Some Fundamentals of Optical Thin Film Growth

Kaiser, Norbert

doi:10.1007/978-3-540-36386-6_3

Cited by 14 publications

(16 citation statements)

References 42 publications

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“…Such reduction may be a difficult task because thin film growth is an extremely complicated phenomena 16 and optical properties of thin films are influenced by many factors, such as columnar and microcrystalline structure, impurities, porosity, etc. Nevertheless, there is an obvious way to reduce the number of unknown parameters in the case when bulk material refractive index is known and film has nearly amorphous structure with densely packed columns.…”

Section: Refractive Index Determination In the Case Of Known Bulk Matmentioning

confidence: 99%

Reliable determination of wavelength dependence of thin film refractive index

et al. 2003

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Depending on the choice of thin film models and measurement data used for the characterization analysis one can obtain essentially different characterization results. It is especially difficult to reliably determine refractive index wavelength dependencies in the case of low accuracy measurement data. We consider possible approaches aimed to improve a stability of refractive index determination. The ways of the verification of characterization results are also discussed. Practical examples used to illustrate the proposed approaches are connected with the most difficult case of the determination of the refractive indices of fluoride films in the VUV spectral region.

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Section: Refractive Index Determination In the Case Of Known Bulk Matmentioning

confidence: 99%

Reliable determination of wavelength dependence of thin film refractive index

et al. 2003

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“…Damage test conditions could also play a role. Aging effects are common, and can result in wavelength shifts in the transmission spectrum of multilayer HR coatings, 24 but here, in the case of this four-layer AR coating, such wavelength shifts were not evident, as was confirmed by a remeasurement of the transmission spectrum of each coating again in the spectrophotometer. Nevertheless, aging resulting from alterations in molecular bonding within the coating structure could lead to relaxation of stress around voids of the columnar coating formations and cause the coating to become more resistant to laser damage.…”

Section: Resultsmentioning

confidence: 49%

Impact of different cleaning processes on the laser damage threshold of antireflection coatings for Z-Backlighter optics at Sandia National Laboratories

Field¹,

Bellum²,

Kletecka³

2014

Opt. Eng

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Abstract. We have examined how three different cleaning processes affect the laser-induced damage threshold (LIDT) of antireflection coatings for large dimension, Z-Backlighter laser optics at Sandia National Laboratories. Laser damage thresholds were measured after the coatings were created, and again 4 months later to determine which cleaning processes were most effective. Coatings that received cleaning exhibited the highest LIDTs compared to coatings that were not cleaned. In some cases, there is nearly a twofold increase in the LIDT between the cleaned and uncleaned coatings (19.4 J∕cm 2 compared to 39.1 J∕cm 2 ). Higher LIDTs were realized after 4 months of aging. The most effective cleaning process involved washing the coated surface with mild detergent, and then soaking the optic in a mixture of ethyl alcohol and deionized water. Also, the laser damage results indicate that the presence of nonpropagating (NP) damage sites dominates the LIDTs of almost every optic, despite the cleaning process used. NP damage sites can be attributed to defects such as nodules in the coating or surface contamination, which suggests that pursuing further improvements to the deposition or cleaning processes are worthwhile to achieve even higher LIDTs.

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“…This effect is well known to take place also in degrading the interfacial multilayer roughness [2] , layer by layer. To make matters worse, when the layer thickness exceeds a critical value (of about 1 to 20 nm, depending on the material and the deposition conditions), the growing layer rearranges its structure in a polycrystalline texture [11] , resulting in a quicker roughness growth and often a porous structure. In the most favourable case, if the multilayer deposition is optimized to generate a little or negligible roughness, then the interfacial roughness will barely replicate the Gold layer topography.…”

Section: Introductionmentioning

confidence: 99%

Thin gold layer in Ni electroforming process: optical surface characterization

et al. 2009

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Mandrel replication by Nickel electroforming is a well-suited process to manufacture X-ray mirrors, making use of Gold layer playing the twofold role of release agent and reflective coating. To increase the optical performances of mirrors it is crucial to minimize the impact of X-ray scattering effects related to surface microroughness, especially when the mirror is intended to operate in hard X-rays. In this case, the Gold layer simply acts as release agent because the reflection is demanded to interferential over-coatings. Even though the replicated optical surface is usually believed to reproduce the smooth topography of the master, a surface degradation is commonly observed. Such a worsening can also suffer from a contribution from the spontaneous roughness growth of the Gold layer itself: if this is the case, the mirror's optical quality could potentially benefit from the utilization of a thin Gold layer (< 100 nm) instead of the traditional thick gold layer (> 100 nm). To prove the effectiveness of the Gold thickness reduction, a microroughness characterization of replicated thin gold layers has been achieved. We report here a preliminary roughness study of 3 electroformed Ni samples replicated from a super-polished Zerodur flat master with various Gold layer thicknesses, in the spectral range 0.02-1000 µm. The study is organized as follows: (a) characterization of the 3 replicated samples; (b) comparison of the Gold roughness for thin vs. thick layers; (c) comparison of the two sides of Gold layers.

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Some Fundamentals of Optical Thin Film Growth

Cited by 14 publications

References 42 publications

Reliable determination of wavelength dependence of thin film refractive index

Reliable determination of wavelength dependence of thin film refractive index

Impact of different cleaning processes on the laser damage threshold of antireflection coatings for Z-Backlighter optics at Sandia National Laboratories

Thin gold layer in Ni electroforming process: optical surface characterization

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