Multi-band chirped mirrors for enhanced dispersion management

Effective dispersion management for broadband and highly dispersive optical systems becomes increasingly vital in ultrafast applications. While chirped mirrors provide a compact solution, their attainable dispersion is often limited by the operational bandwidth. This study introduces innovative multi-band chirped mirror designs that enable the management of group delay differences both within and between bands, further optimizing group delay dispersion across specific spectral regions. Here, we highlight the critical role of transmission group delay within multilayer coatings for broadband dispersion management, shifting the traditional interpretation which relies on the wavelength-dependent penetration of these coatings. We have thus developed a dual-band chirped mirror pair achieving group delay dispersion values of −100 fs in the 0.6–0.8 µm range and −260 fs in the 1.7–2.2 µm range, with the bands separated by more than an octave. Remarkably, this design outperformed a state-of-the-art ultrabroadband mirror pair by three and four times of group delay dispersion in the respective bands. We have also designed and implemented a specialized dual-band mirror pair for nonlinear light microscopy—a prime example of ultrafast applications—and successfully achieved transform-limited pulses for targeted fluorophore excitations. This research emphasizes the transformative potential of strategic group delay distribution, heralding a breakthrough in dispersive optical operations across specific wavelength ranges.