Tunable Photonic Bandgap Structures Research Articles

Tunable resonant Bragg photonic bandgap structures based on active quantum dot layers; crystals with applications in all-optical switches manufacturing

Novel tunable photonic bandgap structures are proposed in this paper. Alternately placed slabs of GaAs (as barriers) and layers containing InAs/InGaAs quantum dots (active dipole elements) are considered as the main building blocks of the proposed crystals. The common transfer matrix method is utilized for characterization of the optical features of the structures. However, to take more physical phenomena into considerations, effective excitonic susceptibility is defined in a way that includes all the homogeneous and non-homogeneous broadenings. Dependences of the optical responses to the structural parameters such as the number of periods, uniformity of the quantum dots, and the size of the barrier/dots are investigated at the first step. Extracting the optimum values, tunability of the optical features of the structures by changing the crystal temperature, light incident angle and also illuminating an external pump laser is investigated then. To study the potential of the proposed structures to be used as all-optical switches, the response of the crystals to the square wave pulse series of 50 ps duration and data sequences of 10101 is studied by turning the pump pulse on and off. Results are notable for less quantum dot size fluctuations and low temperatures.

Electrically tunable photonic band gap structure in monodomain blue-phase liquid crystals

Photonic band gap materials have the ability to modulate light. When they can be dynamically controlled beyond static modulation, their versatility improves and they become very useful in scientific and industrial applications. The quality of photonic band gap materials depends on the tunable wavelength range, dynamic controllability, and wavelength selectivity in response to external cues. In this paper, we demonstrate an electrically tunable photonic band gap material that covers a wide range (241 nm) in the visible spectrum and is based on a monodomain blue-phase liquid crystal stabilized by nonmesogenic and chiral mesogenic monomers. With this approach, we can accurately tune a reflection wavelength that possesses a narrow bandwidth (27 nm) even under a high electric field. The switching is fully reversible owing to a relatively small hysteresis with a fast response time, and it also shows a wider viewing angle than that of cholesteric liquid crystals. We believe that the proposed material has the potential to tune color filters and bandpass filters.

A liquid crystal-based dynamically tunable photonic bandgap structure

A tunable linear photonic bandgap device based on a silicon/liquid crystal dielectric combination has been designed and fabricated. The design features a microstrip line, whose substrate of periodically spaced silicon squares in BL006 (a nematic liquid crystal mixture) induces a bandgap that contracts in response to a low-frequency voltage. Numerical band structure calculations and finite element simulations of the fabricated device showed a bandgap tuning of approximately 10% for the lattice geometries employed. The measured scattering parameters agreed very well with simulations and demonstrated significant tuning of the first bandgap in the range of 6.5–8.4 GHz.

Tunable photonic bandgap structures for optical interconnects

As continued progress towards faster, low power consuming microelectronic devices becomes increasing difficult due to the scaling challenges of electrical interconnects, it becomes even more critical to explore alternative technologies. Tunable porous silicon photonic bandgap structures are viable building blocks for optical interconnects, which present a possible long term solution to the interconnect problem. Forming the structures on a silicon platform provides the advantage of easier integration with current semiconductor processing techniques. In this work, tuning of the optical properties is controlled by liquid crystals (LCs) that are infiltrated into the silicon matrix. Active tuning is demonstrated both out-of-plane, with one-dimensional porous silicon photonic bandgap microcavities, and in-plane, using two-dimensional porous silicon photonic bandgap structures.