  External-cavity diode lasers (ECDL) are widely used as light sources in laser
spectroscopy, atomic physics, and quantum optics. This study demonstrated a
home-made 852-nm ECDL with variable feedback, using the combined dual
narrow-band interference filters (IFs) as the laser longitudinal mode selection
element. The combination of narrow-band IFs, mainly for the current
commercially available narrow-band IFs with the full width at half maximum
(FWHM) of approximately 0.5 nm for 780-895 nm. We designed different
narrow-band IFs combinations to achieve a narrower FWHM, and applied them in
the ECDL. The combination of the dual narrow-band IFs further reduces the laser
linewidth. We measured the laser linewidth using a high-finesse Fabry-Perot
cavity with a linewidth of approximately 10 kHz. The laser linewidth is
approximately 176 kHz for the Single-IF-ECDL and 96 kHz for the Dual-IF-ECDL
with the same feedback. In addition, we have experimentally verified the
results of narrower laser linewidth and larger tuning range with increase in
the feedback. The developed Dual-IF-ECDL has the capability of narrow linewidth
and wavelength tunability and can be applied to precision spectroscopy, cooling
and trapping of neutral atoms.
