PGL Publishes Paper on Out-of-Plane Polarization Dispersion

CARVER, Massachusetts / March 9th, 2026 – The new regime of high repetition rate, short pulse lasers requires novel approaches to improving the damage threshold and thermal resistance of high power laser optics. Diffraction gratings used in pulse compression systems are often considered a bottleneck when increasing average power due to the extremely high fluence incident on the surface of the optics. Historically, gold-coated diffraction gratings have been preferred in femtosecond pulse compressors for their broadband performance and commercial availability. More recently, Plymouth Grating Laboratory (PGL), the leading commercial manufacturer of large aperture, high-performance diffraction gratings for laser systems, has worked with leading laser facilities to introduce dielectric gratings for femtosecond pulse compression.

The use of multilayer dielectric (MLD) gratings for femtosecond pulse compression decreases surface heating compared to metal-coated gratings which absorb significantly more heat. This lower absorption, combined with higher peak efficiency, are desirable qualities of MLD gratings for high repetition rate applications like secondary source generation and inertial confinement fusion. The challenge when switching to MLD gratings is the need to use an out-of-plane compressor configuration.

This new compressor configuration comes with an optical concern in the form of “polarization dispersion,” or a wavelength-dependence of the polarization state. To explore this problem, PGL has published a new paper to Applied Optics which covers the theory of polarization when applied to an out-of-plane pulse compressor. The authors also explore the degree of ellipticity introduced by the out-of-plane gratings and how this could potentially lead to compound pulse-compressor-waveplate constructions in the future.

The abstract and full paper are currently available here, in volume 65, issue 2 of the Applied Optics journal by Optica.