Enhancing Scalability and Efficiency of Self-Phase Modulation-Enabled Spectral Selection

Optimization of self-phase modulation (SPM)-enabled spectral broadening has driven significant advancements in nonlinear compression schemes. SPM-enabled spectral selection (SESS) has emerged as a straightforward and powerful technique for generating femtosecond laser sources with simultaneous spectral peak and bandwidth tunability [1]. Through nonlinear phase accumulation during pulse propagation in Kerr media, SPM-enabled spectral broadening produces broadened spectra with distinct spectral lobes. The outermost lobes are selectively filtered to achieve tunable outputs by varying initial pulse conditions. SESS offers a straightforward and versatile approach for applications in nonlinear spectroscopy and advanced imaging, including multiphoton fluorescence and harmonic generation microscopy [1]–[4]. Despite its advantages, achieving efficient and wide-range spectral tunability presents challenges. While SESS systems typically demonstrate 10-20% conversion efficiencies, efficiency drops significantly at extended wavelengths. For example, hollow-core fiber systems achieve spectral tunability up to 1.7 μm with multi-megawatt peak powers, but efficiency decreases dramatically below 10% beyond 1300 nm due to reduced energy concentration in the outermost lobes [4].