Technique to generate equal amplitude, higher-order optical pulses in rational harmonically modelocked fibre ring lasers

A novel technique of pulse amplitude equalisation in higher-order optical pulses in a rational harmonically modelocked fibre ring laser is proposed and demonstrated. The combination of intracavity optical filtering, and even-order modulation sideband generation using nonlinear characteristics of a Mach-Zehnder intensity modulator can effectively eliminate pulse amplitude instability at higher-order rational harmonic modelocking. The generated optical pulse trains exhibit equal amplitudes with a high degree of spectral purity in terms of a large suppression of supermode noise, low amplitude noise, phase noise, and timing jitter