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Photonics

I have two degrees in Engineers Physics specialising in Photonics, and have become a specialist in Fluorescence Spectroscopy at Edinburgh Instruments Ltd for their Photonics Division. Below you'll find the movie I made explaining Time Correlated Single Photon Counting, as well as my thesis on Superluminescence Diodes.



My Work Movie
This is a 3-minute video I made for the company I work for, Edinburgh Instruments Ltd, where I work for the Photonics Division. The movie is about Fluorescence Lifetime measurements being made using a technique called Time Correlated Single Photon Counting (TCSPC).

This video represents the most amount of effort I've ever given to a video, as it meant learning how to remove the noise from the audio, adding multiple camera shots to a single scene, applying special features to remove the background from certain shots, writing and narrating the script, adding sound effects, recording screen shots from the spectrometer's software/computer, performing the lifetime measurements, editing and rendering the video, etc.

The video has been presented at many exhibtions and universities, is on the company's website, and most recently was featured at the company's Fluorescence Spectroscopy Seminar in Xi'an China in November 2010, and Photonics West in San Francisco in January 2011. The majority of this video was made during my free time, which I completed in June 2010!


My Thesis on Superluminescent Diodes

The work I did for my thesis involved creating a high powered superluminescent diode with extra wide bandwidth. This was accomplished by fabricating the device with two sections to create two emission peaks that combined to form a spectral plateau. The section that produced the lower energy photons was titled the Red Section, and the section that produced the higher energy photons was titled the Blue Section. Both sections combined together to act as a single waveguide, and emission was measured from the Blue Section's facet.

Each section was initially grown with the same heterostructure on an GaAs substrate with InGaAs quantum wells. However the InGaAs quantum well's belonging to the blue section later became altered through a top capping layer of InGaP with an excess of phosphorus and a rapid thermal anneal at ~825 Celsius. This resulted in the excess phosphorus elements travelling to the InGaAs quantum well to replace some of the arsenic elements, thus changing the quantum wells' composition and the positions of its energy levels. The quantum wells were also grown latticed mismatched to their GaAs substrate in order create a slight strain and alter the k-space energy level diagrams. This change is mostly seen with respect to the valence band and results in a greater quantum yield.

In order to prevent the diode from lasing, tilted facets at 7 degrees were used to prevent any optical feedback. For the waveguide, a ridge was created slightly above the quantum wells, which ranged in thickness between 3 and 6 um. The free space to the sides of the ridge created a lower effective refractive index to the side's of the waveguide, which enabled the emission to be contained as it traversed down the waveguide until reaching the diode's facet.

The superluminescent diodes had a steady state emission at approximately 980nm, with 60nm FWHM bandwidth and 38mW of power, at room temperature.

Click here to read my thesis.