Light emitted from single-mode semiconductor lasers generally has large divergence angles, and high numerical aperture lenses are required for beam collimation. Visible and near infrared lasers are collimated using aspheric glass or plastic lenses, yet collimation of mid-infrared quantum cascade lasers typically requires more costly aspheric lenses made of germanium, chalcogenide compounds, or ...

This report summarizes the entire research period. In this program, we performed experiments using a femtosecond mid-infrared pump-probe system implemented for QCL samples operating at 4.6 and 5.3 μm. We employed femtosecond time-resolved pump-probe measurements to probe the nature of the transport through the laser structure via the dynamics of the gain. The gain recovery was determined by the...

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The onset of nonlinear dynamics and chaos is evidenced in a mid-infrared distributed feedback quantum cascade laser both in the temporal and frequency domains. As opposed to the commonly observed route to chaos in semiconductor lasers, which involves undamping of the laser relaxation oscillations, quantum cascade lasers first exhibit regular self-pulsation at the external cavity frequency befor...

We demonstrate a novel laser design for room temperature THz emission from a quantum cascade laser. The device concept is based on THz emission by difference-frequency generation in mid-infrared quantum cascade lasers with giant nonlinear properties. In contrast to previously demonstrated lasers the presented design significantly simplifies and improves the active medium of the quantum cascade ...

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