Red-shifted Dispersive Wave Research Articles

Soliton trapping of dispersive waves during supercontinuum generation in photonic crystal fiber

Using the generalized nonlinear Schrödinger equation, we present a numerical study of trapping of dispersive waves by solitons during femtosecond pumped supercontinuum generation in photonic crystal fiber with single or double zero dispersive wavelength. Numerical simulation results show that the generated supercontinuum in photonic crystal fiber with two zero dispersive wavelengths includes both blue-shifted dispersive wave (B-DW) and red-shifted dispersive wave (R-DW) while the generated supercontinuum in photonic crystal fiber with single zero dispersive wavelength has only blue-shifted dispersive wave. We find a novel phenomenon that not only B-DW but also R-DW can be trapped by solitions via four-wave mixing when the group-velocity matching between the soliton and the dispersive wave is satisfied, thus leading to the generation of new spectral components. In order to clearly display the evolution of soliton trapping of dispersive waves, the spectrogram of output pulses is observed using cross-correlation frequency-resolved optical gating technique.

COHERENT ANTI-STOKES RAMAN SCATTERING MICROSCOPY BY DISPERSIVE WAVE GENERATIONS IN A POLARIZATION MAINTAINING PHOTONIC CRYSTAL FIBER

The polarization maintaining photonic crystal flber (PM- PCF) with two zero dispersion wavelengths is designed and fabricated by the improved stack-and-draw technology in our laboratory. The broadband blue-shifted and red-shifted dispersive waves (DWs) are e-ciently generated from soliton self-frequency shift (SSFS) along the slow axis of PM-PCF. By optimizing the pump parameters and the flber length, the polarized DWs centered in the normal dispersion region can be used as the pump and Stokes pulses for the high resolution coherent anti-Stokes Raman scattering (CARS) microscopy. Moreover, it is demonstrated that the widely tunable relevant CARS wavelengths can be obtained by adjusting the pump wavelength. The CARS microscopy based on DWs can flnd important applications in detecting the biological and chemical samples with the C = N, S-H, C-H, and O-H stretch vibration resonances of 2100 to 2400cm i1 , 2500 to 2650cm i1 , 2700 to 3000cm i1 , and 3000 to 3750cm i1 .

Stabilized soliton self-frequency shift and 0.1- PHz sideband generation in a photonic-crystal fiber with an air-hole-modified core

Fiber dispersion and nonlinearity management strategy based on a modification of a photonic-crystal fiber (PCF) core with an air hole is shown to facilitate optimization of PCF components for a stable soliton frequency shift and subpetahertz sideband generation through four-wave mixing. Spectral recoil of an optical soliton by a red-shifted dispersive wave, generated through a soliton instability induced by high-order fiber dispersion, is shown to stabilize the soliton self-frequency shift in a highly nonlinear PCF with an air-hole-modified core relative to pump power variations. A fiber with a 2.3-microm-diameter core modified with a 0.9-microm-diameter air hole is used to demonstrate a robust soliton self-frequency shift of unamplified 50-fs Ti: sapphire laser pulses to a central wavelength of about 960 nm, which remains insensitive to variations in the pump pulse energy within the range from 60 to at least 100 pJ. In this regime of frequency shifting, intense high- and low-frequency branches of dispersive wave radiation are simultaneously observed in the spectrum of PCF output. An air-hole-modified-core PCF with appropriate dispersion and nonlinearity parameters is shown to provide efficient four-wave mixing, giving rise to Stokes and anti-Stokes sidebands whose frequency shift relative to the pump wavelength falls within the subpetahertz range, thus offering an attractive source for nonlinear Raman microspectroscopy.

Tailoring CW supercontinuum generation in microstructured fibers with two-zero dispersion wavelengths

We theoretically study broadband supercontinuum generation in photonic crystal fibers exhibiting two zero dispersion wavelengths and under continuous-wave pumping. We show that when the pump wavelength is located in between the zero-dispersion wavelengths, a wide and uniform spectral broadening is achieved through modulation instability, generation of both blue-shifted and red-shifted dispersive waves and subsequently through soliton self-frequency shift. This supercontinuum is therefore bounded by these two dispersive waves which allow the control of its bandwidth by a suitable tuning of the fiber dispersion. As a relevant example, we predict that broadband (1050-1600 nm) continuous-wave light can be generated in short lengths of microstructured fibers pumped by use of a 10-W Ytterbium fiber laser.