Ellipsometric function of a film-substrate system: Applications to the design of reflection-type optical devices and to ellipsometry

The ratio ρ = Rp/Rs of the complex amplitude-reflection coefficients Rp and Rs for light polarized parallel (p) and perpendicular (s) to the plane of incidence, reflected from an optically isotropic film-substrate system, is investigated as a function of the angle of incidence ϕ and the film thickness d. Both constant-angle-of-incidence contours (CAIC) and constant-thickness contours (CTC) of the ellipsometric function ρ(ϕ,d) in the complex ρ plane are examined. For transparent films, ρ(ϕ,d) is a periodic function of d with period Dϕ that is a function of ϕ. For a given angle of incidence ϕ and film thickness d (0 ≤ ϕ ≤ 90, 0 ≤ d ≤ Dϕ), the equispaced linear array of points (ϕ,d + mDϕ) (m = 0, 1, 2,…) in the real (ϕ,d) plane is mapped by the periodic function ρ(ϕ,d) into one distinct point in the complex ρ plane. Conversely, for a given film-substrate system, any value of the ellipsometric function ρ can be realized at one particular angle of incidence ϕ and an associated infinite series of film thicknesses d, d + Dϕ, d + 2Dϕ,.... This analysis leads to (1) a unified scheme for the design of all reflection-type optical devices, such as polarizers and retarders, (2) a novel null ellipsometer without a compensator, for the measurement of films whose thicknesses are within certain permissible ranges, and (3) an inversion procedure for the nonlinear equations of reflection ellipsometry that separates the determination of the optical constants (refractive indices and extinction coefficients) of the film and substrate from the film thickness. Extension of the work to absorbing films is discussed

Polarizer-surface-analyzer null ellipsometry for film-substrate systems

Single-pass polarizer-surface-analyzer null ellipsometry (PSA-NE) can be used to characterize film-substrate systems, provided that the film thickness lies within one of a set of permissible-thickness bands (PTB). For a transparent film on a transparent or absorbing substrate, the PTB structure consists of a small number of finite-bandwidth bands followed by a continuum band that extends from a film thickness of about half the wavelength of light to infinity. We show that this band structure is a direct consequence of the periodicity of the ellipsometric function ρ (the ratio Rp/Rs, of the complex amplitude-reflection coefficients for the p and s polarizations) with film thickness. The PTB for the SiO2-Si film-substrate system at He-Ne laser and mercury spectral lines are calculated. The angles of incidence for PSA-NE ona film-substrate system with known film thickness are easily predicted with the help of a graphical construction in the angle of incidence-vs-thickness φdplane. PSA-NE is generally applicable to the determination of both film thickness and optical properties of a film-substrate system. The procedure for its application to the special, but important, case of film-thickness measurement alone, when the optical properties are known, is given and is checked experimentally by the determination of the oxide-film thickness on Si wafers. In an automated form, PSA-NE can be a serious competitor for interferometric reflectance methods

Design of film-substrate single-reflection linear partial polarizers

The results of a preceding paper [J. Opt. Soc. Am. 65, 1464,(1975)] are viewed from a different angleas providing the basis for the design of film-substrate single-reflection linear partial polarizers (LPP),which also operate as reflection optical rotators. The important characteristics of a comprehensive set of discrete designs of SiO2-Si LPP’s at λ = 6328 Å are shown graphically

Design of film—substrate single-reflection retarders

The design steps for film—substrate single-reflection retarders are briefly stated and applied to the SiO2—Si film—substrate system at wavelength 6328 Å. The criterion of minimum-maximum error of the ellipsometric angle ψ is used to choose angle-of-incidence-tunable designs. Use is made of the (Φ-d) plane (angle of incidence versus thickness) to determine whether a given film—substrate system with known optical properties and film thickness can operate as a reflection retarder and to determine the associated angles of incidence and retardation angles. This leads to the concept of permissible-thickness bands and forbidden gaps for operation of a film—substrate system as a reflection retarder. Experimental measurements on one of the proposed designs proved the validity of the method

Ellipsometric function of a film-substrate system: Applications to the design of reflection-type optical devices and to ellipsometry

The ratio ρ = Rp/Rs of the complex amplitude-reflection coefficients Rp and Rs for light polarized parallel (p) and perpendicular (s) to the plane of incidence, reflected from an optically isotropic film-substrate system, is investigated as a function of the angle of incidence ϕ and the film thickness d. Both constant-angle-of-incidence contours (CAIC) and constant-thickness contours (CTC) of the ellipsometric function ρ(ϕ,d) in the complex ρ plane are examined. For transparent films, ρ(ϕ,d) is a periodic function of d with period Dϕ that is a function of ϕ. For a given angle of incidence ϕ and film thickness d (0 ≤ ϕ ≤ 90, 0 ≤ d ≤ Dϕ), the equispaced linear array of points (ϕ,d + mDϕ) (m = 0, 1, 2,…) in the real (ϕ,d) plane is mapped by the periodic function ρ(ϕ,d) into one distinct point in the complex ρ plane. Conversely, for a given film-substrate system, any value of the ellipsometric function ρ can be realized at one particular angle of incidence ϕ and an associated infinite series of film thicknesses d, d + Dϕ, d + 2Dϕ,.... This analysis leads to (1) a unified scheme for the design of all reflection-type optical devices, such as polarizers and retarders, (2) a novel null ellipsometer without a compensator, for the measurement of films whose thicknesses are within certain permissible ranges, and (3) an inversion procedure for the nonlinear equations of reflection ellipsometry that separates the determination of the optical constants (refractive indices and extinction coefficients) of the film and substrate from the film thickness. Extension of the work to absorbing films is discussed

Caffeine inhibits hypoxia-induced nuclear accumulation in HIF-1α and promotes neonatal neuronal survival

© 2019 The Authors Apnea of prematurity (AOP) defined as cessation of breathing for 15–20 s, is commonly seen in preterm infants. Caffeine is widely used to treat AOP due to its safety and effectiveness. Caffeine releases respiratory arrest by competing with adenosine for binding to adenosine A 1 and A 2A receptors (A 1 R and A 2A R). Long before its use in treating AOP, caffeine has been used as a psychostimulant in adult brains. However, the effect of caffeine on developing brains remains unclear. We found that A 1 R proteins for caffeine binding were expressed in the brains of neonatal rodents and preterm infants (26–27 weeks). Neonatal A 1 R proteins colocalized with PSD-95, suggesting its synaptic localization. In contrast, our finding on A 2 R expression in neonatal neurons was restricted to the mRNA level as detected by single cell RT/PCR due to the lack of specific A 2A R antibody. Furthermore, caffeine (200 μM) at a dose twice higher than the clinically relevant dose (36–130 μM) had minor or no effects on several basic neuronal functions, such as neurite outgrowth, synapse formation, expression of A 1 R and transcription of CREB-1 and c-Fos, further supporting the safety of caffeine for clinical use. We found that treatment with CoCl 2 (125 μM), a hypoxia mimetic agent, for 24 h triggered neuronal death and nuclear accumulation of HIF-1α in primary neuronal cultures. Subsequent treatment with caffeine at a concentration of 100 μM alleviated CoCl 2 -induced cell death and prevented nuclear accumulation of HIF-1α. Consistently, caffeine treatment in early postnatal life of neonatal mice (P4-P7) also prevented subsequent hypoxia-induced nuclear increase of HIF-1α. Together, our data support the utility of caffeine in alleviating hypoxia-induced damages in developing neurons

TUBERCULOSE OCULAIRE

Ocular manifestations in tuberculosis are rare, they are observed only in 1 to 2% of cases. With the advent of AIDS, ocular affections in tuberculosis have been encountered with increased frequency. We report a serie of six cases of ocular tuberculosis admitted in our Ophthalmology department between 2004 and 2006. Among the six cases of tuberculosis eye, there is a notion of tuberculosis contagion in one case, extra ocular tuberculosis in three cases. A palpebral nodule is found in one case; follicular conjunctivitis in one case; interstitial keratitis in one case, an uveitis in three cases. The diagnosis is based on the clinical, para-clinical arguments. Chemotherapy was instituted in all patients with treatment-steroidal anti-inflammatory in three cases. Evolution was favourable in five cases. Ocular tuberculosis is an affection less often than before. A resurgence in recent years due to the spread of AIDS and multi-resistant forms. is noted Uveal involving is the most common ocular presentation. The diagnosis is based on a clinical, biological, para-clinical and histological arguments Tuberculosis treatment is principally related to preventive measures. The authors report ocular tuberculosis diagnostic problems on the necessity of regular ophthalmic examination of patients under treatment.Les manifestations oculaires au cours de la tuberculose sont rares, puisqu’elles ne sont observées que dans 1 à 2% des cas. Cette atteinte oculaire connaît actuellement une recrudescence avec l’avènement du SIDA. Nous rapportons une série de six cas de tuberculose oculaire colligée dans notre service d’Ophtalmologie Adulte entre 2004 et 2006. Sur les six cas de tuberculose oculaire, on retrouve une notion de contage tuberculeux dans un cas, une tuberculose extra oculaire dans trois cas. Un nodule palpébral est retrouvé dans un cas ; une conjonctivite folliculaire dans un cas ; une kératite interstitielle dans un cas ; une uvéite dans trois cas.  Le diagnostic est posé sur l’aspect clinique et sur un faisceau d’arguments para-cliniques. La chimiothérapie a été instituée chez tous les malades avec un traitement anti-inflammatoire stéroïdien dans trois cas. L’évolution a été favorable dans cinq cas sur six. La tuberculose oculaire est une affection moins rare qu’auparavant. Elle connaît une recrudescence ces dernières années due à l’extension du SIDA et des formes multi résistantes. L’atteinte du tractus uvéal est la manifestation oculaire la plus fréquente. Le diagnostic repose sur un faisceau d’arguments cliniques, biologiques, para-cliniques et histologique. Le traitement de la tuberculose est d’abord préventif. Les auteurs insistent sur les problèmes diagnostiques de la tuberculose oculaire et sur la nécessité d’une surveillance ophtalmologique régulière des patients sous traitement antibacillaire

Metastatic primary adenocarcinoma of the bladder in a twenty-five years old woman

Primary adenocarcinoma of the bladder is a rare tumor. The classification between primary vesical and urachal is debated. We present the case of a young female who presented clinicopathological features of a metastatic urachal adenocarcinoma, but the histological result revealed primary adenocarcinoma of the bladder contrary to expectancy. To the best of our knowledge this is the first reported case of a metastatic adenocarcinoma of the bladder in a 25 years old female. This case emphasizes the challenge for urologists to recognize and manage this aggressive tumor in the setting described