John-Mark Hopkins, MSci 1995

 

Dr Hopkins is currently a research scientist at the Institute of Photonics at Strathclyde University.

After completing my degree course in Laser Physics and Optoelectronics, I remained at St Andrews for a summer project in mm-waves and then on to a PhD in Wilson Sibbett’s ultrafast femtosecond laser group commonly known as the “W-squad”. Ultrafast lasers produce pulses of the order of a hundredth, millionth, millionth of a second and are some of the shortest man-made events. My PhD concentrated on the production of compact and low cost femtosecond pulse lasers which could challenge the current industry standard technology in some application areas. For me, this study culminated in the production of a battery-operated short-pulse laser which had a footprint no larger than a sheet of A4 paper. This compared very favourably with the archetypal ultrafast laser which was (and still is) considerably larger, power hungry and for the most part confined to the specialised laser lab. My thesis obviously impressed someone as it won a Rank Thesis prize (2nd prize I hasten to add in humility). Looking back, the most pleasing about this research project for me is that the work was continued after I left St Andrews by a number of clever folks who have taken many of the principles and conclusions we arrived at on to other material systems and wavelengths, successively improving laser systems and demonstrating some impressive performance. This area is still obviously very active in St Andrews and the ultrafast laser community generally.

After my PhD, remaining in St Andrews, I joined Alan Miller’s semiconductor spectroscopy group where I learned (or tried to learn) some of the fun that can be had with solid-state physics and semiconductors. I was responsible for creating and looking after some of the ultrafast lasers and optical sources that the group put to good use probing the carrier dynamics within materials, both for scientific betterment and for real-world device-based research. I was mainly involved in a joint project with (the then) BT labs in Ipswich on semiconductor optical amplifiers as fast switching devices for telecoms applications.

After a couple of years I hopped coasts to Glasgow to work at the Institute of Photonics (IOP) at The University of Strathclyde (www.photonics.ac.uk). Here I started a Scottish enterprise “proof-of-concept” program into optically pumped Vertical External Cavity Semiconductor Lasers (VECSELs) which are a new breed of semiconductor laser. The vertical cavity nature of the device means that symmetrical high quality laser modes are accessible, which is not the case for standard edge-emitting diode lasers, and the external or extended cavity allows power scaling to be easily achieved. The project was to create one of these lasers at telecommunication wavelengths, namely 1310nm, using a new semiconductor material system. There were many challenges involved in producing such a device, but we concluded the formal part of the project by demonstrating world record output powers of over 0.5W for the material at 1320nm. This work is now ongoing and we hope to demonstrate similar performance at 1550nm.

The main remit of the IOP is to focus on industrial relevant research as in the above case, and also to work more closely with industry, both within government and privately-funded collaborative frameworks. My current project is an example of such a programme and is centred on high-speed free-space optical communication for urban network distribution or “the last-mile” of broadband connectivity. What does that mean? Well simply put, companies which own a number of buildings within a city want to be able to network their offices at very high data rates but are understandably unwilling to cover the costs of laying fibre in a built up area, which can be a very complex and expensive process. The solution is to create an optical “direct line of sight” network at rooftop level and there are a number of companies that supply free-space optical networking solutions. Our project is a collaboration between Universities and companies to produce an eye-safe system that can span greater distances and exhibit better link times than are currently available. To do this, we are concentrating on using VECSEL technology in the mid-IR at 2.2 micrometres coupled with adaptive optics, more commonly used for astronomical applications, to improve the beam parameters at the transmitter port and the beam quality at the receiver port. For more info. see www.osda.org.uk/projects/ALFONSO.html.

The work is very challenging but also very rewarding, and on a daily basis I get to put into practice many of the transferable skills and much of the knowledge I gained at St Andrews.

Aside from physics, I was hit by the St Andrews marriage statistic bus and married a girl I met in first year. We had a beautiful baby daughter in Dec 03, aawwwww.

First posted by BDS 11.6.04