Modulation characteristics of MFA-MOPAs

The monolithic flared-amplifier master oscillator/power amplifier (MFA-MOPA) has emerged as a preferred technology for obtaining high power, diffraction-limited optical output from a single-frequency semiconductor source. Diffraction-limited operation has recently been demonstrated to an optical output power of 3 W cw with greater than 90% of the optical power in a single diffraction-limited lobe. These devices are useful in applications ranging from frequency doubling to inter-satellite communications. One of the unique advantages of the MOPA approach is that a large change in amplified output power can be obtained by a relatively small change in the injected signal from the master oscillator. In the MFA-MOPA, this means that several watts of optical output can be modulated by changing the master oscillator bias by a few tens of mA. This paper shows that the modulation bandwidth of the MFA-MOPA is essentially that of the master oscillator. Under small-signal modulation, a -3 dB corner frequency of 2.2 GHz is measured