EM algorithm for GTM-FS

We propose a generative topographic mapping (GTM) based data visualization with simultaneous feature selection (GTM-FS) approach which not only provides a better visualization by modeling irrelevant features ("noise") using a separate shared distribution but also gives a saliency value for each feature which helps the user to assess their significance. This technical report presents a varient of the Expectation-Maximization (EM) algorithm for GTM-FS.

Fabrication of high aspect ratio microfluidic devices using direct FS ablation

We present a single stage direct fs ablation results which show that it is possible to make high quality and high aspect ratio devices in a single stage process using a CAD optimised approach.

A comparison of the spectral properties of high temperature annealed long period gratings inscribed by fs laser, UV and fusion-arc

Long period gratings have been inscribed in standard single mode fibre using a fs laser system, a fusion arc and a UV laser and a comparative study carried out of their thermal behaviour. The fs laser induced gratings can survive temperatures in excess of 800°C, however the inscription process can induce considerable birefringence within the device. Annealing studies have been carried out showing that below 600°C, all three grating types show a blue shift in their room temperature resonance wavelengths following cyclic heating, while above 600°C, the UV and arc induced LPGs exhibit a red shift, with the fs LPG showing an even stronger blue shift. High temperature annealing is also shown to considerably reduce the birefringence induced by the fs inscription process.

Sub-50 fs Yb-doped laser with anomalous-dispersion photonic crystal fiber

We report on the generation of 42 fs pulses at 1 µm in a completely fiber-integrated format, which are, to the best of our knowledge, the shortest from all-fiber-integrated Yb-doped fiber lasers to date. The ring fiber cavity incorporates anomalous-dispersion, solid-core photonic crystal fiber with low birefringence, which acts as a broadband, in-fiber Lyot filter to facilitate mode locking. The oscillator operates in the stretched-pulse regime under slight normal net cavity dispersion. The cavity generates 4.7 ps long pulses with a spectral bandwidth of 58.2 nm, which are dechirped to 42 fs via a grating pair compressor outside of the cavity. Relative intensity noise (RIN) of the laser is characterized, with the integrated RIN found to be 0.026% in the 3 Hz-250 kHz frequency range.

Fabrication of high aspect ratio microfluidic devices using direct FS ablation

We present a single stage direct fs ablation results which show that it is possible to make high quality and high aspect ratio devices in a single stage process using a CAD optimised approach.

Sub-100 fs mode-locked erbium-doped fiber laser using a 45°-tilted fiber grating

We demonstrate generation of sub-100 fs pulses at 1.5 μm in a mode-locked erbium-doped fiber laser using a 45°-tilted fiber grating element. The laser features a genuine all-fiber configuration. Based on the unique polarization properties of the 45°-tilted fiber grating, we managed to produce sub-100 fs laser pulses through proper dispersion management. To the best of our knowledge, this is the shortest pulse generated from modelocked lasers with fiber gratings. The output pulse has an average power of 8 mW, with a repetition rate of 47.8 MHz and pulse energy of 1.68 nJ. The performance of laser also matches well the theoretical simulations. © 2013 Optical Society of America.

A comparison of the spectral properties of high temperature annealed long period gratings inscribed by fs laser, UV and fusion-arc

Long period gratings have been inscribed in standard single mode fibre using a fs laser system, a fusion arc and a UV laser and a comparative study carried out of their thermal behaviour. The fs laser induced gratings can survive temperatures in excess of 800°C, however the inscription process can induce considerable birefringence within the device. Annealing studies have been carried out showing that below 600°C, all three grating types show a blue shift in their room temperature resonance wavelengths following cyclic heating, while above 600°C, the UV and arc induced LPGs exhibit a red shift, with the fs LPG showing an even stronger blue shift. High temperature annealing is also shown to considerably reduce the birefringence induced by the fs inscription process.

Generation of 49-fs pulses directly from distributed Kerr-lens mode-locked Yb:YAG thin-disk oscillator

The concept of distributed Kerr-lens mode-locking and a thin-disk Yb:YAG oscillator based on this concept are presented. The described oscillator directly generates pulses with a duration of 49 fs and spectral width of 33 nm

Fabrication of high aspect ratio microfluidic devices using direct fs ablation

We present a single stage direct fs ablation results which show that it is possible to make high quality and high aspect ratio devices in a single stage process using a CAD optimised approach. © 2008 Optical Society of America.