Alignment dependence of relative intensity noise in laser diode fiber pigtailing

In this work, the relative intensity noise (RIN) with relation to alignment parameters of a non-isolator packaging process is reported for the first time. We present the first detailed report on the dependence of the RIN of a fiber pigtailed laser diode on the process of pigtailing to a cleaved single mode fiber. The packaged device might have different RIN value due to the different alignment position where the reflection from the package is different. It is demonstrated that there is an optimal fiber-laser alignment position at which the value of RIN is at a minimum. It is thus important to consider the RIN optimization during fiber-laser alignment, in addition to seeking the maximum optical power coupled into the fiber. This work demonstrates that the RIN measurement is imperative when we prototype any non-isolator laser diode packaging.