Experimental Demonstration of a Mode-Competing Multiline Resonant Laser

A multiline guided-mode resonance (GMR) filter is applied as a reflector to implement an external cavity laser. We design the resonant element using rigorous numerical methods and fashion an experimental prototype by thin-film deposition, patterning, and etching. A ~100-nm TiO₂ grating layer on a ~170-μm-thick glass slab supports thousands of resonant modes. We detect ~10 narrow resonance peaks within a ~10-nm wavelength range centered at the 840-nm wavelength. We apply this multiline GMR device to a gain chip and obtain several simultaneous resonant laser lines that compete for the gain. Precise tuning enables a stable laser line that can be selected from the multiple available resonant lines.