Page 397 - Tunable Lasers Handbook

8 Tunable External-Cavity Semiconductor Losers 357

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LASER DIODE

FIGURE 3 Output beam from laser diode without astigmatism.

LASER DIODE
ASTIGMATISM

FIGURE 4 Output beam from laser diode with astigmatism.

and thus see lower internal losses. Laser diodes usually have TE polarization
ratios of a1 least 100: 1 when biased well above threshold.

2.6 Transverse Device Structures
The coupling between the active region and the external cavity occurs at the
plane where the facet intersects the active region. To design efficient coupling
optics for this interface, it is useful to have a rudimentary understanding of the
mechanisms by which carrier confinement and optical waveguiding are achieved
in the diode laser.