Design and fabrication of photonic crystal resonators for single-mode and vertical surface emission from strain-compensated quantum cascade lasers operating at 4.32 μm

Abstract

Photonic crystal resonators with the C4v symmetry were designed and fabricated on quantum cascade lasers with a strain-compensated multiple quantum well to achieve single-mode and vertical surface emission at 4.32 μm. Their fabrication accuracy was confirmed by high-resolution reflection spectroscopy. The maximum output power was 10 mW at 77 K. A far-field pattern with a small divergence angle below 1 degree was observed. Its main peak had a donut shape, which was attributed to the spatial symmetry of the resonance mode of the photonic crystal.

Improved power and far-field pattern of surface-emitting quantum cascade lasers with strain compensation to operate at 4.3 μm

“…its emission was observable because the momentum selection rule was weakly broken by the finite lateral size of the PC-QCL. 22) For the same reason, the EE of the A 2 mode is also vanishing.…”

“…In our previous study, 22) we successfully integrated the PC resonator to strain-compensated QCLs operating at 4.32 μm and observed the single-mode and vertical surface emission in this wavelength range for the first time. The output power was 10 mW at 77 K and the emitted beam had a donut shape with a divergence angle of less than 2°.…”

“…One is the circular cylinder (PC-QCL-1) that we investigated in Ref. 22 and the other is a pentagonal cylinder (PC-QCL-2). Their top view is illustrated in Figs.…”

“…For PC-QCL-1 with the circular-pillar PC, the B 2 -symmetric mode has the largest Q and overlap factors, so we assumed that lasing took place with this mode. 22) In Sect. 5.1, we verify this fact by the polarization dependence of the far-field pattern (FFP).…”

Study of the spatial characteristics of emission of surface-emitting ring quantum-cascade lasers

“…Quantum-cascade lasers (QCL) of the 8−12 µm spectral range are of interest for the making of chemical element recognition systems (chemical fingerprinting) [1,2], including due to the possibility of integration on one chip [3,4]. Due to the TM polarization of radiation observed in intersubband transition lasers [5], surface out-coupling can be implemented by formation of a one-dimensional [6,7] or two-dimensional diffraction grating (based on photonic crystals [8,9]). At the same time, implementation of lasing in a continuous regime of current pumping in the design of photonic crystals is difficult.…”