Wide spectral range third-order autocorrelator based on ultrafast nonresonant nonlinear refraction: erratum.
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Letter↗
Biomedical subjects
J Stewart Aitchison
Publications and source records attributed to J Stewart Aitchison.
Efficient Raman shifting of high-energy picosecond pulses into the eye-safe 1.5-microm spectral region by use of a KGd(WO4)2 crystal.
We report an efficient transient stimulated Raman conversion of high-energy picosecond pulses at 1350 nm into the eye-safe 1500-nm wavelength range by use of a KGd(WO4)2 crystal. The conversion efficiency into either 1503- or 1537-nm radiation (767- or 901-cm(-1) Raman modes, respectively) is measured to be approximately 10% in a single-pass configuration. The transient Raman gain coefficient is found to be approximately 0.8 cm/GW. Simultaneous generation of multiple Raman lines is also observed.
Journal Article↗
Observation of discrete gap solitons in binary waveguide arrays.
We report an experimental study of discrete gap solitons in binary arrays of optical waveguides. We observe self-focusing indicating soliton generation when the inclination angle of an input beam is slightly above the Bragg angle and show that the propagation direction of the emerging gap soliton is influenced by the effect of interband momentum exchange.
Journal Article↗
Coherent two-photon absorption spectroscopy of the Raman-active KGd(WO4)2 crystal.
We report on the systematic open-aperture Z-scan characterization of the two-photon absorption properties in one of the most efficient solid-state Raman frequency shifters, the crystal potassium gadolinium tungstate [KGd(WO4)2]. The two-photon absorption coefficient was determined in the 370-600-nm wavelength range, with the highest value found to be approximately 1.9 cm/GW at 370 nm. Nonlinear losses are crucial in determining the conversion efficiency of the stimulated Raman scattering process when it is excited with ultrashort laser pulses with photon energy exceeding half of the bandgap. In addition, the results were analyzed within the context of a simple two-parabolic-band theoretical model to yield an effective bandgap energy value for the crystal.
Journal Article↗
Wide spectral range third-order autocorrelator based on ultrafast nonresonant nonlinear refraction.
We demonstrate a simple scheme for a wide spectral range, third-order autocorrelator based on ultrafast nonlinear Kerr-type refraction. The technique was successfully used to characterize high-energy ultrashort pulses at 1550 and 1300 nm, where the pulse's shape and width are two of the most critical parameters. Because of its simplicity, this technique is also a powerful tool for the optimization of high-power chirped-pulse amplified laser systems, in which slight misalignment of the stretcher-compressor gratings can lead to spatiotemporal pulse distortions. In addition, it can be extended to low-power mode-locked oscillators.
Journal Article↗
Controlling light by light in a one-dimensional resonant photonic crystal.
We consider the interaction and stability of gap solitons in a one-dimensional, resonant, photonic crystal with a defect state produced by a linear localized mode, or by an incoherent pump. Soliton propagation is investigated using both an analytical treatment and the direct numerical integration of the two-wave Maxwell-Bloch equations. Our results demonstrate that the soliton can be trapped, reflected from, or tunnel through the defect state.
Journal Article↗
Dispersion of the nonlinear refractive index in sapphire.
The nonlinear refractive index, n2, of sapphire was experimentally measured in the 550-1550-nm wavelength range by use of a picosecond Z-scan technique. It was found that in this spectral region the value of n2 decreases monotonically from approximately 3.3 x 10(-16) to approximately 2.8 x 10(-16) cm2/W. An empirical expression for the wavelength dependence of the nonlinear refractive index in the 270-1550-nm range was obtained.
Journal Article↗
Gap soliton dynamics in a nonuniform resonant structure.
A model for the propagation of coherent pulses along a one-dimensional, resonantly absorbing Bragg grating that includes localized inhomogeneous population inversion at its center is presented. The long-range coupling between the optical field and resonant atoms allows for controllable trapping of a gap soliton by the local inversion, thus opening new opportunities for control of signal transmission and localization of light.
Journal Article↗
Design and fabrication of a silica on silicon integrated optical biochip as a fluorescence microarray platform.
Previous research into the use of Flame Hydrolysis Deposition (FHD) of glasses in integrated optics has focused on the successful commercial exploitation of low cost optical devices within the field of telecommunications and optoelectronics. Recently we have sought to apply these fabrication technologies to the development of optical biochips, utilising their ability to be integrated with microfluidics as a 'Lab-on-a-chip' platform. In this paper, we carry this development forward by seeking to create a microarray of integrated optical sensing elements, addressed using a glass-polymer hybrid technology in which poly(dimethylsiloxane), PDMS, is used as an elastomeric packaging over-layer. In particular, we describe the wide range of modelling and microfabrication processes required for the successful manufacture, integration and packaging of such arrays. The integration of both optical and fluidic circuits in this device avoids precise alignment requirements and results in a compact, robust and reliable device. Finally, in this paper, we describe the implementation of a pumping system for delivering small amounts of fluid across the array together with an optical signal treatment.
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