The beam shaping by illuminators of microlithographic optical systems is a key technological contributor to the advancement of mass production of integrated circuits. The following examines both the requirements and the design of these illumination systems. The importance of partial coherence, off-axis illumination, polarization, telecentricity and uniformity for the lithographic process are discussed. The design sections cover the systems from source to reticle, including the use of diffusers, axicons, kaleidoscopes and fly's eyes arrays.

This paper is an overview of the optical designs used in array-type multispot laser thermal printers. A variety of unique systems have been developed for high-power high-throughput printing applications where laser light is generally transformed into a linear arrangement of modulated beams focused onto light-sensitive media. The typical light source is a monolithic laser diode array that emits a series of anamorphic partially coherent infrared beams. An optical system, comprising anamorphic, micro-optics, and designed according to principles from classical imaging optics, illumination optics, and Gaussian beam optics, is needed to conduct the light to the media. Special optical components, including rod lenses, laser smile correctors, or spatial light modulator arrays may be employed. Because the printing applications are highly sensitive to repetitive artifacts, the designs typically provide light source redundancy and light homogenization. The interaction of the incident light with the thermal media can also affect the design. These various optical design issues, and a number of design solutions, are the subjects of this review paper.

Laser drilling is increasingly being used in fabrication of small components for electronics, aerospace, biomedical, and MEMS applications because it provides rapid, precise, clean, flexible, and efficient process. For laser percussion drilling, the workpiece is subjected to a series of laser pulses at the same spot at a specified laser parameter setting. Large temperature gradient is introduced, which results in a minimal heat affected zone (HAZ) and low heat distortion. In laser percussion drilling of small holes, profile of the HAZ and the geometry of the holes strongly depend on settings of the laser parameters such as peak power, pulse length, pulse repetition rate, focal condition, number of pulses, etc. In addition, the processing results are strongly influenced by geometrical and material properties of the workpiece. This paper presents a study of laser process for percussion drilling of micrometer size holes on thin sheet metals using a pulsed Nd:YAG laser. Experimental investigations are performed to characterize the geometry of the hole and surface topography in their vicinity. Analytical and computational modeling of the temperature distribution is also performed and used to determine profiles of the HAZs. The effects of different combinations of laser parameters and workpiece properties on the hole geometry are summarized and a procedure for laser percussion drilling of small holes on sheet metals is outlined.

Beam shaping is becoming a standard requirement for UV (354.7 nm) Diode Pumped Solid State (UV DPSS) lasers used in industrial micromachining applications, such as microvia drilling, micro trimming and laser direct imaging. These applications have very similar requirements and typically involve the shaping of a Gaussian intensity profile into a uniform intensity beam. The most common method for intensity remapping is the use of diffractive optical elements. This paper will evaluate two substantially different designs with similar input and output parameters for beam shaping. One of the designs is an inline diffractive beam reducer and shaper using standard design principles and the second is a beam reduce and shaper that has a linear phase term added to the design to deflect the beam laterally by approximately 5° so that the zero order beam will miss the second element, so as to minimize ringing effects. Techniques for alignment and performance measurements will be discussed as well as an evaluation of the output characteristics, specifically measuring efficiency, beam output uniformity/quality and a basic comparison of the two designs will be presented.

Laser drilling is very important in many industries such as automotive, aerospace, electronics and materials processing. It can be used to produce critical components with novel hole geometry for advanced systems. Percussion drilling and trepanning are two laser drilling methods. In the conventional trepanning method, a laser beam in scanned along a circular or spiral orbit to remove material to achieve a desired hole shape. These orbits generally trace a circular path at the inner wall of the holes. This suggests that an annular beam can be used to accomplish trepanning, which we referred to as optical trepanning. The ray tracing technique of geometrical optics will be employed in this paper to design the necessary optics to transform a Gaussian laser beam into an annular beam of different intensity profiles. Such profiles include half Gaussian with maximum intensities at the inner and outer surfaces of the annulus, respectively, and full Gaussian with maximum intensity within the annulus.

Low power CO₂ lasers with average powers of < 300 Watts are being manufactured with near diffraction limited beam quality. These lasers are a good source for diffractive beam shaping systems that can produce uniform round, square and lineshape intensity profiles. Several beam shaping configurations will be presented in this study, along with material processing results using these shaped beam systems. Comparative data will be presented for an on axis vs. off axis design and the merits of each will be considered.

In solid immersion lens (SIL) system, both propagating waves and evanescent waves contribute to the total field strength with different properties. By using diffractive optical element to modify the cylindrical vector incident beam, we study how the field strength changes when propagating (evanescent) waves are balanced against each other and the evanescent (propagating) waves dominate the field strength. The simulation results show that for radially polarized incident beam, the rate of slope of axial field strength v.s transverse field strength by evanescent waves contribution is greater than that by propagating waves contribution. With general cylindrical vector incident beams, increasing (the rotation angle of polarization from the radial direction) will also make the axial field strength decrease while the variation of the transverse field strength is small. These methods can be used to control the aspect ratio of three dimensions storage dot, which may find applications in near field optical data storage system.

We've generated high-quality flat-top spatial profiles from a modified Continuum Powerlite 9010 Nd:YAG laser using the Gaussian-to-flat-top refractive beam shaper available from Newport Corporation. The Powerlite is a flashlamp-pumped, Q-switched, injection-seeded Nd:YAG laser manufactured in 1993 that delivers 1.6 J at 10 Hz using an oscillator and two 9 mm diameter amplifier rods. While its pulse energy is impressive, its beam quality is typically poor, an all too common characteristic of research-grade Nd:YAG lasers manufactured in the late 1980's and early 1990's. Structure in its near-field spatial fluence profile is reminiscent of round-aperture diffraction that is superposed with additional hot spots. These characteristics are largely due to poor beam quality from the oscillator coupled with over-filled amplifier rods, and reflect a design philosophy from the era of organic dye lasers. When these older laser systems are used for tasks like pumping optical parametric oscillators (OPO's), or for other applications demanding good beam quality, their designs are simply inadequate. To improve the 9010's beam quality we spatially filter the oscillator beam and remove the resulting Airy rings with an iris, then collimate and magnify the remaining central disk so its diameter is appropriate for input to the refractive shaper. The output of the beam shaper is then double-pass amplified through two amplifier rods with thermally induced focusing compensated by a negative lens before the first pass and by a convex mirror before the second pass. Using this approach we've obtained single-pass energy exceeding 250 mJ with little degradation of the flat-top profile and 950 mJ after double pass amplification. After double-passing the two amplifier rods the beam suffers some degradation in symmetry and uniformity, but is still much improved compared to the beam obtained using the 9010's original factory configuration. We find the modified 9010's flat-top profile improves conversion efficiency when used for our applications in crystal nonlinear optics.

The use of a "Field Mapping" beam shaping technique for generating near field Gaussian intensity patterns from uniform intensity ("flat top") laser beams is described. The design objective was to simulate realistic High Energy Laser (HEL) far field intensity patterns for laser effects testing purposes, without having to propagate the large distances necessary to obtain the true far field intensity profile and beam size typical of realistic target engagement scenarios. The field mapping approach presented uses a continuous surface mirror with a figure designed to redistribute the energy into a Gaussian distribution at the target plane. The use of a reflective system was desired to minimize cost and maximize wavelength diversity and laser damage threshold capability. Physical optics analyses are presented to illustrate the performance characteristics of a totally passive reflective field mapping beam shaper.

The results of an investigation into beam shaping techniques for generating near field Gaussian intensity patterns from uniform intensity ("flat top") laser beams are presented. The motivation for this study was the desire to produce realistic High Energy Laser (HEL) far field intensity profiles for laser effects testing, without propagating the large distances necessary to obtain the true far field pattern and beam size typical of HEL target engagement scenarios. To minimize cost, maximize wavelength diversity, and provide a high laser damage threshold capability, an all reflective optical system was preferred. Though beam shaping systems are commonly used to convert Gaussian beams to flat tops beams, the reverse problem, that of converting flat tops to Gaussians, appears to be new territory. Most beam shaping approaches, particularly those that do not preserve phase, are not reversible. Two simple approaches that use segmented mirrors for converting flat tops to Gaussians are described here. While beam integrators, commonly used to convert Gaussians to flat tops do not work in reverse, the approaches presented use segmented mirrors resembling beam integrators, and have some similar benefits. Geometric and physical optics analyses are presented to illustrate the performance characteristics of the different approaches at wavelengths of 1.315 and 3.8 microns. A simple method to reduce interference effects in the reshaped beam, that are present when a coherent source is used, are discussed.

We have been studying the Chemical Oxygen-Iodine Laser (COIL) Thermal Image Marker System to the far field objects. This system can mark the distinguishable thermal image on the far field objects with the laser beam of the COIL to guide the Imaging Infrared homing air vehicle to the object marked thermal image with pinpoint accuracy. For the development of this system the study of the COIL resonator is the main task to meet the generation of the required high quality laser beam. Therefore, first we made two kinds of the experiments. One is to generate the distinguishable thermal image mark (TIM) on the object with stable resonator of the 13 kW output COIL system in the near field. Another is to improve the laser beam quality with the unstable resonators of the COIL system in the low gain condition. Then we studied the high power unstable resonator design for this system with the numerical simulation based on its experimental data and the two-dimensional Fresnel-Kirchhoff integration method with partially coherent scalar electric field. Finally we made the numerical far field TIM generation to verify the TIM generation with the laser beam of the studied high power unstable resonator. The result of simulation shows the fine TIM generation. The result of the experiment and the resonator design study shows that it is possible to realize the good thermal image mark, the good quality laser beam and the promising unstable resonator for the COIL Thermal Image Marker System.

A method is proposed which makes it possible for beam shaping by superposition of fundamental mode Gaussian beams with different waist parameters. This study includes two topics: 1) Superposition of co-axial fundamental mode Gaussian beams to form flat-topped light beams, and 2) Superposition of tilted fundamental mode Gaussian beams to form Bessel-Gaussian beams.

Geometrical optics is used for design of gradient-index (GRIN) laser beam shapers with the conditions of conservation of energy and constant optical path length for all rays passing through the system. The exact ray intercepts for a Gaussian to top-hat beam transform at the output plane are the ray trace target values used during the optimization process. After constructing a beam shaping merit function, the commercial software ZEMAX has been used to minimize the merit function for a well known two-element plano-aspheric beam shaper to establish the effectiveness of this new beam shaping merit function. Then, this method is used to design of several GRIN laser beam shapers while using ZEMAX's catalog GRADIUM elements from LightPath glass types. The optical component shape and spacing parameters are also used for optimization variables. Both spherical surfaces and conic surfaces of the different elements of the GRIN laser beam shaper are studied. The ZEMAX software was used for performance analysis of the GRIN beam shapers and is discussed.

Laser materials processing has been used increasingly over the wide area of electronic industries, especially for drilling microvias in printed circuit boards, and poly-silicon annealing for thin film transistor of liquid crystal display. To increase a processing speed, it has been developed a beam splitting element of a diffractive optical element (DOE). And the other hand, to obtain higher uniformity, because the intensity distribution of laser beam is usually a non-uniform gaussian profile, beam homogenizer of a DOE has recently been developed and introduced to some promising applications. Through the improvement of optical design algorithms, micro-fabrication techniques of a phase pattern of DOE and new method of optical system, it enables to combine its beam splitting function and homogenizing function. It can produce the simultaneous multi-spot homogenized beam. In this investigation, we introduce a concrete design and fabrication result of multi-spot beam homogenizing system for SHG-YAG laser that can convert a gaussian distribution into the plural number of uniformity intensity distribution, and present the possibility of new laser material processing by using such optics.

Intra-cavity beam shaping, if properly implemented, is much more energy efficient and produces cleaner beams than the traditional external spatial modulation. Our special interest in this work is the generation of high-quality dark, or singular beams, for metrological applications. We show that bi-prism like reflectors possessing a central phase excursion within the range ±(0.3-1) π, can significantly alter the relative diffraction losses among the various oscillating modes, enabling efficient mode selection and shaping.

Short pulse spectral content becomes modified while propagating in dispersive media. However, in dispersive nonlinear media, optical pulses resulting in solitary waves maintain their existence if proper balance is established between nonlinear self-phase modulation on the one hand and linear dispersion on the other. Such invariance pulse shape is critical for data transfer reliability in telecommunication technologies. Robust solitary waves that emerge from collisions unaltered are called solitons. During propagation of optical solitons in inhomogeneous media their trajectories are observed to deviate from straight-line paths to that of oscillatory behavior. Here, we use a spatial optical soliton solution to the nonlinear Schrödinger equation in an inhomogeneous triangular refractive index profile as a small index perturbation to illustrate the oscillation motion. We determine the effective acceleration, give the period of oscillation, and compare results with the Gaussian refractive index profile. Such spatial solitons behave as point masses existing in a Newtonian gravitational potential hole. This novel transverse oscillatory behavior, occurring for various refractive index profiles, results from an effectively bounded acceleration.

Recently, a new class of nondiffracting beams has been demonstrated theoretically. Namely, Parabolic nondiffracting optical wavefields constitute the last member of the family of fundamental nondiffracting wavefields. Additionally, the existence of a new class of parabolic traveling waves associated to these wavefields has been demonstrated along the same lines. We have succeeded in demonstrating experimentally the fundamental odd and even parabolic wavefields in the laboratory. In this work, we present and discuss the experimental generation of higher-order parabolic nondiffracting wavefields. Because these fields show a complex structure, their generation relies in the successful construction of the field.

The radial birefringent filter for shaping a Gaussian profile to uniform or annular beams has been designed and simulated. It consists of a radial birefringent lens sandwiched between two polarizers. Through designing the three essential parameters, the Gaussian beams can be transformed into uniform or annular beams. Certainly other profiles of the out beams can be obtained just by rotating either of the polarizers. Its performance properties and its design procedures in laser beam shaping system are studied in detail. Such a filter has advantages that it is relatively simple to construct as it requires no phase changes and low cost replication is possible, but one inherent disadvantage of it is its energy loss because of the absorption of light in the two polarizers.

In this paper, recurring to the main idea of G-S algorithm, an inverse transmission optimization algorithm is proposed to establish the phase structure of the compensation phase plate, which can realize the shaping of Gaussian beam in far diffraction field. This method not only overcomes the disadvantage of G-S algorithm in convergence which is applied to shape Gaussian beam under the diffraction limits, but the obtained phase plate is more convenient for the practical fabrication. According to the inverse transmission optimization algorithm, we transform successfully Gaussian laser beam into the flat-top, the doughnut-like beam and the two-rings beam within the diffractive limits region. The corresponding numerical results are provided.

Femtosecond pulse shaping for time-to-space conversion of ultrafast optical waveforms is presented, analyzed, and experimentally implemented. Here the temporal pattern for the designed multiple pulses optimized with a preassumed Gaussian spectral distribution of an ultrashort pulse is described. With the simulation of a Gaussian spectral distribution, we realize that the uniformity of the generated multiple ultrafast temporal pulses is relevant to the repeated number, the accuracy of the transition points and the pixel number for the modulation periods of the mask in the spectral plane. Especially, the change of the Gaussian spectral phase of the modulated phase plate with the wavelength that many people do not consider formerly is analyzed in detail in this work. On the other hand, experiments of the shaped femtosecond pulse measurement with the frequency-resolved optical gating (FROG) characterization technique are given in this paper.

Characteristics of superresolution effect of annular amplitude and phase filters are compared in this paper. Numerical simulations show that the phase type filter can achieve the superresolution effect, the circular Dammann effect, the flat-top intensity, and doughnut pattern for different applications, while the two-zone amplitude filter does have the capability of generating the superresolution effect but it cannot generate the circular Dammann effect, doughnut and the flat-top intensity. Two-zone and three-zone phase and amplitude type pupil filters are analyzed in theory and implemented in experiment. The experimental results show that both amplitude and phase filters can achieve superresolution effects evidently. The advantage of an amplitude style filter is that the fabrication technology is much simpler than that for a pure-phase one. The amplitude filter can only be used for the specific superresolution cases where the energy utilization ratio is not the main issue. Generally, the pure-phase superresolution filter is recommended for its higher efficiency and, more importantly, it can achieve special diffraction patterns that are impossible to achieve with an amplitude filter.

This paper describes a fast simulation annealing algorithm for the optimum design and applies to beam shaping by diffractive optical elements. The algorithm introduced the corresponding utilities function, and used Tsallis statistic for optimum design. The simulated results show that to converge the incident energy into the desired region with the same mean square error, our method only cost 1% percent of time that needed by the traditional SA. This algorithm brings forward a new and fast method for the design of Diffractive Optical Elements, and potentially for other optimization problems.

Microlenses were formed directly on a surface of a glass plate by using CO₂ laser. This method has the merit of complete dry processing and presents simple way of microlens fabrication. We discuss about the formation process and mechanism through the characterization of irradiation parameters and the glass composition. When the surface of a glass plate is heated locally to a working point of the glass material by a focused CO₂ laser beam, a microlens is formed owing to surface tension. It was found possible to fabricate microlens easily placed at different focal position by controlling a laser power and an irradiation time. The volume of the fabricated microlens was found to be dependent on laser irradiation energy (laser power x irradiation time) and irradiated position. When a Corning 7059 glass plate was used, a convex microlens was obtained at the energy density smaller than ca.100 (μJ/μm² ). The dynamical stress change of the microlens was measured in-situ by using the ellipsometry analysis to make clear the formation process of microlens. The T-FDP (four detectors polarimeter of transmission type) was used for this analysis.