Aleksandar Aleksov

High-speed performance of Silicon Bridge die-to-die interconnects

Silicon Bridge is a dense multichip packaging architecture that enables high die-to-die interconnect density and corresponding applications. We describe the basic ideas of the concept, discuss density in the die-to-die interconnect context, and report results of electrical high-speed performance simulations, based on both two-dimensional and three-dimensional electromagnetic modeling.

Effect of large deflection angle on the laser intensity profile produced by acousto-optic deflector scanners in high precision manufacturing

Laser beam scanners have found wide applications in a variety of laser-assisted advanced microprocessing technologies such as printing, patterning, and doping. Traditional galvo-scanners affect the accuracy of beam positioning and repeatability in high precision manufacturing due to mechanical motion of the mirrors and backlash errors. The purpose of this study is to analyze an acousto-optic deflector (AOD) to achieve high diffraction efficiency and high deflection angle. Conventional AODs are operated with one-dimensional refractive index variation induced by modulating only the acoustic wave frequency. The effect of two-dimensional refractive index variations, which can be achieved by modulating both the phase and frequency of the acoustic waves, is analyzed. This study, therefore, advances the current AOD technology from just acoustic wave frequency modulation to a new class of AODs involving both phase and frequency modulations. This new type of AOD is designed by developing an analytic model based on...

Dynamic two-dimensional refractive index modulation for high performance acousto-optic deflector.

The performance of an acousto-optic deflector is studied for two-dimensional refractive index that varies as periodic and sinc functions in the transverse and longitudinal directions, respectively, with respect to the direction of light propagation. Phased array piezoelectric transducers can be operated at different phase shifts to produce a two-dimensionally inhomogeneous domain of phase grating in the acousto-optic media. Also this domain can be steered at different angles by selecting the phase shift appropriately. This mechanism of dynamically tilting the refractive index-modulated domain enables adjusting the incident angle of light on the phase grating plane without moving the light source. So the Bragg angle of incidence can be always achieved at any acoustic frequency, and consequently, the deflector can operate under the Bragg diffraction condition at the optimum diffraction efficiency. Analytic solutions are obtained for the Bragg diffraction of plane waves based on the second order coupled mode theory, and the diffraction efficiency is found to be unity for optimal index modulations at certain acoustic parameters.

Two-dimensional analytic modeling of acoustic diffraction for ultrasonic beam steering by phased array transducers

HighlightsFourier model for analytic expression of displacement vector due to acoustic waves.Filon model for quasi‐analytic expression of the displacement vector.Composite wavefront due to interference and diffraction of acoustic waves.Ultrasonic beam steering by phased array transducers.Beam steering can deflect laser beams at large angles in acousto‐optic deflectors. Abstract Phased array ultrasonic transducers enable modulating the focal position of the acoustic waves, and this capability is utilized in many applications, such as medical imaging and non‐destructive testing. This type of transducers also provides a mechanism to generate tilted wavefronts in acousto‐optic deflectors to deflect laser beams for high precision advanced laser material processing. In this paper, a theoretical model is presented for the diffraction of ultrasonic waves emitted by several phased array transducers into an acousto‐optic medium such as TeO2 crystal. A simple analytic expression is obtained for the distribution of the ultrasonic displacement field in the crystal. The model prediction is found to be in good agreement with the results of a numerical model that is based on a non‐paraxial multi‐Gaussian beam (NMGB) model.

A scalable process for manufacturing integrated, washable smart garments applied to heart rate monitoring

We present a new method for building wearable electronic and sensor systems in which all components are permanently integrated directly into garments in high volume except for the battery. We discuss the design and construction of the first such fully-integrated sensor system, wearable heart rate monitoring garments (a sports bra, a compression short, and a compression shirt) that are machine washable. We demonstrate that heart rate measurements can be detected by our systems fabric-based electrodes. We also show experimental results from wash testing of the garment. The process described herein can be applied to the construction of computational and sensor systems for healthcare, sports, virtual reality, and first responder and military personnel monitoring, among others.

Gaussian beam diffraction by two-dimensional refractive index modulation for high diffraction efficiency and large deflection angle

The propagation of Gaussian beams is analyzed for an acousto-optic deflector by varying the refractive index in two-dimensions with a row of phased array piezoelectric transducers. Inhomogeneous domains of phase grating are produced by operating the transducers at different phase shifts, resulting in two-dimensional index modulation of periodic and sinc function profiles. Also different phase shifts provide a mechanism to steer the grating lobe in various directions and, therefore, the incident angle of the laser beam on the grating plane is automatically modified without moving the beam. Additionally, the acoustic frequency can be varied to achieve the Bragg condition for the new incident angle of the laser beam so that the diffraction efficiency of the deflector is maximized. The Gaussian beam is expressed in terms of planes and the second order coupled mode theory is implemented to analyze the diffraction of the beam. The diffraction efficiency is found to be nearly unity for optimal operating parameters of the acousto-optic device.

Effect of large deflection angle on the laser intensity profile produced by AOD scanners in high precision manufacturing

Laser beam scanners have found wide applications in a variety of laser-assisted advanced microprocessing technologies, such as printing, patterning and doping. Traditional galvo-scanners affect the accuracy of beam positioning and repeatability in high precision manufacturing due to mechanical motion of the mirrors and backlash errors. An Acousto-optic Deflector (AOD), which is made of a transparent photoelastic medium bonded to a piezoelectric transducer, is a promising device to overcome these limitations. AODs are commonly used in laser direct writing systems to provide flexible and high-speed beam scanning with high precision and accuracy.We have developed an analytic model based on Bessel functions, which will be referred to as Bessel model, to calculate the strain tensor, stress tensor and stress-induced birefringence, and the change in the refraction index of the crystal. This refraction index variation produces the volume phase grating and provides a mechanism for diffraction, and consequently, deflection of the laser beam as it propagates through the AOD crystal. Various laser parameters, such as the diffraction efficiency and the laser intensity of the diffraction pattern at different deflection angles are studied in this paper.Laser beam scanners have found wide applications in a variety of laser-assisted advanced microprocessing technologies, such as printing, patterning and doping. Traditional galvo-scanners affect the accuracy of beam positioning and repeatability in high precision manufacturing due to mechanical motion of the mirrors and backlash errors. An Acousto-optic Deflector (AOD), which is made of a transparent photoelastic medium bonded to a piezoelectric transducer, is a promising device to overcome these limitations. AODs are commonly used in laser direct writing systems to provide flexible and high-speed beam scanning with high precision and accuracy.We have developed an analytic model based on Bessel functions, which will be referred to as Bessel model, to calculate the strain tensor, stress tensor and stress-induced birefringence, and the change in the refraction index of the crystal. This refraction index variation produces the volume phase grating and provides a mechanism for diffraction, and consequently, de...

Large angle of Bragg diffraction using interfrence of acoustic wave inside acousto-optic deflector

The laser beam is often steered in different directions in a variety of laser-advanced microprocessing technologies, such as laser micromachining, laser patterning and laser selective-area doping. Scanners are traditionally used to direct the beam to different locations on the workpiece. The mechanical motion of x-y mirrors in such scanners affects the accuracy of beam positioning and repeatability in high precision manufacturing. Beam steering without any moving optical component is necessary to overcome the limitations of current scanning technology. Stationary optical devices such as acousto-optic modulators (AOM), acousto-optic deflectors (AOD) and acousto-optic tunable filters (AOTF) have widespread applications in the field of laser microfabrication for intensity modulation and laser beam steering. AODs are commonly used with continuous-wave lasers in laser direct writing systems to provide flexible and high-speed beam scanning with high precision and accuracy.A pair of AODs is mounted orthogonally to provide dual axis (x-y) laser scanning. The deflection scan angle, however, is small due to the finite distance between the two separate deflectors. This optical configuration can be simplified by realizing 2D AO interaction in a single AO crystal. This paper discusses an integrated AOD to allow compact construction and efficient operation with large deflection scan angle. This type of AODs would be useful for large-area processing with high throughput.The laser beam is often steered in different directions in a variety of laser-advanced microprocessing technologies, such as laser micromachining, laser patterning and laser selective-area doping. Scanners are traditionally used to direct the beam to different locations on the workpiece. The mechanical motion of x-y mirrors in such scanners affects the accuracy of beam positioning and repeatability in high precision manufacturing. Beam steering without any moving optical component is necessary to overcome the limitations of current scanning technology. Stationary optical devices such as acousto-optic modulators (AOM), acousto-optic deflectors (AOD) and acousto-optic tunable filters (AOTF) have widespread applications in the field of laser microfabrication for intensity modulation and laser beam steering. AODs are commonly used with continuous-wave lasers in laser direct writing systems to provide flexible and high-speed beam scanning with high precision and accuracy.A pair of AODs is mounted orthogonally ...