Atom trap in an axicon mirror

Hollow-conical atomic beam from a low-velocity intense source

We demonstrate, for the first time, a hollow-conical atomic beam from a standard low-velocity intense source. Experimental results and numerical simulations indicate that the hollow-conical feature is caused by the converging-diverging extraction process. The degree of hollowness can be reduced by using a weaker push beam and extending the length of transverse cooling. Analytical models are proposed to quantitatively describe the hollowness of the atomic beam. This study can find applications where a compact and solid atomic beam is needed, such as coupling cold atoms into matter waveguides or continuous cold atomic beam interferometers.

Bessel-like beam array formation by periodical arrangement of the polymeric round-tip microstructures

Here, we report the formation of Bessel-like beam array from periodic patterns fabricated by the four-beam interference lithography. Characteristics of the generated Bessel-like beams depend on geometrical parameters of the fabricated microaxicon-like structures, which can be easily controlled via the laser processing parameters. The output beam characteristics disclose the attributes of Bessel beams. The demonstrated method enables an easy fabrication of angular-tolerant wavefront detectors, optical tweezers, optical imaging systems or materials processing tools, having a broad range of applications.

Diffractive performance of a photon-sieve-based axilens

An axilens is a combination of an axicon and a Fresnel zone plate to provide a long focal diffractive lens. However, the photon sieve has been known as a high-resolution version of the Fresnel zone plate. Therefore, construction of an axilens on the basis of a photon sieve may yield a high-resolution axilens. To this end, circular zones of an axilens were replaced by a given distribution of pinholes. It is shown that lateral resolution of the axilens is increased due to the replacement. The impact of different distributions of pinholes on the focusing properties of the axilens were also examined. Results indicate that by implementing different distributions of pinholes resolution and focal depth are changed and hence, are manageable. Theoretical results are verified by experimental work.

Highly compact imaging using Bessel beams generated by ultraminiaturized multi-micro-axicon systems

Employing Bessel beams in imaging takes advantage of their self-reconstructing properties to achieve small focal points while maintaining a large depth of focus. Bessel beams are efficiently generated using axicons, and their utility in scanning imaging systems, such as optical coherence tomography (OCT), has been demonstrated. As these systems are miniaturized to allow, for example, endoscopic implementations, micro-axicons are required to assure the maintenance of a large depth of focus. We demonstrate here the design, fabrication, and application of molded micro-axicons for use in silicon-based micro-optical benches. It is shown that arrangements of multiple convex and concave axicons may be implemented to optimize the depth of focus in a miniaturized OCT system, using a telescopic optical arrangement of considerably shorter optical system length than that achievable with classical micro-optics.

Generation of Bessel beams using a magnetic liquid deformable mirror

A deformable mirror made of a magnetic liquid has been used to produce conical surfaces with subwavelength (λ/4) accuracy. The surface profile of the liquid mirror is controlled by 91 small magnetic coils. The mirror exhibits a linear response with respect to the currents driving the coils, and it allows for real-time changes of its surface profile. The magnetic liquid deformable mirror has been used to produce reflected beams having a conical wavefront; the propagation of the reflected beams was verified to be consistent with that of Bessel beams in the near and far field. The large dynamic range of such a deformable mirror has made it possible to generate Bessel beams with a broad range of beam parameters.

Three-dimensional field distribution in the focal region of low-Fresnel-number axicons

Three-dimensional intensity and phase distributions generated by microaxicons are evaluated in the low-Fresnel-number regime. Apertured and nonapertured conical wavefronts may generate transverse patterns with notable deviations from the expected nondiffracting Bessel beam. First-order analytical expressions are proposed for the evaluation of the wave field produced by axicons of different Fresnel number in the focal region.