Demonstration of a low-pressure Rb amplifier with an FADOF-coupled ultra-narrowed diode pumping source.

Area of Science:

• Atomic, Molecular, and Optical Physics
• Laser Physics and Photonics

Background:

• Diode-pumped alkali lasers (DPALs) are key for high-energy applications.
• Traditional DPALs use broad-linewidth lasers (∼100 pm) requiring high buffer gas pressures.
• Buffer gases broaden alkali absorption lines to match pump spectra, increasing operational pressure.

Purpose of the Study:

• To develop a low-pressure DPAL system.
• To investigate the use of an ultra-narrow diode laser as a pump source.
• To demonstrate effective amplification in rubidium vapor at reduced buffer gas pressures.

Main Methods:

• An ultra-narrow diode laser with a pm-level linewidth was developed.
• An Rb Faraday anomalous dispersion optical filter (FADOF) was used for wavelength stabilization.
• The narrow-linewidth laser was employed to pump a rubidium vapor amplifier with varying CH4 pressures.

Main Results:

• The diode laser linewidth was narrowed to 3.9 pm (1.9 GHz) by locking to the Rb D2 line.
• Effective amplification was achieved at CH4 pressures as low as 50 Torr.
• An amplification factor of ∼344 was obtained at 200 Torr CH4, comparable to 400 Torr.

Conclusions:

• Ultra-narrow diode lasers enable efficient low-pressure DPAL operation.
• This approach reduces buffer gas requirements and maintains high amplification.
• Low-pressure DPALs offer potential for high-energy laser power scaling with improved efficiency and beam quality.