  The coherent population trapping (CPT) atomic clock is very promising for use
in next-generation spaceborne applications owing to its compactness and high
performance. In this paper, we propose and implement a CPT atomic clock based
on the direct modulation of a large-modulation-bandwidth and narrow-linewidth
distributed Bragg reflector laser, which replaces the usually used external
bulk modulator in the high-performance CPT clock. Our method retains the high
performance while significantly reducing the size. Using this highly compact
bichromatic light source and simplest CPT configuration, in which a circularly
polarized bichromatic laser interrogates the ^{87}Rb atom system, a CPT signal
of clock transition with a narrow linewidth and high contrast is observed. We
then lock the local oscillator frequency to the CPT error signal and
demonstrate a short-term frequency stability of 3.6 \times 10^{-13}
{\tau}^{-1/2} (4 s \le {\tau} \le 200 s). We attribute it to the ultralow laser
frequency and intensity noise as well as to the high-quality-factor CPT signal.
This study can pave the way for the development of compact high-performance CPT
clocks based on our scheme.
