Diode laser spectrometer for high-resolution spectroscopy in the visible range

A high-resolution diode laser spectrometer operating at 657 nm is described. To achieve a narrow linewidth and a high power, a master-slave laser system is employed. The master laser is an extended cavity diode laser whose linewidth is reduced to less than 100 Hz by the FM sideband technique. The slave laser is an AR-coated diode laser and characteristics of injection locking are experimentally studied. The injection current of the slave laser is utilized to stabilize the output power or to produce pulsed output. Using this spectrometer, we probed the intercombination line of Ca and observed high-contrast optical Ramsey fringes with a linewidth of 10 kHz. A velocity-selective Ramsey fringe is also observed in the pulse-mode operation.