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MM waveguide 2.9 THz QCL . Measured intensity in the far field. As shown in the Inset, and are the tangential and azimuthal angles, respectively. The center of the facet is at , . The measurement was performed by scanning a Golay cell detector on a 6 cm radius sphere. The detector was mounted on a motorized two-axis rotation stage.
(a) Schematic top and side views of the TEM-HA MM waveguide QCL used in the experiment. Dimensions are not to scale. (b) SEM picture of a 2 mm long ridge with a 1 mm long TEM-HA. (c) Voltage/current and light/current characteristics of the device with (black) and without (red) TEM-HA. Light was collected with an parabolic mirror.
(a) Computed far-field intensity pattern of the MM waveguide 2.8 THz QCL used in the experiment (see Fig. 2 for dimensions). (b) Measured far-field intensity pattern for the same device. (c) Measured far-field intensity pattern for the same device of panel (b) without the TEM-HA. The dashed curves are guides to the eyes.
Computed figures of merit (see text) as a function of the ridge width for the and modes of a MM waveguide 2.8 THz QCL. The waveguide is thick. Inset: computed 2D intensity profiles for the wide ridge used in the experiment. The computed losses and overlap factor are and 0.99 for the , and and 0.95 for the mode.
(a) Measured and (b) computed far-field pattern for a 2 mm long, wide, and thick MM waveguide QCL emitting at 2.0 THz. A 1 mm long TEM-HA is mounted on one facet (, ). Both and guided modes were excited in the simulation.
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