[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Phase-Locked Programmable Femtosecond Pulse Bursts from a Regenerative Amplifier

摘要： We demonstrate phase-controlled pulse-burst amplification based on differential pathlength stabilization between the master oscillator and the amplifier cavities. This technique boosts the safe level of extractable burst energy and suppresses fluctuations in various burst-mode applications. OCIS codes: (190.4410) Nonlinear optics, parametric processes; (320.5540) Pulse shaping; (320.7160) Ultrafast technology Generation of amplified bursts of femtosecond pulses with tunable and extremely high, reaching into the THz regime, intra-burst frequencies is in high demand for various ultrafast laser applications such as burst-mode femtosecond ablation for materials processing [1], multipulse laser-induced breakdown spectrometry, several types of nonlinear and/or time-resolved spectroscopies and molecular quantum-information technologies [2]. In many cases, the desired inter-pulse spacing within a burst must range from 10 fs to several ps and is limited on the short side by the duration of an individual compressed fs pulse that dictates the minimum pulse separation without significant temporal overlap. In this contribution, we explore the opposite limit of the Vernier technique[3] and generate THz burst frequencies, which requires us to solve the problem of a nearly complete temporal overlap of the chirped pulse replicas enclosed in the RA and present a method for interferometrically stabilizing the relative pathlength difference between ?(cid:2)?(cid:4) and control of the carrier-envelope phases, CEP, of the pulses forming the (Fig.1a). We note, that the standard method practiced in femtosecond comb metrology and synchronously pumped OPOs are not appropriate in our case because the roundtrip time of one of the cavities must be flexibly varied to ensure continuous tuning of (cid:5)(cid:6)(cid:7)(cid:8)(cid:9)(cid:10). Therefore, our approach relies on direct ?(cid:2) stabilization with a readout of a spectral interference fringe produced by overlapping an outgoing MO pilot pulse that has completed a roundtrip through the RA cavity with the next incoming MO pulse at the full MO repetition rate, (cid:5)(cid:11)(cid:12)(cid:13) 76 MHz. Active RA cavity length stabilization is achieved via a PZT on one of the fold mirrors. The CEP scrambling, needed to suppress the formation of spectral modes, is achieved by programming the RF signal in the AOM which permits simultaneous and independent phase and amplitude shaping of each successive MO pulse. Fig.1b proves that in this way it is feasible to control the mode formation in the amplified burst spectrum without affecting the temporal envelope of the burst. Without the CEP scrambling, the energy performance of the RA would be very significantly restricted because the optical damage threshold is lowered as a result of inter-pulse interference[3]. Fig 1c shows the resulting interference recorded in the reference arm at 8 seconds the control electronics is switched off and the cavity is left floating.