  An extended cavity diode laser operating in the Littrow configuration
emitting near 657 nm is stabilized via its injection current to a reference
cavity with a finesse of more than 10^5 and a corresponding resonance linewidth
of 14 kHz. The laser linewidth is reduced from a few MHz to a value below 30
Hz. The compact and robust setup appears ideal for a portable optical frequency
standard using the Calcium intercombination line.
