http://www.researchonline.mq.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:11416 We present a synthesis algorithm and design example for birefringent equalizing filters, suitable for dispersion compensation in wavelength division multiplexed (WDM) communication systems. A WDM equalizer with dispersion 2003 ps/nm over an operational frequency range of 10 GHz was designed with maximum deviation of the group delay of 3.86 ps. The effects of various factors on the equalizer performance were discussed. 2011-01-20T23:40:05.968Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:5772 Narrowband pulsed 822 nm signal radiation from an injection-seeded optical parametric oscillator (OPO) system is used to record fluorescence-detected sub-Doppler two-photon excitation (TPE) spectra of atomic cesium. An optical-heterodyne technique is used to monitor the frequency chirp as well as the fluctuating central frequency of successive OPO output pulses, thereby providing a novel way to record sub-Doppler TPE spectra. The measured TPE linewidth approaches the ultimate limit imposed by the Fourier transform of the pulse's temporal profile, demonstrating the utility of this system for pulsed laser spectroscopy applications that require the highest possible resolution. 2010-01-27T22:26:41.740Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:5866 We demonstrate compression of low-power 6 ps pulses to 420 fs around 1550 nm in a compact all-fiber scheme utilizing the strong nonlinearity and positive-normal dispersion of a single-mode As₂Se₃ fiber, in combination with a tailored chirped fiber Bragg grating. The value and sign of the dispersion, coupled with the high nonlinearity of the chalcogenide, produces a smoothly broadened spectrum with a monotonic chirp via self phase modulation. Measurements of the phase and time evolution of the laser pulses using frequency resolved optical gating are performed showing excellent agreement with theory. We also discuss the limiting influence of two-photon absorption. 2010-01-27T22:25:23.046Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:5879 Waxes and thermopolymers are commonly used to mount optical and photonic materials prior to polishing and singularization. After demounting, residual wax/thermopolymer can adhere to the component surface, frequently in the form of particles. Dry, ultraviolet-pulsed laser cleaning has been demonstrated to effectively remove paraffin wax particles, prepared on a glass surface using a wax aerosol technique. This method produces dome-shaped particles. Experimental evidence suggests the dome-shaped particles are vaporized by the absorption of the energy from the laser pulse. A theoretical model based on vaporization has been developed and this leads to predictions of the critical fluence for single laser pulse removal of dome-shaped particles which is in good agreement with that experimentally measured (220 mJ/cm²). The model also gives insight into the geometries and relative thermal properties of the "particles" and surface, which are important in determining whether removal by vaporization is a viable process 2010-01-27T22:25:12.177Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:5880 Silica and microscope slides that had been pretreated with a variety of wet chemical, ultrasonic and laser irradiation surface preparation methods were contaminated with alumina particles of around 3 µm. The samples were prepared and processed without delay so as to avoid capillary condensation in a high humidity environment and thus ensuring that the process is dry laser cleaning. They were then irradiated with a pulse of 248 nm radiation from a KrF excimer laser, over a range of fluences. The laser cleaning results show that, in this case, the surface preparation method appears to have little effect on the laser cleaning efficiency. They also demonstrate that the threshold fluence for particle removal of silica is approximately eight times higher than that for microscope slides, when so prepared. In contrast, application of Arnold et al.'s thermal expansion model of laser cleaning in the quasistatic limit to this material system predicts that the threshold fluence for silica will be about 15 times greater than that for glass. One possible explanation for this discrepancy may be that the particle's absorptivity (0.16) is inaccurate. A value of 0.35 gives good agreement between theory and experiment. 2010-01-27T22:25:12.132Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:6534 Optical surface profilometry is a technique that has advantages over other profilometry techniques (stylus profilometry, AFM) of being non-contact and being able to profile comparatively large areas in a single "z-scan". Thus, it is employed in monitoring surface quality and measuring surface form in high technology manufacturing processes and quality assurance, as well as being applied as a diagnostic in research and development contexts. Its application to optical materials has been limited due to issues relating to the low reflectance of the surfaces. A feasibility study for profiling laser induced optical damage and "loose" microscopic sized pieces of optical material (particles introduced by design) on optical substrates is reported. Progress on profiling these difficult samples has been achieved. 2010-01-27T22:16:38.947Z ]]>