We report a fully–correlated multi–mode pumping architecture optimized for dramatic noise reduction of a class–A dual–frequency Vertical External Cavity Surface Emitting Laser (VECSEL). Thanks to amplitude division of a laser diode, the two orthogonally polarized modes emitted by the VECSEL oscillating at 852 nm are separately pumped by two beams exhibiting fully in–phase correlated intensity noises. This is shown to lead to very strong and in–phase correlations between the two lasing modes intensities. As a result, the phase noise power spectral density of the RF beat note generated by the two modes undergoes a drastic reduction of about 10 to 20 dB throughout the whole frequency range from 10 kHz to 20 MHz and falls below the detection floor above a few MHz. A good agreement is found with a model which uses the framework of rate equations coupled by cross–saturation. The remaining phase noise is attributed to thermal effects and additional technical noises and lies mainly within the bandwidth of a phase–locked–loop.

We demonstrate the signal-to-noise ratio (SNR) and/or the recording speed improvement of dual comb spectroscopy (DCS) with time- programmed electro-optically modulated (EOM) frequency combs, in a simple all-fiber architecture. Unlike mode-locked laser based combs, where time-programming requires complex locking mechanisms, time-programming in EOM combs is simple and robust. Thus by directly engineering time-shifts into the pulse train of an EOM comb, the dead time of the interferogram signal in DCS is reduced. The utilized time-shifting technique is theoretically analyzed and the results are experimentally verified. A SNR improvement of 11.6 dB or a 12 times reduction in recording speed is demonstrated experimentally with this simple method. These results open new possibilities for improvement of SNR and/or recording speed of EOM-based multi-comb spectroscopic techniques.

This paper presents a novel approach to dual-frequency comb generation utilizing a single fiber Fabry–Perot resonator, advancing the implementation of these sources in fiber-based systems. Dual-comb applications such as spectroscopy, ranging, and imaging, known for their high-resolution and rapid data acquisition capabilities, benefit significantly from the stability and coherence of optical frequency comb sources. Our method leverages the birefringent property of the resonator induced by the optical fiber to generate two orthogonally polarized optical frequency combs in a monolithic resonator. This approach allows for the generation of two different frequency combs with slightly different repetition rates, exhibiting excellent mutual coherence, making it highly relevant for dual-comb applications. The 40 nm bandwidth generated combs are induced by switching-waves in a normal dispersion fiber Fabry-Perot resonator. These comb types have the advantage of being easily generated by a pulse pumping scheme, which is employed in this study. Finally, the potential of the source is demonstrated by a proof-of-concept spectroscopy measurement.