This PDF file contains the front matter associated with SPIE Proceedings Volume 9581 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Significant interest has been devoted to tailoring optical fields that transversely accelerate during propagation in the form of Airy, Weber and Mathieu beams. In this work, we introduce a new type of optical field that exhibits controlled angular acceleration during propagation which is achieved by superpositions of Bessel beams with non-canonical phase functions. We demonstrate these angular accelerating fields by modulating the phase and amplitude of a supercontinuum source with the use of a phase-only spatial light modulator (SLM). We illustrate that by considering only the first diffraction order when the SLM is encoded with a blazed grating, the SLM is capable of tailoring the spatial profile of broadband sources without any wavelength dependence. By digitally simulating free-space propagation on the SLM, we compare the effects of real and digital propagation on the angular rotation rates of the resulting optical fields for various wavelengths. The development of controlled angular accelerating optical fields will be useful in areas such as particle manipulation, plasma control, material processing and non-linear optics.

We analyze and demonstrate, numerically and experimentally, the self-healing effect in scaled propagation invariant beams, subject to opaque obstructions. The effect is quantitatively evaluated employing the Root Mean Square deviation and the similarity function.

Vector beams are defined by spatially inhomogeneous states of polarization, that is, the spatial distribution and polarization state of the beam are non-separable. These beams have found interest in a variety of optical fields such as microscopy, interferometry and optical tweezing. It is therefore important to determine the degree to which these beams are non-separable or to determine the vectorness of such beams. We show that the nonseparability of vector beams is analogous to that of entangled quantum states and as such, we use traditionally quantum techniques such as a Bell inequality, to determine the vectorness of our generated vector vortex beams.

Intracavity laser beam shaping has been achieved by adding intensity or phase filters to a Fabry-Perot resonator. Changing the output beam from one mode to another is a tedious process, requiring the replacing of custom optical elements, and careful realignment. The digital laser [1] is an innovation which allows the laser beam produced by a laser to be dynamically controlled by a computer. Essentially, one of the resonator mirrors is replaced by a spatial light modulator (SLM), which is a computer controlled, pixellated, liquid-crystal device. While the concept is the device is simple, the implementation revealed subtle properties of spatial light modulators and the liquid crystals contained in them. These properties had to be well understood before their undesirable characteristics could be overcome, allowing the laser to function as conceived in the design.

Higher-order Laguerre–Gaussian beams with zero radial index and nonzero azimuthal index are known to carry orbital angular momentum (OAM), and they are routinely created external and internal to laser cavities. Previous reports on the generation of such modes from laser cavities suffer from inconclusive evidence of the real electromagnetic field. In this paper we demonstrate a simple method of selectively generating higher-order doughnut modes using a digital laser and we show that an observed doughnut beam from a laser cavity may not be a pure Laguerre–Gaussian azimuthal mode but can be an incoherent sum of petal modes, which do not carry OAM. We also demonstrate a method that could be used for future analysis of such fields from laser resonators.

The development of metamaterials operating at visible light wavelengths requires metamaterials to be produced with nanoscale structure over large areas. Improvements in the efficiency of electron beam lithography (EBL) could play an important role in accelerating this development. In this paper we show the production of a shaped probe for use in EBL. A phase structured electron wave containing vortices can be focused to produce a C-shaped cross section. Local spatial frequency analysis shows that both the gap and overall size of the C-shape can be easily controlled. We present the generation of such a C-shaped electron beam using a holographic binary amplitude diffraction mask. Thin AlF₃ film is exposed to the C-shaped diffraction order and demonstrates the facile production of both a metallic C-shaped structure as well as the etching of a C-shaped hole.

We propose electronically controlled optical tweezing based on space-time-wavelength mapping technology. By using time-domain modulation, the location and the polarity of force hot-spots created by Lorentz force (gradient force) can be controlled. In this preliminary study we use 150 fs optical pulses that are dispersed in time and space to achieve a focused elliptical beam that is ~20 μm long and ~2 μm wide. We use an electro-optic modulator to modulate power spectral distribution of the femtosecond beam after temporal dispersion and hence change the intensity gradient along the beam at the focal spot. We present a theoretical model, and simulation results from a proposed experimental setup. The results show that we can achieve ±200 pN forces on nano objects (~100 nm) without mechanical beam steering. The intensity of wavelengths along the spectrum can be manipulated by using different RF waveforms to create a desired intensity gradient profile at the focal plane. By choosing the appropriate RF waveform it is possible to create force fields for cell stretching and compression as well as multiple hot spots for attractive or repulsive forces. 2D space-time-wavelength mapping can also be utilized to create tunable 2D force field distribution.

We experimentally demonstrate an information encoding protocol using the two degrees of freedom of Laguerre Gaussian modes having different radial and azimuthal components. A novel method, based on digital holography, for information encoding and decoding using different data transmission scenarios is presented. The effects of the atmospheric turbulence introduced in free space communication is discussed as well.

We generate Hermite-Gauss and Ince-Gauss beams by using kinoform phase holograms encoded onto a liquid crystal display. The phase transmittance of this holograms coincide with the phases of such beams. Scale versions of the desired beams appear at the Fourier domain of the KPHs. When an appropriated pupil size is employed, the method synthesizes HG and IG beams with relatively high accuracy and high efficiency. It is noted that experimental and numerical results are agreement with the theory.

Sometimes to improve the performance of industrial or scientific laser technology it is desired to transform an intensity distribution from Gaussian to the flattop. The adjusting of the intensity profile can be implemented by means of adaptive optics. In this paper we present laser beam control with bimorph deformable mirrors. Shack-Hartmann wavefront sensor is used to determine the control signal for the bimorph deformable mirror while focal spot is observed with CCD camera to check the result of beam shaping.

Lossless transformation of round Gaussian to square shaped flat-top collimated beam is important in building highpower solid state laser systems to improve optical pumping or amplification. There are industrial micromachining applications like scribing, display repair, which performance is improved when a square shaped spot with uniform intensity is created. Proved beam shaping solutions to these techniques are refractive field mapping beam shapers having some important features: flatness of output phase front, small output divergence, high transmittance, extended depth of field, operation with TEM00 and multimode lasers. Usual approach to design refractive beam shapers implies that input and output beams have round cross-section, therefore the only way to create a square shaped output beam is using a square mask, which leads to essential losses. When an input laser beam is linearly polarized it is suggested to generate square shaped flat-top output by applying beam shaper lenses from birefringent materials or by using additional birefringent components. Due to birefringence there is introduced phase retardation in beam parts and is realized a square shaped interference pattern at the beam shaper output. Realization of this approach requires small phase retardation, therefore weak birefringence effect is enough and birefringent optical components, operating in convergent or divergent beams, can be made from refractive materials, which crystal optical axis is parallel to optical axis of entire beam shaper optical system. There will be considered design features of beam shapers creating square shaped flat-top beams. Examples of real implementations and experimental results will be presented as well.

Employing aspherical lenses to reduce aberrations to improve focusing qualities is a well-known concept. But the potpourri of aspheric surfaces offers way more possibilities, even the chance for flexible beam shaping setups. Since these are refractive optical elements the beam shaping is robust with respect to wavelength changes. Being able to generate ring shaped light distributions is interesting for various applications. Here the most uncommon aspheric surface – an axicon – is utilized. Axicons are glass cones, which convert the incoming light into Bessel beams. Those are characterized by their concentric ring structure and long depth of focus, which makes them very interesting for material processing. Above that, combining such an axicon with a focusing lens leads to a ring focus. Its size is not only determined by the choice of the axicon angle and the lens properties, but also through the diameter of the incoming beam. Thus, for optimal usage a flexible beam expander, which leaves the beam quality unaltered is mandatory. The remarkable properties of these beam shaping set-ups are shown in theory and experimentally. Furthermore, a configuration consisting of two axicons and interchangeable focusing lenses is presented. For one thing, this set-up allows for tuning of the working distance in any required way for optimal material processing. For another thing, the induced chromatic focal shift of the focusing lens that occurs by a change of wavelength can be compensated for by adapting the distance of the axicons and leaving the working distance unchanged.

The optical system working with focused Gaussian beam carrying a higher order optical vortex is considered. Additionally the optical vortex movement inside the beam is proposed allowing the precise scanning of the sample inserted into the beam. The analytical formula for the Fresnel diffraction integral with the shifted optical vortex has been calculated and compared with the numerical results. The experimental validation of this problem has been also presented.

Due to their several unique properties, propagation invariant laser beams (PILBs) are playing an increasingly important role in several photonics applications. This paper describes some practical aspects of producing propagation invariant laser beams with different symmetries and structured light field distributions. Both intra-cavity and extra-cavity schemes can be employed. In the case of extra-cavity implementations, we show several practical layouts of anamorphic optical systems (AOSs) for shaping the propagation-invariant laser beams based on the size and waist locations of the input laser beams. We also establish matrix equations required to quantify the influence of input PILBs lateral and angular misalignments with respect to the AOSs onto the spatial characteristics of the produced output PILBs, and present examples of the resulting PILBs affected by the input PILBs misalignments.

We present the fabrication and characterization of a mechanically induced long period grating (MLPG) using a grating period of 400 μm and 1m of NZ-DSF. Pressure is gradually applied up to 120 Lb at different angles like 0, 30, 45 and 60 degrees. An attenuation band is observed centered at a wavelength around 1064nm using a fiber position of 30 degrees with respect to the grating´s metal plate and a maximum pressure of 145 Lb. The loss band presents a maximum depth of 22dB and a bandwidth of approximately 10nm. Torsion and curvature characterizations did not change the output spectrum of the optical grating. However, temperature characterization depicted a small shifting which could be insignificant for some applications. Still, there is 16dB attenuation as temperature increases in a range from room temperature up to 450°C. These preliminary studies show that this 1064 nm centered wavelength MILPG might be used in a low linear dynamic range with temperature (75-300)°C as a temperature sensor.

In this paper we experimentally demonstrate intra-cavity selective excitation of Higher-Order Laguerre–Gaussian modes with nonzero radial index and zero azimuthal index using a simple absorbing ring implemented on a digital laser. We show selective excitation of modes with radial order of zero to five using a non-segment absorbing rings. We then reduce the losses of the cavity that is associated with the absorbing ring by cutting the rings into segments. We then experimentally demonstrate that excited modes using half-circular segmented absorbing rings have a lower threshold compared to using a full ring while at the same time maintaining mode volume, purity and slope efficient of the laser.