Experimental setup for the linewidth reduction of a DFB diode laser using a fiber interferometer with short arm imbalance. DFB; distributed feedback diode laser, ISO; optical isolator, AP; anamorphic prism pair, HWP; half-wave plate, PBS; polarizing beam splitter, FC; 2×2 fiber coupler, SMF; 5-m-long single mode fiber, PD; photodiode, PID; proportional-integral-derivative controller.
Frequency of DFB diode laser before and after the frequency stabilization started at time of 0 h, which was measured by a high resolution wavelength meter. Room temperature is shown at right axis.
Frequency instability (Allan deviation) of the frequency-locked DFB diode laser (filled red circles) and that of the free running one (open black circles). The Allan deviation of the frequency-locked DFB diode laser, when the room temperature was more stable, is also shown (filled blue squares). The wavelength meter stability limit is shown with open triangles.
Frequency noise power spectral density versus Fourier frequency of the free-running DFB diode laser (open circles), the stabilized DFB diode laser (in-loop with red line and out-of-loop with black line), and the measurement limit (gray line).
The beat note between the DFB diode laser and the ECDL stabilized by an optical cavity when the DFB diode laser is free-running (gray line) and stabilized by a fiber MZI (black line). The inset shows the beat note between the stabilized lasers with a higher resolution.
Long-term frequency measurement of the DFB diode laser stabilized by a fiber MZI. The daytime measurement was obtained from 9:00 to 18:00, and the night-time measurement was obtained from 18:00 to 9:00.
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