Fiber-interferometric second harmonic generator with dual-color standard quantum-limited noise performance

We present a novel fiber-interferometric device that achieves dual functionality: simultaneous amplification of the pulsed input signal and generation of its second harmonic while effectively suppressing the intensity noise in both modes, reaching the standard quantum -limit. The underlaying mechanism is based on phase -biased nonlinear polarization rotation coupled with type -I phase -matched second harmonic generation, a concept that is both theoretically investigated and experimentally verified. In the experiment, a fiber-optic system is constructed capable of generating 42 MHz ultra -low noise sub -150 fs output pulse trains simultaneously at 1030 nm and 515 nm, with average powers of 165 mW and 50 mW, respectively. Systematic frequency -resolved intensity noise measurements confirm dual wavelength, quantum -limited noise suppression beyond 100 kHz offset -frequency, with suppression levels up to 14 dB, showing correlation with local maxima in average power in both fundamental and second harmonic mode.