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Proceedings Paper

Recent results of blue and green InGaN laser diodes for laser projection
Author(s): Stephan Lutgen; Dimitri Dini; Ines Pietzonka; Soenke Tautz; Andreas Breidenassel; Alfred Lell; Adrian Avramescu; Christoph Eichler; Teresa Lermer; Jens Müller; Georg Bruederl; Alvaro Gomez-Iglesias; Uwe Strauss; Wolfgang G. Scheibenzuber; Ulrich T. Schwarz; Bernhard Pasenow; Stephan Koch
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Paper Abstract

Mobile laser projection is of great commercial interest. Today, a key parameter in embedded mobile applications is the optical output power and the wall plug efficiency of blue and green lasers. We report on improvements of the performance of true blue riedge waveguide InGaN lasers at 452nm with cw-output power up to 800mW in overstress and mono mode operation up to 500mW in a temperatures range of 20°C to 80°C. We succeeded in high and almost temperature independent wall plug efficiencies >20% at stable output power levels from 200 to 500mW in cw-operation. Due to several improvements of our blue laser diodes we now estimate life times is in the order of 40khrs for 80mW output power in cw-operation at 40°C. Additional overstress degradation tests at power levels up to 200mW show a strong dependency of lifetime with output power. Furthermore, we present pioneering results on true green InGaN laser diodes on c-plane GaN-substrates. The technological challenge is to achieve In-rich InGaN-quantum wells with sufficiently high material quality for lasing. We investigated the competing recombination processes below laser threshold like nonradiative defect recombination by electro-optical measurements, such confirming that low defect densities are essential for stimulated emission. A model for alloy fluctuations in In-rich InGaN-MQWs based on spectral and time resolved photoluminescence measurements yields potential fluctuations in the order of E0=57meV for our blue laser diodes. To get a closer insight into the physics of direct green InGaN-Laser we investigated the inhomogeneous broadening of experimentally measured gain curves via Hakki-Paoli-measurements in comparison to calculated gain spectra based on microscopic theory showing the importance of strong LO-phonon coupling in this material system. Investigations of current dependent gain measurements and calculations yield a factor of 2 higher inhomogeneous broadening for our green lasers than for our blue laser diodes on c-plane GaN. Based on the improvements of the material quality and design we demonstrate true green InGaN-Laser in cw-operation at 522nm with more than 80mW output power on c-plane GaN. The combination of low laser threshold ~60-80mA, high slope efficiency ~0.65W/A and low operating voltage 6.9-6.4V of our green monomode RWG-Laser results in a high wall plug efficiency of 5-6% in a temperature range of 20-60°C.

Paper Details

Date Published: 16 February 2011
PDF: 12 pages
Proc. SPIE 7953, Novel In-Plane Semiconductor Lasers X, 79530G (16 February 2011); doi: 10.1117/12.874757
Show Author Affiliations
Stephan Lutgen, OSRAM Opto Semiconductors GmbH (Germany)
Dimitri Dini, OSRAM Opto Semiconductors GmbH (Germany)
Ines Pietzonka, OSRAM Opto Semiconductors GmbH (Germany)
Soenke Tautz, OSRAM Opto Semiconductors GmbH (Germany)
Andreas Breidenassel, OSRAM Opto Semiconductors GmbH (Germany)
Alfred Lell, OSRAM Opto Semiconductors GmbH (Germany)
Adrian Avramescu, OSRAM Opto Semiconductors GmbH (Germany)
Christoph Eichler, OSRAM Opto Semiconductors GmbH (Germany)
Teresa Lermer, OSRAM Opto Semiconductors GmbH (Germany)
Jens Müller, OSRAM Opto Semiconductors GmbH (Germany)
Georg Bruederl, OSRAM Opto Semiconductors GmbH (Germany)
Alvaro Gomez-Iglesias, OSRAM Opto Semiconductors GmbH (Germany)
Uwe Strauss, OSRAM Opto Semiconductors GmbH (Germany)
Wolfgang G. Scheibenzuber, Fraunhofer IAF (Germany)
Ulrich T. Schwarz, Fraunhofer IAF (Germany)
Bernhard Pasenow, Univ. Marburg (Germany)
Stephan Koch, Univ. Marburg (Germany)

Published in SPIE Proceedings Vol. 7953:
Novel In-Plane Semiconductor Lasers X
Alexey A. Belyanin; Peter M. Smowton, Editor(s)

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