The Response of An Optical Lever
Faculty Mentor Name
Andri Gretarsson
Format Preference
Poster
Abstract
The detector response of the humble optical lever over its full dynamic range is both non-linear and complicated but can be modeled with known functions. We derived the detector response and approximations relevant to practical use cases.
A typical optical lever consists of a well-collimated laser reflecting from a surface whose angular motion is to be measured. The reflected beam is directed to a two-element “split photodiode” (SPD), and the difference between the photocurrents from the individual elements is a function of the angular motion of the reflective surface.
We have evaluated the full analytical model for the response of the photodiode to the beam motion and compared it to real data gathered through an optical lever experiment. Additionally, we consider the conditions under which the response is linear and provide approximations for the slope of the response in the limits of small displacement and small inter-element gap. These analytic expressions are useful for calibration of optical levers, e.g., through fitting the various geometric parameters to the measured response.
The Response of An Optical Lever
The detector response of the humble optical lever over its full dynamic range is both non-linear and complicated but can be modeled with known functions. We derived the detector response and approximations relevant to practical use cases.
A typical optical lever consists of a well-collimated laser reflecting from a surface whose angular motion is to be measured. The reflected beam is directed to a two-element “split photodiode” (SPD), and the difference between the photocurrents from the individual elements is a function of the angular motion of the reflective surface.
We have evaluated the full analytical model for the response of the photodiode to the beam motion and compared it to real data gathered through an optical lever experiment. Additionally, we consider the conditions under which the response is linear and provide approximations for the slope of the response in the limits of small displacement and small inter-element gap. These analytic expressions are useful for calibration of optical levers, e.g., through fitting the various geometric parameters to the measured response.