Evaluation of 2.1μm DFB Lasers for Space Appications

Evaluation of 2.1μm DFB Lasers for Space Appications

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J. Barbero 1, D. López 1, I. Esquivias 2, J.M.G. Tijero 2, M. Fischer 3, K. Roessner 3,  J. Koeth 3,  M Zahir 4
(1) Alter Technology Group Spain,Majada 3, 28760 Tres Cantos (Spain)
(2) Universidad Politécnica de Madrid, ETSI  Telecommunicación, Avenida Complutense s/n, Ciudad Universitaria, 28040 Madrid (Spain)E-mail: esquivia@tfo.upm.es
(3) nanoplus GmbH, Nanosystems and Technologies Oberer Kirschberg 4, D-97218 Gerbrunn (Germany)  E-mail: marc.fischer@nanoplus.com
(4) European Space Agency, ESTEC Keplerlaan 1 – PO Box 299 –2200 AG Noordwijk ZH (The Netherlands) E-mail: Mustapha.Zahir@esa.int
This paper presents the results obtained in the frame of an ESA-funded project called “Screening and Preevaluation of Shortwave Infrared Laser Diode for Space Application” with the objective of verifying the maturity of state of the art SWIR DFB lasers at 2.1µm to be used for space applications (mainly based on the occultation measurement principle and spectroscopy). The paper focus on the functional and environmental evaluation test plan. It includes high precision characterization, mechanical test (vibration and SRS shocks), thermal cycling, gamma and proton radiation tests, life test and some details of the Destructive Physical Analysis performed. The electro-optical characterization includes measurements of the tuning capabilities of the laser both by current and by temperature, the wavelength stability and the optical power versus laser current.

SWIR wavelength variation

SWIR wavelength variation (dark blue line; right axis) with ambient temperature cycling for a laser diode TEC controlled temperature of 20ºC (light blue line). The red line is the actual chamber temperature and the purple line is the laser package temperature measured with an additional thermocouple.

I. INTRODUCTION   
Semiconductor lasers (or laser diodes) operating in the wavelength region of 1.8 µm to 3 µm are attractive light sources for applications including remote sensing, laser spectroscopy or pollutant detection. Highly strained InGaAs Quantum Wells (QW) grown on InP substrates can operate up to wavelengths slightly higher than 2 µm. GaInAsSb active layers on GaSb substrates have potential emission in the 1.7-3.5 µm range.
GaSb based DFB lasers emitting at 2 µm were reported for the first time by the University of Würzburg in 2001 [1]. They achieved room temperature emission with output powers up to 10 mW and Side Mode Suppression Ratio (SMSR) of 31 dB. DFB laser diodes can additionally be tuned by changing the operation temperature and the driving current, as a consequence of the dependence of the effective refractive index on temperature.

This makes this type of source a potential candidate for space applications and first results of investigated fibrecoupled Butterfly type devices emitting in the 2.1µm wavelength range for applications in a space environment will be described in this contribution.