AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

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UNCLASSIFIED/;'POR: OPPICIAE USE 014Lf
Typical HPFLs that use fiber optical oscillators or amplifiers as an alternative to bulk
rods and slabs have the following technical features [31]:
•
Active Gain Medium:
-
Common
host glasses and their combinations:
Silicates;
silicates and
phosphates; silicates, phosphates, and fluorides; silicates, germanates, and
fluorides; silicates and fluorides.
-
Impurity lasing ions deposited (or doped) in host: Neodymium (Nd 3+ ),
Ytterbium
(Yb3+),
Erbium
(Er3+),
Thulium
(Tm 3+),
Holmium
(HoH),
Praseodymium (Pr3+).
-
Range of beam wavelengths (11.) produced: 0.48 µm to 2. 9 µm.
-
Stretched doped rod into a long thin fiber.
-
Simplifies heat removal (large surface area per unit volume).
•
Pump (see Figure 24):
-
Surround lasing fiber with optically transparent jacket.
-
End pump optical jacket with diode lasers.
-
Single diodes or diode bars are coupled into undoped pump fibers
• Pump fibers are spliced or drawn together with the doped lasing fiber.
• Pump light is coupled to the outer, undoped outer fiber.
-
Active medium pumped along entire length
• Pump light then couples into the lasing fiber all along its length.
-
Resonator optics are coupled to the ends of the doped fiber.
•
Large Diameter Fibers (see Figure 25):
-
Handle more power.
-
Larger divergence with less beam quality.
-
Longer output fibers before limits are hit.
•
Small Diameter Fibers (see Figure 25):
-
Better divergence with greater beam quality.
-
Handle less power before limits:
• Material limits - melt.
• Stimulated Brillion Scattering (SBS).
• Stimulated Raman Scattering (SRS).
-
Shorter output fibers.
UNCLASSIFIED'I i'FAA: 061i1Clali.k W&& 8PtLY
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