Fabrication and replication of micro-optical structures for growth of GaN-based light emitting diodes
07 Dec 2013-Vol. 8923, pp 682-691
TL;DR: In this paper, the exact shape of pattern milled into Al 2 O 3 was replicated into a 0.4mm-thick shim of Ni by electroplating.
Abstract: GaN light emitting diodes (LEDs) on sapphire substrates can be improved by micro-patterning substrate to perform epitaxial over-growth which drastically reduces defects' density in the light emitting region. We patterned Al 2 O 3 with focused ion beam and show a successful overgrowth of GaN. The exact shape of pattern milled into Al 2 O 3 was replicated into a 0.4-mm-thick shim of Ni by electroplating. The surface roughness of Ni was ~5:5 ±2 nm and is applicable for the most demanding replication of nano-rough surfaces. This technique can be used to replicate at micro-optical elements Fresnel-axicons defined by electron beam lithography made on sub-1 mm areas without stitching errors (Raith EBL). Shimming of macro-optical elements such as car back- reflectors is also demonstrated. Ni-shimming opens possibility to make replicas of nano-textured small and large area patterns and use them for thermal embossing and molding of optically-functionalized micro-fluidic chips and macro-optical elements.
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TL;DR: In this paper, a critical review of ripple formation mechanisms is presented, discussed, and formation conjectures are presented, and it is shown that formation of plasma at subcritical or critical densities on the surface and in the bulk specific to the high-intensity ultra-short laser pulses has to be considered to account for the experimental observations.
234 citations
18 Dec 2020
TL;DR: In this paper, a co-axial pump (optical)-probe (x-rays) experimental concept and show performance of the optical component are presented and different realisations of optical pump are discussed.
Abstract: We put forward a co-axial pump (optical)-probe (x-rays) experimental concept and show performance of the optical component. A Bessel beam generator with a central 100 µm diameter hole (on the optical axis) was fabricated using femtosecond (fs) laser structuring inside a silica plate. This flat-axicon optical element produces a needle-like axial intensity distribution which can be used for the optical pump pulse. The fs-x-ray free electron laser (X-FEL) beam of sub-1 µm diameter can be introduced through the central hole along the optical axis onto a target as a probe. Different realisations of optical pump are discussed. Such optical elements facilitate alignment of ultra-short fs-pulses in space and time and can be used in light–matter interaction experiments at extreme energy densities on the surface and in the volume of targets. Full advantage of ultra-short 10 fs-X-FEL probe pulses with fs-pump (optical) opens an unexplored temporal dimension of phase transitions and the fastest laser-induced rates of material heating and quenching. A wider field of applications of fs-laser-enabled structuring of materials and design of specific optical elements for astrophotonics is presented.
10 citations
Cites background from "Fabrication and replication of micr..."
...The variation of intensity profile between the two planes shows the evolution of the ring pattern which is the characteristic of an axicon [14] as the conical phase expands....
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...The circular grating can convert a Gaussian beam or a uniform illumination into a Bessel-like beam [14]....
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TL;DR: In this article, a fundamental diffractive optical element, binary axicon-axicon with two phase or amplitude levels, has been designed in three configurations namely conventional axicon, photon sieve axicon (PSA) and sparse PSA and directly milled onto a sapphire substrate.
Abstract: Fabrication of large area (sub-1 cm cross-section) micro-optical components in a short period of time (~ 10 min) and with lesser number of processing steps is highly desirable and cost-effective. In the recent years, femtosecond laser fabrication technology has revolutionized the field of manufacturing by offering the above capabilities. In this study, a fundamental diffractive optical element, binary axicon–axicon with two phase or amplitude levels, has been designed in three configurations namely conventional axicon, photon sieve axicon (PSA) and sparse PSA and directly milled onto a sapphire substrate. The fabrication results revealed that a single pulse burst fabrication can produce a flatter and smoother profile than pulse overlapped fabrication which gives rise to surface damage and increased roughness. The fabricated elements were processed in IsoPropyl alcohol and potassium hydroxide to remove debris and redeposited amorphous sapphire. An incoherent illumination was used for optical testing of the components and a non-linear optical filter was used for cleaning the noisy images generated by the diffractive optical elements.
6 citations
Posted Content•
TL;DR: In this paper, a co-axial pump (optical)-probe (X-rays) experimental concept and show performance of the optical component are presented. But the performance of optical pump is limited to the case of femtosecond X-ray free electron laser (FEL).
Abstract: We put forward a co-axial pump(optical)-probe(X-rays) experimental concept and show performance of the optical component. A Bessel beam generator with a central 100 micrometers-diameter hole (on the optical axis) was fabricated using femtosecond (fs) laser structuring inside a silica plate. This flat-axicon optical element produces a needle-like axial intensity distribution which can be used for the optical pump pulse. The fs-X-ray free electron laser (X-FEL) beam of sub-1 micrometer diameter can be introduced through the central hole along the optical axis onto a target as a probe. Different realisations of optical pump are discussed. Such optical elements facilitate alignment of ultra-short fs-pulses in space and time and can be used in light-matter interaction experiments at extreme energy densities on the surface and in the volume of targets. Full advantage of ultra-short 10 fs X-FEL probe pulses with fs-pump(optical) opens an unexplored temporal dimension of phase transitions and the fastest laser-induced rates of material heating and quenching. A wider field of applications of fs-laser-enabled structuring of materials and design of specific optical elements for astrophotonics is presented.
3 citations
26 May 2020
TL;DR: In this paper, a co-axial pump (optical)-probe (X-rays) experimental concept and show performance of the optical component are presented. But the performance of optical pump is limited to the case of femtosecond X-ray free electron laser (FEL).
Abstract: We put forward a co-axial pump(optical)-probe(X-rays) experimental concept and show performance of the optical component. A Bessel beam generator with a central 100 micrometers-diameter hole (on the optical axis) was fabricated using femtosecond (fs) laser structuring inside a silica plate. This flat-axicon optical element produces a needle-like axial intensity distribution which can be used for the optical pump pulse. The fs-X-ray free electron laser (X-FEL) beam of sub-1 micrometer diameter can be introduced through the central hole along the optical axis onto a target as a probe. Different realisations of optical pump are discussed. Such optical elements facilitate alignment of ultra-short fs-pulses in space and time and can be used in light-matter interaction experiments at extreme energy densities on the surface and in the volume of targets. Full advantage of ultra-short 10 fs X-FEL probe pulses with fs-pump(optical) opens an unexplored temporal dimension of phase transitions and the fastest laser-induced rates of material heating and quenching. A wider field of applications of fs-laser-enabled structuring of materials and design of specific optical elements for astrophotonics is presented.
2 citations
Cites background from "Fabrication and replication of micr..."
...The circular grating can convert a Gaussian beam or a uniform illumination into a Bessel-like beam [13]....
[...]
References
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TL;DR: In this article, a two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint phase discontinuities on propagating light as it traverses the interface between two media.
Abstract: Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale of the wavelength. A two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint such phase discontinuities on propagating light as it traverses the interface between two media. Anomalous reflection and refraction phenomena are observed in this regime in optically thin arrays of metallic antennas on silicon with a linear phase variation along the interface, which are in excellent agreement with generalized laws derived from Fermat’s principle. Phase discontinuities provide great flexibility in the design of light beams, as illustrated by the generation of optical vortices through use of planar designer metallic interfaces.
6,763 citations
TL;DR: In this article, a simple optical interference method to fabricate microperiodic structures was demonstrated, where a femtosecond laser pulse was split by a diffractive beam splitter and overlapped with two lenses.
Abstract: A simple optical interference method to fabricate microperiodic structures was demonstrated. Femtosecond laser pulse was split by a diffractive beam splitter and overlapped with two lenses. Temporal overlap of the split femtosecond pulses, which requires 10 μm order accuracy in optical path lengths, was automatically achieved by this optical setup. One-, two-, and three-dimensional periodic microstructures with micrometer-order periods were fabricated using this method.
295 citations
TL;DR: In this paper, the advantages and limitations of various femtosecond laser microfabrication techniques for the preparation of photonic crystals and elements of microelectromechanical and micro-optofluidic systems are discussed.
Abstract: Femtosecond laser fabrication of three-dimensional structures for photonics applications is reviewed. Fabrication of photonic crystal structures by direct laser writing and holographic recording by multiple beam interference techniques are discussed. The physical mechanisms associated with structure formation and postfabrication are described. The advantages and limitations of various femtosecond laser microfabrication techniques for the preparation of photonic crystals and elements of microelectromechanical and micro-optofluidic systems are discussed.
196 citations
TL;DR: In this article, the fabrication of two-dimensional periodic structures by means of multibeam interference of femtosecond pulses was reported, and the possibility of controlling the period of the lattice, rod thickness, and rod shape were demonstrated.
Abstract: Femtosecond laser pulses are useful for laser microfabrication through multiphoton absorption. However, it is difficult to create interference of femtosecond pulses for the fabrication of periodic structures. In this letter, we report the fabrication of two-dimensional periodic structures by means of multibeam interference of femtosecond pulses. Scanning electron microscopy revealed a rod structure arranged into a square lattice. The possibility of controlling the period of the lattice, rod thickness, and rod shape were demonstrated.
180 citations
TL;DR: In this article, the femtosecond laser-induced multi-photon polymerization of a zirconium-silicon based sol-gel photopolymer was employed for the fabrication of a series of micro-optical elements with single and combined optical functions: convex and Fresnel lenses, gratings, solid immersion lenses on a glass slide and on the tip of an optical fiber.
Abstract: The femtosecond laser-induced multi-photon polymerization of a zirconium–silicon based sol–gel photopolymer was employed for the fabrication of a series of micro-optical elements with single and combined optical functions: convex and Fresnel lenses, gratings, solid immersion lenses on a glass slide and on the tip of an optical fiber. The microlenses were produced as polymer caps of varying radii from 10 to 90 µm. The matching of refractive indices between the polymer and substrate was exploited for the creation of composite glass-resist structures which functioned as single lenses. Using this principle, solid immersion lenses were fabricated and their performance demonstrated. The magnification of the composite solid immersion lenses corresponded to the calculated values. The surface roughness of the lenses was below ~ 30 nm, acceptable for optical applications in the visible range. In addition, the integration of micro-optical elements onto the tip of an optical fiber was demonstrated. To increase the efficiency of the 3D laser polymerization, the lenses were formed by scanning only the outer shell and polymerizing the interior by exposure to UV light.
160 citations