Page 473 - Tunable Lasers Handbook

8 Tunable External-Cavity Semiconductor Lasers 433
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DIRECTIONAL
COUPLER
pq OPTICAL FIBER
EXT CAV

AMPS

OPTICAL
SPLITTER ANALYZER
RF GEN ..
.I I,
(PHASE CONT . I * .

DIGITAL . I I . . I
OSCILLOSCOPE * , II
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FIGURE 50 Setup for demonstration of optical net\vorh anal) bis with an acousto-opticaliy
tuned ECL.

include analysis of process gas purity. chemical refining, combustion diagnos-
tics, and pollution monitoring.

18.5 Metrology
A grating tuned ECL has been used in an optically pumped cesium-beam
frequency standard (1581. X pair of optically phase-locked ECLs mas used in a
laser-coolled cesium atomic-fountain clock [ 159.1601.

18.6 Second Harmonic Generation

Ther: is a great deal of interest in generating blue light for optical data stor-
age. The cost and size constraints of this application dictate the use of diode
lasers. While blue diode lasers based on 11-VI semiconductors appear to be on
the horizon. the technology for near-infrared 111-V semiconductor lasers is
mature and inexpensive. There have therefore been investigations into second
harmonic generation of 850-nm laser diodes using nonlinear crystals. In second
harmonic generation. PZw 0~ Pf. Therefore, high fundamental power is required
for efficient harmonic generation. In addition, the phase-matching condition
requires a fundamental bandwidth of a few tenths of a nanometer. The nonlinear