Influence of a half-wave plate–polarizer attenuator on broadband femtosecond laser pulses

Spectral and temporal influence of a conventional half-wave plate–polarizer attenuator on broadband 50-fs laser pulses is experimentally investigated. Strong spectral modulation, pulse narrowing, and pulse shape variation of the transmitted femtosecond laser beam are recorded at maximum attenuation together with substantial depolarization effect. A simplified theoretical model is developed to take account of the wavelength dependence of the wave plate, which provides satisfactory explanations to the experimental observations.