Page 438 - Tunable Lasers Handbook

398 Paul Zorabedian

8. SURVEY OF EXTERNAL-CAVITY LASER DESIGNS

8.1 Grating-Tuned Lasers
In terms of optical performance, the diffraction grating is arguably the best
filter for tuning an ECL, because it combines high efficiency and nearly enough
resolution to resolve a single external-cavity longitudinal mode. The following
examples from the literature are organized by cavity class as defined earlier.

8. 7. I Grating-Tuned Extended Cavities
The grating-tuned extended-cavity laser is by far the most commonly reported
type of ECL, with dozens of papers in the literature. The design most commonly
used is the "standard" Littrow configuration (Fig. 26). Table 6, which lists some
published grating-tuned extended-cavity designs, is far from complete; it is a rep-
resentative sampling and points out some noteworthy features and innovations.
8. 7.2 Grating-Tuned Double-Ended External Cavities
A double-ended ECL based on an 830-nm AlGaAs diode was described by
Fleming and Mooradian [38] (Fig. 31). Camera lenses were used as the collima-
tors. The large-diameter beam produced by the collimators made the laser very
sensitive to acoustic and thermal disturbances. A space frame constructed of
superinvar rods was used for the cavity support structure. and the laser was oper-
ated inside a Lucite enclosure.

TUNING
AXIS
u
DIFFRACTION 1
-3

ALIGNMENT
AXIS

AR CGA.TlNG

COLLIMATING
OBJECTIVE
OUTPUT
FlGU RE 26 Standard Littrow-grating ECL. (Reproduced with permission from Zorabedian and
Trutna [60].)