  We present a simple and effective method to implement an active stabilization
of a diode laser with injection locking, which requires minimal user
intervenes. The injection locked state of the diode laser is probed by a
photodetector, of which sensitivity is enhanced by a narrow laser-line filter.
Taking advantage of the characteristic response of laser power to spectral
modes from the narrow laser-line filter, we demonstrate that high spectral
purity and low intensity noise of the diode can be simultaneously maintained by
an active feedback to the injected laser. Our method is intrinsically
cost-effective, and does not require bulky devices, such as Fabry-Perot
interferometers or wavemeters, to actively stabilize the diode laser. Based on
successful implementation of this method in our quantum gas experiments, it is
conceivable that our active stabilization will greatly simplify potential
applications of injection locking of diode lasers in modularized or integrated
optical systems.
