In this paper, the current time delay (TD) and the voltage difference (VD) modes for some practic... more In this paper, the current time delay (TD) and the voltage difference (VD) modes for some practical lateral effect position sensing detectors are investigated, simulated, and compared. Some advantages of the current time delay mode are more linear response, independent position from magnitude and frequency, background illumination-independent response, and no need to signal normalization.
Photonic crystal fibers (PCFs) are highly suitable transmission media for wavelength-division-mul... more Photonic crystal fibers (PCFs) are highly suitable transmission media for wavelength-division-multiplexing (WDM) systems, in which low and ultra-flattened dispersion of PCFs is extremely desirable. It is also required to concurrently achieve both a low confinement loss as well as a large effective area in a wide range of wavelengths. Relatively low dispersion with negligible variation has become feasible in the wavelength range of 1.1 to 1.8μm through the proposed design in this paper. According to a new structure of PCF presented in this study, the dispersion slope is 6.8×10-4ps/km.nm2 and the confinement loss reaches below 10-6 dB/km in this range, while at the same time an effective area of more than 50μm2 has been attained. For the analysis of this PCF, finite-difference time-domain (FDTD) method with the perfectly matched layers (PML) boundary conditions has been used.
The optical communication systems need a waveguide with low confinement loss and low dispersion. ... more The optical communication systems need a waveguide with low confinement loss and low dispersion. A conventional fiber optic is widely used in these systems. As an alternative, a photonic crystal fiber (PCF) can be used. It is highly suitable transmission media for optical communication systems. Low confinement loss, large effective area in a wide range of wavelengths, and ultra-flattened dispersion of PCFs is extremely desirable. In this paper, we design and simulate a new structure of dispersion flattened photonic crystal fiber (DF-PCF). Also, we investigate the tolerance analysis of the PCF deformations including tolerances of the pitch size and outer air holes diameter.
Misalignment and deviation angle in the optical interferometer directly decrease the accuracy of ... more Misalignment and deviation angle in the optical interferometer directly decrease the accuracy of nanometrology system by producing a periodic nonlinearity error. In this paper, the effect of non-orthogonally polarized beams on the displacement measurement error in the advanced nanometrology system is presented. A system for reduction of non-orthogonality effect including linear polarizer, half-wave plate and modified signal conditioner, based on the nonlinearity compensation in a two-mode laser interferometer, is also proposed. The simulations results confirm that the peak error in the nano-displacement measurement is considerably decreased from 0.89 nm to 15 pm by using the modified optics and signal conditioner.
... to Improve Laser-Range Finder Performance Shahram Mohammad Nejad, Kiazand Fasihi andSaeed Oly... more ... to Improve Laser-Range Finder Performance Shahram Mohammad Nejad, Kiazand Fasihi andSaeed Olyaee Department ... used in the industrial applications because of their performances, small size, easy to ... et al., 1994; Journet et al., 1996, 2001 ; Mohammad Nejad and Olyaee ...
In this paper, an approach based on neural network (NN) for nonlinearity modeling in a nano-metro... more In this paper, an approach based on neural network (NN) for nonlinearity modeling in a nano-metrology system using three-longitudinal-mode laser heterodyne interferometer (TLMI) for length and displacement measurements is presented. We model nonlinearity errors that arise from elliptically and non-orthogonally polarized laser beams, rotational error in the alignment of laser head with respect to the polarizing beam splitter, rotational error in the alignment of the mixing polarizer, and unequal transmission coefficients in the polarizing beam splitter. Here we use a neural network algorithm based on the multi-layer perceptron (MLP) network. The simulation results show that multi-layer feed forward perceptron network is successfully applicable to real noisy interferometer signals.
Quantitative analysis has been applied extensively for modeling and compensation of periodic nonl... more Quantitative analysis has been applied extensively for modeling and compensation of periodic nonlinearities since the invention of heterodyne laser interferometers. In this article, we mathematically analyze and modele the nonlinearity resulting from non-orthogonality and ellipticity of the polarized laser beams for a modified high-resolution nano-displacement measuring system based on a three-mode laser interferometer. Also, we present a simple method to compensate for the periodic nonlinearity in the modified system based on a two-mode type nonlinearity reduction method. The results reveal that the factor of nonlinearity reduction can reach a value of 99.9% for some special cases of deviations resulting from non-ideal polarized light. In addition to the nonlinearity compensation, we show that the resolution of the displacement measurement in the modified system is doubled and quadrupled with respect to the conventional three- and two-mode laser heterodyne interferometers, respectively.
In this paper, the current time delay (TD) and the voltage difference (VD) modes for some practic... more In this paper, the current time delay (TD) and the voltage difference (VD) modes for some practical lateral effect position sensing detectors are investigated, simulated, and compared. Some advantages of the current time delay mode are more linear response, independent position from magnitude and frequency, background illumination-independent response, and no need to signal normalization.
Photonic crystal fibers (PCFs) are highly suitable transmission media for wavelength-division-mul... more Photonic crystal fibers (PCFs) are highly suitable transmission media for wavelength-division-multiplexing (WDM) systems, in which low and ultra-flattened dispersion of PCFs is extremely desirable. It is also required to concurrently achieve both a low confinement loss as well as a large effective area in a wide range of wavelengths. Relatively low dispersion with negligible variation has become feasible in the wavelength range of 1.1 to 1.8μm through the proposed design in this paper. According to a new structure of PCF presented in this study, the dispersion slope is 6.8×10-4ps/km.nm2 and the confinement loss reaches below 10-6 dB/km in this range, while at the same time an effective area of more than 50μm2 has been attained. For the analysis of this PCF, finite-difference time-domain (FDTD) method with the perfectly matched layers (PML) boundary conditions has been used.
The optical communication systems need a waveguide with low confinement loss and low dispersion. ... more The optical communication systems need a waveguide with low confinement loss and low dispersion. A conventional fiber optic is widely used in these systems. As an alternative, a photonic crystal fiber (PCF) can be used. It is highly suitable transmission media for optical communication systems. Low confinement loss, large effective area in a wide range of wavelengths, and ultra-flattened dispersion of PCFs is extremely desirable. In this paper, we design and simulate a new structure of dispersion flattened photonic crystal fiber (DF-PCF). Also, we investigate the tolerance analysis of the PCF deformations including tolerances of the pitch size and outer air holes diameter.
Misalignment and deviation angle in the optical interferometer directly decrease the accuracy of ... more Misalignment and deviation angle in the optical interferometer directly decrease the accuracy of nanometrology system by producing a periodic nonlinearity error. In this paper, the effect of non-orthogonally polarized beams on the displacement measurement error in the advanced nanometrology system is presented. A system for reduction of non-orthogonality effect including linear polarizer, half-wave plate and modified signal conditioner, based on the nonlinearity compensation in a two-mode laser interferometer, is also proposed. The simulations results confirm that the peak error in the nano-displacement measurement is considerably decreased from 0.89 nm to 15 pm by using the modified optics and signal conditioner.
... to Improve Laser-Range Finder Performance Shahram Mohammad Nejad, Kiazand Fasihi andSaeed Oly... more ... to Improve Laser-Range Finder Performance Shahram Mohammad Nejad, Kiazand Fasihi andSaeed Olyaee Department ... used in the industrial applications because of their performances, small size, easy to ... et al., 1994; Journet et al., 1996, 2001 ; Mohammad Nejad and Olyaee ...
In this paper, an approach based on neural network (NN) for nonlinearity modeling in a nano-metro... more In this paper, an approach based on neural network (NN) for nonlinearity modeling in a nano-metrology system using three-longitudinal-mode laser heterodyne interferometer (TLMI) for length and displacement measurements is presented. We model nonlinearity errors that arise from elliptically and non-orthogonally polarized laser beams, rotational error in the alignment of laser head with respect to the polarizing beam splitter, rotational error in the alignment of the mixing polarizer, and unequal transmission coefficients in the polarizing beam splitter. Here we use a neural network algorithm based on the multi-layer perceptron (MLP) network. The simulation results show that multi-layer feed forward perceptron network is successfully applicable to real noisy interferometer signals.
Quantitative analysis has been applied extensively for modeling and compensation of periodic nonl... more Quantitative analysis has been applied extensively for modeling and compensation of periodic nonlinearities since the invention of heterodyne laser interferometers. In this article, we mathematically analyze and modele the nonlinearity resulting from non-orthogonality and ellipticity of the polarized laser beams for a modified high-resolution nano-displacement measuring system based on a three-mode laser interferometer. Also, we present a simple method to compensate for the periodic nonlinearity in the modified system based on a two-mode type nonlinearity reduction method. The results reveal that the factor of nonlinearity reduction can reach a value of 99.9% for some special cases of deviations resulting from non-ideal polarized light. In addition to the nonlinearity compensation, we show that the resolution of the displacement measurement in the modified system is doubled and quadrupled with respect to the conventional three- and two-mode laser heterodyne interferometers, respectively.
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Papers by Saeed Olyaee