Page 465 - Tunable Lasers Handbook

8 Tunable External-Cavity Semiconductor Lasers 425

R,,, = 0.005
5T
..
- 4 ..

Rlnt = .01
Rex, = 20

d3

RI,, = 0.025

WAVELENGTH
FIGURE 43 Threshold gain versus navelength for various combinations of facet and external-
cavity refectances. demonhtrating evolution of regions of bistabilit). (Reproduced with perniission
from Zorabedian er al. [Z]. 0 1987 IEEE.)

25 30
CURRENT ImAI
FIGURE 44 Light output versus current curve for a bistable ECL. (Reproducsd nith perms-
sion from Zorabedian Yt a/ [23]. 0 1987 IEEE )

wavelengths. The stability analysis shows that the tolerance of the laser to resid-
ual facet reflectance is increased by increasing external feedback strength and
reducing 01. There are limits to the effectiveness of either approach. First. it is
difficult to obtain external feedback in excess of the feedback of an uncoated