Pulse control in a wide frequency range for a quasi-continuous wave diode-pumped cesium atom vapor laser by a pump modulation in the spectral domain.

Diode-pumped alkali-atom laser (DPAL) has attracted intense attention due to its inherently high quantum efficiency, a good beam quality, and a high potential in the power scaling. However, most of DPAL research has been confined to the continuous wave and only a few pulsed operations have been attempted with limited performances. Here, we proposed and experimentally demonstrated a new scheme using a fast mode-hopping in the pump laser diode (LD), which enabled the quasi-continuous-wave (QCW) pulse modulation in a cesium (Cs) DPAL to control both the pulse width and the repetition rate. The pump wavelength was efficiently modulated in a fast cycle within discrete spectral ranges provided by the mode-hopping in the pump LD. The spectral range was successfully adjusted to include the resonant D absorption line of Cs atom to result in an effective gain modulation. Using this proposed scheme, we successfully achieved Cs-DPAL QCW modulation, whose pulse width was varied from tens of microseconds to a few milliseconds and the repetition rate was also variable in a wide frequency range from 10 Hz to 7.0 kHz. Detailed pump modulation method and the corresponding laser characteristics are discussed. The proposed method can be readily applied to pulse modulation of other types of alkali vapor lasers overcoming the previous limitations of DPAL to further expand applications in various light-matter interactions.