This Small Business Innovation Research (SBIR) Phase I project will demonstrate the technical feasibility of growing potassium lithium niobate (KLN) frequency doubling crystals for blue and ultraviolet (UV) laser applications. The incorporation of frequency-doubling crystals composed of KLN, a non-linear optical material with desirable properties, has the potential to improve the performance and reduce the cost of blue and UV lasers. However, potassium lithium niobate (KLN) crystals have not entered the commercial mainstream because it is impossible to grow them reproducibly, and with the required performance and cost, by conventional techniques such as the Czochralski method. We have developed a proprietary process based on the laser heated pedestal growth (LHPG) technique that will eliminate the technical barriers to commercializing KLN crystals. In this project, we will determine the precise composition of KLN required for non-critical phase matching at 795 nanometers, optimize the quality of KLN crystals with the required composition, and then maximize the conversion efficiency of KLN crystals by precise doping to increase their transparency. The Phase I technical goal is to create KLN crystals capable of receiving 16 watts of infrared laser power at 795 nm and generating 2 watts of laser power at 397.5 nm.
The broader impact/commercial potential of this project will be the availability of frequency doubling crystals which will improve the performance of UV lasers for inspecting photomasks, and patterned and unpatterned wafers in the semiconductor industry. The market for inspection systems for these applications has grown to 200 systems per year and is valued at $500 million. The KLN crystals to be developed will enable laser manufacturers to commercialize higher-power, more robust, lower-cost UV lasers, in turn enabling semiconductor equipment manufacturers to develop improved inspection and metrology systems. These inspection systems will enable chip makers to commercialize future generations of higher-performance integrated circuits, and to increase their yields. This project will be undertaken in close collaboration with Spectra-Physics, a leading laser manufacturer, which will assist in testing the resulting crystals, allowing us to accelerate market acceptance.
I. Results of the Phase I Project The goal for this Small Business Innovation Research Phase I project was to demonstrate the technical feasibility of growing potassium lithium niobate frequency doubling crystals of sufficient quality to improve the performance of blue and UV lasers. Commercially, this research is significant because it will enable laser manufacturers to improve the performance and reduce the cost of blue and UV lasers by incorporating frequency doubling crystals made from potassium lithium niobate (KLN), a nonlinear optical material with highly desirable properties. Scientifically, this research is significant because it will allow the fast exploration and confirmation of a still controversial part of the phase diagram of potassium lithium niobate as the composition gets closer to stoichiometry. It will also allow exploring the potential of the material in the UV, which has never been done before. Potassium lithium niobate (KLN) crystals have not entered the commercial mainstream because it is impossible to grow them reproducibly with the required performance and cost by conventional techniques such as the Czochralski method. Shasta Crystals has developed a proprietary improvement on the laser heated pedestal growth (LHPG) technique that will eliminate the technical barriers to commercializing KLN crystals. We propose to determine the precise composition of KLN required for non-critical phasematching at 795 nm, optimize the quality of KLN crystals with the required composition, and then optimize the conversion efficiency of KLN crystals by experimenting with dopants (magnesium and zinc) that can increase their transparency In phase I, we have shown that we can generate 397.5nm with KLN, and that the addition of dopants will increase the transparency range further into the UV. We have completed these technical objectives described in our phase I proposal. Determined the precise composition required for noncritical phase matching at 397.5nm. Ordered and assembled testing equipment to optimize the quality of KLN crystals with the required composition. Optimized the transparency range of KLN at 397.5nm by adding the dopants magnesium or zinc. This work justified the support of the NSF, established that we can grow a composition of KLN which is likely to work for the envisioned application and confirmed the commercial potential of the innovation as evidenced by the continued support and enthusiasm of our customer SpectraPhysics. Our achievement of most of the technical objectives makes us confident that we will be able to demonstrate an optimized crystal and pilot manufacturing in the scope of our Phase 2 proposal.
