High Speed Directly Modulated DFB Lasers Having MQW Based Passive Reflectors

We have fabricated $1.3~\mu \text{m}$ band InP based high speed directly modulated distributed feedback (DFB) lasers having passive distributed Bragg reflector (DBR). Because of the feed back from the DBR section, the modulation bandwidth of the lasers is over 25 GHz, which is notably larger than the 19 GHz for a normal single section DFB laser. The reflector of the devices has the same multi-quantum wells (MQWs) as the DFB section, which simplifies the device fabrication greatly, helping to lower the device cost. For the DBR integrated DFB lasers, experimental results show that a larger modulation current efficiency can be obtained when the DFB wavelength is more positively detuned relative to the reflection peak of the DBR reflector. This indicates that a static detune between the DFB wavelength and the DBR reflection peak can be introduced into a distributed reflector laser to get a good detune condition, helping to lower the device cost of high speed directly modulated lasers.