Cavity-like filters with absorbing layers.

Two narrowband filter types are presented: narrowband reflector and narrowband absorber. Both are related to the familiar narrowband pass cavity filter, but include a thin absorbing layer.

An unusual cause of free air in the abdomen: emphysematous cystitis with bladder diverticulum perforation.

A 64-year-old male, with a history of chronic urinary outflow obstruction secondary to benign prostatic hyperplasia, presented with haematuria and urinary retention following spontaneous removal of his long-term catheter. The patient was septic on admission and a CT examination of the abdomen and pelvis showed an acutely inflamed urinary bladder diverticulum and extensive intra-abdominal free air. The patient was treated medically for emphysematous cystitis centred on a perforated bladder diverticulum, which was thought to be caused by the underlying infectious/inflammatory process.

Optical interference coating design contest 2019: a non-polarizing beam splitter and a color-mixing challenge [Invited].

A non-polarizing beam splitter and a light color-mixing challenge were the topics of the design contest held in conjunction with the 2019 Optical Interference Coatings topical meeting of the Optical Society of America. A total of 10 designers from China, France, Germany, Japan, and the United States submitted over 70 designs for problems A and B. The design problems and the submitted solutions are described and evaluated.

Narrowband angle filter.

Narrowband pass filters are generally poor as narrowband angle filters. A tilted narrowband pass filter, however, is an improved narrowband angle filter, but only for rays in one plane of incidence. It is shown that a combination of two tilted narrowband pass filters will select light from all narrow angle patches in an incident cone.

Optical interference coating design contest 2016: a dispersive mirror and coating uniformity challenge.

A dispersive mirror and a coating uniformity challenge were the topics of the design contest held in conjunction with the 2016 Optical Interference Coatings topical meeting of The Optical Society (OSA). A total of 18 designers from China, France, Germany, Japan, and the United States submitted 38 total designs for problems A and B. Michael Trubetskov submitted the winning designs for all four design challenges.

Flip-flop coating synthesis revisited.

The flip-flop synthesis method is robust with rapid convergence, but the solutions are often not the best. Modifications to the flip-flop algorithm have been developed, one of which puts it on par with needle synthesis.

Omnidirectional mirror design with quarter-wave dielectric stacks.

Quarter-wave stacks may be designed to reflect both polarizations of a specific wavelength band at all angles of incidences (omnidirectional). Expressions are given for both the omnidirectional band center wavelength and the bandwidth for selected values of the low- and the high-refractive-index layer values. It is shown that selecting the low refractive index near 1.

Extended-bandwidth reflector designs by using wavelets.

Optical interference coatings have been designed by using combinations of wavelets (fully apodized sine-wave refractive index groups). Like a single-line rugate filter, a single wavelet produces a stop band without harmonics and, in addition, has no sidelobes. The rules for combining wavelet refractive index structures have been derived for extended-bandwidth reflectors.

Focal-plane pixel-energy redistribution and concentration by use of microlens arrays.

A physical-optics calculation was performed to study the effects of a microlens array placed over a focal-plane detector array. In certain conditions the light is further concentrated to a spot size that is smaller than the point-spread function of the receiver optics. It is also shown that the microlens refocuses a sinc-squared point-spread function to a shape that is more uniform as well as narrower.

Antireflection surfaces in silicon using binary optics technology.

Binary optics processing methods were applied to a silicon substrate to generate an array of small pillars in order to enhance transmission. The volume fraction of the silicon in the pillars was chosen to simulate a single homogeneous antireflection layer, and the pillar height was targeted to be a quarter-wave thickness. A mask was generated, using a graphics computer-aided design system; reactive-ion etching was used to generate the pillars.

Ray tracing kinoform lens surfaces.

An exact ray trace (Snell's law of refraction) of discontinuous surfaces of kinoform lenses (surface relief lenses) is used to evaluate optical performance when used alone or when used in conjunction with conventional optical surfaces. A phase-based merit function that is generated by ray tracing is useful for the design and optimization of such systems including color correction. This ray trace approach can also explain and evaluate the dual focal length features of kinoform lens designs.

Using apodization functions to reduce sidelobes in rugate filters.

Appending gradient-index matching regions and apodization, which is an amplitude modulation of the rugate sinusoidal index profile, are two effective means to reduce and nearly eliminate the sidelobes. When a combination of these methods is used in the rugate design, the resulting filter will have good sidelobe suppression both near to and far from the stopband and will have high reflectance in the stopband.

Rugate filter sidelobe suppression using quintic and rugated quintic matching layers.

Sine wave rugate index profiles may be superimposed on a slowly varying average index in such a way as to reduce sidelobes over broad spectral regions and at the same time maintain the strength of the stopband reflectance.

Codeposition of continuous composition rugate filters.

Rugate filters are optical thin film interference structures with sinusoidal refractive index profiles. Two-wavelength reflection filters have been fabricated by codeposition of SiO(2) and TiO(2). Composition modulation was monitored and controlled using quartz crystal rate controllers.

Maximum likelihood phase-retrieval algorithm: applications.

The maximum likelihood estimator approach is shown to be effective in determining the wave front aberration in systems involving laser and flow field diagnostics and optical testing. The robustness of the algorithm enables convergence even in cases of severe wave front error and real, nonsymmetrical, obscured amplitude distributions.

Gradient-index antireflection coatings.

Thin-film gradient-index profiles have been analyzed and new profiles have been synthesized for broadband antireflection coatings on dielectric surfaces. It is shown that the control of the index gradient as a design parameter can significantly enhance the performance of interference coatings.

Rectangular Luneburg-type lenses for integrated optics.

Compact Luneburg-type lenses of rectangular outline as viewed from above have been made by thermal evaporation of As2S3 glass onto single-mode LiNbO(3):Ti waveguides through suitably shaped masks and subsequent exposure of the glass to ultraviolet light. The best lenses had speeds of f/5.5 at an aperture of 10 mm and focal spots at reduced aperture about 1.

Planar optical waveguide lens design.

Achieving diffraction-limited planar waveguide lenses is not an easy task in practice. However, conventional lens design principles (ray tracing, intercept and OPD errors, point spread functions, and optimization techniques) may be used to evaluate performance, reduce cost or complexity, and provide alignment and manufacturing tolerances. Presented here (as an example of an optimization technique) is a new diffraction-limited planar waveguide lens.

Virtual-source theory of unstable resonator modes.

A new method for understanding and calculating unstable resonator modes has been developed. It consists of propagating an initial uniform plane wave N round trips through the resonator, as in the Fox and Li [Bell Syst. Tech.

Reflective optics for irradiance redistribution of laser beams: design.

The output irradiance of a typical unstable resonator with circular symmetry has a central obscuration and is peaked near the obscuration. A method is presented for designing two-mirror optical systems to convert this beam into a beam of arbitrary obscuration ratio and more uniform irradiance. A method is also given for analyzing the alignment sensitivity of such a system.

Multilayer coating design achieving a broadband 90 degrees phase shift.

For nonnormal incidence angles, it has been shown that the polarization state may be controlled through the use of specially designed multilayer coatings. An optimization technique has been used to determine layer thicknesses for a coating design that produces a 90 degrees phase shift between the p- and s-polarization components over a wavelength range of Deltalambda/lambda(0) = +/-5% while maintaining high reflectivities for both components. A tolerance analysis indicates that the coating layers must be deposited within +/-1% to achieve a +/-3 degrees phase shift error over the spectral range of the design.

Effect of infrared coating nonuniformity on optical systems.

For precision optical systems, the focus and tilt errors caused by coating thickness nonuniformity can be a serious concern. These errors are wavelength dependent and hence cannot be compensated in an IR optical system by aligning and focusing with an auxiliary visible alignment laser. It is shown here that the coating design can be modified so as to make the aberrations caused by coating thickness nonuniformity approximately equal at the IR design wavelength and the wavelength of the auxiliary laser.