Comparison of laser performance for diode-pumped Tm:YLF of various doping concentrations

Single-end-pumped laser performance of 2, 4, and 6at.% Tm-doped YLF rods is reported. For the pumping configuration employed, crystal fracture was observed to occur for a thermal load per unit absorption length of ~13W/cm. The 2at.% Tm-doped crystal was found to have a quantum yield of ~90% of that of 4at.% Tm. However, due to a lower thermal loading density, the maximum possible incident pump power is predicted to be >60% higher, hence offering a greater output power per rod for the lower doping concentration. Power scaling considerations are discussed with reference to cross-relaxation, upconversion, and thermal loading of the host crystal

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

Idler-resonant femtosecond optical parametric oscillator with high mid-infra-red beam quality

We report an idler-resonant femtosecond optical parametric oscillator (OPO) with average output power of 520 mW, repetition-rate of 80 MHz, pulse duration of 90 fs and nearly diffraction-limited beam quality at ~2.4 µm

Novel fabrication technique for planar glass waveguides

A novel technique has been developed for the deposition of low-loss planar glass waveguides by directly spin coating from the liquid, thus overcoming the problems of reproducing glass stoichiometry when depositing from the vapour

Comprehension of wh-questions in a case of mixed dementia

We investigated processing of wh-questions and declarative sentences with differing syntactic complexity in a case of mixed dementia (FA). FA was impaired in her ability to understand syntactically complex declarative sentences and syntactically complex wh-questions beginning with which but not complex who questions. This profile, novel in dementia, is similar to that reported for people with agrammatic aphasia and discerns a ‘‘fault line’’ of the language system along a syntactic/semantic paramete

Fabrication of a single mode laser by UV-writing in neodymium doped silica-on-silicon

We describe the fabrication of a waveguide laser by UV-writing in neodymium doped silica-on-silicon. The substrate is fabricated by Flame Hydrolysis Deposition and solution doping techniques. Lasing at 1048-1056nm was observed with a slope efficiency of 33% and threshold of 4mW for the transition. Lasing was also observed at 1356nm

Crystal waveguide lasers, liquid epitaxy and ion-implantation

Fabricating low loss planar waveguides in crystal laser hosts can lead to very large inversion densities for relatively low pump powers due to the confinement of light to small dimensions over longer lengths than normally allowed by diffraction. Thus very high gain per unit pump power amplifiers and very low threshold lasers are made possible. Planar waveguides also allow easy access to the guided wave which can be useful for integrated functions (gratings, modulators etc) and good heat removal in high power devices. Here two methods of producing planar waveguide lasers in a variety of interesting host crystals are discussed

16-µJ pulse energy, picosecond, narrow-linewidth master oscillator power amplifier using direct amplification

We present a gain-switched-diode-seeded 1034.5nm master oscillator power amplifier, employing direct amplification through standard commercial Yb3+-doped fibres to generate 15.6µJ-pulse-energy, 126kW-peak-power, picosecond pulses with 3dB spectral bandwidth of 0.87nm

Graphene Q-switched mode-locked waveguide laser operating at 1535 nm

A diode-pumped Er,Yb:glass waveguide laser, Q-switched mode-locked using a graphene saturable absorber is presented. Mode-locked pulses at a repetition rate of 6.8 GHz are achieved at an output power of 27 mW and a wavelength of 1535 nm