Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - HOLDON (HgCdte APD Optimization for Lidar Detection Of greeNhouse gases)

Teaser

LIDAR remote sensing of the earth’s atmosphere is one of the main challenges in coping with the effects and causes of global warming caused by the emission of greenhouses gases. LIDAR is the acronym of light imaging, detection and ranging, it refers to a surveying method...

Summary

LIDAR remote sensing of the earth’s atmosphere is one of the main challenges in coping with the effects and causes of global warming caused by the emission of greenhouses gases. LIDAR is the acronym of light imaging, detection and ranging, it refers to a surveying method that measures distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor. Concerning the atmospheric monitoring, the present operating Lidar missions are all implanted on large satellite platforms due to the size of the telescope and high energy laser modules required to ensure a sufficient collection of light to extract the signal from the detector noise. The HOLDON project aims to develop a new and versatile detection chain which will improve the performance of the Lidars and/or to reduce the Lidar payload to be integrated in future mini-satellites.
The performance increase is obtained by the optimization of high quantum efficiency HgCdTe avalanche photodiodes (APD) that will be hybridized to a specifically designed CMOS readout circuit (ROIC) providing two operation modes. The devices are expected to meet the most demanding specifications for Lidar applications, from ultraviolet to near-infrared wavelengths, in terms of sensitivity, dynamic range, and temporal resolution (high dynamic range down to single photon sensitivity). 7 European partners (CEA/LETI, DLR, AIRBUS, IDQ, LMD, ALTER and ABSISKEY) are working together to address three objectives:
- Design and manufacturing of a cutting-edge photon noise limited LIDAR detection chain.
- Demonstrate the improvement achieved with the detection chain for green-house gases detection (notably CO2, CH4).
- Validate the adequacy between Lidar detection key performances and requirements for future space missions.

Work performed

During the first year of project, the technical partners started by fully defining the specifications of the HOLDON detection chain (APD, ROIC, optical and electronic interfaces, including cryo-cooling conditions) in order to meet the needs of greenhouse gas and altimetry LIDAR measurements. The specifications were justified after an analysis of different relevant space and ground atmospheric LIDAR scenarios for wavelengths varying between 350 nm to 2 µm. Most of the scenarios are included in a dynamic range between 106 to 1012 photons/s for a shot noise limited detection of the signal.
Besides, specifications of the overall control and acquisition chain have been defined so that the system should be compatible with different user cases (laser trigger in/out, different control signals useful during the measure, software interface, etc). The back-end electronics development is in progress.
Different potential architectures of the read-out circuit were studied and a simulation campaign has been carried out. The ROIC architecture has now been freezed, offering a dual-operation mode, either a continuous mode (with several gains to cover the large required dynamic range) either an on-chip-sampling mode (switchable). Specifications of the mask set for the technological process of APD batches have been written and first HgCdTe layers grown by epitaxy are ready for processing.
In parallel, for laboratory tests, a Lidar signal simulator design and manufacturing is on-going. The equipment aims at emulating signals to be detected by the HgCdTe APD at three wavelengths (UV to NIR), with for short-pulsed or long echos. Setups were implemented for 1064nm and 532nm and are being optimized. Initial tests of the 355nm setup were done.
Also, a specific 2-µm laser source has been developed for CO2 differential absorption LIDAR application. The performances of the laser have been assessed. The laser operation (pulse repetition frequency and pulse energy) can be adapted to the detector chain and Lidar signal level.

Some dissemination tools have finally been implemented to publicly communicate on the HOLDON advances: website, posters and flyers at conference/workshop booths, and social media (LinkedIn account). In the next period, with incoming results, those materials will be even more used to amplify the dissemination activity.

Final results

The ambitious specifications for the dual-mode HOLDON LIDAR module that outperforms the state-of-the art have been confirmed by the partners and the design and manufacturing has well started. We expect to foster scientific excellence in Europe by conserving a leading position in the physics and applications of HgCdTe APDs, and by enabling new scientific collaborations and new applications using the HOLDON-type detector.
Also, a versatile Lidar detection chain (from near UV to mid-IR) showing low payload will pave the way to a commercial (European) offer for atmospheric and space LIDAR applications with similar needs, with a potential industrial exploitation by some interested companies.
The project website audience hasn\'t stopped to increase since its creation, which shows that more and more people (from and outside the EU) got interest into the project progress.
In a context where the global warming is a major issue for the future decades, a breakthrough observation of the atmosphere with much more precise datas will help to better survey the environment and assess emissions above cities, industrial or geological sites, carbone capture or dispersion modelling.

Website & more info

More info: http://holdon-h2020.eu.