Fiber-Interferometric Second Harmonic Generator with Dual-Color Standard Quantum-limited Noise Performance

We present a novel experimental 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 160 mW and 42 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.