, the CO2 concentration along a 2-3 km test path will be measured on ground and compared with the results provided by an existing DIAL system. For the DIAL test, the receiver unit will be developed in addition. The achievement of the project objectives should provide a substantial progress in the availability of compact, and highly efficient laser sources for the detection and monitoring of greenhouse gases in future earth observation missions and therefore to improve the position of Europe in this field. In a more general context the project will pave the way of using high brightness semiconductor lasers in space applications requiring simultaneously high power, beam quality'

Introduzione (Teaser)

Measuring sources and sinks of greenhouse gases from space is constrained due to a lack of effective monitoring tools. EU-funded researchers are developing semiconductor-based laser sources for active optical instruments for this purpose.

Descrizione progetto (Article)

Monitoring greenhouse gas from space requires laser sources with high power output and high beam quality. However, existing laser sources for Earth observations are based on bulky solid state lasers. Within the http://www.britespace.eu/ (BRITESPACE) (High brightness semiconductor laser sources for space applications in Earth observation) project, the researchers aim to demonstrate that semiconductor-based lasers can be used for remote sensing of atmospheric gases.

Thanks to their compact size and high reliability, the new generation of high-brightness semiconductor lasers brings significant advantages over other laser sources. Such semiconductor lasers emitting at two different wavelengths between 1 500 - 1 600 nanometres has been designed for light detection and ranging (LIDAR) measurements. It would be mounted in a space-compatible laser module with beam forming optics and control electronics.

During the first reporting period of the BRITESPACE project, prototypes of the system have been developed. These consist of a commercially available laser as the transmitter and opto-electrical elements for signal detection (integrating sphere, photon counting detector, filter, and guide laser for alignments). The final system will be used as the transmitter unit of a LIDAR system enabling measurements of carbon dioxide in the atmosphere.

The parametric studies carried out to date promise a relatively high sensitivity for measurements of carbon dioxide concentration from a space-borne and a ground-based platform. On the other hand, simulations reveal that the performance of the proposed LIDAR system suffers from ambient light noise and noise from the detector dark count.

The BRITESPACE project has enhanced our knowledge about semiconductor lasers and identified areas that need to be addressed for Earth observation applications. Advanced LIDAR technology enabling faster and more reliable monitoring of greenhouse gases in the atmosphere should also help in the struggle against global warming.