DOCSLIB.ORG

Lens Design Tips

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lens Design Tips Lens Design Tips Richard Juergens Adjunct Fellow in Optical Design [email protected] Opti 517 Anatomy of a Lens Edge thickness (ET) Usually fine ground Edge blackening reduces stray light Outer diameter (OD) Clear aperture (which Clear may go to the annulus) aperture (CA) Annulus or sag flat Sag Center thickness (CT) Sharp corners (≤ 90°) usually chamfered to 0.5 mm face width 2 Used Optical Beams and Footprints Beam footprint(s) Outer diameter (OD) On-axis beam Coating aperture or clear aperture (CA) Lens diameter does not necessarily define the used footprint for a given field 3 Lens Geometry: Edge Thickness • Lenses are usually oversized 1-2 mm during fabrication – Chipping may occur at the edges, prompting the oversize margin – If too little margin, scratch/dig specifications may be compromised • On steep radii surfaces, allow for more oversize margin • In CODE V, the MNE general constraint (minimum edge thickness) in AUTO only constrains the ET over the clear apertures – To constrain ET over a larger physical diameter during AUTO, use ET Sk MEC [overage_factor [overage_constant]] > target ET > 1.0 mm Oversized for fabrication Margin for manufacturing Max ray heights Margin for mounting and coating tooling Final ET sized appropriately 4 Lens Geometry: Long Radius • Long radii are hard to test – During use of test plates in production – On a radius slide or on an interferometer • If a radius approaches 20x the outer diameter, make the surface flat • To constrain this in CODEV, use a user-defined constraint in AUTO @ratio_sj == 0.5*absf((rdy sj)/(sd sj)) DSP ratio_sj @ratio_sj < 20 < 20 Radius Outer Diameter (OD) 5 Lens Geometry: Aspect Ratio • High aspect ratios risk surface irregularities due to springing after deblocking • In CODE V, the aspect ratio can be constrained during AUTO with ATC Sk [MEC [overage_factor [overage_constant]]] >=< target ATE SK [MEC [overage_factor [overage_constant]]] >=< target For example, ATC S3 MEC 1.0 1.0 > 3 < 12.5 ET 3 < < 12.5 Outer Outer diameter CT diameter (OD) (OD) = = 6 Lens Geometry: Focal Length • Lens centering machines (e.g., from Trioptics) work off beam deviations • Long focal length singlets and doublets can lead to measurement errors • Simple optimization constraint can save fabrication difficulties with centering – |EFLcomponent| < 500 mm to avoid problems – In CODE V, use the constraint in AUTO EFY Sj..k < pos_target or EFY Sj..k > neg_target – You can also use @EFLjk == absf((efy sj..k)) DSP @EFLjk @EFLjk < target Trioptics top w/ headlens V-Chuck Spins about vertical axis Trioptics bottom 7 Spherical Aberration as an Assembly Metric • A well-designed optical system balances every surface’s spherical aberration to minimize the sum of the spherical aberration content at the image plane • Lateral shear of spherical wavefronts produces coma • Coma produces the largest MTF drop to MTF compared to other aberrations • Constraining the maximum surface spherical aberration reduces the sensitivity of the surface to decenter and reduces the costs of tolerances and assembly TS Diff. Limit TS 0.0000, 3.0000 (deg) TS 0.0000, 0.0000 (deg) 1.0000 TS 0.0000, 2.1213 (deg) 1.0 0.9000 0.9 0.8000 0.8 0.7000 0.7 0.6 0.6000 0.5 0.5000 Wavefront 0.4 0.4000 0.3 0.3000 λ/15 PTV Modulus of the OTF 0.2 0.2000 λ/50 RMS 0.1 0.1000 0.0 0 160 320 480 640 800 960 1120 1280 1440 1600 Spatial Frequency in cycles per mm 0.0000 Centered Polychromatic Diffraction MTF Interferogram between reference beam and Configuration 1 V1Enoch.len V1Enoch.len 5/24/2018 5/24/2018 Y Data for 0.4861 to 0.6563 µm. 0.5461 µm at 0.0000, 0.0000 (deg). Surface: Image Peak to Valley = 0.0656 waves, Fringes/Wave = 1.0000. X Z Surface: Image V1Enoch.zmx Exit Pupil Diameter: 4.1908E+000 Millimeters V1Enoch.zmx Configuration 1 of 1 Xtilt = 0.00, Ytilt = 0.00. TS Diff. Limit TS 0.0000, 3.0000 (deg) TS 0.0000, 0.0000 (deg) 1.0000 TS 0.0000, 2.1213 (deg) 1.0 0.9000 0.9 0.8000 0.8 0.7000 0.7 0.6 0.6000 0.5 0.5000 Wavefront 0.4 0.4000 0.3 3λ PTV 0.3000 Modulus of the OTF 0.2 0.2000 λ/2 RMS 0.1 0.1000 0.0 0 160 320 480 640 800 960 1120 1280 1440 1600 Spatial Frequency in cycles per mm 0.0000 Polychromatic Diffraction MTF Interferogram between reference beam and Configuration 1 V1Enoch.len V1Enoch.len +100µm Decenter 5/24/2018 5/24/2018 Y Data for 0.4861 to 0.6563 µm. 0.5461 µm at 0.0000, 0.0000 (deg). 8 Surface: Image Peak to Valley = 3.2451 waves, Fringes/Wave = 1.0000. X Z Surface: Image V1Enoch.zmx Exit Pupil Diameter: 4.1903E+000 Millimeters V1Enoch.zmx Configuration 1 of 1 Xtilt = 0.00, Ytilt = 0.00. Surface Spherical Aberration Theory Figures from “Optical Shop Testing”, Malacara Reduce Reduce Tolerance? surface SA! Reduced surface SA reduces axial coma induced by tilted and decentered elements 9 SA Desensitization in Optical Design Optical Design iteration #1 without Surface SA constraints Optical Design iteration #2 With Surface SA constraints Minimizing the maximum surface SA "spreads the pain" among all the elements 10 Surface SA Goal Based on F/# and MTF Drop These are empirically based on measured data for many lens assemblies fabricated at Edmund Optics Target the maximum surface SA based on the allowable MTF drop and the system f/number 11 Constraining the Maximum Surface SA • To constrain the surface spherical aberration in waves for surface Sk in AUTO, use the following (for dimensions in mm) AUTO ... ^sa_target == 2 ^ref == (ref) ^sa_sk == absf((sa sk)/8/((wl w^ref)/1e6)/2) dsp ^sa_sk ^sa_sk < ^sa_target ... 12 Optical System Color Correction Regimes • Refractive optical systems have to color correct for the defocus due to glass dispersion • There are many solutions available, primary, achromatic, apochromatic, etc. • The level of correction and first order optical properties can impose heavy requirements on glass tolerances 13 Achromatic Lens Design • Correcting secondary color requires consideration of a parameter called the partial dispersion • Partial dispersion is defined for four wavelengths across the spectral band P = (nl1 - nl2) / (nl3 - nl4) • Correcting secondary color takes special glasses whose partial dispersions are different from "normal" glasses – These glasses cost significantly more than "normal" glasses – Most glasses follow a "normal" line • The technique is to find two glasses that have reasonably similar partial dispersions, but have different V values – Use these glasses with the standard achromatic equations to solve for the lens powers • If the V values are too close together, the lens powers will be strong, and the lenses will be "fat" – This will introduce significant spherochromatism (change in spherical aberration with wavelength) due to the higher angles of incidence 14 Partial Dispersion Map Normal line PSK53 10 X Cost of BK7 15 Reduction of Secondary Color PSK53 – KZFSN4 BK7 – SF2 PSK53 is10x cost of BK7 SF2 is 1x cost of BK7 KZFSN4 is 6x cost of BK7 0.0060 0.0040 0.0030 0.0040 0.0020 0.0010 0.0020 0.0000 480. 520. 560. 600. 640. 680. 0.0000 480. 520. 560. 600. 640. 680. -0.0010 FOCUS SHIFT (in) FOCUS SHIFT (in) -0.0020 -0.0020 -0.0030 -0.0040 -0.0040 WAVELENGTH (nm) WAVELENGTH (nm) 16 Apochromatic Design • Apochromatic lenses (significantly reduced secondary color) can be designed using three different glasses Tij is the slope of the line between glasses i and j All three lenses will be as weak as possible if glasses are selected with large E1, E2, E3 17 Apochromatic Design Example 0.345 0.340 0.335 S-TIL27 0.330 0.325 S-FPL51 0.320 0.315 0.310 0.305 Partial Value 0.300 0.295 S-NPH2 0 20 40 60 80 V Value 18 Apochromatic Example Performance Compare with standard N-BK7 – F2 doublet 19 Surface Axial Color • Optical design tools for material selection have become very adept at locating new solutions for color correction – Glass substitution and Hammer in Zemax – Glass Expert in Code V • Unfortunately, solutions can be found which are very sensitive to material dispersion tolerances – Commercial dispersion tolerances typically range between 0.8% and 0.5% • Surface axial color is proportional to glass tolerances 20 Sensitivity to Glass Dispersion 21 Controlling Surface Axial Color • In CODE V, use a user-defined constraint for each sensitive lens – For example, AUTO ... ^LCA_Target == 0.01 @LCA_E2 == absf((ax s3)+(ax s4)) @LCA_E2 < ^LCA_TARGET ... • Use third-order coefficients (THO output) to identify sensitive lenses 22 Sample Design • Linescan lens requirement: – Polychromatic focus, high resolution – Red, green, or blue monochromatic high resolution without refocus – Apochromatic solution too costly (elements with short EFL and sensitive to mount) • Solution: Achromat with secondary color ~1/2 diffraction-limited DoF Reducing surface axial color in half allowed the use of standard grade catalog glasses vs. requiring melt fitting 23 Passive Athermalization • Due to lenses' CTEs and dn/dTs and the housing's CTE, optical systems often go out of focus with changes in temperature – This is OK if you have a focus adjustment (man-in-the-loop) • For stand-alone systems (no man-in-the-loop), it may be necessary to design the optical system to be passively athermal • A lens can be represented by its plano-convex equivalent – F = r/(n-1) • The thermal derivative of this is dF 1 dr r dn ræ 1 dr 1 dn ö æ 1 dn ö = -2 =ç - ÷ =F ç a - ÷ dT n----- 1 dT (n 1) dT n 1è r dT n 1 dT ø è n 1 dT ø • The change in focal length is then DF = n FDT where 1 dn n = a - n- 1 dT – n is often referred to as the thermo-optic coefficient 24 n Values of Optical Materials (x106/°C) • Visible glasses N-BK7 -1.5
Load more

Recommended publications
  • Simple Method for Measuring the Zero-Dispersion Wavelength in Optical Fibers Maxime Droques, Benoit Barviau, Alexandre Kudlinski, Géraud Bouwmans and Arnaud Mussot
    Simple Method for Measuring the Zero-Dispersion Wavelength in Optical Fibers Maxime Droques, Benoit Barviau, Alexandre Kudlinski, Géraud Bouwmans and Arnaud Mussot Abstract— We propose a very simple method for measuring the zero-dispersion wavelength of an optical fiber as well as the ratio between the third- and fourth-order dispersion terms. The method is based on the four wave mixing process when pumping the fiber in the normal dispersion region, and only requires the measurement of two spectra, provided that a source tunable near the zero- dispersion wavelength is available. We provide an experimental demonstration of the method in a photonic crystal fiber and we show that the measured zero-dispersion wavelength is in good agreement with a low-coherence interferometry measurement. Index Terms— Photonic crystal fiber, four-wave-mixing, chromatic dispersion, zero-dispersion wavelength. I. INTRODUCTION Group velocity dispersion (GVD) is one of the key characteristics of optical fibers. It is thus important to be able to accurately measure this parameter. The techniques developed to reach this goal can be divided into two main categories: the ones based on linear processes, such as time-of-flight, phase-shift or interferometric measurements [1-4]; and the ones based on nonlinear effects, such as four wave mixing (FWM), mainly [5-8]. The main advantage of these last ones is that the GVD measurement can be made in fiber samples ranging from a few meters up to hundred of meters long, while linear techniques are restricted to either very short samples (in the meter range) or to very long ones (in the kilometer range).
    [Show full text]
  • Tauc-Lorentz Dispersion Formula
    TN11 Tauc-Lorentz Dispersion Formula Spectroscopic ellipsometry (SE) is a technique based on the measurement of the relative phase change of re- flected and polarized light in order to characterize thin film optical functions and other properties. The meas- ured SE data are used to describe a model where layers refer to given materials. The model uses mathematical relations called dispersion formulae that help to evaluate the material’s optical properties by adjusting specific fit parameters. This technical note deals with Tauc-Lorentz dispersion formula. Theoretical model The real part εr,TL of the dielectric function is derived from the expression of εi using the Kramers-Kronig integration. Jellison and Modine developed this model (1996) using Then, it comes the following expression for εi: the Tauc joint density of states and the Lorentz oscillator. The complex dielectric function is : 2 ∞ ξ ⋅ε ()ξ ε ()E = ε ()∞ + ⋅ P ⋅ i dξ ()5 ~ε =ε + i ⋅ε =ε + i ⋅(ε × ε ) (1) r r π ∫ ξ 2 − E 2 TL r,TL i,TL r,TL i,T i, L Eg Here the imaginary part εi,TL of the dielectric function is where P is the Cauchy principal value containing the resi- given by the product of imaginary part of Tauc’s (1966) dues of the integral at poles located on lower half of the dielectric εi,T function with Lorentz one εi,L. In the approx- complex plane and along the real axis. imation of parabolic bands, Tauc’s dielectric function de- According to Jellison and Modine (Ref. 1), the derivation scribes inter-band transitions above the band edge as : of the previous integral yields : E − E 2 ⎛ g ⎞ 2 2 εi,T ()E > Eg = AT ⋅⎜ ⎟ ()2 A⋅C ⋅a ⎡ E + E + α ⋅ E ⎤ ⎜ E ⎟ ln 0 g g ⎝ ⎠ εr,TL ()E = ε∞ + 4 ⋅ln⎢ 2 2 ⎥ where : 2⋅π ⋅ζ ⋅α ⋅ E0 ⎣⎢ E0 + Eg − α ⋅ Eg ⎦⎥ -A is the Tauc coefficient T A a ⎡ ⎛ 2⋅ E + α ⎞ - E is the photon energy − ⋅ a tan ⋅ π − arctan⎜ g ⎟ + 4 ⎢ ⎜ ⎟ K -Eg is the optical band gap π ζ ⋅ E0 ⎣ ⎝ C ⎠ The imaginary part of Tauc’s dielectric function gives the ⎛ α − 2⋅ E ⎞⎤ response of the material caused by inter-band mecha- g + arctan⎜ ⎟⎥ nisms only : thus εi, T (E ≤ Eg) = 0.
    [Show full text]
  • Section 5: Optical Amplifiers
    SECTION 5: OPTICAL AMPLIFIERS 1 OPTICAL AMPLIFIERS S In order to transmit signals over long distances (>100 km) it is necessary to compensate for attenuation losses within the fiber. S Initially this was accomplished with an optoelectronic module consisting of an optical receiver, a regeneration and equalization system, and an optical transmitter to send the data. S Although functional this arrangement is limited by the optical to electrical and electrical to optical conversions. Fiber Fiber OE OE Rx Tx Electronic Amp Optical Equalization Signal Optical Regeneration Out Signal In S Several types of optical amplifiers have since been demonstrated to replace the OE – electronic regeneration systems. S These systems eliminate the need for E-O and O-E conversions. S This is one of the main reasons for the success of today’s optical communications systems. 2 OPTICAL AMPLIFIERS The general form of an optical amplifier: PUMP Power Amplified Weak Fiber Signal Signal Fiber Optical AMP Medium Optical Signal Optical Out Signal In Some types of OAs that have been demonstrated include: S Semiconductor optical amplifiers (SOAs) S Fiber Raman and Brillouin amplifiers S Rare earth doped fiber amplifiers (erbium – EDFA 1500 nm, praseodymium – PDFA 1300 nm) The most practical optical amplifiers to date include the SOA and EDFA types. New pumping methods and materials are also improving the performance of Raman amplifiers. 3 Characteristics of SOA types: S Polarization dependent – require polarization maintaining fiber S Relatively high gain ~20 dB S Output saturation power 5-10 dBm S Large BW S Can operate at 800, 1300, and 1500 nm wavelength regions.
    [Show full text]
  • Examples of Translucent Objects
    Examples Of Translucent Objects Chancier and ecclesiological Chan never nebulise his heroes! Afternoon and affirmable Garvin often arterialised some yokes glisteringly or nuggets jealously. Rationalist and papist Erastus attunes while frogged Robb descant her mercs anaerobically and misclassifies moistly. You wish them, a whole and water droplets in translucent materials, like to be directed to translucent, and translucency is pumpkin seed oil. Learn more energy when the error you found that is diffused and table into light? Light can see more light through the image used in illumination affects the number of the materials differ. Explain the examples of a technically precise result. Assigned two example, the teaching for online counselling session has. If the object scatters light. Opaque objects examples intersecting volumes clad in translucency rating increases with textiles and we examined the example of these materials, it can you? Learn from objects examples of translucency controls are called translucent object has a great instructors. Opaque materials which the example of light to authenticated users to work the question together your new class can exit this activity to contact with. Please reload this means cannot see through a lahu man smoking against the of examples of how the choice between a few moving parts that a meaning they transmit. You study the object is. Here ߤ and examples of object looktranslucent or water spray, they interact with every day. Raft product for example of objects, the patterns and to. Students to object, but it allows us improve the example of material appears here is. Emailing our online counselling session expired game yet when describing phenomena such objects? You some examples of translucency image as an example of.
    [Show full text]
  • Chapter 19/ Optical Properties
    Chapter 19 /Optical Properties The four notched and transpar- ent rods shown in this photograph demonstrate the phenomenon of photoelasticity. When elastically deformed, the optical properties (e.g., index of refraction) of a photoelastic specimen become anisotropic. Using a special optical system and polarized light, the stress distribution within the speci- men may be deduced from inter- ference fringes that are produced. These fringes within the four photoelastic specimens shown in the photograph indicate how the stress concentration and distribu- tion change with notch geometry for an axial tensile stress. (Photo- graph courtesy of Measurements Group, Inc., Raleigh, North Carolina.) Why Study the Optical Properties of Materials? When materials are exposed to electromagnetic radia- materials, we note that the performance of optical tion, it is sometimes important to be able to predict fibers is increased by introducing a gradual variation and alter their responses. This is possible when we are of the index of refraction (i.e., a graded index) at the familiar with their optical properties, and understand outer surface of the fiber. This is accomplished by the mechanisms responsible for their optical behaviors. the addition of specific impurities in controlled For example, in Section 19.14 on optical fiber concentrations. 766 Learning Objectives After careful study of this chapter you should be able to do the following: 1. Compute the energy of a photon given its fre- 5. Describe the mechanism of photon absorption quency and the value of Planck’s constant. for (a) high-purity insulators and semiconduc- 2. Briefly describe electronic polarization that re- tors, and (b) insulators and semiconductors that sults from electromagnetic radiation-atomic in- contain electrically active defects.
    [Show full text]
  • Principles and Applications of CVD Powder Technology
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Open Archive Toulouse Archive Ouverte Principles and applications of CVD powder technology Constantin Vahlas, Brigitte Caussat, Philippe Serp and George N. Angelopoulos Centre Interuniversitaire de Recherche et d’Ingénierie des Matériaux, CIRIMAT-UMR CNRS 5085, ENSIACET-INPT, 118 Route de Narbonne, 31077 Toulouse cedex 4, France Laboratoire de Génie Chimique, LGC-UMR CNRS 5503, ENSIACET-INPT, 5 rue Paulin Talabot, BP1301, 31106 Toulouse cedex 1, France Laboratoire de Catalyse, Chimie Fine et Polymères, LCCFP-INPT, ENSIACET, 118 Route de Narbonne, 31077 Toulouse cedex 4, France Department of Chemical Engineering, University of Patras, University Campus, 26500 Patras, Greece Abstract Chemical vapor deposition (CVD) is an important technique for surface modification of powders through either grafting or deposition of films and coatings. The efficiency of this complex process primarily depends on appropriate contact between the reactive gas phase and the solid particles to be treated. Based on this requirement, the first part of this review focuses on the ways to ensure such contact and particularly on the formation of fluidized beds. Combination of constraints due to both fluidization and chemical vapor deposition leads to the definition of different types of reactors as an alternative to classical fluidized beds, such as spouted beds, circulating beds operating in turbulent and fast-transport regimes or vibro- fluidized beds. They operate under thermal but also plasma activation of the reactive gas and their design mainly depends on the type of powders to be treated. Modeling of both reactors and operating conditions is a valuable tool for understanding and optimizing these complex processes and materials.
    [Show full text]
  • Optical Properties and Phase-Change Transition in Ge2sb2te5 Flash Evaporated Thin Films Studied by Temperature Dependent Spectroscopic Ellipsometry
    Optical properties and phase-change transition in Ge2Sb2Te5 flash evaporated thin films studied by temperature dependent spectroscopic ellipsometry J. Orava1*, T. Wágner1, J. Šik2, J. Přikryl1, L. Beneš3, M. Frumar1 1Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Cs. Legion’s Sq. 565, Pardubice, 532 10 Czech Republic 2ON Semiconductor Czech Republic, R&D Europe, 1. máje 2230, Rožnov pod Radhoštěm, 756 61 Czech Republic 3Joint Laboratory of Solid State Chemistry of the Institute of Macromolecular Chemistry AS CR, v.v.i. and University of Pardubice, Studentská 84, Pardubice, 53210 Czech Republic *Corresponding author: tel.: +420 466 037 220, fax: +420 466 037 311 *E-mail address: [email protected] Keywords: Ge2Sb2Te5, optical properties, ellipsometry, amorphous, fcc PACs: 07.60.Fs, 77.84.Bw, 78.20.-e, 78.20.Bh Abstract We studied the optical properties of as-prepared (amorphous) and thermally crystallized (fcc) flash evaporated Ge2Sb2Te5 thin films using variable angle spectroscopic ellipsometry in the photon energy range 0.54 - 4.13 eV. We employed Tauc-Lorentz model (TL) and Cody- Lorentz model (CL) for amorphous phase and Tauc-Lorentz model with one additional Gaussian oscillator for fcc phase data analysis. The amorphous phase has optical bandgap opt energy Eg = 0.65 eV (TL) or 0.63 eV (CL) slightly dependent on used model. The Urbach edge of amorphous thin film was found to be ~ 70 meV. Both models behave very similarly and accurately fit to the experimental data at energies above 1 eV. The Cody-Lorentz model is more accurate in describing dielectric function in the absorption onset region.
    [Show full text]
  • The Plumbers Telescope-English
    240.BLT KLAUS HÜNIG than 10mm. Use sandpaper to smooth the hole and then roughen the inside of the plug The Plumber’s Telescope to provide a good base for the glue. Remove Kit for an astronomical refracting telescope with Put a small amount of glue evenly all dust and loose plastic bits. 30x magnification, fromusing any 40mm local drain DIY pipes store around the inner side of the end with the Step 8: tags, again without drops or strings. Apply a generous amount of glue onto the Push the eyepiece into the holder from disk holding the eyepiece and fit it into the the tag side and slide it into place by socket plug so that the hole in the disk sits pushing it onto the work surface so it is centrally over the hole in the plug. Again flush with the six tags. take care that no glue gets onto the surface of the lens. After the glue has set, push the plug into the second push-fit coupling. This •Achromatic objective lens, finishes the construction of the eyepiece Ø 40mm, f +450mm holder. •Colour corrected Plössl eyepiece, 15mm, f +15mm Step 5: D. The final assembly Ø Open the 11mm central hole in Part C Step 9: •Tripod adapter (without tripod) Remove the rubber seal from the open end of (blind) using a sharp knife and then •Indestructible HT tubing Shopping list for the DIY store: remove the part from the cardboard. the eyepiece holder. Then fit the eyepiece Fold the six tags backwards and glue the holder on the open end of the objective lens •Shows Moon craters, phases tube.
    [Show full text]
  • Chemical Vapour Deposition of Graphene—Synthesis, Characterisation, and Applications: a Review
    molecules Review Chemical Vapour Deposition of Graphene—Synthesis, Characterisation, and Applications: A Review Maryam Saeed 1,*, Yousef Alshammari 2, Shereen A. Majeed 3 and Eissa Al-Nasrallah 1 1 Energy and Building Research Centre, Kuwait Institute for Scientific Research, P.O. Box 24885, Safat 13109, Kuwait; [email protected] 2 Waikato Centre for Advanced Materials, School of Engineering, The University of Waikato, Hamilton 3240, New Zealand; [email protected] 3 Department of Chemistry, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait; [email protected] * Correspondence: [email protected]; Tel.: +965-99490373 Received: 8 July 2020; Accepted: 18 August 2020; Published: 25 August 2020 Abstract: Graphene as the 2D material with extraordinary properties has attracted the interest of research communities to master the synthesis of this remarkable material at a large scale without sacrificing the quality. Although Top-Down and Bottom-Up approaches produce graphene of different quality, chemical vapour deposition (CVD) stands as the most promising technique. This review details the leading CVD methods for graphene growth, including hot-wall, cold-wall and plasma-enhanced CVD. The role of process conditions and growth substrates on the nucleation and growth of graphene film are thoroughly discussed. The essential characterisation techniques in the study of CVD-grown graphene are reported, highlighting the characteristics of a sample which can be extracted from those techniques. This review also offers a brief overview of the applications to which CVD-grown graphene is well-suited, drawing particular attention to its potential in the sectors of energy and electronic devices.
    [Show full text]
  • Different Types of Dispersions in an Optical Fiber
    International Journal of Scientific and Research Publications, Volume 2, Issue 12, December 2012 1 ISSN 2250-3153 Different Types of Dispersions in an Optical Fiber N.Ravi Teja, M.Aneesh Babu, T.R.S.Prasad, T.Ravi B.tech Final Year Students (ECE) ,KL University, Vaddeswaram, Andhra Pradesh, India. Abstract- The intended application of our Different Types of Dispersions in an optical fiber. In this report we discuss about the III. ADVANTAGES OF FIBER OPTICS Optical Fiber and its advantages, Theory and principles of the Fiber Optics has the following advantages: fiber optics, Fiber geometry, Types of optical fiber, Different (I) Optical Fibers are non-conductive (Dielectrics). parameters and characteristics of fiber are also explained. Fiber (II) Electromagnetic Immunity: has linear and non-linear characteristics. Linear characteristics (III) Large Bandwidth (> 5.0 GHz for 1 km length) are wavelength window, bandwidth, attenuation and dispersion. (IV) Small, Lightweight cables. Non-linear characteristics depend on the fiber manufacturing, (V) Security. geometry etc.Dispersion is the spreading of light pulse as its travels down the length of an optical fiber. Dispersion limits the Principle of Operation - Theory bandwidth or information carrying capacity of a fiber. Total Internal Reflection - The Reflection that Occurs when a Light Ray Travelling in One Material Hits a Different Material Index Terms- Optical Fibers, Dispersions, Modal Dispersions, and Reflects Back into the Original Material without any Loss of Material Dispersion, Wave Guide Dispersions, Polarization Light Dispersions, Chromatic Dispersions. I. INTRODUCTION opper wires have been used in data transmission since the C invention of the telephone in 1876. But as the demand increased, the use of copper wires consistently got reduced due to many reasons such as low bandwidth, short transmission length and inefficiency.
    [Show full text]
  • Porcelain Enamel Coatings, from the Past to the Future: Solved and Unsolved Issues for the Improvement of Their Mechanical Properties
    Porcelain enamel coatings, from the past to the future: solved and unsolved issues for the improvement of their mechanical properties. Created by: Stefano Rossi , Francesca Russo Version received: 1 May 2020 Porcelain enamel coatings have their origins in ancient times when they were mainly used for decorative and ornamental purposes. From the industrial revolution onwards, these coatings have started to be used also as functional layers, ranging from home applications up to the use in high-technological fields, such as in chemical reactors. The excellent properties of enamel coatings, such as fire resistance, protection of the substrate from corrosion, resistance to atmospheric and chemical degradation, mainly depend and originate from the glassy nature of the enamel matrix itself. On the other side, the vitreous nature of enamel coatings limits their application in many fields, where mechanical stress and heavy abrasion phenomena could lead to nucleation and propagation of cracks inside the material, thus negatively affecting the protective properties of this coating. Many efforts have been made to improve the abrasion resistance of enamelled materials. On this regard, researchers showed encouraging results and proposed many different improvement approaches. Now it is possible to obtain enamels with enhanced resistance to abrasion. Differently, the investigation of the mechanical properties of enamel coatings remains a poorly studied topic. In the literature, there are interesting methodological ideas, which could be successfully applied to the mechanical study of enamelled materials and could allow to have further insights on their behaviour. Thus, the path that should be followed in the future includes the mechanical characterization of these coatings and the search for new solutions to address their brittle behaviour.
    [Show full text]
  • Buying a Home Microscope
    Buying a Home Microscope The process of ecological restoration requires many tools. I initially learned about prescribed burns, pumper units, backpack sprayers, and Parsnip Predators. But there are 2 other tools that I’ve found important in my quest to learn more about all aspects of ecological restoration, a camera and a microscope! I imagine my journey through restoring prairies, savannas, woodlands, and wetlands began in about the same as many others…learning about the plants and learning techniques for managing the plants. I dove into this head first! I began taking photos of every aspect of the plants that I could. I wanted photos of stems, leaves, petals, stamens, sepals, and seeds. I wanted photos of each plant through their growth stages from seedlings, to vegetation, to flowering, to senescence. The more photos I took and the more I learned, the bigger the picture of the restoration became. I realized there were many aspects working together to make this restoration successful. There was the soil and its ecosystem and processes and there were the insects, the birds, the mammals, the reptiles, the amphibians, and the fungi to consider. The biggest question that niggled at me was how could I possibly create a management plan when the only aspect of the land I knew about were the plants. Well, I also knew a great deal about the birds and their relationship to the plants, but I needed to know much more. I began studying the other aspects!! And once I was through the mammals, reptiles, and amphibians, the subjects started getting smaller and smaller and smaller.
    [Show full text]