Page 463 - Tunable Lasers Handbook

8 Tunable External-Cavity Serniconductoi Lasers 42

TABLE 8 Frequency Stabilization Experiments

Type of Laser Wavelength Frequency standard Reference

Extended-cavity laser 850 nrn Cs-D, line
Solitary laser diode 850 nm Fabq-Perot etalon
DFB laser 1.3 um Ar (optogalvanic effect)
DFB !aser 1.5 Fm Kr (optogalvanic effect)
Extended-cavity laser 1.5 pm NH, absorption line
3FB laser 1.5 pm Rb (second harmonic generation of
laser output in organic fiberi
Xing external-cavity laser 1.3 ,um Fiber resonator
Extended-cavity laser 180 nm sjRb 5S,:2+5D,,,
DFB laser 1.5 prn CIH, absorption line
DFB laser 1560 nm b7Rb D, line at 180 nm (second harmonic
generation in KNbO; crystalj
Extended-cavity laser 1.15-1.54 pm Sumey of 26 atomic transitions for fre-
quency stabilization by optogalvanic effect

where n is ithe semiconductor index of refraction and vq is the q'th longitudinal
mode of the solitary gain chip Fabry-Perot cavity. If tz and vq are assumed to be
constants, tlhen we obtain an approximately sinusoidal variation of the threshold
gain with respect to v [44]. However, it is actually quite important to take into
account the back reaction of the threshold gain on the index of refraction, which
is given by

where 17 and gth, respectively. denote the index of refraction and threshold gain in
the presence of external feedback at the frequency v. and i?o and go are the corre-
sponding qluantities for the solitary laser diode in the absence of external feed-
back. Incoqporation of the gain-dependent refractive index shift described by Eq.
(95 j into the phase part of the threshold condition described by Eq. (94) results in