We model output characteristics of the 1645 nm 8 mJ 10 ns 100 Hz Q-switched Er:YAG DPSSL. The laser is end pumped at a wavelength of 1532 nm. Fiber-coupled diode laser module was 10 nm FWHM, 12 W CW, 200 μm, NA 0.22. Various tapering of the active rod has been considered for 1 mm diameter, 20 mm long and 0.5% Er doping. We discuss the heat deposition process, the energy storage efficiency and the average power limitations for Q-switched regime of generation and amplification, and find the system scalable for the high power operation.
Electrically driven optical antennas are attracting much attention, in particular, due to necessity to develop integrated electrical source of surface plasmons for future plasmonic nanocircuitries. By default, this term denotes a metal nanostructure, in which electromagnetic oscillations at optical frequencies are excited by electrons, tunneling between metallic parts of the structure when a bias voltage is applied between them. Instead of relying on an inefficient inelastic light emission in a tunnel gap, we are suggesting to use ballistic nanoconstrictions as the feed element of an optical antennas in order to excite electromagnetic plasmonic modes. Similarly to tunneling structures, the voltage applied at the constriction falls over the contact of nanoscale length. Electron passing through the contact ballistically can gain the energy provided by the bias ~1eV and exchange it into an mode of the optical antenna. We discussed the underlying mechanisms responsible for the optical emission, and show that with nanoscale contact, one can reach quantum efficiency orders of magnitude larger than with standard tunneling structures.
Quantum emitters, such as q-dots and dye molecules, in the immediate vicinity of plasmonic nanostructures, resonantly excite surface plasmon-polaritons (SPPs) under incoherent pump. The efficiency in the excitation of SPPs per emitter increases with the number of the emitters, because the SPP field synchronizes emission of the coupled emitters, in analogy with the superadiance (SR) in free space. Using fully quantum mechanical model for two emitters coupled with a metal nanorod, we predict up to 15% increase in the emission yield of single emitter compared to only one emitter near the nanorod. Such emission enhancement is stationary and should be observable even with strong dissipation and dephasing under incoherent pump of emitters. Solid-state quantum emitters with blinking behaviors may be utilized to demonstrate such plasmonic SR emission enhancement. Plasmonic SR may find implications in the excitation of nonradiative modes in plasmonic waveguides, in lowing threshold of plasmonic nanolasers.
We demonstrate a pulse-bursting phenomenon in Yb:Er glass laser operating at 1.54 μm. Glass-ceramic material with a low value of saturation threshold based on Co2+:β-ZnSiO4 nanocrystals was used as a passive gate for pulse-burst operation. The bursts of pulses were 1.5 ms long, each burst consisted of 40-55 pulses with 9-30 μJ energy per pulse and 0.2-3 μs pulse width. Bursting outputs arise via a coupling between slow switching arising via a slow pump modulation and fast pulsations resulting from Q-switch mechanism. We show that absorption cross-section strongly affects the mode of laser operation ranging from relaxation oscillations corresponding to low cross-section values to bursting and conventional Q-switch operation in the case of their higher values.
We control the optical comb in Nd:YVO4 mode-locked lasers with intracavity frequency doubling based on KTP crystals via changing the cavity length and its dispersion properties and achieve high-purity radiofrequency (RF) signals. The laser output wavelength (532 nm) is in the range of the molecular iodine absorption spectrum with narrow (1.5 kHz) homogeneously broadened lines. We propose to stabilize the two longitudinal modes on two narrow iodine absorption lines. The third derivative of the absorption line could be obtained by heterodyning the absorption signal with the third harmonic of the modulation signal. The resulting RF error signal could be used to stabilize two locked longitudinal modes separated by 1.37 GHz which results in stabilized beat note signal.
Photoelectric properties of metamaterials comprising asymmetrically shaped, similarly oriented metallic nanoparticles embedded in a homogeneous semiconductor matrix are theoretically and numerically studied. The asymmetric shape of the nanoparticles is found to result in the existence of a preferred direction where “hot” photoelectrons are emitted from the nanoparticle surface under the action of the localized plasmonic resonance excited in the nanoparticles. The resulting directional photocurrent flow occurring when nanoparticles are uniformly illuminated by a homogeneous plane wave is the direct analogy of the photogalvanic effect known to exist in naturally occurring non-centrosymmetric media. This plasmonic bulk photovoltaic effect is intermediate between the inner photoelectric effect in bulk media and the outer photoelectric effect at macroscopic interfaces. The results obtained are valuable for characterizing photoemission and photoconductive properties of plasmonic nanostructures. They can find many uses for photodetection-related and photovoltaic applications.
In order to improve the photoconversion efficiency, we consider the possibility of increasing the photocurrent in solar
cells exploiting the electron photoemission from small metal nanoparticles into a semiconductor. The effect is caused by
the absorption of photons and generation of local surface plasmons in the nanoparticles with optimized geometry. An
electron photoemission from metal into semiconductor occurs if photon energy is larger than Schottky barrier at the
metal-semiconductor interface. The photocurrent resulting from the absorption of photons with energy below the
bandgap of the semiconductor added to the solar cell photocurrent can extend spectral response range of the device.
We study the effect on a model system, which is a Schottky barrier n-GaAs solar cell, with an array of Au nanoparticles
positioned at the interface between the semiconductor and the transparent top electrode. Based on the simulations, we
chose to study disk-shaped Au nanoparticles with sizes ranging from 25nm to 50nm using electron beam lithography.
Optical characterization of the fabricated devices shows the presence of LSP resonance around the wavelength of
1250nm, below the bandgap of GaAs.