Event Title

Linear Position Detector with High Bandwidth

Faculty Advisor

Gabriel Spalding

Graduation Year

2019

Location

Center for Natural Sciences, Illinois Wesleyan University

Start Date

21-4-2018 9:00 AM

End Date

21-4-2018 10:00 AM

Description

Position-Sensitive Detectors currently described in the literature can be divided into distinct categories: ‘Spatial Light Separation Methods’ (e.g., Quadrant Photodiodes or D-Shaped Mirrors) and ‘Electronic Signal Separation’ (e.g., so-called Position Sensitive Detectors). We argue that Spatial Light Separation Methods do not generally give true centroid positions and while Electronic Signal Separation Methods do give a linear response they come at a cost to bandwidth (< 100 kHz), which limits the kinds of systems that can be studied to those where the dynamics are ‘not extreme.’ Our project focuses on creating a ‘hybrid’ kind of detector, which is both accurate and extremely fast, a linear gradient “reflective filter” coupled to two small-area (i.e., fast) photodiodes. Further, through the use of a DMD, which is an array of actuatable micro-mirrors that are highly reflective across the spectrum, such linear gradients may be multiplexed. The advantage, then, of the DMD-based approach over alternative methods of creating a linear gradient is that we can dynamically change (at 8 kHz) the gradient imposed, from horizontal to vertical, and even to radial gradients, thereby allowing “time-shared” measurements of x, y, and z motion of the centroid, where our measurement bandwidth (100 MHz or higher) is limited only by the photodiodes utilized, and not by the DMD. Anatolii Kashchuk, et al.[1] have demonstrated multiplexed high-bandwidth measurements within the context of one specific application (namely, tracking of an optically trapped bead). Our aim is to extend such methods to additional applications and further our own knowledge on the topics at hand.

1. “High-speed position and force measurements in optical tweezers,” A.V. Kashchuk, A.B. Stilgoe, T.A. Nieminen, H.H. Rubinsztein-Dunlop, Optical Trapping & Optical Micromanipulation (San Diego, Aug., 2017), Presentation 10347-44.

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Apr 21st, 9:00 AM Apr 21st, 10:00 AM

Linear Position Detector with High Bandwidth

Center for Natural Sciences, Illinois Wesleyan University

Position-Sensitive Detectors currently described in the literature can be divided into distinct categories: ‘Spatial Light Separation Methods’ (e.g., Quadrant Photodiodes or D-Shaped Mirrors) and ‘Electronic Signal Separation’ (e.g., so-called Position Sensitive Detectors). We argue that Spatial Light Separation Methods do not generally give true centroid positions and while Electronic Signal Separation Methods do give a linear response they come at a cost to bandwidth (< 100 kHz), which limits the kinds of systems that can be studied to those where the dynamics are ‘not extreme.’ Our project focuses on creating a ‘hybrid’ kind of detector, which is both accurate and extremely fast, a linear gradient “reflective filter” coupled to two small-area (i.e., fast) photodiodes. Further, through the use of a DMD, which is an array of actuatable micro-mirrors that are highly reflective across the spectrum, such linear gradients may be multiplexed. The advantage, then, of the DMD-based approach over alternative methods of creating a linear gradient is that we can dynamically change (at 8 kHz) the gradient imposed, from horizontal to vertical, and even to radial gradients, thereby allowing “time-shared” measurements of x, y, and z motion of the centroid, where our measurement bandwidth (100 MHz or higher) is limited only by the photodiodes utilized, and not by the DMD. Anatolii Kashchuk, et al.[1] have demonstrated multiplexed high-bandwidth measurements within the context of one specific application (namely, tracking of an optically trapped bead). Our aim is to extend such methods to additional applications and further our own knowledge on the topics at hand.

1. “High-speed position and force measurements in optical tweezers,” A.V. Kashchuk, A.B. Stilgoe, T.A. Nieminen, H.H. Rubinsztein-Dunlop, Optical Trapping & Optical Micromanipulation (San Diego, Aug., 2017), Presentation 10347-44.