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

Abstract

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.

Optomechatronic Choppers with Rotating Elements: Design Programs

“…To characterize the overlapping of the blades and of the beam section, a parameter m was defined [4] as the angular width of the beam section (as seen from the pivot O) and the ratio between the angular width of the window; thus m D 2ı/˛.…”

“…We have presented in previous studies [7,4] the different types of modulation functions we had developed for these different choppers [5,6]. Experimental modules were also designed and manufactured, as well as prototype wheels [7] with the different profiles presented above.…”

“…The next step of this work is to achieve design programs for the two main types of choppers. A first presentation of this program for the classical devices was done in [4], for top-hat (with constant intensity over the entire section) and Gaussian laser beams. In the present chapter this work is further expanded, but for both types of scanners-classical and eclipse-and for three types of the most used laser beams: top-hat, Gaussian, and Bessel.…”

Building an optomechatronics group in a young university in Western Romania

“…The scope is to be able to obtain a certain profile of the laser impulses produced, and for this the parameters of the device have to be chosen properly [43];…”

Towards a research pole in photonics in Western Romania

“…Our activity, mainly focused on Optomechatronic devices and systems, is presented in detail in [6]. These research directions include: (i) Optomechanical choppers [7][8][9], for which we developed the analysis and design of classical chopper wheels with windows with linear edges [10], introduced and developed a new device, the "eclipse chopper", with wheels with windows with semi-circular edges [11], built prototypes [12], and developed a program for their design (for top-hat, Gaussian and Bessel beams), to chose the parameters of the device in order to obtain a desired profile of the output laser impulses [13]; (ii) Laser scanners: monogon [7,14,15]; polygonal [14,16], which we have analysed [17]; galvanometerbased [18,19], for which we demonstrated [20,21] the optimal scanning functions to be used (which has to be linear plus parabolic [20], not linear plus sinusoidal, as previously stated in literature [19]), and for which PG (and UG) students are working on a variety of topics including optimal control architecture [22,23] and driving algorithms; Risley prisms [24][25][26], on which student projects are studying their exact patterns [27], as well as driving solutions; (iii) Radiometry of optical systems [28], including optical attenuators [29], as well as colorimetry; (iv) Optical metrology -for industrial measurements [30], with on-going UGs projects [15,31]; (v) OCT [32,33] and related subassemblies [34,35] -including swept laser sources scanned in frequency …”