Teaching UbiComp with Sense

Modern computer science education has to take account of the recent changes towards smart ubiquitous computing devices. In addition, existing programming languages are needlessly difficult for novice programmers to learn concepts. We have developed Sense, an extension to the graphical programming language Scratch, and an associated sensor/actuator board. Together, these will allow novice undergraduate students to quickly develop their own smart devices while learning the fundamentals of programming. Students will first study with Sense in 2011 but developmental feedback has been positive

Efficient superfluorescent light sources with broad bandwidth

We demonstrate various efficient broad-band light sources at ~1µm wavelength with a 3dB bandwidth of up to 65nm at 108mW output power, based on rare-earth doped silica fibers and a simple adjustable spectral filter

Lifetime quenching in Yb doped fibres

We have discovered that in ytterbium-doped silica fibres the excited state lifetime of a fraction of the Yb ions can be quenched to a very small value, leading to a strong unbleachable loss. This unexpected behaviour seems to be caused by some, yet unidentified, impurity or structural defect. It is of considerable relevance for various Yb doped lasers and-amplifiers including Er:Yb codoped fibres as used in telecommunication amplifiers although it should also be emphasized that fibres can be produced that are free from the quenching effect

Single-frequency ytterbium-doped fibre laser stabilised by spatial hole burning

We have exploited spatial hole burning to achieve remarkably stable single-frequency operation and mode-hop-free tuning over 300 free spectral ranges in an ytterbium-doped fiber laser with a sample standing-wave geometry. This approach makes possible stable and narrow-linewidth single-frequency fiber lasers that do not require components such as Faraday isolators, fiber couplers, and Fabry-Perot filters

1.5W diode-pumped monolithic planar waveguide laser

We describe a compact and efficient Nd:YAG waveguide laser pumped by a diode-bar. An output of 1.5W is obtained for 6W incident power, with significant brightness enhancement

High power femtosecond source based on passively mode-locked 1055nm VECSEL and Yb-fibre power amplifier

We report 5 ns pulses at 160 W average power and 910 repetition rate from a passively mode-locked VECSEL source seeding an Yb-doped fibre power amplifier. The amplified pulses were compressed to 291 fs duration

1.9µm operation of a Tm:Lead germanate glass waveguide laser

We report what we believe to be the first planar-technology waveguide laser in the 2-µm region. Laser operation of the 3H4 to 3H6 transition of Tm3+ ions in a lead germanate glass host has been observed in an ion-implanted planar waveguide

Infrared-induced photodarkening in Tm-doped fluoride fibres

We have observed a new type of infrared-induced photodarkening in high-numerical-aperture fluoride fibers doped with 3000 and 10,000 parts in 106 by weight of Tm. The loss induced in the visible region by 1140-nm radiation is very strong (as high as 25 dB in a 50-cm piece) and broadband it can be removed by irradiation with the same pump wavelength at lower powers

Non-photorefractive cw Tm-indiffused Ti:LiNbO₃ waveguide laser operating at room temperature

We report laser operation at 1.81µm and 1.85µm in a Tm3+:LiNbO3 Ti-diffused waveguide doped by thermal indiffusion at high temperature. We believe this is the first time lasing has been seen in Tm:LiNbO3 at room temperature. Continuous-wave operation was achieved at room temperature with a threshold of ~42 mW absorbed power. The output power was observed to be stable, without any sign of photorefractive damage

Ion-implanted Nd:MgO:LiNbO₃ planar waveguide laser

Laser oscillation in an ion-implanted planar Nd:MgO:LiNbO3 waveguide is demonstrated for the first time to our knowledge. Details of the waveguide structure, spectroscopic properties, photorefractive effects. and laser performance are given. A simple calculation of the absorbed power threshold gives ~8mW, in fair agreement with the experimental value of ~17mW