Matched Self-Phase Modulation BLR Interferometer

Broadband Laser Ranging (BLR) is a new optical diagnostic for measuring the position of rapidly moving surfaces and projectiles in ballistic or explosive experiments. BLR systems

typically consist of a femtosecond pulse laser, an interferometer, and a lensed fiber to deliver the pulse to the target. A major consideration in the design and development of BLR systems is the pulse energy delivered to the target, higher pulse energies can potentially provide better signal-to-noise but in practice the pulse energy is limited due to Self-Phase-Modulation (SPM), an effect where a non-linear phase is accumulated as the pulse propagates in the fiber. In a standard BLR interferometer only the target arm has significant SPM as the pulse in the reference arm has low energy, here we propose a modification to the BLR interferometer where the SPM is balanced or matched on both arms, this can be achieved by tuning the laser power in the reference arm. Simulations of pulse propagation in the fiber show that a matched-SPM interferometer can potentially sustain higher pulse energies by more than an order of magnitude. The expected challenges for experimental realization of an MSPM interferometer are shortly discussed as well.