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Multiscale Hydrologic Remote Sensing: Perspectives and Applications
output pulse energy at 942–943 nm is obtained by dual-end pumping with LDs. The
narrowband output of the Nd:GSAG laser is generated using the injection seeding
technique. A distributed feedback diode laser is used as seeder, the wavelength of
which is stabilized by an active control loop based on transmission measurements
of the seed beam through the absorption cell. The seed beam is injected into the
laser cavity via the polarizer. To stabilize the output wavelength of the Nd:GSAG
laser, the cavity length is matched to the wavelength of the seed beam by a PZT element attached to the high-reflectivity mirror. The spectral linewidth of the seeded
Nd:GSAG laser is measured to be 50 MHz, and the spectral purity is 99%. The
M3 Pinhole Filter PD
M2
ISO2
HWP
RP
L2
QWP3
Seed laser
EOM
HR
PZT
OC
Electronic
controller
QWP1
QWP2
45° DM
45° DM
M4
Pulse
generator
Pump
LD
Pump
LD
Nd:GSAG
Delay
generator
ISO1 M1
L1
Cls
0
2 1
FIGURE 14.20  Schematic diagram of the injection-seeded Nd:GSAG laser.
Seed laser system
Pump laser
Data acquisition (obscured)
Detector box
48 cm telescope
OPOs
1 m
FIGURE  14.19  Compact design of the four-wavelength DIAL for the Falcon 20 aircraft
Nd-doped laser-based transmitter.