Injection-Locking of Blue Laser Diodes and Its Application to the Laser Cooling of Neutral Ytterbium Atoms

Abstract

We present a simple, laser-diode-based ultraviolet light source with sufficient power and narrow linewidth. In this scheme, an injection-locking technique was applied, for the first time to our knowledge, to a GaN blue laser diode (LD). By injecting ∼5 mW output light of the external cavity laser diode (ECLD) into two free-running blue slave LDs, we could obtain an output power of over 30 mW from the injection-locked slave LDs. The characterisitics of the injection-locked slave LD were studied in detail. We also present an absolute frequency-locking scheme with about a 500 MHz locking bandwidth, where we achieved offset-locking of the frequencies of two ECLDs. As an interesting example of the application of these developments, we demonstrated laser cooling and trapping of ytterbium atoms.