Hectowatt Double-pass Chirped-pulse Amplification Seeded by an mW-level Phase-locked Yb-fiber Optical Frequency Comb

Hectowatt fiber optical frequency combs (OFCs) are significant laser sources for the generation of ultraviolet, visible, and mid-infrared pulses, and they are normally obtained through single-pass cascaded fiber amplifiers, wherein these multistage structures hinder the integrated optimization of size and weight. Here, we demonstrate a double-pass chirped-pulse amplification (DPCPA) system seeded by an mW-level phase-locked Yb-fiber OFC. This DPCPA system directly emitted a 100 W ultrafast pulse train at an injected seed power of just 20 mW, exhibiting a high amplification gain of 37 dB and an energy efficiency of 42.4%. The fine dispersion matching was accomplished using a well-designed stretcher and compressor, achieving clean compressed pulse duration of 311 fs. Moreover, the detailed noise property revealed that the output relative intensity noise was mainly limited by the pump noise of the main amplifier, and the in- and out-of-loop phase noise characteristics of the DPCPA OFC were contrastively analyzed. Such a double-pass system paves the way for the further development of compact high-power OFCs from low-power injected seed lasers.