Characterization of Exotic Material Heat Sinks for Laser Diode Arrays
- PDF / 178,351 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 83 Downloads / 274 Views
FF3.2.1
Characterization of Exotic Material Heat Sinks for Laser Diode Arrays
Edward.F. Stephens Northrop Grumman - Cutting Edge Optronics 20 Point West Blvd St. Charles, MO 63301
ABSTRACT Low duty cycle, high peak power, conductively cooled laser diode arrays have been manufactured for several years by a number of different vendors. Typically these packages have been limited to a few percent duty cycles due to thermal problems that develop in tight bar pitch arrays at higher duty cycles. Traditionally these packages are made from some combination of copper and BeO or Tungsten/copper and BeO. Trade-offs between thermal conductivity and CTE matching are always made when manufacturing these devices. In addition, the manufacturability of the heat sinks plays a critical role in creating a cost effective, high performance solution. In this discussion we examine several different exotic materials that have been manufactured and tested as heat sinks for laser diode arrays.
INTRODUCTION Laser diode arrays are a key component to Diode Pumped Solid State Lasers (DPSSLs). Manufacturing the laser diode array pump sources has been a mature process for many years. In the early years of laser diode array production the quality of the laser diode bar was the main determining factor of lifetime. In particular, the epitaxial structure design, epitaxial growth quality, and dielectric coatings played large roles in device lifetime. Improvements in those parameters have led to devices capable of operating at much higher power levels and duty cycles. The increased power capabilities have, in turn, taxed the capabilities of the heat sinks designed to keep these devices cool. In this paper we outline various laser diode packaging concepts and present some of the problems in developing cost effective heat sink solutions for high volume manufacturing.
TYPICAL LASER DIODE CONSTRUCTION The typical components of a packaged laser diode are shown in figure 1 below. The basic package consists of a laser diode bar with at least one side soldered to a heat sink (usually the pside). Either an electrical contact or a second heat sink may be attached to the opposite side of the laser diode bar. In general, the heat sink is water or conductively cooled. The output of a laser diode bar is made up of series of emitting regions separated by non-emitting regions. A typical emitting region size is on the order of 100 µm. The ratio of the sum of the emitting regions divided by the total length of the bar is known as the fill factor. Pulsed laser diode bars tend to have higher fill factors (~90%) and CW bar have less (~50 % or less).
FF3.2.2
Heat Sink or Electrical Contact
Solder Bonds Laser Diode Bar n-side
(a) Primary Heat Sink
Laser Diode Bar p-side
Light Output Primary Heat
(b) BeO substrate
(c)
Figure 1. (a) Front view of a packaged laser diode bar. Light output is out of the page, (b) Side view of a laser diode bar package, (c) Photo of a packaged laser diode bar.
IMPORTANT FACTORS During the construction, several important physical prope
Data Loading...
