ABSTRACT
Within a narrow spectral region around the wavelength of zero-group-velocity dispersion of a nonlinear-optical waveguide, phase-matched four-wave mixing couples the Stokes Raman sideband of a pump field to its anti-Stokes counterpart. This wave coupling suggests a sensitive probe for linear and nonlinear-optical parameters of the waveguide, enabling the detection of nanoscopic size variations of microchannel waveguides in photonic-crystal fibers, and facilitates the generation of broadband supercontinuum radiation.
ABSTRACT
We demonstrate time-resolved coherent anti-Stokes Raman scattering (CARS) by using a frequency-tunable femtosecond soliton output of a silica photonic-crystal fiber (PCF) as a Stokes field. This approach allows quantum beats originating from two close Raman modes to be resolved in the time-domain CARS response. The nonresonant CARS background is efficiently suppressed by introducing a delay time between the probe pulse and the pump-Stokes pulse dyad, suggesting a convenient fiber-optic format for the Stokes source in time-resolved CARS and allowing sensitivity improvement in PCF-based CARS spectroscopes and microscopes.
ABSTRACT
Hollow-core photonic-crystal fibres (PCFs) for the delivery of high-fluence laser radiation capable of ablating tooth enamel are developed. Sequences of picosecond pulses of 1.06 microm Nd:YAG-laser radiation with a total energy of about 2 mJ are transmitted through a hollow-core photonic-crystal fibre with a core diameter of approximately 14 microm and are focused on a tooth surface in vitro to ablate dental tissue. The hollow-core PCF is shown to support the single-fundamental-mode regime for 1.06 microm laser radiation, serving as a spatial filter and allowing the laser beam quality to be substantially improved. The same fibre is used to transmit emission from plasmas produced by laser pulses on the tooth surface in the backward direction for detection and optical diagnostics.
Subject(s)
Crystallization/methods , Dental Enamel/radiation effects , Dental Enamel/surgery , Fiber Optic Technology/instrumentation , Laser Therapy/instrumentation , Laser Therapy/methods , Oral Surgical Procedures/instrumentation , Dental Enamel/pathology , Dose-Response Relationship, Radiation , Equipment Failure Analysis , Fiber Optic Technology/methods , Humans , In Vitro Techniques , Lasers , Oral Surgical Procedures/methods , Porosity , Scattering, RadiationABSTRACT
Sequences of picosecond pulses of 1.06-microm Nd:YAG laser radiation with a total energy of approximately 2 mJ are transmitted through a hollow-core photonic-crystal fiber with a core diameter of approximately 14 microm and are focused onto a tooth's surface in vitro to ablate dental tissue. The hollow-core photonic-crystal fiber is shown to support the single-fundamental-mode regime for 1.06-microm laser radiation, serving as a spatial filter and allowing the laser beam's quality to be substantially improved. The same fiber is used to transmit emission from plasmas produced by laser pulses onto the tooth's surface in the backward direction for detection and optical diagnostics.
