A tunable ECDL at 480 nm for $^{\mathrm{87}}$Rb Rydberg physics

We have designed and built a tunable nominal 50 mW external cavity diode laser at 480 nm to excite $^{\mathrm{87}}$Rb atoms to high-lying Rydberg states via the two-photon 5S$_{\mathrm{1/2\thinspace }}\to $ 5P$_{\mathrm{3/2}} \quad \to $ nD$_{\mathrm{5/2\thinspace }}$pathway (in conjunction with a 780 nm laser). Our design is based on a low-cost nominal 488 nm single transverse mode laser diode, without any special coating or wavelength post-selection requested of the manufacturer. Stable and mode-hop free tuning over a wide frequency range has been achieved through a careful analysis of the grating feedback geometry. We have also designed and started construction of an optical transfer cavity stabilization system to achieve a nominal 10 kHz laser linewidth.