Characterization of Photocathode Excitation Pulses

The fundamental limiting factor limiting Free Electron Laser (FEL) brightness is the electron source, or photoinjector. One solution to improve brightness is to use specifically shaped ultraviolet pulses to excite the photocathode, improving the electron cloud shape injected into the accelerator. Ultraviolet spatiotemporal ultrafast pulse measurement is needed to develop these pulse shapes In this SBIR/STTR, we are developing new methods for temporal and spatiotemporal measurement of ultraviolet ultrafast laser pulses to support the development of laser pumped ultra-bright electron sources. These methods need to provide high fidelity measurements with high dynamic range and high spectral resolution to monitor and help design photocathode driving pulses. In Phase I, we demonstrated the feasibility of our proposed techniques for high spectral resolution and high dynamic range pulse measurement of deep-ultraviolet ultrafast laser pulses. We further demonstrated a combined spatiotemporal pulse electric field characterization in the near infrared. In Phase II, we built a prototype instrument that makes real-time, high fidelity, UV pulse measurements with ultra-fine spectral resolution. We also developed a UV spectral wavefront tool for integration into spatiotemporal UV pulse measurements. In Phase IIB, we will reduce instrument component costs while preserving performance to increase commercial uptake. We will support scientific needs by synthesizing challenging pulse shapes that are of great importance to the FEL community and validating measurement performance. Our ultraviolet ultrafast laser pulse measurement technology will provide badly needed diagnostics in commercial markets. Deep ultraviolet ultrafast pulses are used in both scientific instruments and the semiconductor industry. This SBIR project will also develop new technologies for telecommunications applications.