We present a 13C2H2 frequency-stabilized λ/4-shifted distributed feedback laser diode (DFB LD) with an external fiber ring cavity. By controlling the λ/4-shifted DFB passband to track one Fabry-Pérot mode associated with the fiber ring cavity, the oscillation frequency was continuously tuned over 1.2 GHz without mode-hopping. The optical frequency was stabilized to a 13C2H 2 absorption line with an external frequency modulation scheme that enabled us to realize an output beam without additional modulation. As a result, we obtained a frequency stability as high as 1.4 × 10-10 for τ =1 s and 1.3 × 10-11 for τ =100 s. In addition, we simultaneously achieved a linewidth of 2.6 kHz and a relative intensity noise of less than -135 dB/Hz.
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