Three coating chambers are dedicated to dielectric films, with a fourth assigned to metal film deposition. A Denton DV-SJ/20c cryo-pumped system (capable of 10-8 torr) is used solely for UV/VIS/NIR applications of oxide and fluoride films. It's e-beam gun can evaporate materials from a four pocket crucible onto substrates cleaned by a cold-cathode ion source. Deposition rate control and film thickness monitoring is performed using quartz oscillator and optical interference techniques. The optical system was designed and built by Cleveland Crystals to provide the fine control necessary for most of our designs. The first of three customized diffusion pumped/cold trapped systems is used for NIR to FIR applications. The second uses an e-beam gun heated 4 pocket crucible system for depositing films for the visible to FIR. These systems also use quartz and optical monitoring. Gold and chrome film deposition is handled by a third (smaller) diffusion pumped/cold trapped system. It is equiped with custom tooling to provide uniform films on either planar or cylindrical substrates.
Single layer /4 designs are available for all substrates except MgF2, which may be handled by our Sol-Gel capability. These economical coatings provide broad band AR performance. The reflectivity at the center wavelength may be <0.1%/surface for certain substrates, where there is a good match between the substrate index of refraction and the appropriate thin film index. A good match is often available in the visible (VIS) and UV. In the IR, /4 designs typically provide 0.2-0.5%/surface, due to the high indices of the substrates and limited choice of coating materials. Opto-mechanical properties are usually quite good for all wavelengths due to the relatively thin single layer. Generally, laser damage thresholds are moderately high in both the UV-VIS region and in the IR, with our coated surfaces setting the standards of performance against which others are compared.
Multiple layer V and VV designs are available for all substrates, except LBO. These more complex coatings provide enhanced, single or dual wavelength AR performance. The reflectivity at the center wavelengths may be <0.1%/surface for most substrates and wavelength combinations. This level of performance can usually be obtained in the visible and UV. In the IR, 0.2-1%/surface would be typical. Again, the greater reflectivity in the IR is due to the higher refractive indices of the substrates and limited choice of coating materials suitable for use with the various substrates. Opto-mechanical properties are usually excellent in the UV-VIS and adequate in the IR. In the IR, disparate coefficients of thermal expansion, surface adhesion issues and resistance to water absorption must be balanced against the desired AR coating optical performance. Generally, the resulting optimization achieves good optical performance with reduced mechanical strength in the coating. This is especially true for the very thick stacks required for VV designs at long wavelengths. Generally, laser damage thresholds are high in the UV-VIS region and moderately high in the IR. Cleveland Crystal's polishing and coatings have been found superior to our competitors, thus for example, allowing us to increase our market share of BBO and AgGaSe2 sales. Repeated attempts over two years by one major firm to replace our polishing/coating capability failed.
Multiple layer VVV and OPO designs are available for all substrates, except LBO. These custom coatings provide transmission windows for three wavelength bands, thus making them ideal for THG, DFM and OPO applications. The reflectivity at the center of each window may be <0.1%/surface for most substrates and wavelength combinations. Again, this level of performance can usually be obtained in the visible and UV. In the IR, 0.2-1%/surface would be typical. Opto-mechanical properties are similar to the VV designs in both the UV-VIS and IR. The OPO designs incorporate a broad long wave transmission band to allow efficient extraction of the idler (longest wavelength 1), while maintaining low insertion losses for the pump (shortest wavelength 3) and signal wavelengths (middle wavelength 2). In addition mid-IR, high and partial reflector, and AR designs incorporating low moisture and film absorption have been developed. Generally, laser damage thresholds are moderately high in the UV-VIS region and high in the IR. Cleveland Crystals VVV designs have been found to be more consistent and exhibit superior durability in use. The OPO designs have proven adequate in service over the last 5-6 years and in the IR are unique to Cleveland Crystals.
Metallic coatings, such as aluminum, silver, gold and chrome, are available as vacuum deposited films for use as electrodes, high and/or partial reflectors. Typical substrates include, but are not limited to: KDP/KD*P, KTP/KTA, BBO, optical glasses and fused silica. High quality electrodes for Pockels cells is the primary goal. These films must be durable, uniform and optimized for the low temperature coating requirements of highly deuterated KD*P.
 Prototype films