Filamentation in air is a profound effect caused by high energy photons. While it has been studied in a wide-range of laser systems, there still exist wavelength regimes where filamentation hasn’t been created, due to lack of sources. Using a tunable near-infrared femtosecond laser, we generated filamentation in air by wavelengths from 1.2 to 2.5 µm. The observed filaments produced harmonic and continuum generation well into the visible spectrum; a rainbow of colors.
Zinc Selenide (ZnSe) has long been recognized as a nonlinear optical material and is used in many optoelectronic devices such as light emitting diodes. ZnSe is known for its remarkably wide transmission range for infrared radiation leading to its use in infrared laser applications. In this report, we discuss higher order harmonic generation when exposing ZnSe to tunable femtosecond mid-IR laser pulses with wavelengths ranging from 2.7 μm to 8.0 μm and pulse energies between 3 and 17 μJ. Higher order harmonic generation was in some instances strong enough to be directly seen by the unaided eye. We also compare these results with measurements taken for other optical materials.
We study supercontinuum (SC) generation in large-mode-area (LMA) photonic crystal fibers with various core sizes and lengths, pumped by a picosecond Nd:YVO<sub>4</sub> laser. Micro-joule level SC pulse energy is achieved, and the spectrum extends beyond 1600 nm, corresponding to an effective Raman detection range over 3000 wavenumbers. A multiplex CARS setup based on the SC source is constructed, and we demonstrate CARS acquisition in air, and compare the signal obtained with different LMA fiber parameters.
Calcium fluoride, BK7 and fused silica are common optical materials used in lenses and windows. In this report, we discuss supercontinuum generation using tunable femtosecond mid-IR laser pulses with wavelengths ranging from 2.7 μm to 7.0 μm and pulse energies between 3 and 18 microjoules. We observed harmonic generation in fused silica and BK7, but not supercontinuum generation. Other borosilicate targets generated supercontinuum in both visible and near infrared regions of the spectrum. The visible supercontinuum was, in some instances, strong enough to be observed directly by the human eye. These results contribute to ongoing work being done to refine eye safety standards for femtosecond lasers.