940nm QCW diode laser bars with 70% efficiency at 1 kW output power at 203K: analysis of remaining limits and path to higher efficiency and power at 200K and 300K

C. Frevert; F. Bugge; S. Knigge; A. Ginolas; G. Erbert; P. Crump

doi:10.1117/12.2210942

4 March 2016 940nm QCW diode laser bars with 70% efficiency at 1 kW output power at 203K: analysis of remaining limits and path to higher efficiency and power at 200K and 300K

C. Frevert, F. Bugge, S. Knigge, A. Ginolas, G. Erbert, P. Crump

Author Affiliations +

Proceedings Volume 9733, High-Power Diode Laser Technology and Applications XIV; 97330L (2016) https://doi.org/10.1117/12.2210942
Event: SPIE LASE, 2016, San Francisco, California, United States

Abstract

Both high-energy-class laser facilities and commercial high-energy pulsed laser sources require reliable optical pumps with the highest pulse power and electro-optical efficiency. Although commercial quasi-continuous wave (QCW) diode laser bars reach output powers of 300…500 W further improvements are urgently sought to lower the cost per Watt, improve system performance and reduce overall system complexity. Diode laser bars operating at temperatures of around 200 K show significant advances in performance, and are particularly attractive in systems that use cryogenically cooled solid state lasers. We present the latest results on 940 nm, passively cooled, 4 mm long QCW diode bars which operate under pulse conditions of 1.2 ms, 10 Hz at an output power of 1 kW with efficiency of 70% at 203 K: a two-fold increase in power compared to 300 K, without compromising efficiency. We discuss how custom low-temperature design of the vertical layers can mitigate the limiting factors such as series resistance while sustaining high power levels. We then focus on the remaining obstacles to higher efficiency and power, and use a detailed study of multiple vertical structures to demonstrate that the properties of the active region are a major performance limit. Specifically, one key limit to series resistance is transport in the layers around the active region and the differential internal efficiency is closely correlated to the threshold current. Tailoring the barriers around the active region and reducing transparency current density thus promise bars with increased performance at temperatures of 200 K as well as 300 K.

Citation Download Citation

C. Frevert, F. Bugge, S. Knigge, A. Ginolas, G. Erbert, and P. Crump "940nm QCW diode laser bars with 70% efficiency at 1 kW output power at 203K: analysis of remaining limits and path to higher efficiency and power at 200K and 300K", Proc. SPIE 9733, High-Power Diode Laser Technology and Applications XIV, 97330L (4 March 2016); https://doi.org/10.1117/12.2210942

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