Mach-Zehnder modulator condition for a low chirp factor versus DC bias

An analysis of the Mach-Zehnder modulator's chirp factor alpha versus DC bias is presented. Unlike the well-known belief that alpha is infinite at 0 and pi biases, it is shown that alpha can be zero at these biases under a careful balance of the modulations in the two modulator arms. Derivation of the condition to achieve this effect is given, and practical verifications are presented, where an excellent agreement with the theory is obtained. It is shown that modulators with a lowresidual chirp over a wide range ofDCbias are achieved by designing theRFdriving such that ff would be minimized at zero bias instead of at quadrature bias as used currently in the modulator design. (C) 2022 Optica Publishing Group