Dr. Joe Shiefman Profile

Dr. Joe Shiefman

Optical Engineer

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Publications (5)

Proceedings Article | 30 August 2005 Paper

Interfacing optical system software to finite-difference time-domain (FDTD) software

Joe Shiefman

Proceedings Volume 5875, 58750E (2005) https://doi.org/10.1117/12.624405

KEYWORDS: Finite-difference time-domain method, Systems modeling, Magnetism, Diffraction, Binary data, Wave propagation, Spatial filters, Fourier transforms, Gaussian beams, Polarization

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SPIE Journal Paper | 1 August 2004

Insertion loss comparison of microcollimators used to propagate light in and out of single-mode fibers

Joe Shiefman

OE, Vol. 43, Issue 08, (August 2004) https://doi.org/10.1117/12.10.1117/1.1768537

KEYWORDS: Collimators, GRIN lenses, Lenses, Beam propagation method, Refraction, Manufacturing, Single mode fibers, Tolerancing, Optical alignment, Error analysis

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Most telecom components use lenses to collimate the beam emerging from a single-mode fiber and again, after some manipulation of the beam, to focus the beam back into an output fiber. In response to the drive for smaller components, collimator lenses have shrunk and a number of new microcollimator types been introduced. Several of the newer collimator types involve lenses that are fused to the fiber. Optical software was used to model six different types of microcollimators divided into three different size categories. Because not all of the six types were applicable in all three of the size categories, a total of eleven different collimator systems were modeled. A collimator system consists of an input collimator and an identical output collimator. Each collimator includes a single-mode fiber and a collimating lens. In order to achieve equivalence, all of the collimators in the same size category produce an intermediate waist with the same mode field diameter and distance from the lens surface to the intermediate waist. An algorithm is presented to determine the necessary physical parameters (lengths and radii) for a collimator to produce the appropriate beam criteria for a given size category. Once the physical parameters for the collimator systems were determined, all of the collimator systems were examined for insertion loss in their ideal configuration as well as in the presence of fabrication and alignment errors. All of the insertion loss analyses were performed using coherent field propagation starting from the fundamental fiber mode of the input fiber, through the collimating lenses, and finishing with the calculation of the overlap integral of the field inside the output fiber with the fundamental fiber mode. No thin lens or paraxial propagation assumptions are made...The results indicate that the collimator types involving lenses that are fused to the fiber are less sensitive to longitudinal fiber and collimator shifts than the components with the fiber and lens not in direct contact.

Proceedings Article | 6 November 2003 Paper

Using software to model coherent metrology systems

Joe Shiefman

Proceedings Volume 5174, (2003) https://doi.org/10.1117/12.513111

KEYWORDS: Systems modeling, Reflection, Reflectivity, Monochromatic aberrations, Tolerancing, Sensors, Fizeau interferometers, Spherical lenses, Interferometers, Metrology

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Proceedings Article | 4 September 2002 Paper

Using software to model, analyze, and determine manufacturing tolerances for coherent optical systems

Joe Shiefman

Proceedings Volume 4769, (2002) https://doi.org/10.1117/12.481184

KEYWORDS: Systems modeling, Tolerancing, Beam splitters, Calcite, Coherent optics, Polarization, Wave plates, Wave propagation, Sensors, Interferometers

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There is a long tradition of analyzing lens designs and establishing their manufacturing tolerances in software. The lens-design codes used for this process are based on sequential, geometric ray tracing techniques and the tolerances are based on geometric image quality as determined by system aberration content. More recently, largely due to the rapid expansion of optical telecom applications, there has been increased interest in the non-sequential propagation of complex optical fields, rather than geometric rays, through optical systems. Starting with sources of varying degrees of coherence or from the output from fibers or waveguides, fields can be non-sequentially propagated through optical systems, and the amplitude and phase of these fields can be examined at any position in space. This has enabled an enormous increase in the ability to analyze and tolerance coherent optical systems used in two main categories of optical systems: (1) measurement systems and (2) systems used to propagate coherent optical signals. This paper addresses the methodology involved in modeling, analyzing, and tolerancing coherent systems and highlights the main differences between the methods used with coherent systems and traditional lens designs. Coherent systems models include components that require modeling diffraction and interference effects. They typically extend the path length of the model, beginning at the source and continuing through to a detailed description of the detector or a coupling into an output waveguide. They may even include a measurement algorithm within the system model. Additionally, unlike the traditional lens-design models, the performance parameters used in establishing the manufacturing tolerances of these coherent systems, are not necessarily based on the image quality of the system. Instead, tolerancing of coherent systems is usually more directly related to the functionality of that system. To further demonstrate the methodology of modeling, analyzing, and tolerancing coherent systems in software, two examples of coherent system models, an interferometer and a telecom component, are presented. Some of the tolerancing results from these systems are presented.

Proceedings Article | 1 June 1990 Paper

Technique for the determination of best focus for ultratech 1X steppers in a production environment using aerial image analysis

Victoria Rivera, Joe Shiefman, David Chui

Proceedings Volume 1261, (1990) https://doi.org/10.1117/12.20080

KEYWORDS: Semiconducting wafers, Integrated circuits, Metrology, Inspection, Mirrors, Process control, Image analysis, Sensors, Diffraction gratings, Reticles

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A new version of the Stepper Image Monitor (SIM) has been designed to evaluate best focus on Ultratech steppers. The SIM is a portable unit which will support a number of steppers in a fab. Each stepper has a permanently mounted detector assembly which uses a mirror to pick off the dark field image (except for a small portion required for Ultratech alignment) above the fold mirror. To run SIM, a chrome on glass amplitude diffraction grating with many 1 - 1.Sum wide by 1mm long windows on a Sum pitch is placed in the reticle position on the stepper. A SIM wafer with a similar number of 03 - 1.Oum wide by 1mm long bars on a Sum pitch is placed on the stage. The wafer is instructed to move by an external Run Mode 8 Ultratech stepper program, first in X and then in Y, across the Sum pitch in a number of discrete steps (typically 20). The intensity values measured by the SIM detector at each step are used to construct a discrete intensity profile that represents the aerial image of the grating. This procedure is repeated at several Z positions (typically 5). Each intensity profile is correlated to the appropriate diffraction limited intensity profile for the system being used. A parabolic fit is made from the correlation values at the various Z positions. The Z value for the maximum of the parabola is considered to be best focus. This method has several advantages over other methods currently in use for checking Ukratech focus: (1) More precise measurement; (2) Operator independent; (3) Faster; (4) No effects due to the resist or to processing; (5)SIM is a permanent artifact (i.e. no variation due to wafer differences). Results from beta site testing show that the method is very repeatable, with sigma =0.lSum being typical. SIM results also correlate very well to results obtained by conventional methods. It also tracks well to changes in Z offset dialed into the stepper. SIM has been shown to be an effective tool for quantifying the relationship between lens heating and focus shift on the Ultratech stepper. These improvements in speed and precision of focus measurements on the Ultratech stepper will lead to more usable stepper time and better stepper performance, which in turn translates directly into more throughput and higher yields. OAI would like to acknowledge the help of Suzanne Scullen and Synergy Semiconductor Corporation for their help and the use of their Ultratech stepper.

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