Wavelength Modulation Spectroscopy
341
Fig. 9 Tuning coefficient of a 2004 VCSEL, b QCL (HHL-490) and c QCL (HHL-513). Notice
that the response of the QCLs is an order of magnitude less than that of the VCSEL and the roll-off
is also much faster
Fig. 10 Phase variation of the VCSEL, the two QCLs and an edge-emitting laser that exhibits very
different behaviour
341
Fig. 9 Tuning coefficient of a 2004 VCSEL, b QCL (HHL-490) and c QCL (HHL-513). Notice
that the response of the QCLs is an order of magnitude less than that of the VCSEL and the roll-off
is also much faster
Fig. 10 Phase variation of the VCSEL, the two QCLs and an edge-emitting laser that exhibits very
different behaviour