Fluorescent color centers in laser ablated 4H-SiC nanoparticles

.Nanostructured and bulk silicon carbide (SiC) has recently emerged as a novel platform for quantum nanophotonics due to its harboring of paramagnetic color centers, having immediate applications as a single photon source and spin optical probes. Here, using ultra-short pulsed laser ablation, we fabricated from electron irradiated bulk 4H-SiC, 40-50 nm diameter SiC nanoparticles, fluorescent at 850-950 nm. This photoluminescence is attributed to the silicon vacancy color centers. We demonstrate that the original silicon vacancy color centers from the target sample were retained in the final nanoparticles solution, exhibiting excellent colloidal stability in water over several months. Our work is relevant for quantum nanophotonics, magnetic sensing, and biomedical imaging applications

Photoluminescence from voids created by femtosecond-laser pulses inside cubic-BN

Photoluminescence (PL) from femtosecond-laser-modified regions inside cubic-boron nitride (c-BN) was measured under UV and visible light excitation. Bright PL at the red spectral range was observed, with a typical excited state lifetime of ∼ 4ns. Sharp emission lines are consistent with PL of intrinsic vibronic defects linked to the nitrogen vacancy formation (via Frenkel pair) observed earlier in high-energy electron-irradiated and ion-implanted c-BN. These, formerly known as the radiation centers, RC1, RC2, and RC3, have been identified at the locus of the voids formed by a single femtosecond-laser pulse. The method is promising to engineer color centers in c-BN for photonic applications

Characterization of optical polarization converters made by femtosecond laser writing

Recently, new types of silica polarization converters fabricated by femtosecond lasers have been introduced. These devices use spatially arranged nanogratings found under certain femtosecond laser exposure conditions in fused silica to create arbitrary polarization states by shaping spatially and locally the retardance of an incoming beam. Using this principle, radial and azimuthal polarization converters were demonstrated. These devices make use of a large density of femtosecond laser spots, introducing localized defects, affecting the performance of the converter. To optimize the writing and the post-processing annealing step of these kind of devices, here we introduce a novel fluorescence lifetime imaging microscope (FLIM) working with deep UV (240-280 nm) wavelength excitations. Specifically, we demonstrate the potential of this technique and more generally, how it can be used for characterizing a variety of femtosecond laser induced modifications in fused silica. This UV-FLIM can be used with micro-fluidic and bio-samples to characterize temporal characteristics of fluorescence

High-order harmonic generation from a dual-gas, multi-jet array with individual gas jet control

We present a gas jet array for use in high-order harmonic generation experiments. Precise control of the pressure in each individual gas jet has allowed a thorough investigation into mechanisms contributing to the selective enhancement observed in the harmonic spectra produced by dual-gas, multi-jet arrays. Our results reveal that in our case, the dominant enhancement mechanism is the result of a compression of the harmonic-producing gas jet due to the presence of other gas jets in the array. The individual control of the gas jets in the array also provides a promising method for enhancing the harmonic yield by precise tailoring of the length and pressure gradient of the interaction region

Characterization of optical polarization converters made by femtosecond laser writing

Recently, new types of silica polarization converters fabricated by femtosecond lasers have been introduced. These devices use spatially arranged nanogratings found under certain femtosecond laser exposure conditions in fused silica to create arbitrary polarization states by shaping spatially and locally the retardance of an incoming beam. Using this principle, radial and azimuthal polarization converters were demonstrated. These devices make use of a large density of femtosecond laser spots, introducing localized defects, affecting the performance of the converter. To optimize the writing and the post-processing annealing step of these kind of devices, here we introduce a novel fluorescence lifetime imaging microscope (FLIM) working with deep UV (240-280 nm) wavelength excitations. Specifically, we demonstrate the potential of this technique and more generally, how it can be used for characterizing a variety of femtosecond laser induced modifications in fused silica. This UV-FLIM can be used with micro-fluidic and bio-samples to characterize temporal characteristics of fluorescence

Fluorescent color centers in laser ablated 4H-SiC nanoparticles

In this study, using ultra-short pulsed laser ablation, 40–50 nm diameter silicon carbide (SiC) nanoparticles were fabricated from electron irradiated bulk 4H-SiC, which had fluorescent at 850–950 nm. This photoluminescence is attributed to the silicon vacancy color centers. We demonstrate that the original silicon vacancy color centers from the target sample were retained in the final nanoparticles solution, exhibiting excellent colloidal stability in water over severalmonths. This study is relevant for quantum nanophotonics, magnetic sensing, and biomedical imaging applications