Optical parametric chirped pulse amplifier at 1600 nm with all-optical synchronization

Abstract

Abstract:We demonstrate the amplification of 1.6 µm pulses by a KTA optical parametric chirped-pulse amplifier based on an all-optical synchronization scheme as a scalable approach to generation of high power tunable mid infrared.With ultrafast mid-infrared (MIR -2 µm to 20 µm) spectroscopy it is possible to probe structural dynamics of molecules and with sufficient peak power drive strong field control of molecular processes to sample far from equilibrium coordinates. However, generating the high peak power, ultrashort, IR pulses needed in those experiments is challenging as there are few suitable laser mediums and the wavelengths needed cover a broad range. The current MIR systems rely on optical parametric amplifiers (OPAs) pumped by Ti:Sapphire amplified systems [1].Because the pump wavelength is relatively short, the MIR radiation is generated after two cascaded nonlinear processes which greatly limit the efficiency and the scalability of such a scheme. This downfall could be avoided by using a longer pump wavelength.Erbium-doped fiber lasers (EDFLs) operating at 1.56 µm can generate 100-fs pulses and would be a great candidate for MIR OPA pump laser. However, it is difficult using standard approaches to amplify EDFLs to the watt level while keeping the bandwidth needed for 100-fs pulses. A way around this problem is to use optical parametric chirped-pulse amplifiers (OPCPAs) which exhibit high gain for large bandwidth. Furthermore, since the gain is generated via a nonlinear parametric process, it is possible to tune the amplifier to the desired wavelength.We report on the performance of an OPCPA based on an all-optical synchronization scheme to couple well established high power amplifiers in the 1 µm range to extend the power class of mid IR systems. OPCPAs require tight synchronization between the pump and the seed lasers. This can be achieved using electronic phase-lock loops controlling the cavity length of the oscillator. Although those systems can be quite good, they are not unconditionally stable and require continuous monitoring and adjustment. All-optical synchronization schemes can be, in principle, made robust enough to facilitate everyday use. In our OPCPA, an all optical synchronization method is achieved by shifting the wavelength of part of the EDFL output to seed the amplifier. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.