2-Micron Diode-Pumped Laser

Time period

Summer 2002 to Present

Project description

Welch Mechanical Designs (WMD) was brought into a NASA diode-pumped laser development team to provide mechanical design and manufacturing consulting. The NASA team was researching methods to build ruggedized diode-pumped lasers suitable for deployment in the field. The research team had built their own oscillator that pumped a LuLF crystal at 790nm to produce 2 micron wavelength laser light at a repetition rate of 10Hz. WMD's primary goal was to improve the liquid cooling efficiency that would, in turn, increase the lifetime of the pump diodes.

Since the laser was water cooled, a major effort of the design required optimizing the cooling efficiency of the water channels. The original design made the coolant flow serially through the laser diode mounts. However, the plumbing lines used for this method required too much space. The new design used a built-in manifold to split the single incoming flow into three parallel flows for the three banks of diodes. This reduced the packaging size of the oscillator significantly. However, it reduced the relative flow rate for each diode compared to the serial design. WMD coordinated fluid flow analyses to improve the heat transfer coefficient. The final design increased the flow rate enough to achieve turbulent flow which increased the heat transfer coefficient. This allowed the NASA team to use their current chiller with a limited maximum flow capacity.

WMD also coordinated efforts to implement an optical technique to improve the efficiency of the design. We created coating masks and coordinated the efforts of both an optics manufacturer and an optics coater to make these components. The optics will be integrated into an oscillator assembly during the summer of 2003 and the performance improvements will be determined then.

Challenges and lessons learned

WMD took on more systems-level work during this project. We coordinated the efforts of analysts, optical manufacturers, rapid prototyping shops, and our usual metal fabrication shops. We hope to continue growing in this direction and to apply the systems design techniques we learned here to future projects.

Currently, we have designed and built the structure for the laser oscillator. Future efforts on this project will involve designing an amplifier and packaging the entire laser into a rugged and stable package suitable for field deployments.