Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1999-08-27
2000-10-31
Epps, Georgia
Optical: systems and elements
Optical modulator
Light wave temporal modulation
359618, 359122, 359189, G02F 103
Patent
active
061411361
ABSTRACT:
Active phase-shift control is achieved in a hybrid etalon by selecting appropriate elements in the photodiode array 22, 22' of FIG. 2 for a prescribed phase-shift. A negative lens 20, (20") is used to expand the beam spot of the output beams P.sub.2 16, (P.sub.1 18) to the line length of the photodiode array 22, (22'). The signal beam 14 and the LO (local oscillator) beam 12 are angularly misaligned by the incident beam angle .delta. 26 to the 2-face 8 and .delta.' 26' to the 1-face 10 (.delta.'.noteq..delta.), thus resulting in the misaligned signal and LO beamlets inside the etalon 6. The beamlets from the 2-face 8 comprise the P.sub.2 beam 16 and the beamlets from the 1-face 10 comprise the P.sub.1 beam 18. The photodiode array 22, 22' detects an interference fringe pattern in the output beams P.sub.1 18 and P.sub.2 16 due to the misaligned input beams. The beamlets from the 2-face 8 and the 1-face 10 have been expanded for illustrative purposes in FIG. 2 lie within the initial beam diameters of the signal 14 and LO 12 beams. Both input beams 12, 14 are linearly polarized, and the signal beam 14 has a variable polarization angle. For a conventional etalon 6 the polarization angle of the LO beam 12 bisects the crystal axes of the input quarter-waveplate 24. The input quarter-waveplate 24 in the signal channel allows the polarization angle of the signal beam to combine into the overall phase angle of the output beams of the hybrid and thereby makes possible to have simultaneous phase- and polarization-diversity properties in the hybrid.
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Epps Georgia
Thompson Timothy
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