An enhanced tunable Littrow-configuration externalcavity
diode laser (ECDL) is constructed from inexpensive
commercial components and then characterized.
The introduction of an additional mirror parallel
to the diffraction grating allows the laser to be
tuned without changing the direction of the output
beam. The 785 nm ECDL has a typical power output
of 4 mW at 56.0 mA of current input with an
effective tuning range of 13 nm and exhibits excellent
output-beam directional stability. An upper limit on
its linewidth is placed at 63.0 MHz.
beam with respect to the grating, otherwise known as
the Littrow angle θ. Thus, by changing the Littrow
angle, precise wavelength tuning can be achieved.
The Littrow configuration offers the advantage of
high efficiency and power but also faces problems of
mode-hopping and beam angular displacement as the
grating angle is adjusted.