Defense Intelligence Reference Document Laser Lightcraft Nanosatellites

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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
Ytterbium (Yb 3+), Erbium (Er3+),
Praseodymium (Pr 3+).
doped) in host: Neodymium
Thulium (Tm 3+), Holmium
- Range of beam wavelengths(),) 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
(Nd 3+),
(Ho 3+),
■ 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.
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