Jinfa Tang

Transparent conducting indium doped ZnO films by dc reactive S-gun magnetron sputtering

Transparent conducting ZnO films have been prepared by modified S-gun reactive dc magnetron sputtering using an indium doped Zn target. Films with a resistivity of 1.08 x 10(-3) Omega cm and average transmittance of over 80% in the visible region were obtained. The influence of indium content at the surface of Zn target on the resistivity and transmittance of ZnO films was investigated. Optical properties of ZnO films in the 0.2-2.5-microm range were modeled by the Drude theory of free electrons. The reflectance of ZnO films in the 2.5-26.0-microm region was calculated.

Damage thresholds of (ZrO 2 –Y 2 O 3 )/SiO 2 reflectors used for XeCl lasers

An excimer laser reflector at the wavelength of 308 nm (XeCl) consisting of materials of ZrO(2)-Y(2)O(3) and SiO(2) is prepared. The reflectance reaches ~99.5% and the laser-induced damage threshold is raised to ~8.5 J/cm(2). The ZrO(2)-Y(2)O(3) mixture is proven to be a film material with a high laser damage resistance.

Optical properties of extremely thin films: studies using ATR techniques

The optical constants and optical properties of extremely thin ZnS, SiO(2), Al, and Ag films are studied and compared by attenuated total reflection (ATR) techniques. The optical constants and optical absorptance as a function of film thickness are measured. The experimental results agree well with theoretical prediction. It is found that there is no discontinuity in optical constants and absorptance when an extremely thin layer changes from isolated islands to a continuous film for all the measured materials. The critical thicknesses at which they form continuous films show great differences for the various materials and deposition methods. The dependence of absorptance on thickness of extremely thin layers is studied experimentally and theoretically.

Optical modified signed-digit addition module based on Boolean polarization-encoded logic algebra

The modified signed-digit (MSD) number system satisfies the requirements of totally parallel addition using identical units and enables the addition of any two numbers in three sucessive steps. We show a simple and compact design of the parallel optical addition module based on MSD number representation using Boolean polarization-encoded logic algebra (BPLA). The four transforms of MSD addition are ex- pressed mathematically and the realization of the transform module us- ing liquid crystal devices (LCDs) are also given.

Properties of dielectric coatings produced by ion assisted deposition

Some metal oxides, fluorides, and ZnS films deposited by ion assisted deposition are investigated as a function of ion energy, ion variety, and ion source type. Both optical and mechanical properties, such as optical stability, absorption and scattering losses, laser damage threshold, and durability, are examined for samples deposited with the assistance of four kinds of ion source and various preparation conditions.

Apparatus for wideband monitoring of optical coatings and its uses.

A computer controlled rapid-scanning monochromator has been constructed for monitoring optical coatings in situ, determining the optical constants of films, and measuring the optical instability of filters. In this paper are given the main specifications of the apparatus, some results in the production of a number of broadband AR coatings, and characterization of some passband filters.

New automatic design technique for optical coatings

A new automatic design method for optical thin-film systems is presented in which the effect of the errors in monitoring the optical multilayer coatings on the performance is considered. The merit function in the design involves both the optical properties and the calculated yield of finished products of the multilayer coatings. The highest yield of finished products is taken as an end optimization goal. The thin-film systems designed by this method not only satisfy the desired optical properties but also have larger manufacturing tolerances. Some examples of designs of broadband and double-band antireflection coatings are given.

Spectrophotometer for measuring spectral reflectance and transmittance

The development of a computer-controlled spectrophotometer that enables measurement of spectral transmittance, reflectance, and optical loss of thin-film specimens is discussed. We also describe the design and testing procedure of the spectrophotometer, incorporating test sample performance data. In the visible region the overall photometric accuracy is verified to be 0.1% and 0.2% for transmittance and reflectance, respectively. The wavelength scale is accurate to within 0.5 nm with a reproducibility of 0.1 nm.

Estimation of optical constants of thin film by the use of artificial neural networks.

A system for analyzing single-layer optical thin films has been formulated by the use of artificial neural networks. The training data sets stem from the computational results of the physical model of thin films, and they are used to train the artificial neural network, which, when done, can give values of film parameters in the millisecond time regime. The fast backpropagation algorithm is employed during training. The results of training are also given.

Measurement of weak absorption in optical thin films

An adiabatic laser calorimeter for measuring weak absorption in optical thin films is presented. It consists of three main parts which are used to control and measure temperature, and for calibration. The controlling temperature part is a set of automatic temperature controls mainly composed of a PID adjuster. The temperature difference between specimen and environment is always less than +/-0.006 degrees C during the measurement process. There is almost no energy exchange between specimen and environment. The specimen temperature increment is measured by a high precision thermistor set. Its measuring temperature sensitivity is 0.003 degrees C and the accuracy is +/-0.004 degrees C. The absolute electrical calibration part is used to obtain absorptance of a specimen immediately without needing to know the mass and specific heat of the specimen. Absorptance as small as 1 x10(-5) can be detected when a 1.5-W argon-ion laser is used.