Compound prism design principles, III: linear-in-wavenumber and optical coherence tomography prisms

We extend the work of the first two papers in this series [Appl. Opt. 50, 4998-5011 (2011), Appl. Opt. 50, 5012-5022 (2011)] to design compound prisms for linear-in-wavenumber dispersion, especially for application in spectral domain optical coherence tomography (OCT). These dispersive prism designs are believed to be the first to meet the requirements of high resolution OCT systems in direct-view geometry, where they can be used to shrink system size, to improve light throughput, to reduce stray light, and to reduce errors resulting from interpolating between wavelength- and wavenumber-sampled domains. We show prism designs that can be used for thermal sources or for wideband superluminescent diodes centered around wavelengths 850, 900, 1300, and 1375 nm.     

Compound prism design principles, II: triplet and Janssen prisms

Continuing the work of the first paper in this series [Appl. Opt. 50, 4998-5011 (2011)], we extend our design methods to compound prisms composed of three independent elements. The increased degrees of freedom of these asymmetric prisms allow designers to achieve greatly improved dispersion linearity. They also, however, require a more careful tailoring of the merit function to achieve design targets, and so we present several new operands for manipulating the compound prisms' design algorithm. We show that with asymmetric triplet prisms, one can linearize the angular dispersion such that the spectral sampling rate varies by no more than 4% across the entire visible spectral range. Doing this, however, requires large prisms and causes beam compression. By adding a beam compression penalty to the merit function, we show that one can compromise between dispersion linearity and beam compression in order to produce practical systems. For prisms that do not deviate the beam, we show that Janssen prisms provide a form that maintains the degrees of freedom of the triplet and that are capable of up to 32° of dispersion across the visible spectral range. Finally, in order to showcase some of the design flexibility of three-element prisms, we also show how to design for higher-order spectral dispersion to create a two-dimensional spectrum.     

Method of noncontact optical measurement of the diameter of transparent tubes

Translated from Izmeritel'naya Tekhnika, No. 6, pp. 13–14, June, 1990.     

Second-order nonlinear optical susceptibility measurement of crystal with a glass prism in total-reflection geometry

Second-harmonic generation in a uniaxial crystal in total-reflection geometry is precisely measured. A Y-cut plate and a Z-cut plate of quartz crystals were used as samples. The incident wave is totally reflected by a glass prism in contact with the sample crystal, and an evanescent wave penetrates into the sample as a fundamental wave. The results gave the quantitative values of the components for a nonlinear optical susceptibility tensor with various polarizations and with Y-cut and Z-cut quartz plates. This technique can be applied to various samples to evaluate their nonlinear optical efficiencies.     

Refractive-index measurement of bulk materials: prism coupling method

A simple method of measuring refractive indices of bulk materials using a prism coupling procedure is described. Refractive indices are determined from the measurement of the angle incident to the prism at which total reflection on the prism base breaks. This method is shown to possess the advantages of its simple procedure and sample preparation. The accuracy is comparable with that of minimum deviation method if the prism is well calibrated. Experimental results for several materials are given with an evaluation of possible errors.     

Simple technique for the measurement of two-dimensional linear retardation distributions of wave plates with a phase-shifting Nomarski prism

What we believe to be a new technique for the measurement of two-dimensional retardation distributions of a wave plate (WP) is presented. Phase-shifting interferometry has been applied for determining the relative retardation distribution using a Nomarski prism (NP) as a phase shifter. Absolute retardation distribution is obtained by accurately determining the position of zero retardation in the interference field using white light interference fringes and adjusting the phase distribution with respect to the zero retardation position. The measured absolute retardation distribution of the NP is subtracted from that obtained for the combination of the WP and NP, to get the desired retardation distributions for the WP. The technique is suitable for the measurement of phase retardation of both single and multiple order WPs, as the actual phase retardation distributions are obtained. Results obtained for WPs are presented.     

Long-term optical quality of the photoablated cornea

High-order coreal wavefront analysis was performed in a population of 60 myopic eyes that underwent photorefractive keratectomy. Corneal aberration data over 3, 5, and 7 mm pupils were collected for up to three years after surgery. The optical performance of the anterior cornea was characterized by estimation of the modulation transfer function (MTF) and the point-spread function. The high-order corneal wavefront aberrations were shown to stabilize one year after surgery. Over photopic pupils, after an early slight increase, corneal RMS-high-order aberrations (HOA) tended to decrease toward preoperative values. On the other hand, over mid- and large-pupil sizes, corneal HOA significantly increased compared with the preoperative state, while the optical performance of the cornea was diminished. The MTF ratio showed a distinct decline in the optical quality of postoperative corneas at low and middle spatial frequencies over larger pupils in the range between 6 and 19 c/deg, especially for deeper ablations.     

The design,preparation and optical measurement of thin film polarizers

The general approach to the design of thin film polarizers is outlined by reference to the principle of equivalent layers, and an analytical expression is derived for the number of quarter-wave layers required in a mirror structure to provide a specified polarization transmittance ratio $\text{(ifP =}\text{T}{}_{\mathrm{?}}\text{T}{}_{\mathrm{\perp }}\text{)}$. It is shown that the high polarization ratio and the small sensitivity of this parameter to the angle of incidence are conflicting specifications which require a compromise solution in practice. Also, to achieve simple and precise monitoring of the optical properties of the layers during deposition, double half-wave filter systems are shown to be preferable to multilayer quarter-wave mirrors as polarizers.The results of measurements on double half-wave polarizers for use with large aperture Pockel's cell shutters and Faraday isolators in high power neodymium glass lasers are presented with particular reference to transmittance, polarization ratio, superficial unifromity and laser damage threshold.     

Videokeratoscope for accurate and detailed measurement of the cornea surface

A videokeratoscope based on the imaging of a gridlike pattern is introduced. Unlike conventional videokeratoscopes that rely on Placido disks, the new measurement principle allows an exact reconstruction of the surface and the display of fine details. The experimental instrument was tested on precision glass spheres; the maximum error of the height data was less than 3 microm. The sensitivity and the potential to resolve fine details were demonstrated with irregular surfaces of specially prepared contact lenses. Structures with height deviations of 0.1 microm are well identifiable. The eyes of 18 individuals were investigated, and fine structures were found on these cornea surfaces. Conventional videokeratoscopes do not resolve such detail.     

Accidents and sociotechnical systems: principles for design

Recent industrial accident studies have noted that various organizational variables, e.g. department boundaries, management—worker communication, training programs, can have a high impact on accident occurrence. They have also noted a lack of methodology for organizational design that reflects the needs of safety. Sociotechnical systems theory is outlined as a possibly useful structure and methodology. The redesign of an underground mine is presented as a case study where safety was an important issue. Principles derived from numerous Sociotechnical designs are analyzed as to their potential applicability to safety problems.     

Increasing the accuracy of laser beam diameter measurement

A procedure for determining the diameter of a focused laser beam based on the measurement of laser damage to a thin film is described. This method has several advantages over the spatial methods of using calibrated diaphragms and the measurement of relative power density distribution with subapertures.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 23–24, June, 1995.     

Electron microscopic and optical studies of prism faces of synthetic quartz

Spirals on quartz are very seldom seen. The centre of the spirals and screw ledges are studied in detail using electron and optical microscopic techniques. Unusual profiles of spirals have been found with overhanging kinks on one side of the centre of these spirals. It is suspected that the complicated structures might have been developed after the completion of the growth of the crystals. It is also conjuctured that such structures would arise when growth-inhibiting substances are adsorbed on the crystal faces and result in imperfect crystals.Victawet, a proprietary wetting agent, available from one or more suppliers of electron microscopy materials and accessories.     

Molecular design and synthesis of branched bichromophore-attached linear fluorinated polyimides for nonlinear optical applications

A branched structure bichromophore was developed to increase the nonlinearity of optical polymers. The branched bichromophore was incorporated into the polymer backbone to prepare a novel nonlinear optical (NLO) side-chain fluorinated polyimide with high optical nonlinearity and good thermal stability. The novel nonlinear optical side-chain fluorinated polyimide exhibits a large electro-optic (E-O) coefficient (γ₃₃) (34 pm/V at 1550 nm) which is larger than that of the conventional side-chain optical polyimide. This is mainly attributable to an increased chromophore concentration and high polarizing efficiency derived from the branched structure. The branched structure of the bichromophore is incorporated into a polymer backbone to result in a high chromophore concentration. Moreover, the three-dimensional (3D) architecture and large molecular size of the branched bichromophore can spatially shield from strong interchromophore electrostatic interactions to enhance the poling efficiency. The side-chain fluorinated polyimide exhibits excellent solubility in common organic solvents, good film-forming property, high glass-transition temperature (T _g) (190 °C) and thermal stability up to 235 °C.     

Extensions to a lens design program for the ray-optical design of waveguide lenses and prism couplers

Abstract

The design of integrated optical lens systems requires special software because such systems contain both three-dimensional and twodimensional elements (e.g. bulk prisms and planar waveguide lenses), and the waveguides are often anisotropic. We extended the popular optical computer-aided design program OSLO SIX so that it can evaluate and optimize systems that contain coupling prisms and planar waveguide lenses. We describe our software extensions and through examples we demonstrate their usage and benefits. We confirm our computations by measurement results. Finally, we present a ray-optical interpretation of transverse image line inclination and a method for its elimination.     

The optimal design of photonic crystal optical devices with step-wise linear refractive index

In the paper, we have studied one-dimensional step-wise linear photonic crystal with and without defect layer, and analyzed the effect of defect layer position, thickness, refractive index real part and imaginary part on the transmissivity, electric field distribution and output electric field intensity. By calculation, we have obtained a set of optimal parameters, which can be optimally designed optical device, such as optical amplifier, attenuator, optical diode by the step-wise linear photonic crystal.     

The opportunistic route and the role of design principles

This paper describes some aspects of the opportunistic mode of design which, it is held, most designers adopt, particularly for the step from concept to embodiment, or means to form, in which it is most characteristically seen. Simple examples are given which show the operation of constraints in directing the designer, and the strengths and weaknesses of the approach are discussed. Suggestions are made as to the important role design principles can play, and how their systematic introduction could help. Some notes are given on a computer aid which is being developed to prompt the designer in the use of appropriate principles at the appropriate stage in the work.     

Two-dimensional cadmium selenide electronic and optical properties: first principles studies

Structural, electronic and optical properties of two-dimensional (2D) cadmium selenide (CdSe) structures with \(2\times 2\) periodicities are investigated. First principles total energy calculations are performed within the periodic density functional theory. Initially, the structural properties are determined using the local density approximation as implemented in the PWscf code of quantum ESPRESSO package. To investigate the electronic properties, the GW method is applied to determine the energy gap within the plasmon pole and the random phase approximations. Optical properties are investigated to determine the dielectric constant and the Bethe–Salpeter theory is used to calculate the exciton binding energies. Zinc blende and wurtzite phases are considered to calculate the bulk energy gaps, which are compared to the experimental values, finding good agreement. The 2D structure exhibits an energy gap larger than that of the bulk, indicating the effects of reduction in dimensionality; these changes can be attributed to the dangling bonds that are present in the 2D layer.