Model-based Wavelength Estimation with Tunable Color Filter and Single Photodiode

Abstract

Wavelength measurement and control of lasers is of paramount importance and has found vast application in areas such as linear and nonlinear spectroscopy, multichannel wavelength division multiplexing, laser meteorology and applications which involve testing of laser and LED light sources to ensure spectral purity and power distribution. While the state of the art optical wavelength measuring devices such as the AQ6317 Yokogowa Optical spectrum analyzer have high spectral resolution of about 0.015nm at the cost price of 50,000 euro, and the Thorlabs FT Michelson Spectrometer with a resolution of about 0.001nm has a cost price of about 23,000 euros, other easy to use table top Wavelength Meter developed in recent time provide limited resolution and accuracy. The tradeoff is cost, resolution, size and accuracy. The major research question in this thesis is how do we realize an optical wavelength measurement machine which has the capability of providing a spectral resolution better than 0.015nm with an accuracy better than 0.1nm at a low-cost? In this thesis we presents a novel and simple approach to optical wavelength measurement and the working principles is demonstrated with a tunable color filter and a single photodiode. A simple and lowcost solution that could lead to realising the functionality of the state of the art equipment at a cost of less than 700 euros is therefore proposed in this thesis work.