All-optical switching

OPO for 1 to 2 µm

Photonic crystal micrograph,
hole-spacing 200 nm

Photonic integrated circuit

Part of the cleanroom

Microlaser schematic

Polymer light-emitters

 Multiple quantum well semiconductors

 Electron spin gratings have been produced in MQWs for the first time. These unique gratings are allowing the microscopic motion of electrons to be studied. This has lead to the first optical measurements of both electron and hole drift mobilities in MQW structures. Electron spin relaxation rates and the different contributions to excitonic optical nonlinearities are being characterised.
Principal Contact: Alan Miller

 Resonant electron tunnelling and other cross-well transport phenomena are vital to the operation of most MQW devices. Field dependent tunnelling and thermionic emission rates have been determined in MQW p-i-n devices using ultrashort laser pulse techniques.
Principal Contact: Alan Miller

 All-optical switching devices based on semiconductor waveguides and amplifiers offer the potential for developing faster optical communications systems. All-optical switching at the transparency point of semiconductor lasers and the use of carrier sweep-out to speed the recovery of semiconductor devices have been pioneered at St Andrews.
Principal Contacts: Wilson Sibbett, Alan Miller

 Waveguide and micro-cavity MQW lasers exhibit very unusual effects on ultrashort timescales. The ultrafast gain dynamics of the latest semiconductor lasers including vertical micro-cavity surface emitting devices are being investigated using femtosecond pulses.
Principal Contact: Alan Miller

 New ultrashort pulse lasers are being optimised in support of these time-resolved MQW semiconductor studies in collaboration with the laser group. Newly developed lasers include a picosecond optical parametric oscillator and a dual wavelength, sub-100fs Ti:sapphire source.
Principal Contacts: Alan Miller, Majid Ebrahimzadeh

 Formal collaborations exist between the St Andrews semiconductor physics group and many elsewhere, including U. Oxford, U. Glasgow, UCL, BT Labs, Hughes Research Labs, Malibu, Sandia National Labs, Albuquerque, and CREOL, U. Central Florida, Orlando.  Principal Contact: Alan Miller

Photonic crystals are artificial periodic structures, tyically with high refractive index contrast, e.g. 3:1 (semiconductor:air). In our newly-established cleanroom, we are fabricating 2-dimensional structures in gallium arsenide and are developing novel fabrication techniques for these structures using optical and electron-beam lithography, thin film deposition techniques, as well as reactive and ion beam etching. Information from the Group
Principal Contact: Thomas Krauss

Photonic integrated circuits based on photonic crystals. The key driving force of this research is the miniaturisation and increase of the functionality of photonic circuits. The application of photonic crystal technology allows us to design waveguides, couplers, and routers on a much smaller scale than previously possible, thus allowing the design of high-density integrated circuits. Applications of this work are in telecommunications, e.g. for devices that manage high-speed, high volume data (e.g. internet) traffic.
Principal Contact: Thomas Krauss

Novel Semiconductor lasers and light emitters. Research into high Q cavities and new types of resonators based on photonic microstructures is motivated by the desire of understanding and manipulating the fundamental physics of the light emission process and the aim of developing efficient light sources (e.g. for lighting, displays) and novel types of optical sensors, e.g. for biomedical applications.
Principal Contact: Thomas Krauss

Cleanroom    Many devices are fabricated in our new cleanroom, which was completed in 2001.

 Formal collaborations exist between the St Andrews photonic crystal group and Glasgow University, Sheffield University; Bookham Technology in Oxford, Pirelli Cavi e Sistemi in Milan and Photon Design in Oxford.  Principal Contact: Thomas Krauss

Light Emitting Polymers are the subject of research in Ifor Samuel's group.    These remarkable materials combine novel semiconducting electronic properties with the favourable processing characteristics of polymers. They offer the prospect of new flexible displays and broad-band optical amplifiers. The researchers aim to understand the physics of these materials and then to apply that understanding to improving them, so their activities range from fundamental to applied science. The group has pioneered work on a new molecular architecture for light-emitting materials. Another exciting result has been their use of photonic microstructure to double the efficiency of light-emitting diodes. They have demonstrated how light-emission can be controlled by molecular,optical and device design. Information from the group.
Principal Contact: Ifor Samuel