Diffraction gratings are important optical components with a periodic structure which splits, diffracts and disperses light into several beams traveling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light. Diffraction gratings find optical applications in spectrometers, spectral multiplexers and demultiplexers and in monochromators.
At LLNL large area diffraction gratings have been produced with high laser induced damage threshold (LIDT) for both high-energy pulse compression and high-average power Spectral Beam Combining (SBC) applications. Scientists at the lab have developed large area multi-layer dielectric (MLD) grating fabrication techniques well suited for high-energy pulse and high average power laser applications.
LLNL has developed several MLD grating technologies that extend the state of the art in overall laser optical power handling capability. LLNL MLD grating optics are the convolution of the following key technologies:
- Optical coating designs utilizing >100 thin film layers - enables ultra-low-loss, ppm transmission levels through the coating, high diffraction efficiency, and large bandwidth.
- Dispersive surface relief structure design - perfectly impedance matched to the thin film stack for optimum optical performance.
- Ability to fabricate dispersive surface relief structure and advanced optical thin film coating on superior thermally conductive materials such as silicon and silicon carbide.
- Processing techniques permitting the fabrication of optimum optical design.
These innovative MLD gratings solutions improve the performance, reliability and lifetime of optics permitting higher power operation without laser induced optical damage.
The primary application for the LLNL MLD gratings technology is in high power laser facilities to enable significant scaling in output energy and average power for next generation ultrafast and spectrally-combined laser systems.
LLNL has filed several patent applications for its MLD gratings:
“Innovative Solutions for Improving Laser Damage Performance of Multi-Layer Dielectric Gratings”. This invention consists of four key technologies to reduce optics damage in both high-energy pulse compression gratings and high-average power lasers.
“Gold-overcoated dielectric diffraction grating for high average power operations”. This invention is a new class of gold-overcoated diffraction grating developed for high average power laser pulse compression.
“System for improving the laser damage threshold of multilayer dielectric gratings in chirped pulse amplification of lasers”. This invention consists of a system configuration that significantly improves the laser damage threshold of multi-layer dielectric gratings for lasers applications.