The FDTD section presents an example of using FDTD for laser absorption simulations of locks. Fabrication of Si/glass AR coating by dual-beam pulsed laser deposition. a) Schematic representation of the entire experimental procedure for the fabrication of a Si/glass graded AR coating. Content profile and reflectance measurement results and FDTD simulation results for AR coatings without glass layer. a) XPS content profile measurement result for linear profile.
Content profile and reflectance measurement results and FDTD simulation results for AR coatings with a 400nm glass layer. a) XPS content profile measurement result for the linear profile. FDTD simulation results with a 1000 nm light on the focal point reduction of the graded layer. XPS peak fit example for the location shown with a blue arrow in (a) and (d); (d) Calculated DLC volume percentage at each location within the graded layer.
Imaging tests for the GRIN lens array with different microscopies. a) Image of total internal reflection microscopy with a halogen lamp; (b) Image of a photoactivated localization super-resolution microscopy with a laser beam of 1000 nm wavelength.
LIST OF TABLES
NOMENCLATURE
P: Laser power;
Current density;
Electric field;
Magnetic field;
- BACKGROUND AND MOTIVATION
- Introduction of Functionally graded coating depositions
- Pulsed laser deposition (PLD) .1 Mechanisms of PLD
- DUAL BEAM PULSED LASER DEPOSITION AND PULSE CONTROL SCHEME FOR FAST AND PRECISE DEPOSITIONS
- Pulsed laser deposition experimental setup
- Content profile design and pulse control scheme
- ELECTRODYNAMIC SIMULATION AS A DESIGN TOOL FOR OPTICAL COATINGS
- Maxwell equations for FDTD
- An example of using FDTD for electrodynamic simulations
- Conclusions
- BROADBAND ANTIREFLECTION COATING FOR SILICON- BASED SOLAR CELLS
- Introduction of AR coatings
- Design of the graded AR coating
- Fabrication of the graded AR coating
- Measured results
- Conclusions
- YSZ graded thermal barrier coatings for high temperature applications
- Introduction of thermal barrier coating
- Design of the thermal barrier coating
- Results of the graded thermal barrier coating
- FABRICATION OF ULTRA-SHORT FOCAL LENGTH INDEX- GRADED MICROLENS ARRAYS BY A FEMTOSECOND LASER
Functionally graded type, where the graded part serves as the working structure of the applications;. Depending on the types of materials and the functions of the applications, there are many different manufacturing methods for physical vapor deposition (PVD) and chemical vapor deposition (CVD) for the functionally divided materials, but all the methods can be divided into two groups. depending on their manufacturing types: mass transport or constructive processing[12, 13]. Some of the popular techniques in this category are listed in Figure 3[7, 11], such as powder metallurgy (PM), self-propagating high temperature synthesis (SHS) method for powder stacking method; PVD or CVD, or PVD/CVD combined, plasma spray method, laser coating method, pulsed laser deposition method, eletro deposition method for coating depositions[7, 11-18].
These low-energy particles land on the surface of the substrate and form a nucleus, initiating nucleation. For PLD, it is necessary to carefully decide on the appropriate laser energy flux for the PLD process of better quality coatings. Although the microstructure and quality of the applied coating are more related to the temperature of the substrate.
Depending on the location of the substrate, different particles (as in different appearances) can be deposited on the surface. Prior to any manufacturing process, the deposition rate of each material must be precisely known for the accurate design and manufacture of the graded layer. Knowing the deposition data for each material, the deposition scheme can be designed and calculated.
In this proposal, the FDTD algorithm is adopted for electrodynamic simulations of PLD-deposited optical coatings. And the possibility and quality of the process strongly depends on the amount of energy absorbed by the laser. The laser beam is numerically focused on the upper surface of the lock and propagates downwards.
This intense heating of the bottom region is clearly shown in Figure 11 (and also some cases in Figure 12). In Figure 17 we demonstrate the schematic of the manufacturing process of a functionally classified AR coating. Experimentally measured optical constants of the deposited silicon and glass were used for simulations (Figure 18a, b).
The same 355nm laser with a pulse pattern control technique is also used to design and manufacture the thermal protective coating. The atomic ratio between Fe(2p) and Zr(3d) can be calculated by knowing the XPS peak area ratios. This means that due to the graded content of SUS in the coating, the adhesion strength of the graded coating is good between the coating and the substrates.
ASSISTED WET ETCHING AND DUAL BEAM PULSED LASER DEPOSITION FOR NIR APPLICATIONS
Introduction
- Fabrication of concave lens template mold with femtosecond laser and wet etching Femtosecond laser assisted wet etching has been proved to be a very powerful and viable technique
- Fabrication of convex lenses with a replication process
- Graded deposition with a dual beam pulsed laser deposition
A novel dual-beam pulsed laser deposition technique was used to realize a 600 nm graded carbon/Si layer on top of the PDMS microlenses, making the lenses graded and shortening the focal length even more. This is the shortest focal length reported, and the first experimental realization of GRIN microlens arrays with dual beam pulsed laser deposition, to the best of the authors' knowledge. Imaging tests were also performed for the lenses before and after deposition, clear and uniform images were captured, showing very good optical imaging properties of the lenses.
Finally, a dual-beam pulsed laser deposition is performed to form a graded layer on top of the fabricated PDMS lenses, making the lenses graded in Figure 34c. The femtosecond laser (1030 nm, 220 fs, 200 kHz) is initially focused on the top surface of the fused silica substrate. Based on the measured results and the hyperbolic fitting curve of the lens profile, the focal length 𝑓 of the lens can be calculated based on the following equation[92],.
The calculated focal length of the microlenses is approximately 4.5 μm. a) SEM observations (tilted 45°) of the fabricated PDMS convex microlens array; (b) (c) Confocal measurements for 2D and 3D surface morphology of the fabricated PDMS lenses; (d) Measured lens profile and a hyperbolic fitting line. The intensity distribution (measured with a Laser Scanning Confocal Microscopy FV1000, Olympus) of the PDMS lens array is also examined with microscopes and CCD cameras. Figure 37.Image performance of the PDMS microlens array with a halogen lamp as the light source and a letter “S” as the image object.
Knowing the obtained deposition data for DLC and Si, the graded coatings can now be produced. Si and graphite are the main constituents of the graded coating, and the sputter etch rate ratio is assumed to be Si:C≈ 1:1 for simplicity. Therefore, 100% carbon or Si cannot be reached at both ends of the graded coating.
A dual-beam pulsed laser deposition was used to fabricate a 600 nm resolution DLC/Si layer on top of the PDMS microlenses, graduating the lenses and further shortening the focal length. The focal length has been increased by 29.6% and the N.A. has been increased by ~66% due to the existence of the 600 nm coating.
CONCLUSIONS AND FUTURE WORK
In this study, the experimentally measured keyhole shapes were used for simulation, and the beam divergence, polarization, and laser focusing characteristics were matched. In this case, concentrated heating will occur and the lower opening will be forced to open again. This is supposed to be the mechanism for opening and closing the bottom opening of the lock.
For uncoated steel, the lock absorption decreases as Iot1/2 increases, and the pattern is very regular. For galvanized steel, the absorption of the lock first decreases sharply and then increases slightly to follow the trend of uncoated steel. AR coatings were deposited on silicon substrates and the graded index was achieved by continuously controlling the volume fraction of silicon and glass along the coating thickness direction based on the rule of mixture for the refractive index.
In the case of the Southwell profile with a 400 nm clear glass layer, the AR performance was found to be 2.2~4%, which can be considered close to the theoretically best performance of silicon-based solar cells with a protective cover glass. It can simplify the structure of solar cells significantly because from the solar cell to the outer cover glass the composition changes continuously from silicon to glass and the whole structure can be fabricated by a PLD procedure. The deposited YSZ coatings showed a good thermal barrier characteristic (thermal conductivity of ∼1.14W/(m·K)) and the classified area provided much improved adhesion strength compared to the pure YSZ coatings.
In this study, the successful design, fabrication, and characterization of an index-graded ultra-short focal length microlens array is reported. The negative microlens array was used as a template for duplicating convex polydimethylsioxane (PDMS) microlens arrays. It is proven that the fabricated positive PDMS microlens array has an ultra-small lens diameter of ~6 μm and a sag height of ~1.6 μm, yielding an ultra-short focal length of ~4.12 μm and a high NA value of 0.73.
The content profile of the sorted area is confirmed by XPS depth profiling analysis, the measured results are in good agreement with the design, so the sorted index profile is expected. Due to the defocusing effect caused by material ablation during deposition, we need to move the target materials to maintain a continuous and strong plasma, and this problem can be solved by dynamic control of the target holders.
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ACKNOWLEDGEMENTS
