Page 164 - High Power Laser Handbook

CHAPTER 6

High-Power

Diode Laser

Arrays

Hans-Georg Treusch
Director, Trumpf Photonics, Cranbury, New Jersey

Rajiv Pandey
Senior Product Manager, DILAS Diode Laser Inc., Tucson, Arizona

6.1 Introduction
During the past decade, significant increases in electro-optical effi-
ciency of diode lasers—from values typically below 50 percent to
record values of greater than 73 percent (see Chap. 5)—have enabled
demonstrated maximum power levels of up to 1 kW from a 10-mm-
wide laser bar in a lab environment. This increased efficiency, in turn,
has resulted in reduced heat load and internal losses in the material.
The latter has enabled laser resonator cavities that are longer than the
typical 1 mm cavities of 10 years ago—up to 4–5 mm for the highest
current power levels. Spreading out the heat by a factor of 4 with the
larger footprint and cutting the heat load in half have resulted in the
record value of 1 kW. 1
In addition to the improved performance of high-power diode
laser arrays with wavelength in the near-infrared (NIR), new materi-
als have been developed to extend the range for the wavelength into
the visible and midinfrared (MIR) regions. These new materials are
aimed at new applications in the medical field, as well as at the pump-
ing of eye-safe solid-state lasers in the MIR. The efficiency of these
new materials is lower than traditional NIR diode lasers (Fig. 6.1),
and high-yield assembly processes, as well as high-efficiency optical
coupling methods, are required to establish usable products.

133