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Making use of the attractive properties of silicon (Si), a wide array of highly functional photonic devices have been demonstrated over the past few decades [1]. Although planar platforms are still the most prominent choice for integrated systems, more recently silicon fibres have gained increased attention due to their simple fabrication methods and flexible device designs [2]. However, despite their...
Ring-type and whispering-gallery mode microresonators combine strong light confinement with high optical non-linearity to give rise to and enable efficient nonlinear optical parametric frequency conversion processes [1], stimulated Brillouin and Raman scattering.
Special laser applications ranging from laser material processing, especially micromachining, to medical applications, metrology and spectroscopy demand transform limited ps pulses, often synchronized with a fs source [1]. Here, we present spectral compression of fs pulses inside a regenerative Yb:YAG laser amplifier [2] generated by a mode-locked Yb:KGW oscillator (see Fig. 1a). For spectral shaping...
Methylammonium lead halide perovskites (MAPbX3, where X = I, Cl, and Br) have come in the spotlight as alternative devices of silicon for next-generation solar cells owing to its extraordinary photovoltaic property, ease of fabrication, and low cost, which has exhibited power conversion efficiencies of up to 20.5% [1]. In addition, perovskites have recently shown the further application in optically-controllable...
Generating correlated photons is an essential technology for photonic quantum information experiments. Increasing the generation efficiency of photon pairs via the enhancement of material nonlinearity is important for various applications including a near-on-demand single photon source based on multiplexed photon pair sources [1]. In this regard, photonic crystal nanocavities are attractive nonlinear...
Microresonators and lasers on the micro- and nanoscale are potential candidates for spectroscopic applications and sensing elements. The optical properties of these devices enable highly sensitive elements in biophotonics. They can be integrated in lab-on-chip platforms and act as biosensors for label-free detection of molecules in point-of-care diagnosis. One of the most promising resonators type...
Optical rectification of ultrashort laser pulses in electro-optic crystals is an established technique of terahertz generation. In this technique, the pump optical pulse produces a nonlinear polarization that moves with the group velocity of the optical pulse and acts as a source of terahertz radiation. The up-to-date generation schemes based on this principle utilize both the standard collinear phase...
Most non-conductive materials and non-polar liquids are transparent to terahertz frequencies (0.2–2THz), and due to their non-ionizing photon energies there is great interest and potential in imaging in the THz regime [1], However, the long wavelengths (1.5–0.15mm) mean that even diffraction limited imaging will fail to resolve structures of micron size many of which have interesting THz interactions...
Novel nonlinear optical crystals have attracted considerable interests due to their wide applications in frequency shifting, terahertz generation, optical communications, display, sensing, and so on. Because terahertz radiation is sensitive to free carriers and lattice vibrations in solid states, terahertz time-domain spectroscopy (THz-TDS) has become a pivotal tool in investigating fundamental dynamics...
Their inherently broadband gain and high value of the third order nonlinearity makes quantum cascade lasers (QCLs) ideal candidates for frequency comb generation in the terahertz (THz) and mid-infrared (midIR) spectral ranges. In recent years, it has been demonstrated that free running QCLs can produce broad comb spectra, even without any special endeavour to induce phase-locking of the lasing modes...
Near-field imaging techniques have great potential in many applications, ranging from the investigation of the optical properties of solid state and 2D materials to the excitation and direct retrieval of plasmonic resonant modes, to the mapping of carrier concentrations in semiconductor devices. Further to this, the capability of performing imaging with non-ionizing terahertz (THz) radiation on a...
According to rigorous diffraction theory, monochromatic electromagnetic waves reflected from a material surface form a mixture of propagating and evanescent waves. During propagation, light fields suffer a progressive spatial filtering that depends exponentially on the size of the subwavelength image detail, a peculiar multiscale distortion in the image that spans the near-field of the sources, occurs...
Terahertz (THz) sources are indispensable for various applications such as THz time-domain spectroscopy. A promising approach to generate broadband THz radiation is to employ laser-induced gas plasmas, which has already been demonstrated for various settings [1, 2]. In order to miniaturize such sources, it has been proposed to exploit single-color laser-induced microplasmas [3]. Then, a conical THz...
Laser Terahertz Emission Microscopy (LTEM) is a method which has been developed in order to study intrinsic carrier dynamics in semiconductors with a spatial resolution which is only limited by the wavelength of the incident fs laser [1]. More recently, it has been shown that the spatial resolution in a terahertz (THz) spectroscopy experiment can be improved even further by utilizing plasmonic coupling...
Currently lasers are perceived as unique light that can produce specific states of matter through selective manipulations that could not be realized using any other conventional incoherent addition of thermal or electronic energy to a system. Although the selective laser chemistry is still a dream, the selective control of material processing done by optimization of laser intensity, as well as the...
We report the generation of tuneable THz radiation (0.75–3 THz) through second order nonlinear effects in the excitation of excitons in GaAs/AlAs multi-quantum wells (MQWs), using readily available continuous wave (CW) laser diodes at room temperature. A MQW GaAs/AlAs sample was designed to have excitonic resonances at a wavelength accessible by commercially available lasers (850nm, 260mW), and have...
Thin metal wires are known to be a low loss and very low dispersion terahertz (THz) waveguide [1]. Recently, generation of a strong THz surface wave was demonstrated by irradiating a wire surface with a ultrahigh intensity femtosecond laser [2]. Such THz light sources driven by femtosecond laser induced plasma are expected to have a high potential as a power scalable source. However, the characteristics...
Terahertz (THz) technologies have been gaining a great deal of interests, but current THz optics is still facing various challenges in their functionality and performance. Metamaterials, which are artificial structures consisting of many periodical units smaller than the wavelength of electromagnetic waves, are attracting attention as a new tool for the development of THz optics because the optical...
One of the promising methods of the terahertz (THz) radiation generation is the use of the two-color laser field (ω-2ω) focused in the gas medium [1]. Typically, the polarization of the low frequency THz field generated in gas is linear [2], but, in some conditions, it can be elliptical due to modulation of the laser pulse phase and its polarization in the gas plasma [3]. For some practical applications,...
Generation and use of orbital angular momentum (OAM) of light is finding more and more interest in a wide variety of fields of photonics: communications, optical trapping, quantum optics, and many more [1]. In the investigation of such behavior, twisting of photonic crystal fibers shows interesting physical phenomena [2]. We previously reported the ability to create helical hollow fibers by mechanically...
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