Analytic solutions for broadband pulse generation from near-infrared to near-ultraviolet by induced-phase modulation in a gas-filled hollow waveguide

Summary form only given. Generation of an ultra-broadband optical pulse with a fluent frequency-dependency of the phase is important, for example, for shaping multi-wavelength optical pulses and monocyclization. When two optical pulses, one fundamental, the other generated by second harmonic generation, are co-propagated in a nonlinear waveguide, induced-phase modulation between them, as well as self-phase modulation, can be used to broaden the spectrum of each pulse. Since the second-harmonic wave as well as the fundamental wave are generated from one common femtosecond pulse, the carrier-phase difference between their waves is constant and these can be synthesized constructively after propagation. In this research, we analyzed the case where a capillary fiber filled with noble gas is used as an almost-dispersionless, nonlinear waveguide. Since the optical field is not completely confined in the glass capillary during propagation, the loss always occurs in this method. We consider a case where two optical pulses with different center frequencies and widths are co-propagating in a capillary fiber. The analytic equations for nonlinear chirps with loss, but without dispersion are obtained for two Gaussian input-pulses using slowly varying envelope approximations.