Judith M. Dawes

Spectral characterization and diode-pumped laser performance of Yb:YCOB

Infrared and visible absorption and fluorescence spectra of the novel laser crystal Yb:Ca4YB3O10 (Yb:YCOB) were recorded and spectral parameters were calculated. Infrared laser output powers of 446mW were realized from a 1.86mm thick Yb:YCOB crystal pumped by a 1.6W fiber-coupled 976nm diode, with slope efficiency of 73% and threshold of 55mW. Self-frequency-doubled green light was also observed.

Widely tunable green lasers based on the self-frequency doubling material Yb:YAB

We report widely tunable infrared (70nm) and self-frequency-doubled operation, (with 25-450mW output power), in Yb:YAB, covering the wavelengths of the copper vapor laser (510nm), Argon ion (514nm), doubled Nd:YAG (532nm) and green HeNe (543nm).

High Efficiency, High Power, Self-Frequency Doubled Q-Switched Operation in Yb:YAB

We report 95 % conversion from the optimised Q-switched fundamental output to green output in the self-frequency doubling material Yb:YAB. Maximum average green powers of 2.27 W were obtained at 520-522 nm.

Crystal Characterization and "Natural Quasi-Phase Matching" in Nd- and Yb:YAB

We characterize nonlinear conversion in Yb:YAB and demonstrate a simple non-destructive technique for measuring crystal quality. Imaging the nonlinear conversion onto a CCD camera we observe phase matching characteristics similar to that of quasi-phase-matched crystals.

Photonic crystal based circuitry fabricated using laser-assisted processes

Recently, photonic crystals (PCs) have gained interest due to their ability to influence the propagation of light [1]. This paper describes a simple and novel approach for the fabrication of micron and nanometer scale photonic crystal based circuitry with an arbitrary degree of control. Laser ablation using a femtosecond Ti:Sapphire [2] laser is used to form a template from which the photonic crystal device is castRecently, photonic crystals (PCs) have gained interest due to their ability to influence the propagation of light [1]. This paper describes a simple and novel approach for the fabrication of micron and nanometer scale photonic crystal based circuitry with an arbitrary degree of control. Laser ablation using a femtosecond Ti:Sapphire [2] laser is used to form a template from which the photonic crystal device is cast

Fabrication of Tilted Fibre Grating for Medical Applications

Fibre gratings are used in a multitude of telecommunication systems but their application to other fields has been somewhat overlooked. In recent years, the application of fibre gratings to other fields such as sensor systems has been growing. Optical fibre devices are also increasingly being used in medicine for endoscopes and keyhole surgery. In these cases optical fibres are employed in an end-firing configuration. However, for surgical applications such as those used in the treatment of atrial fibrillation, a side-firing system is desired. At Macquarie University, tilted fibre gratings have been fabricated for such an application. The characteristics of tilted fibre gratings fabricated using a frequency doubled copper vapour laser will be presented.Fibre gratings are used in a multitude of telecommunication systems but their application to other fields has been somewhat overlooked. In recent years, the application of fibre gratings to other fields such as sensor systems has been growing. Optical fibre devices are also increasingly being used in medicine for endoscopes and keyhole surgery. In these cases optical fibres are employed in an end-firing configuration. However, for surgical applications such as those used in the treatment of atrial fibrillation, a side-firing system is desired. At Macquarie University, tilted fibre gratings have been fabricated for such an application. The characteristics of tilted fibre gratings fabricated using a frequency doubled copper vapour laser will be presented.

Characterisation of waveguides written in bulk materials with femtosecond laser pulses

With the goal of fabricating photonic devices for optical networking applications, significant attention has recently been directed to the use of femtosecond laser pulses for inscribing optical components inside transparent materials. In particular, it has been demonstrated that a tightly focussed Ti: Sapphire laser pulse can induce a change in the refractive index inside bulk glass without damage. Using this mechanism it is possible to fabricate a range of waveguide devices; such as beam splitters, couplers and interferometers, inside a wide range of materials without the need for linear absorption. At CUDOS @ Macquarie we have fabricated and characterised a number of structures in a variety of glasses. A review of this research will be presented.With the goal of fabricating photonic devices for optical networking applications, significant attention has recently been directed to the use of femtosecond laser pulses for inscribing optical components inside transparent materials. In particular, it has been demonstrated that a tightly focussed Ti: Sapphire laser pulse can induce a change in the refractive index inside bulk glass without damage. Using this mechanism it is possible to fabricate a range of waveguide devices; such as beam splitters, couplers and interferometers, inside a wide range of materials without the need for linear absorption. At CUDOS @ Macquarie we have fabricated and characterised a number of structures in a variety of glasses. A review of this research will be presented.

Laser based fabrication of micro and nano-structures using sacrificial layers

When using ultra-short laser pulses it is possible to machine areas smaller than the focal spot by restricting the threshold light intensity to the centre of the spot. However, even smaller and cleaner features can be achieved by utilising a sacrificial material on top of the layer being machined. In particular, we have found that features can be reduced by up to a factor of two and the heat-affected-zone by a factor of three in polymers. These results have implications for improved fabrication of fluid and gas delivery systems and optical devices such as photonic crystals and related devices.When using ultra-short laser pulses it is possible to machine areas smaller than the focal spot by restricting the threshold light intensity to the centre of the spot. However, even smaller and cleaner features can be achieved by utilising a sacrificial material on top of the layer being machined. In particular, we have found that features can be reduced by up to a factor of two and the heat-affected-zone by a factor of three in polymers. These results have implications for improved fabrication of fluid and gas delivery systems and optical devices such as photonic crystals and related devices.

Active waveguides written in rare-earth doped materials with femtosecond laser pulses

Optical waveguides can be fabricated inside various glasses by using tightly focussed femtosecond laser pulses to induce a change in the refractive index. Researchers have shown this direct-write technique has the potential to generate both planar and three-dimensional photonic devices for optical networking applications inside a wide range of materials. In particular, waveguides can be written in Erbium-doped phosphate glass and demonstrate a net gain when used as an active element in a standard waveguide amplifier. We report results of a detailed study optimising the beam delivery configurations and fabricating photonic waveguides and devices in both passive and active glasses.Optical waveguides can be fabricated inside various glasses by using tightly focussed femtosecond laser pulses to induce a change in the refractive index. Researchers have shown this direct-write technique has the potential to generate both planar and three-dimensional photonic devices for optical networking applications inside a wide range of materials. In particular, waveguides can be written in Erbium-doped phosphate glass and demonstrate a net gain when used as an active element in a standard waveguide amplifier. We report results of a detailed study optimising the beam delivery configurations and fabricating photonic waveguides and devices in both passive and active glasses.

Measurement of polarization-dependent loss mechanisms in Cr 4+ :YAG

Using a polarized pump-probe technique, we studied the continuous-wave absorption and emission polarization anisotropy of Cr4+:YAG crystals and modeled the ground state absorption and excited state absorption loss. We propose a twisted mode laser cavity to compensate for this anisotropic loss and achieve narrow linewidth output.