Tunable Visible Laser for Photocathode Characterization

Current electron accelerator technologies are fundamentally limited by the photoinjector, where efficient generation of electron bunches with low emittance is required for high performance electron beams. Many facilities currently use photocathode materials with excitation by high power ultraviolet pulses, which places extreme demands on system components. Therefore, photocathode materials with excitation bands in the visible spectrum are being developed. One impediment to a systematic survey and characterization of these materials is the lack of a suitable high power excitation laser that can be tuned across a wide range with high performance. We propose to develop a laser-driven optical parametric amplification system, which will provide tunable picosecond pulses in the visible spectrum at high energy and high repetition rate. Our system emphasizes efficiency in the choice of laser, design of the optical parametric amplifier, and form of the broadband amplified light. In Phase I, we will demonstrate the feasibility of our proposed technique for the generation of tunable visible pulses with tens of picoseconds pulse duration. We will build a prototype of our novel seed source and construct an initial optical parametric amplifier to test performance. We will numerically model scaling the proposed technique to systems with > 100 W average power. Our proposed instrument will provide a valuable tool that can ultimately enable next generation electron accelerator user facilities to operate on a smaller footprint, be built at lower cost, and enhance availability, therefore increasing applications in the medical, research, and security sectors. Our proposed instrument also serves the ultrafast laser market by providing both tunable picosecond pulses, and amplified femtosecond pulses in spectral regions that lack broad gain bandwidths in standard laser materials.