Polycrystalline materials can mediate efficient frequency up-conversion for mid-infrared light. Motivated by the need to understand the properties of the harmonic and supercontinuum radiation from such media, we utilize realistic numerical simulations to reveal its complex temporal and spatial structure. We show that the generated radiation propagates in the form of long-duration pulse trains that can be difficult to compress and that optical filamentation in high-energy pulses gives rise to fine-structured beam profiles. We identify trends concerning pulse energy, sample length, and the microstructure of the material that can inform optimization for different applications.

We experimentally and theoretically investigate the nonlinear frequency conversion of transparent chalcogenide optical materials using ultrashort midwave infrared laser pulses at 3.6 microns. Evidence of the structure of second through sixth harmonic generation demonstrates different levels of filamentation related to laser intensity, sample thickness, and sample position. Simulations using a (3+1)D model with experimentally measured n(2) values and random quasi phase matching provide good qualitative agreement with experimental data. Together, the data suggests that focusing geometry and material structure play a significant role in harmonic generation in these materials.

We focus intense, ultrashort, 3.6 micron-wavelength pulses into three single-crystal zincblende chalcogenide samples, ZnS(100), ZnS(110), and ZnSe(100). Symmetry properties of the generated harmonics are studied by rotating the crystals and measuring the output polarization.

Using ~3.6pm, 200fs, 500Hz laser pulses, we observed supercontinuum generation in 50 and 150pm outer dameter uidoped, single-crystal YAG fibers with sol-gel cladding. We note differences in supercontinuum based on diameter and cladding thickness.

We investigate the nonlinear optical properties of transparent optical materials using ultrashort midwave infrared laser pulses between 3 and 4 microns. Random quasi-phase matching in polycrystalline materials generates multiple frequency harmonics of both odd and even orders throughout the transmission window of the target. We also investigate single crystal and amorphous materials and demonstrate a range of frequency conversion and pulse broadening. Simulations using a nonlinear polarization model enhanced with ionization and experimentally measured n(2) values provide good qualitative agreement with experimental data.

Using intense $3.6\ \mu \mathrm{m}$, 200 fs, 500 Hz laser pulses, non-linear spectral broadening, filamentation and 2nd-9th harmonic generation in ZnS (Cleartran™) with 3–40 mm propagation distance were observed. Non-linear index of Cleartran was also measured. © 2019 The Author(s)

Nonlinear refraction coefficients are measured via the Z-scan technique in the mid-infrared spectral region for infrared transmitting materials. Harmonic and supercontinuum generation are modeled using the experimentally obtained values and compared to experimental observations.

We investigated the nonlinear optical properties of single- and poly-crystalline optical materials using ultrashort mid-infrared laser pulses between 3 and 4 μm. We compared visible to mid-infrared spectra between the materials. Measured energy conversion into all-order harmonics in polycrystalline materials exceeded 30%.

High harmonic generation in polycrystalline ZnSe is modeled as an effective medium. The non-perturbative behavior observed experimentally was recreated, showing that an effective model captures the underlying physics. © 2019 The Author(s)

Polycrystalline ZnSe is an exciting source of broadband supercontinuum and high-harmonic generation via random quasi phase matching, exhibiting broad transparency in the mid-infrared (0.5 - 20 mu m). In this work, the effects of wavelength, pulse power, intensity, propagation length, and crystallinity on super-continuum and high harmonic generation are investigated experimentally using ultrafast mid-infrared pulses. Observed harmonic conversion efficiency scales linearly in propagation length, reaching as high as 36%. For the first time to our knowledge, n(2) is measured for mid-infrared wavelengths in ZnSe: n(2) (lambda = 3.9 mu m) = (1.2 +/- 0.3) x 10(-14) cm(2)/W. Measured n(2) is applied to simulations modeling high-hannonic generation in polycrystalline ZnSe as an effective medium. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

This work seeks to explore the interplay between material differences in the nonlinear index of refraction n2 and zero group velocity dispersion wavelength λGVD in the formation of spectral broadening and supercontinuum generation. We present mid-wave infrared (MWIR) spectroscopic data of the transmitted 200 fs (FWHM) laser pulse through polycrystalline zinc selenide and polycrystalline zinc sulfide (Cleartran™) optical materials. Using MWIR laser wavelengths between 3.3 and 3.8 μm, we vary the laser energy between roughly 1 and 126 μJ and focus the laser pulses into the materials using lenses of four different focal lengths. This allows us to analyze not only how the nonlinear frequency broadening of the fundamental wavelength varies with increasing pulse energy, but also how it varies with increasing peak intensities when the pulse energy is kept fixed. These results are discussed along with possible implications on the importance of both laser energy and peak intensity in producing supercontinuum for a material with a given n2 and λGVD. Understanding of these practical considerations is essential for assessing material effects to MWIR ultrashort pulsed lasers.

We investigate the nonlinear optical properties of ZnSe and ZnS using ultrashort (pulse duration approximately 200 fs) midwave infrared laser pulses between 3 and 4 μm. Multiple harmonic generation in both materials was observed, as well as significant spectral modification of the fundamental pulse. Simulations using a nonlinear polarization model enhanced with ionization compared favorably with experimental data. Random quasi phase matching in the materials is the likely generator of the observed harmonics.

We investigate the nonlinear optical properties of ZnSe and ZnS using ultrashort mid-wave infrared laser pulses. Multiple harmonic generation in both materials was observed, as well as significant spectral modification of the fundamental pulse.

Strong-field MIR laser-solid interactions have recently generated great interest. Harmonic continuum was generated in ZnSe with MIR pulses. Power scaling of the harmonics was non-perturbative with conversion efficiency as high as 26%.

The incorporation of lanthanide pnictide nanoparticles and films into III-V matrices allows for semiconductor composites with a wide range of potential optical, electrical, and thermal properties, making them useful for applications in thermoelectrics, tunnel junctions, phototconductive switches, and as contact layers. The similarities in crystal structures and lattice constants allow them to be epitaxially incorporated into III-V semiconductors with low defect densities and high overall film quality. A variety of growth techniques for these composites with be discussed, along with their growth mechanisms and current applications, with a focus on more recent developments. Results obtained from molecular beam epitaxy film growth will be highlighted, although other growth techniques will be mentioned. Optical and electronic characterization along with the microscopy analysis of these composites is presented to demonstrate influence of nanoinclusion composition and morphology on the resulting properties of the composite material.

Filament-induced periodic surface structures are generated on a wide variety of materials with near-IR and UV lasers. The surface structure features demonstrate the relation to laser wavelength and polarization and energy distribution in a filament.

We propose and systematically justify a band structure for TbAs nanoparticles in GaAs and In0.53Ga0.47As host matrices. Fluence-dependent optical-pump terahertz-probe measurements suggest the TbAs nanoparticles have a band gap and provide information on the carrier dynamics, which are determined by the band alignment. Spectrophotometry measurements provide the energy of optical transitions in the nanocomposite systems and reveal a large blue shift in the absorption energy when the host matrix is changed from In0.53Ga0.47As to GaAs. Finally, Hall data provides the approximate Fermi level in each system. From this data, we deduce that the TbAs:GaAs system forms a type I (straddling) heterojunction and the TbAs:In0.53Ga0.47As system forms a type II (staggered) heterojunction.

By analyzing how carrier relaxation rates depend on pump fluence and sample temperature, we conclude that states of TbAs embedded in GaAs are saturable. This suggests the existence of a bandgap for TbAs nanoparticles.