We report a repetition frequency tunable, passively mode-locked vertical-external-cavity surface-emitting semiconductor laser (VECSEL) with continuous repetition frequency tuning between 2.78 and 7.87 GHz using mechanical tuning of the laser cavity length. The laser emits near-transform-limited, sub-500-fs pulses over almost an octave tuning range between 2.78 and 5 GHz. At repetition rates abo...

Finding alternative optoelectronic mechanisms that overcome the limitations of conventional semiconductor devices is paramount for detecting and harvesting low-energy photons. A highly promising approach is to drive a current from the thermal energy added to the free-electron bath as a result of light absorption. Successful implementation of this strategy requires a broadband absorber where car...

A simple design of an ultrathin six-band polarization-insensitive terahertz perfect metamaterial absorber (PMMA) composed of a metal cross-cave-patch resonator (CCPR) placed over a ground plane was proposed and investigated numerically. The numerical simulation results demonstrate that the average absorption peaks are up to 95% at six resonance frequencies with high quality-factors (>65). In ad...

ELECT Three different metamaterial absorbers based on ultra-thin multi-layer structures, with different bandwidth characteristics, are presented. The proposed structure is composed of three vertically stacked metaldielectric layers backed by a metal ground. All the metallic patches are of crossed dipole shape and have different geometrical dimensions, which can be manipulated to design triple-b...

We design a dual-band absorber formed by combining two cross-shaped metallic resonators of different sizes within a super-unit-cell arranged in mirror symmetry. Simulations indicate that absorption efficiencies greater than 99% can be achieved at two different frequencies under normal incidence. We employ a design scheme with graphene integration, which allows independent tuning of individual a...

Technological obstacles to the use of rotary-type swing arm actuators to actuate optical pickup modules in small-form-factor (SFF) disk drives stem from a hinge's skewed actuation, subsequently inducing off-axis aberrations and deteriorating optical quality. This work describes a dual-stage seesaw-swivel actuator for optical pickup actuation. A triple-layered bimorph bender made of piezoelectri...

The emergence of third-generation photovoltaics based on Si relies on tunable bandgap materials with embedded nanocrystalline Si. One of the most promising approaches is based on the mixed-phase Si1 - xCx. We have investigated the light absorption controllability of nanocrystalline Si-embedded Si1 - xCx produced by thermal annealing of the Si-rich Si1 - xCx and composition-modulated superlattic...

Tunable frequency is highly sought-after task of researcher, because of the potential for applications in selecting frequency, absorber, imaging and biomedical diagnosis. Here, we report the original observation of thermal frequency shift of dielectric relaxation in La/Nd doped BiFeO3 (BFO) in X-band from 300 to 673 K. It exhibits an unexpected result: the relaxation shifts to lower frequency w...

Methods for spectrally controlling light absorption in optoelectronic devices have attracted considerable attention in recent years. It is now well known that a Fabry-Perot nanocavity comprising thin semiconductor and metal films can be used to absorb light at selected wavelengths. The absorption wavelength is controlled by tailoring the thickness of the nanocavity and also by nanostructure pat...