Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1995-03-17
1996-10-01
Hellner, Mark
Optical: systems and elements
Optical modulator
Light wave temporal modulation
385 2, 359276, G02F 103
Patent
active
055615465
ABSTRACT:
An intracavity-modulated laser includes a gain element, an electro-optic modulator (EOM), a frequency selective coupler (FSOC), and an optical isolator coupled in such a way that a ring laser cavity is formed. The EOM selectively affects the optical input in intensity, phase, or frequency according the radio frequency (RF) input signal applied. The FSOC is a three-port device that receives light at a first port and passes narrowbands of light out a second port and directs the remaining optical spectrum out a third port. The optical isolator assures single direction lasing. When the gain is sufficient to overcome the ring losses, the laser cavity will oscillate with longitudinal modes corresponding to the pass bands of the FSOC. The light exiting the second port of the FSOC is amplified by the laser gain element and is directed to the EOM. The EOM modulates each carrier (longitudinal mode) of the laser cavity thereby creating optical modulation sidebands associated with each carrier. The FSOC selectively couples the modulation sidebands out of the laser cavity. Since the FSOC contains no active elements, the frequency selective coupling operation is essentially noise-free. In this way an optical source is formed which can be modulated to frequencies limited only by the EOM bandwidths, reduces the RF input voltages required to produce a given modulation depth, effectively couples out only the modulation of the longitudinal modes allowing efficient use of optical components, and improves system performance without adding noise.
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Hellner Mark
McDonnell Thomas E.
Stockstill Charles
The United States of America as represented by the Secretary of
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