Diffractive optics for spectral control of the supercontinuum generated in sapphire with femtosecond pulses

Abstract

Abstract:We propose the use of kinoform diffractive lenses to focus near infrared femtosecond pulses in sapphire crystals for supercontinuum generation. It is shown that a strongly peaked structure appears in the blue region of the supercontinuum spectra. The central wavelength of this peak can be easily controlled by simply changing the lens-crystal distance. Moreover, when compared with the supercontinuum generated with a refractive lens in analogous conditions, the spectral extension of the sogenerated continuum is larger. Our results were corroborated for sapphire plates with different thicknesses as well as in other transparent dielectrics such as fused silica. ©2011 Optical Society of America

Controlled Multibeam Supercontinuum Generation With a Spatial Light Modulator

“…This is achieved by changing independently the efficiency of each microlens. Moreover, the spectrum of the generated SC was tuned by slightly changing the focal length of the lenses, in agreement with previous observations [24]. …”

“…However, in practical applications an increase in the input energy is undesirable because it could easily lead to a permanent damage in the sample [26]. Recently, it has been demonstrated [24] that when a femtosecond beam is focused with a diffractive lens, wavelength tunability in the SC signal can be achieved by simply changing the lens-sample relative distance. It was found that the depth at which the filament is formed is closely connected to the SC spectrum [27].…”

Ultrafast supercontinuum generation in bulk condensed media

“…Figure 20(b) shows an example how the spectral intensity within certain spectral regions and the overall shape of the resulting SC spectrum is modified by varying the time delay between the co-filamenting fundamental and second harmonic pulses. An efficient control of the SC spectrum was also performed by changing the relative position of the focus in the nonlinear medium by means of diffractive optics [264,265] or by varying the spatial phase of the input beam with spatial light modulators [266,267]. Fine adjustment of the position of the nonlinear focus was demonstrated by varying the carrier envelope phase of a few-cycle input pulse [268].…”

On-axis non-linear effects with programmable Dammann lenses under femtosecond illumination

“…However, under certain circumstances, the spatiotemporal properties of the pulse focusing itself can be exploited to gain control over the nonlinear mechanisms taking place. In this sense, diffractive lenses have been recently employed for SHG [8] or in super continuum generation [9]: the strong chromatic aberration induced by diffraction changes the spectral properties of the pulse.On the other hand, Dammann diffraction gratings are binary phase distributions of alternate 0, π zones for well-defined transient points [10,11]. For continuous wave (CW) illumination, these gratings generate diffraction patterns characterized by a number N of diffracted orders with the same peak intensity.…”

“…However, under certain circumstances, the spatiotemporal properties of the pulse focusing itself can be exploited to gain control over the nonlinear mechanisms taking place. In this sense, diffractive lenses have been recently employed for SHG [8] or in super continuum generation [9]: the strong chromatic aberration induced by diffraction changes the spectral properties of the pulse.…”