0.04 Hz relative optical-frequency stability in a 1.5 mu m distributed-Bragg-reflector (DBR) laser

The optical frequency of a 1.5- mu m distributed-Bragg-reflector (DBR) laser is stabilized against that of a master laser by heterodyne-type frequency locking with a phase-locked loop (PLL). Despite the laser's wide linewidth of 16 MHz, stable PLL operation with an optical hold-in range of 26 GHz is realized, and residual frequency fluctuations are reduced to 0.04 Hz at an averaging time of 500 s. The combination of DBR laser and PLL is, therefore, suitable for frequency-controlled light sources. The offset error from the settled frequency caused by the bandlimited beat spectrum is discussed.<
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