Manipulating random lasing correlations in doped liquid crystals.

Random lasers are highly configurable light sources that are promising for imaging and photonic integration. In this study, random lasing action was generated by optically pumping N-(4-methoxybenzylidene)-4-butylaniline (MBBA) liquid crystals infiltrated with gold nanoparticles and a laser dye (pyrromethene 597 (PM597)). By varying the pump energy near a lasing threshold, we show that it is possible to control intensity correlations between random lasing modes. The correlations in the system were phenomenologically characterized using the Levy statistics of the emission spectrum survival function. We also find that correlations and persistence of lasing action are correlated. These results demonstrate the possibility to dynamically control a key physical feature of random lasers, which may find applications in biomedical settings and network communications.

Active mid-infrared ring resonators.

High-quality optical ring resonators can confine light in a small volume and store it for millions of roundtrips. They have enabled the dramatic size reduction from laboratory scale to chip level of optical filters, modulators, frequency converters, and frequency comb generators in the visible and the near-infrared. The mid-infrared spectral region (3-12 µm), as important as it is for molecular gas sensing and spectroscopy, lags behind in development of integrated photonic components. Here we demonstrate the integration of mid-infrared ring resonators and directional couplers, incorporating a quantum cascade active region in the waveguide core. It enables electrical control of the resonant frequency, its quality factor, the coupling regime and the coupling coefficient. We show that one device, depending on its operating point, can act as a tunable filter, a nonlinear frequency converter, or a frequency comb generator. These concepts extend to the integration of multiple active resonators and waveguides in arbitrary configurations, thus allowing the implementation of purpose-specific mid-infrared active photonic integrated circuits for spectroscopy, communication, and microwave generation.