A method to reduce the spectral linewidth of a laser source by direct phase noise compensation is proposed and demonstrated experimentally. To extract the phase noise information, the laser output is phase modulated and the in- and quadrature-phases are detected by homodyne mixing. Phase noise compensation is achieved by simply applying an error signal to an external phase modulator, where the error signal is generated to keep the same power level for the detected in- and quadrature-signals. The spectral linewidth of the laser is reduced significantly from 450 to 60 kHz.

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Spectral width reduction of a laser source by external phase noise compensation

References

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