We apply the Hydroxide Catalysis Bonding (HCB) technique to phosphate glass and measure the reflectivity and Light Induced Damage Threshold (LITD) of the newly formed interface. HCB is a room temperature, high performing process which was designed for astronomical research glass assemblies and played a key role in the detection of gravitational waves, a breakthrough in contemporary science. The bonds have numerous assets including mechanical strength, stability, no outgassing and resistance to contamination which are of high interest in the precision optics industry. However only little research has been done on their optical properties and mostly on silica based materials. In this paper, we use HCB to bond phosphate glass at room temperature with the goal of designing composite components for solid state laser gain media. We change the solution parameters to identify how they influence the final properties of the bonds: the LIDT at 1535 nm in long pulse regime and the reflectivity at 532 nm are investigated. The measurement of the incidence dependent reflectance allows estimating the thickness and refractive index of the bond in a non destructive process. The best performing set of parameters yields a LIDT of 1.6 GW/cm<sup>2</sup> (16 J/cm<sup>2</sup>) and a reflectivity below 0.03 % which makes it suitable for use in high power lasers. The bond thickness is derived both from Scanning Electron Microscopy and the reflectivity measurements and is in the range of 50-150 nm depending on the parameters. Finally, the bonds survive cutting and polishing which is promising for manufacturing purpose.
Because of its ease of growth and large electro-optic effect, lithium niobate is the preferred choice for Q-switching
mobile lasers. Temperature-induced pyro-electric charges however may lead to premature lasing. We manufactured and
characterized temperature-stable LN Q-switch. A thermo-chemical anneal was performed creating a conductive material
layer 0.5mm thick with increased conductivity. While this increases optical insertion loss by a few percent, this is
tolerable in high gain lasers. We present details of treatment, the surface charge creation and dissipation mechanism and
the setup used to assess the cold-performance used to demonstrate improved charge dissipation when compared to
For many years Gooch and Housego have been supplying very high laser induced damage threshold coated parts to projects such as the National Ignition Facility. We have optimised our substrate preparation and coating processes to achieve repeatable performance well in excess of 10Jcm<sup>-2</sup>, 1064nm 3ns pulses. This has used electron beam deposition technology. While this has performed well in the controlled environments of the science labs, it is well known that the coatings produced are porous and therefore susceptible to absorbing water and other chemicals from the atmosphere, modifying the coating performance. The traditional solution has been to select ion beam sputtering deposition techniques, but these are typically expensive, with smaller capacity chambers and produce high stress coatings. Therefore they are not optimal for higher volume components and thin substrates. We present the results of our development to optimise an ion-assisted deposition technique offering the possibility of trading off various design parameters including coating porosity and laser damage threshold, to optimise the coating performance of optics located where they can suffer contamination and outgassing. The coatings can be deposited in a large chamber at reasonable speeds suited to higher volume throughputs. Such coatings include the challenging design of a dual band visible and 1064nm optimised for both visible transmission range and LIDT performance at 1064nm.
Large mirrors are required for a wide variety of applications. Two key constraints are mirror stability and mirror mass. Low expansion glass ceramics remain a useful material because of its excellent thermal stability, relative ease of processing and lower cost compared to alternatives. However there is room for the improvement of the manufacturing techniques over the traditional methods of milling and etching, which are high risk, expensive and time consuming. A solid blank is milled out using high speed diamond tooling to leave fragile webs of supporting material. The final process steps are the highest risk, when it is possible for catastrophic flaws to appear. We present a novel method of producing a monolithic structure from component pieces that provide a lower risk, lower cost method of producing stable and light-weighted mirrors. Individual smaller components are machined and then bonded together. The bonding process results in near substrate strength components without compromising the very low thermal expansion of the glass ceramic. It also allows the creation of novel designs with hollow cavities embedded within the structure. Prior to commencing the fabrication the mechanical design was modelled to predict the stability of candidate designs. Tests were carried out on witness pieces to prove the relative strength of the bonds. Prototypes were then fabricated and tested for thermal stability.
A new sputter deposition process has been developed based upon remote generation of plasma by a dedicated Plasma
Source (PLS). This technique is referred to as high target utilisation sputtering (HiTUS). In contrast to ion beam and
magnetron sputtering processes, HiTUS allows fast deposition rates of low stress, high density films from a high
percentage (>90%) of the target surface. The process has not previously been applied to thin films for high laser damage
threshold applications. The paper will present results of the
anti-reflection (AR) coating trials and compare them to two
other coating deposition processes - standard e-beam evaporation and hollow cathode ion-assisted e-beam deposition.