High‐energy femtosecond fiber lasers based on pulse propagation at normal dispersion

TLDR

Ultrashort pulse generation in fiber lasers is limited by nonlinear phase shifts, causing performance lag compared to bulk lasers, but new normal‑dispersion modes with highly chirped pulses offer a theoretical framework that could unify and improve fiber‑laser operation. The article reviews several new modes of pulse formation and propagation in fiber lasers. It examines modes that use large normal cavity dispersion and spectral filtering of phase‑modulated pulses to shape highly chirped pulses. These modes enable high‑energy, 10 nJ/100 fs pulses and comparable performance to solid‑state lasers, offering practical advantages of fiber systems.

Abstract

Abstract The generation and stable propagation of ultrashort optical pulses tend to be limited by accumulation of excessive nonlinear phase shifts. The limitations are particularly challenging in fiber‐based devices, and as a result, short‐pulse fiber lasers have lagged behind bulk solid‐state lasers in performance. This article will review several new modes of pulse formation and propagation in fiber lasers. These modes exist with large normal cavity dispersion, and so are qualitatively distinct from the soliton‐like processes that have been exploited effectively in modern femtosecond lasers but which are also quite limiting. Self‐similar evolution can stabilize high‐energy pulses in fiber lasers, and this leads to order‐of‐magnitude increases in performance: fiber lasers that generate 10 nJ pulses of 100 fs duration are now possible. Pulse‐shaping based on spectral filtering of a phase‐modulated pulse yields similar performance, from lasers that have no intracavity dispersion control. These new modes feature highly‐chirped pulses in the laser cavity, and a theoretical framework offers the possibility of unifying our view of normal‐dispersion femtosecond lasers. Instruments based on these new pulse‐shaping mechanisms offer performance that is comparable to that of solid‐state lasers but with the major practical advantages of fiber.