ABSTRACT
Advances in cryobiology techniques commonly target either the cooling or the warming cycle, while little thought has been given to âªrepairâ« protocols applicable during cold storage. In particular, crystallization is the dominant threat to cryopreserved samples but proceeds from small nuclei that are innocuous if further growth is forestalled. To this end, we propose a laser editing technique that locally heats individual crystals above their melting point by a focused nanosecond pulse, followed by amorphization during rapid resolidification. As a reference, we first apply the approach to ice crystals in cryoprotected solution and use Raman confocal mapping to study the deactivation of crystalline order. Then, we examine dimethyl sulfoxide trihydrate crystals that can germinate at low temperatures in maximally freeze concentrated regions, as commonly produced by equilibrium cooling protocols. We show how to uniquely identify this phase from Raman spectra and evidence retarded growth of laser-edited crystals during warming.
ABSTRACT
Numerical simulation of a fiber optic parametric oscillator to produce picosecond narrowband pulses for coherent anti-Stokes Raman spectroscopy has been performed by an open source Python-based library using an extremely wide range of parameters, such as the pump pulse duration, parametric frequency shift, spectral bandwidth of the pump, and the parametric pulses. It required an extremely large calculation window, both in time and spectral domains. We managed to speed up the simulation 50 times using a graphic processor unit that allowed us to define the areas of stability for different lengths of standard passive (5-100 m) and photonic crystal (23-100 cm) fibers used in the external linear oscillator cavity. It was shown that highly chirped dissipative solitons at a wavelength about 800 nm can be generated with energy up to 55 nJ, which is limited by the pump depletion and self-phase modulation effects.
ABSTRACT
Frequency doubling of multimode diode-pumped GRIN-fiber Raman laser with improved beam quality (M2=1.9-2.6 depending on configuration) in a simple single-pass scheme with 5-mm PPLN crystal is studied. After scheme optimization and elimination of back reflection and crystal heating effects, an efficient conversion into blue spectral range with output power of about 0.4 W@488â nm and 0.64 W@477â nm has been demonstrated.
