2.1 Generation of Broadband Terahertz Radiation
27
Femtosecond
optical pulse
THz pulse
Time
+V
-V
(a)
Time
Charge carriers
(b)
Photocurrent
Time
Charge carriers
(c)
Photocurrent
Charge carriers
(d)
Photocurrent
Charge carriers
(e)
Photocurrent
Generation of
charge carriers
Photocurrent
Time
Time
(f)
Masking layer
Substrate
Electrically
insulating layer
Electrical
contacts
Fig. 2.1 a THz generation from a photoconductive emitter. Panels b–e show the generation of new
charge carriers (brown curve) and the photocurrent in the device (pink curve) at each respective
step in panel (a). f Electrode geometry of an interdigitated photoconductive emitter