Phase-Lock Control Considerations for Multiple, Coherently Combined Lasers.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO SCHOOL OF ENGINEERING
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This paper presents design considerations and fundamental performance limitations of phase-lock control loops used to coherently combine an array of lasers. A two-laser control loop designed to lock the differential frequencyphase between two lasers to a specified reference is first investigated. An integro-differential equation, valid for the linearized operating region of the loop, is derived in terms of the specified desired phase control, the phase measurement heterodyne noise, and the laser phase noise instabilities. Solution of the equation results in an expression for the lasers phase error variance in terms of the closed-loop noise equivalent bandwidth, the 100 measurement noise, and the lasers field linewidths. Loop acquisition time, frequency pull-in range, and steady state phase error are also examined.
- Lasers and Masers