Unidirectional mode selection in bistable quantum cascade ring lasers.

Ideal ring resonators are characterized by travelling-wave counter-propagating modes, but in practice travelling waves can only be realized under unidirectional operation, which has proved elusive. Here, we have designed and fabricated a monolithic quantum cascade ring laser coupled to an active waveguide that allows for robust, deterministic and controllable unidirectional operation. Spontaneous emission injection through the active waveguide enables dynamical switching between the clockwise and counterclockwise states of the ring laser with as little as 1.

Engineering optical emission in sub-diffraction hyperbolic metamaterial resonators.

Sub-diffraction hyperbolic metamaterial resonators are promising structures for engineering light-matter interactions in semiconductor-based emitters and materials. The optical properties of these resonators are determined by a number of device characteristics including the metamaterial permittivity and resonator geometry. In this letter, we develop an optical model based on the modified long wavelength approximation to calculate the radiative and non-radiative photon loss of the resonators.

Wavelength independent normal incident quantum cascade detectors.

We demonstrate a novel technique for normal-incident absorption in intersubband infrared detectors by taking advantage of light scattering from the side-walls of a wet-etched mesa. We fabricate 'spiral' and 'hairpin' shaped quantum cascade detector at a peak wavelength of 6.6 μm, and compare their performance with a standard rectangular mesa.

Sub-diffraction negative and positive index modes in mid-infrared waveguides.

We characterize a strongly anisotropic waveguide consisting of alternating 80 nm layers of n(+)-InGaAs and i-AlInAs on InP substrate. A strong increase in the transverse magnetic (TM) reflection at lambda = 8.4 microm corresponds to a characteristic low-order mode cutoff for the left-handed waveguide.

Cavity ringdown spectroscopic detection of nitric oxide with a continuous-wave quantum-cascade laser.

A spectroscopic gas sensor for nitric oxide (NO) detection based on a cavity ringdown technique was designed and evaluated. A cw quantum-cascade distributed-feedback laser operating at 5.2 mum was used as a tunable single-frequency light source.