Cobalt-doped magnesium aluminate spinel, Co:MgAl2O4, is a saturable absorber for passive Q-switching around 1.2–1.6 µm, including Er:glass systems. Initial transmission, aperture and coating determine the operating configuration. The legacy topic label uses MgAl2O3; the technical description identifies MgAl2O4.
Properties, applications and specifications
Co2+:MgAl2O4 (or Co:Spinel) is a relatively new material for saturable absorber passive Q-switching in lasers emitting from 1.2 to 1.6 microns, in particular, for eye-safe 1.54 μm Er:glass laser.High absorption cross section of 3.5 x 10-19 cm2 permits Q-switching of Er:glass laser.High absorption cross section of 3.5 x 10-19 cm2 permits Q-switching of Er:glass laser without intracavity focusing both with flash lamp and diode-laser pumping. Negligible excited-state absorption results in high contrast of Q-switch, i.e. the ratio of initial (small signal) to saturated absorption is higher than 10.
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Characteristics of Spinel Crystal
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crystals structure
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cubic
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Spatial group
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Fd3m
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Element ary cell parameters,
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0.8086nm
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Thermal Conductivity
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17W/m.k @20deg.
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Thermal Expansion
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7.33x10-6/k
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Modulus of elasticity
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2.3x 10^5
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Density,
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3.58g/cm 3
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Mohs hardness
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8
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Melting point,
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2105 ° C
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Refraction index
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1.6.-1.75
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486.1nm
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1.72433
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546.1nm
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1.71976
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589.3nm
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1.71611
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656.3nm
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1.71268
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Working wavelength range, 1.2 – 1.6μm Absorption cross-section, 3.5×10-19 (at 1.54 μm)cm2
Specifications:
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T0
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From 30% to 98% 1540nm
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Dimension tolerance
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(W ± 0.1 mm) x (H ± 0.1 mm)
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Transmitting wavefront distortion:
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L/8 @ 633 nm
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Clear aperture:
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> 90% central area
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Flatness:
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L/8 @ 633 nm
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Scratch/Dig code:
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10/5 to MIL-O-13830A
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Parallelism:
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better than 20 arc seconds
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Perpendicularity:
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5 arc minutes
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Angle tolerance:
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Dq < ±0.5°, Df < ± 0.5°
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AR coating:
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R< 0.2% at 1540nm
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Note: When ordering Co:MgAl2O4 crystal, please specify the aperture, initial transmission(To) and coatings.
