Loss-reduction in midinfrared photonic crystal quantum cascade lasers using metallic waveguides

Abstract

We describe a mechanism for plasmonic loss reduction in midinfrared metallic photonic crystals and apply it to surface-plasmon quantum cascade lasers. We obtain pulsed, room-temperature operation of surface-emitting photonic crystal quantum cascade lasers operating at λ≈7.4 μm. The photonic crystal resonator is patterned in the de- vice top metallization, and laser operation is obtained on a band-edge mode of the photonic band structure. The emission is spectrally single mode, with a side-mode suppression ratio of 20 dB, and on-chip tun- ability is obtained over a wavelength range of ≈0.52 μm. Simulations based on a finite elements approach and on the finite-difference time- domain method allow us to study the photonic-band structure, the elec- tromagnetic field distributions, and especially, the influence of the device parameters on the losses. The comparison between the measured and simulated far-field emission patterns and polarization proves the lasers operate on a monopolar-symmetry mode C 2010 Society of Photo-Optical Instru-