Spatial characterization of Bessel-like beams for strong-field physics

Abstract

We present a compact, simple design for the generation and tuning of both the spot size and effective focal length of Bessel-like beams. In particular, this setup provides an important tool for the use of Bessel-like beams with high-power, femtosecond laser systems. Using a shallow angle axicon in conjunction with a spherical lens, we show that it is possible to focus Bessel-like modes to comparable focal spot sizes to sharp axicons while maintaining a long effective focal length. The resulting focal profiles are characterized in detail using an accurate high dynamic range imaging technique. Quantitatively, we introduce a metric (R_0.8) which defines the spot-size containing 80% of the total energy. Our setup overcomes the typical compromise between long working distances and small spot sizes. This is particularly relevant for strong-field physics where most experiments must operate in vacuum.

Lens-axicon separation to tailor aberration free focused Bessel-Gaussian beams in the paraxial regime

“…The width of the central core and the concentric side lobes narrow down and tilt towards the vicinity of the focus of the lens as we move along the axial direction. Consequently, the effective Bessel zone length reduces [22]. The reduction can be mitigated by reducing the distance between the lens and the axicon.…”

“…(1) without allowing for variation in the axial beam profile [21]. Using only a single lens separated from an axicon has been investigated for a number of reason; The advantage of tailoring the diameter of the far field ring by changing the distance [19]; The behaviour in the Bessel region experimentally for high power lasers using long focal length lenses and shallow axicons to avoid spherical aberrations [22]; and also enabling non-linear harmonic generation by optimizing the phase matching condition [23,24]. In this work, we present an analytical scalar model that accounts for the separation between the lens and the axicon for generating aberration free focused Bessel-Gaussian beams.…”

Higher order harmonic generation and strong field ionization with Bessel-Gauss beams in a thin jet geometry

“…Here we specifically investigate using Bessel-Gauss (BG) beams [19,20], also known as Bessel-like [21,22], for the generation of the XUV radiation. In the past we have characterized the properties of such beams and their relevance for strong field science [23]. BG beams have a series of enticing properties [24,25].…”

“…Among the most notable is the ability to overcome limitations of the Rayleigh range [26,27]. Bessel-like beams maintain focused, on-axis peak intensity for much longer distances than focused Gaussian beams [23]. This allows for the use of an extended generation target geometry as well as potentially more favorable phase matching conditions.…”

Detecting the Extremely Small Angle of an Axicon by Phase-Shifting Digital Holography

“…Such properties make Bessel beams attractive for a broad range of applications, such as optical tweezers and particle trapping [6][7][8][9]. Bessel beams are also particularly involved in the applications in strong-field science, laser machining, biomedical imaging, and confocal microscopy [10][11][12][13][14][15][16]. Given the specific properties and important applications, the generation of Bessel beams is of considerable importance.…”