Octavian Cira

Transmission functions of optical choppers for Gaussian beam distributions: modeling and simulations

The paper presents a mathematical modeling of the transmission / modulation functions of the classical optical chopper wheels - with windows with linear edges. Based on our previous analytical analysis on constant intensity distributions (top-hat) laser beams, in the present paper the complete modeling and simulation of the chopping process of the light beam sections with Gaussian distributions is proposed. The different possible cases of the relationships between the geometry of the chopper blades and of the beam section in the plane of the wheel are considered. The three relevant situations that can be met are approached: (i) large blades in front of the beam section (that can be thus completely covered by each blade): (ii) narrow single blade in front of the (larger) beam section; (iii) multiple narrow blades placed simultaneously in front of the beam section. The experimental chopper module we have built with different chopper wheels that we have designed and fabricated as prototypes is also reviewed. Perspectives and future work on other types of optical chopper configurations conclude the study.

Optomechatronics Applications of the Theory of Mechanisms with Active Student Involvement in Research

The paper presents some of our current investigations in the multi-disciplinary field of optomechatronics, based in part on different applications of the theory of mechanisms. Classical mechanism applications approached mostly with undergraduate students are presented in the first part of the paper. Scanners, choppers and attenuators—optomechatronic devices, in general—are considered in the second part, with both kinematical and dynamical aspects, and some of our relevant results in the field are pointed out. Student involvement (both under and postgraduate) in these researches is presented, as well as some of the implementation of the results and expertise gained through research in the curricula of the Mechanical and Electrical Engineers in our university.

Towards a research pole in photonics in Western Romania

We present our efforts in establishing a Research Pole in Photonics in the future Arad-Timisoara metropolitan area projected to unite two major cities of Western Romania. Research objectives and related training activities of various institutions and groups that are involved are presented in their evolution during the last decade. The multi-disciplinary consortium consists principally of two universities, UAVA (Aurel Vlaicu University of Arad) and UMF (Victor Babes Medicine and Pharmacy University of Timisoara), but also of the Arad County Emergency University Hospital and several innovative SMEs, such as Bioclinica S.A. (the largest array of medical analysis labs in the region) and Inteliform S.R.L. (a competitive SME focused on mechatronics and mechanical engineering). A brief survey of the individual and joint projects of these institutions is presented, together with their teaching activities at graduate and undergraduate level. The research Pole collaborates in R&D, training and education in biomedical imaging with universities in USA and Europe. Collaborative activities, mainly on Optical Coherence Tomography (OCT) projects are presented in a multidisciplinary approach that includes optomechatronics, precision mechanics and optics, dentistry, medicine, and biology.

Design programs for optical chopper wheels with different configurations

Optical choppers are a most used device in laser setups (including in biomedical applications) for generating laser impulses, accurate attenuation, obscuration or elimination of different wavelengths. We present the design programs we are developing for macroscopic optical choppers with rotational wings. We have proposed previously the analysis of different types of chopper wheels with windows: (i) with linear margins (the “classical” device) and (ii) with semicircular margins, inward or outward (the “eclipse” choppers). The latter has been, to the best of our knowledge, of our proposal (patent pending). This rigorous mathematical analysis took into account all the possible relationships between the constructive and kinematics parameters of the device. This theory allowed for developing a design program for each type of choppers – to obtain a specific type of output laser impulse. Examples of applying this program are presented, for each type of laser beams that has been considered so far: top-hat (with constant intensity distribution over the entire beam section), Gaussian and Bessel. A discussion on the laser impulses obtained with each type of device and laser beam concludes the paper.

Building an optomechatronics group in a young university in Western Romania

We present our experience regarding the establishing of an interdisciplinary group with Optics as one of its main topic at the Aurel Vlaicu University of Arad (UAVA) – linked with the improvement through research of our educational activities. The 3OM Group (in Opto-Mechatronics, Optical Metrology, and Optics and Mechanics) is described in its evolution from optomechanics to photonics, the latter with a focus on OCT (Optical Coherence Tomography) – with the national and the international collaborations established, with universities from Romania, Europe and USA. While the research directions of the 3OM Group are presented, they are linked with the educational components implemented in the various subjects we teach, for both undergraduate and graduate students, both in Mechanical and in Electrical Engineering. The main effort is to integrate education and research, to move teaching beyond the classical aspects to put the stress on hands-on-experiments, as well as on research-based activities – even with undergraduates. The main goals of this approach are to obtain an early orientation towards innovation and discovery, with a taste for novelties and with a clear focus on international standards. While this account is only one of many, it offers our experience in passing through the difficulties of developing both research and education in Optics in a young university in an emergent economy in Eastern Europe.

The Algorithm that Determines the Start Iteration of the Halley-Altman Method

The paper is devoted to the Ostrowski-Kantorovich type convergence theorem for the Halley-Altman method, with the S-order of convergence equal to 3, for nonlinear operator equations in Banach spaces. The main result of the article is the algorithm that determines the start iteration from the cubic convergence sphere of the Halley-Altman method. The Mathcad implementation treats the finite dimensional case.

The Optimum Convergence Condition for the Durand-Kerner Type Simultaneous Inclusion Method

In order to solve the algebraic equation, where the complex polynomial has only simple zeros, one can use the simultaneous inclusion methods. The quadratic convergence condition for the Durand-Kerner simultaneous inclusion method, using point estimation theory is w(0) < d(0)/(an+b), where n is the polynomial degree, d(0) the minimum distance between the initial iterations and w(0) is the absolute maximum of the Weierstrass factors. This paper determines the optimum quadratic convergence condition for a generalized Durand-Kerner type simultaneous inclusion method

Optical choppers with rotational elements: modeling, design and prototypes

We present a brief overview of our contributions regarding the analysis and design of optical choppers. Their applications range numerous domains, from optical sensing in radiometry or telescopes to laser manufacturing and biomedical imaging – for example for the controlled attenuation of light, the elimination of selected spectral domains, or the switching of optical paths. While these aspects are pointed out, the paper describes our analysis, modeling, and manufacturing of prototypes for choppers with: (a) wheels with windows with linear margins; (b) wheels with windows with non-linear margins (semi-circular or elliptical), outward or inward; (c) rotational shafts with different shapes, with slits or with holes. While variant (a) represents classical choppers, variant (b) represents the “eclipse” choppers that we have developed and also patented for the solution with two adjustable wheels that can produce circular windows. Variant (c), of choppers with shafts is also a patent application. Their transmission functions are discussed, for the shape of the laser pulses produced and for the attenuation coefficients obtained. While this discussion has been completed analytically for top-hat laser beams, it has been modeled using simulations for Gaussian and Bessel beams. Design, manufacturing aspects, and prototypes of the different chopper configurations complete the presentation.

Non-conventional optomechanical choppers: analysis and design of novel prototypes

Optical choppers are widely used in laser systems – for light modulation and/or attenuation. In their most used and wellknown configuration, they are built as a rotational wheel with windows, which transforms a continuous-wave laser beam into a series of impulses with a certain frequency and profile. We briefly present the analysis and design we have completed for the classical chopper wheels (i.e., with windows with linear margins) for both top-hat and Gaussian laser beams. Further on, novel chopper wheels configurations, with outward or inward semi-circular (or with other non-linear shaped) margins of the windows is pointed out; we completed for them both analytic functions and simulations, for both top-hat and Gaussian beams, in order to deduce their transmission functions (i.e., the time profile of the laser impulses generated by the device). The stress of the presentation is put on the novel choppers with shafts (patent pending); their transmission functions are pointed out for top-hat laser beams. Finally, an example of such choppers is considered, with regard to the necessary Finite Element Analysis (FEA) that has to be performed for their rotational shaft. Both the mechanical stress and the deformations in the shaft have to be taken into account, especially at high rotational speeds of the mobile element.

Analytic functions of optical choppers for Gaussian laser beams

The paper presents a report on our current work on obtaining the analytic functions of the laser impulses generated by optical choppers with disks in their classical configuration - with windows that have linear margins. With regard to our previous researches, focused on choppers working with top-hat (i.e., with constant intensity) laser beams, in the present work Gaussian laser beam distributions of the light beams to be chopped have been considered, for the most common case, of a light bundle of a sufficient small diameter in the plane of the disk; this type of section can therefore be completely obscured and uncovered by the chopper wings and windows, respectively. The functions of the transmitted light flux of the device are approached. This allows for the designing calculus of choppers for different applications, taking into account their specific requirements. A comparison between analytical results obtained in this work and results from our previous numerical modeling is pointed out.