Frequency stabilization of quantum-cascade lasers by use of optical cavities.
We report a heterodyne beat with a linewidth of 5.6+/-0.6 Hz between two cavity-stabilized quantum-cascade lasers operating at 8.5 microm . We also present a technique for measuring this beat that avoids the need for extreme isolation of the optical cavities from the environment, that of employing a third servo loop with low bandwidth to force one cavity to track the slow drifts and low-frequency fluctuations of the other. Although it is not fully independent, this technique greatly facilitates heterodyne beat measurements for evaluating the performance of cavity-locked lasers above the bandwidth of the third loop.
Taubman
Matthew S
MS
Myers
Tanya L
TL
Cannon
Bret D
BD
Williams
Richard M
RM
Capasso
Federico
F
Gmachl
Claire
C
Sivco
Deborah L
DL
Cho
Alfred Y
AY