Goals

Mission Objectives

Main objective of this project is the realization of narrow-linewidth laser diodes emitting at a wavelength of 435.9 nm. Such diodes are required for spectroscopic applications, especially for the excitement of mercury atoms.

A stand-alone diode with the front facet coated with an antireflection layer (AR diode) is not a functioning laser cavity. It will only emit an enhanced spontaneous radiation when the drive current is reached. Only the formation of a cavity by means of an external diffraction lattice (ECDL) leads to laser emission at a wavelength of 435.9 nm, eventually allowing  excitation of mercury atoms.

Hg atoms are especially attractive for use in atomic traps because their optical excitement is comparatively easy and they can be cooled easily, too. Furthermore, the lifetime of this state is sufficiently long. There is a direct relation between population and power density required for cooling. Hg atom resonances at 253, 313, 365, 405, and 435.9 nm are suitable cooling wavelengths.

Access to the application at 435.9 nm can also be reached using eagleyard Photonics components that are today already available. This, however, requires extreme efforts from customers: They have to buy as one component a standard AR diode with amplification at 870 nm that must be integrated into an external cavity. A power between 30 … 50 mW at a wavelength of 871.8 nm is obtained, what needs to be amplifiedin another assemblage stage into the 500 mW class by means of a tapered amplifier (also available from eagleyard Photonics). The largest amount of optical poweris lost during the following frequency doubling and ray path shaping, leaving 10 mW at best for the Hg atom excitement. With the development of the envisaged diode customers save themelfes two steps which are both technically demanding and cost-expensive.