A high‐power, power‐modulated transversely excited atmosphere (TEA) CO2laser system is developed with the intention of applying it to high‐temperature plasmas for diagnostic purpose. Two‐mode pulse injection locking is adopted to obtain the required output pulses of the TEA CO2laser. Together with the power modulation, the gain‐switched spike of the output pulses are also suppressed by the adopted method, resulting in pulse lengthening. Two feedback loops are incorporated for reliable power modulation. The power‐modulated output so obtained is used to excite electrostatic plasma waves in laboratory plasmas.