Search

Two methods were proposed and implemented for the fabrication of channel waveguides in an Er-doped Tellurite glass. In the first method, channel waveguides were fabricated by implanting 1.5 MeV and 3.5 MeV energy N+ ions through a special silicon mask to the glass sample at various fluences. Those waveguides implanted at a fluence of 1.0 × 1016 ions/cm2 operated up to 980 nm, and showed green upconversion of the Erbium ions. In the second method, channel waveguides were directly written in the Er3+: TeO2W2O3 glass using an 11 MeV C4+ ion microbeam with fluences in the range of 1 · 1014–5 · 1016 ions/cm2. The waveguides worked in single mode regime up to the 1540 nm telecom wavelength. Propagation losses were reduced from the 14 dB/cm of the as-irradiated waveguides by stepwise thermal annealing to 1.5 dB/cm at λ = 1400 nm. [ABSTRACT FROM AUTHOR]

Two methods were proposed and implemented for the fabrication of channel waveguides in an Er-doped Tellurite glass. In the first method, channel waveguides were fabricated by implanting 1.5 MeV and 3.5 MeV energy N+ ions through a special silicon mask to the glass sample at various fluences. Those waveguides implanted at a fluence of 1.0 × 1016 ions/cm2 operated up to 980 nm, and showed green upconversion of the Erbium ions. In the second method, channel waveguides were directly written in the Er3+: TeO2W2O3 glass using an 11 MeV C4+ ion microbeam with fluences in the range of 1 · 1014–5 · 1016 ions/cm2. The waveguides worked in single mode regime up to the 1540 nm telecom wavelength. Propagation losses were reduced from the 14 dB/cm of the as-irradiated waveguides by stepwise thermal annealing to 1.5 dB/cm at λ = 1400 nm.

• Daylight harvesting system using ball lens as static collector. • Small footprint daylight harvesting system. • Continuous solar tracking using light sensors and microcontroller. • LED compensated hybrid daylight harvesting system. We demonstrate a prototype for a compact, hybrid daylight harvesting system that collects and transports sunlight to illuminate dark spaces, up to two levels underground. The prototype is designed to have a compact size so that it can be mounted on top of a conventional lamp post at ground level and the system serves an additional purpose of a streetlamp for ground level illumination during nighttime. The system utilizes an acrylic ball lens as solar concentrator, and the focused sunlight is directly coupled into a single plastic optical fiber that transports it to indoor spaces. The spherical symmetry of the ball lens allows it to be static, while the position of focused light spot varies gradually underneath it, in accordance with the solar position in the sky. Therefore, only the light-collecting optical fiber needs to be moved under the ball lens, obviating the need for heavy-duty motors typically used to align solar concentrators along the direction of sun's rays. The focused sunlight under the ball is tracked using a microcontroller-based tracking mechanism. This design is the first demonstration of a daylight harvesting system, to the best of our knowledge, using a ball lens as static sunlight collector and a movable optical fiber tracking the focused spot underneath the ball. The moving parts in the proposed system are lightweight and are well concealed from environmental hazards like dust, wind and moisture. [ABSTRACT FROM AUTHOR]

We consider the excitation of leaky mode resonances (LMRs) in an optical fiber that originate from light coupling initiated by small angle (<21°) tilted fiber Bragg gratings (TFBGs), through sub-micrometric grating inscription using a femtosecond laser. The femtosecond laser inscription triggers the interaction between the fiber's guided mode and backward coupling to the LMRs, a process that requires tight control of the grating period, reflection angle, order and the strength of the modified refractive index. The TFBG itself exhibits very low spectral polarization dependence, whereas the LMRs display strong polarization dependence in specific wavelength ranges, allowing for easy mode selection and opening avenues for various applications related to sensing and optical filtering. The tailored-for-LMR-generation optical filters were characterized for torsion, temperature and strain, exhibiting a very large negative strain sensitivity of –2 pm/μϵ and a temperature sensitivity of 14.73 pm/°C that when compared with the grating response led to an exceptionally large strain response and remarkably well-behaved conversion matrix for the separation of strain and temperature in a single measurement. The LMR also proves to be insensitive to bend. The nature of LMRs is considered and confirmed by measuring their radiation field using an infrared camera, simulating their resonance wavelength using a finite element method and by experimentally observing their behavior, while changing the ambient refractive index. [ABSTRACT FROM AUTHOR]

Abstract Background Low-stress soldering techniques can guarantee a minimized input of thermal energy allowing for the design and later assembly of more robust and miniaturized optical devices. However, in order to build miniaturized optical devices, these small-induced stresses produced by soldering techniques have to be investigated to guarantee that the stress-induced birefringence effects do not alter the device optical properties and requirements. Methods An analytical method that relates the stress-induced birefringence of laser components with their corresponding lasing capabilities has been compared to the real induced-stress results created in components packaged using solderjet technology. The main goal was to optimize the optical component packaging by using this low induced-stress soldering technique. The optimization was carried out by assessing components miniaturization while still assuring high robustness of the bond strength without creating a beam depolarization ratio of more than 1%. Results The outcome of the study showed the possibility of assembling laser optical components down to sizes of around 300 μm, creating a bond strength of 5 N and higher, and a depolarization ratio much lower than the proposed target of 1%. Conclusions Our results in terms of induced stress agreed with the finite element method result, which would imply correct post-processing laser simulations. This suggested that the solderjet bumping technique could robustly join components down to the laser emission beam size without strongly affecting the optical properties.

We introduce a method of inscribing in-fiber devices using a femtosecond laser that is applicable to crucial components, such as cladding waveguides (CWGs), cladding Mach–Zehnder interferometers (MZIs), embedded waveguide Bragg gratings (WBGs), and waveguide Fabry–Perot cavities using the same key femtosecond laser parameters, via an “inscribe and step,” plane-by-plane approach, applied as necessary on two orthogonal axes. This leads to femtosecond laser-inscribed cladding waveguides and ultra-compact MZIs that can support functional, integrated fiber Bragg gratings; the unique sensing characteristics of the filters are maintained and provide complementary measure and information. This ensures a single inscription process, offering reliability and repetition in component manufacture, as the basic conditions to inscribe the here-demonstrated elements are common. We characterize CWG-WBG devices for axial strain, bend, and response to refractive index. The MZI-WBG is exposed to temperature and humidity excursions, confirming that the unique sensor responses are maintained for this compact, compound sensor. The MZI exhibits response to external refractive index, a large, negative wavelength response with temperature and high sensitivity to humidity, whereas the MZI-located WBG displays a similar sensitivity to conventional core-based Bragg grating sensors to temperature and no response to relative humidity. We consider that this research is an important step in the development of compact, smart optical fiber sensors. [ABSTRACT FROM AUTHOR]

Abstract An approach is presented that allows an electrically variable liquid crystal lens to operate as a spherical lens, then be switched into a variable prism, axicon, etc. This is achieved by a simple phase optimization algorithm enabled by the presence of a weakly conductive layer in the so called "modal control" lens approach with a segmented peripheral electrode. The proposed design and control method enable important additional control tools via the choice of the driving frequency and voltage values. Because the component has no electrodes in the clear aperture area, this allows the generation of a rich variety of interchangeable wavefronts and beams (such as Gaussian, Bessel, Airy, etc.) transforming it into a powerful adaptive optical device that can be used in many photonic applications. [ABSTRACT FROM AUTHOR]

Street lighting, which is one of the main players in energy waste and light pollution at night, still faces the challenge of efficient lighting of roadways with curved and twisted shapes. To meet this challenge, we propose an effective and efficient adaptive light-emitting diode (LED) luminaire. This LED lamp delivers a roadway-shape light pattern, which maximizes illumination performance. The light is efficiently and homogeneously directed only where is needed; which reduces glare, and improves both the eye comfort and the visual discrimination ability of car drivers and pedestrians. The proposed luminaire is very practical in that it only requires to replace the cover plate, which is a special microlens array sheet, to produce different shape light patterns. The adaptive mechanism is simple and effective: LED light is first collimated and then efficiently distributed on a freeform roadway by the special microlens sheet. We present an extensive analysis of the lighting adaptability of the proposed luminaire by Monte Carlo ray tracing. In particular, we studied the effect of the main microlens structural parameters in the shape and size of the delivered illumination distribution on the roadway. We present a design example, a prototype construction, and an experimental confirmation on a scale street lighting system. Simulations and experimental results show the advantages of adaptive luminaires over the traditional nonadaptive approaches.

In this paper, a new structure of spatial-coded coating phosphor is proposed and effectively benefits the efficiency enhancement in the white light-emitting diodes (LEDs). The spatial-coded phosphor plate contains two subregions. One subregion is of the yellow phosphor for providing the greatest extracted yellow light, and the other subregion is the open windows for preventing the blue light from the absorption by the yellow phosphor and the Stoke loss in the wavelength conversion. In the design process, the thickness and the concentration of the phosphor and photon recycling in a high-reflectivity cavity are all simulated and optimized. Finally, the predicting spectra of the resultant white LEDs with the spatial-coded phosphors by the simulation model are all in very good agreement with the corresponding spectra from the practical measurements. Moreover, as the correlated color temperature (CCT) is around 6500 K, the maximal packaging efficiency of the white LEDs with the spatial-coded phosphors is as high as 68.0% in the measurement, and the corresponding simulation is 71.8%. It is much higher even than the optimal packaging efficiency of the conventional conformal or remote-dome phosphor packaging structure.

Abstract Recent research has shown that the computer-controlled fluid jet polishing (FJP) process can generate nanometer-level form accuracy on free surface optical components. The key issues affecting the machining accuracy of the FJP process, including the deviation of the removal function, dynamic response of the moving tables and the change of material removal rates at a small-scale dwell time, have been investigated. Approaches using signal filtering and alignment methods to reduce the measurement errors of the removal functions in FJP are presented. An enhancing algorithm is proposed to improve the rotational symmetry of the removal function, with correction factors being included in the quality assessment to adjust the change in the quality of the removal function with different dwell times. The dynamic responses and moving accuracy of the worktable were measured, and their effects on the FJP polishing process were analyzed. Fluid jet polishing experiments using small-scale dwell time (less than 5 s) under intermittent motion and continuous motion modes were also performed. The experimental results show that the fluctuation of enhanced removal functions is less than that of the original functions. The residual information on the surface, related to the path distance, is barely noticeable when the distance is less than 0.4 mm, when a nozzle with a diameter of 1 mm diameter is used. The material removal experiments with small-scale dwell times indicate that the removal rate is stable when the worktable is in continuous motion. Highlights • Key issues affecting the machining accuracy of the FJP process, including the deviation of the removal function, dynamic response of the moving tables and the change of material removal rates at small-scale dwell time, have been investigated. • Approaches using signal filtering and alignment methods to reduce the measurement errors are presented. • An enhancing algorithm is proposed to improve the rotational symmetry of the removal function, with adjusting the change of removal function quality with different dwell time. • It has been found that the depth of the removal function at the small scale dwell time has a nonlinear relationship with that obtained at the large scale dwell time, whilst the depth over width ratios under these two conditions are also different. [ABSTRACT FROM AUTHOR]

An achromatization method optimized for dual-channel imaging is developed. Dichroic mirrors are employed to split and recombine narrowband signals, and separation between catoptric components is used to minimize the longitudinal chromatic shift. An achromatic system based on this principle could be built from singlet lenses, since refractive element properties such as dispersion and power are not utilized to optimize wavelength-dependent performance. To demonstrate the validity of the proposed solution, a prototype miniature fluorescence microscope optimized for two emission lines of acridine orange (525 and 650 nm) is built. To reduce the cost and accelerate assembly, the system is built from commercially available optical components. The optical train consisted of two plastic singlet lenses combined with a pair of dichroic mirrors. Optical performance of the prototype is evaluated by imaging a bar line target at both design wavelengths. To demonstrate the potential of the proposed design strategy, the achromatic system prototype is used to measure a two-part white blood cells differential count on a venous blood sample. Data from the prototype fluorescence microscope are compared against results from a commercially available blood analyzer, and the difference between both instruments is within 20%. [ABSTRACT FROM AUTHOR]

This article presents a chip-scale package (CSP) based filament light-emitting diodes (LEDs) with a stacked-type structure and a segmented-type luminescence design for higher luminous efficiency and better electrical stability. The innovation strategy improves the luminous efficiency by 7.69% and 18.97% than the traditional dispensing packaged LED filament when the current is at 30 mA and 210 mA, respectively, and reduces the use of red phosphors and green phosphors by 66.7% and 26.2%, respectively. With the increase of the current, the luminous efficiency variations of the stacked-packaged filament are lower than that of the traditional dispensing packaged filament. Moreover, the color temperature of the filament is no longer determined by the calculation of the ratio of various phosphors. The stacked structure and the segmented design can help us to adjust the specified color temperature quickly by changing the proportion and position of the blue chips and the red CSP LEDs. [ABSTRACT FROM AUTHOR]

In this study, we introduce two key improvements that overcome limitations of existing polygon scanning microscopes while maintaining high spatial and temporal imaging resolution over large field of view (FOV). First, we proposed a simple and straightforward means to control the scanning angle of the polygon mirror to carry out photomanipulation without resorting to high speed optical modulators. Second, we devised a flexible data sampling method directly leading to higher image contrast by over 2‐fold and digital images with 100 megapixels (10 240 × 10 240) per frame at 0.25 Hz. This generates sub‐diffraction limited pixels (60 nm per pixels over the FOV of 512 μm) which increases the degrees of freedom to extract signals computationally. The unique combined optical and digital control recorded fine fluorescence recovery after localized photobleaching (r ~10 μm) within fluorescent giant unilamellar vesicles and micro‐vascular dynamics after laser‐induced injury during thrombus formation in vivo. These new improvements expand the quantitative biological‐imaging capacity of any polygon scanning microscope system. [ABSTRACT FROM AUTHOR]

Optical nanostructures can control the optical absorption and emission properties of surfaces and are therefore being investigated for solar thermophotovoltaics, thermophotovoltaics, solar thermal, infrared sensing, infrared sources, incandescent light sources, and thermal imaging applications, among many others. This review article describes various modeling methods available for design of optical nanostructures to control light absorption and emission properties of surfaces, as well as various methods available for the fabrication of large area nanostructured surfaces. Throughout the review, we provide examples of state of the art energy generation devices using such optical nanostructures. A discussion of outstanding obstacles for the achievement of high efficiency solar thermophotovoltaics systems is provided along with examples of systems showing exceptional promise. [ABSTRACT FROM AUTHOR]

In this paper, we presented a new method to directly fabricate 3D microlens array (MLA) without the pattern transfer and substrate reshaping process. Gas-assist deformed concave Polydimethylsiloxane (PDMS) film was used as the molding template. The template was fixed on the curved micro-hole array with a micro cavity during the injection molding process. The curved micro-hole array was fabricated by 3D printing in order to avoid the interference from microlens nearby. In addition, the micro-hole array is detachable, thus allowing it to be assembled onto the MLA automatically. Less than few minutes, the formation of 3D MLA can be realized by which the polymeric lens material is capable of being cured within dozens of seconds. Multi-focusing MLA was designed to reduce the defocus. And the focal length of each microlens varied according to the different diameter of micro-holes. This novel method is time-saving, cost-effective and precision. A single microlens has a radius of 250–500 μm, and the accuracy can reach 30 μm. Performance of the 3D MLA has been optically characterized. The introduction of micro-holes array can effectively reduce the crosstalk between the eyes and the influence of stray light. The curved MLA have has a FOV over 70°. [ABSTRACT FROM AUTHOR]

In this paper, we used a freeform lens in a long-wave, un-cooled, refractive infrared (IR) thermal imager and present the design strategy and test results. This optical system is composed of only one freeform lens and several spheres. It can correct the distortion issue inherent to wide field-of-view systems more effectively, and achieve a better thermal imaging performance simultaneously compared to traditional aspheric optical lenses. Such a design model can alleviate the calculation load and cater for the demand of the ultra-precision turning on single crystal germanium. It satisfies the design idea of freeform surfaces with machining feasibility. The refractive freeform IR imager can be realized from the theoretical design to the engineering applications. The research contents of this paper are helpful for the further application of the freeform lens to a more complex cooled infrared refractive thermal imager. [ABSTRACT FROM AUTHOR]

A micro-resonator based on porous silicon ridge waveguides is implemented by a large scale standard photolithography process to obtain a low cost and sensitive sensor based on volume detection principle instead of the evanescent one usually used. The porous nature of the ridge waveguides allows the target molecules to be infiltrated in the core and to be detected by direct interaction with the propagated light. Racetrack resonator with radius of 100 μm and a coupling length of 70 μm is optically characterized for the volume detection of different concentrations of glucose. A high sensitivity of 560 nm/RIU is reached with only one micro-resonator and a limit of detection of 8.10 −5 RIU, equivalent to a glucose concentration of 0.7 g/L, is obtained. [ABSTRACT FROM AUTHOR]

The figure of merit is proposed for all-dielectric waveguides for absorption overtone spectroscopy as the measure of probing efficiency of molecular overtones. It is defined as the power in the evanescent tail over the total power carried by the guided mode. The figure of merit was calculated for the proposed waveguide structures and then compared. We address each waveguide structure in probing overtones. We show that the figure of merit can be substantially increased due to the downscaling of the physical dimensions of the waveguide and microfiber. Such a configuration enables integration possibilities for ultrasensitive devices harnessing evanescent excitation of molecular overtones on miniature and portable chips. [ABSTRACT FROM PUBLISHER]

In this paper, a new structure of spatial-coded coating phosphor is proposed and effectively benefits the efficiency enhancement in the white light-emitting diodes (LEDs). The spatial-coded phosphor plate contains two subregions. One subregion is of the yellow phosphor for providing the greatest extracted yellow light, and the other subregion is the open windows for preventing the blue light from the absorption by the yellow phosphor and the Stoke loss in the wavelength conversion. In the design process, the thickness and the concentration of the phosphor and photon recycling in a high-reflectivity cavity are all simulated and optimized. Finally, the predicting spectra of the resultant white LEDs with the spatial-coded phosphors by the simulation model are all in very good agreement with the corresponding spectra from the practical measurements. Moreover, as the correlated color temperature (CCT) is around 6500 K, the maximal packaging efficiency of the white LEDs with the spatial-coded phosphors is as high as 68.0% in the measurement, and the corresponding simulation is 71.8%. It is much higher even than the optimal packaging efficiency of the conventional conformal or remote-dome phosphor packaging structure. [ABSTRACT FROM PUBLISHER]

An optical design for a see-through head-mounted display with high visibility is described. This design, which is based on a light guide plate with triangular microstructures, can overcome the limitations of the balance in optical efficiency. [ABSTRACT FROM AUTHOR]

This article presents a chip-scale package (CSP) based filament light-emitting diodes (LEDs) with a stacked-type structure and a segmented-type luminescence design for higher luminous efficiency and better electrical stability. The innovation strategy improves the luminous efficiency by 7.69% and 18.97% than the traditional dispensing packaged LED filament when the current is at 30 mA and 210 mA, respectively, and reduces the use of red phosphors and green phosphors by 66.7% and 26.2%, respectively. With the increase of the current, the luminous efficiency variations of the stacked-packaged filament are lower than that of the traditional dispensing packaged filament. Moreover, the color temperature of the filament is no longer determined by the calculation of the ratio of various phosphors. The stacked structure and the segmented design can help us to adjust the specified color temperature quickly by changing the proportion and position of the blue chips and the red CSP LEDs.

Street lighting, which is one of the main players in energy waste and light pollution at night, still faces the challenge of efficient lighting of roadways with curved and twisted shapes. To meet this challenge, we propose an effective and efficient adaptive light-emitting diode (LED) luminaire. This LED lamp delivers a roadway-shape light pattern, which maximizes illumination performance. The light is efficiently and homogeneously directed only where is needed; which reduces glare, and improves both the eye comfort and the visual discrimination ability of car drivers and pedestrians. The proposed luminaire is very practical in that it only requires to replace the cover plate, which is a special microlens array sheet, to produce different shape light patterns. The adaptive mechanism is simple and effective: LED light is first collimated and then efficiently distributed on a freeform roadway by the special microlens sheet. We present an extensive analysis of the lighting adaptability of the proposed luminaire by Monte Carlo ray tracing. In particular, we studied the effect of the main microlens structural parameters in the shape and size of the delivered illumination distribution on the roadway. We present a design example, a prototype construction, and an experimental confirmation on a scale street lighting system. Simulations and experimental results show the advantages of adaptive luminaires over the traditional nonadaptive approaches. [ABSTRACT FROM PUBLISHER]

The present study examined the tunability of wave polarization splitting and conversion in a one-dimensional photonic crystal (1DPC) structure containing anisotropic electro-optical material. The 4 × 4 transfer matrix method was used to study the transmission properties of the structure. The incident light was assumed to be perpendicular to the optical axes of the anisotropic defect layer. The results indicate that, in the absence of an applied external electric field, for an incident plane wave with P- or S-polarization, a single P- or S-polarized defect mode, respectively, appears with the photonic band gap. Application of the external electric field create two P-polarized and two S-polarized defect modes of equal intensity. As the applied field increased, the splitting mode increased. The photonic band edges of the induced P(S)-polarized mode decreased (increased) as the field increased. The results of this communication can be useful in the design of tunable mode-selecting optical filters. [ABSTRACT FROM AUTHOR]

We presented the optimal surface relief heights of multilayer diffractive optical elements (MLDOEs) with the extended scalar diffraction theory. Comparisons of diffraction efficiency and polychromatic integral diffraction efficiency (PIDE) with different periods are described and simulated with extended scalar diffraction theory and scalar diffraction theory. The results show that the limits of scalar diffraction theory for MLDOEs and the minimum zone width of MLDOEs is different from that of traditional single-layer diffractive optical elements. [ABSTRACT FROM AUTHOR]

Diamond turning of high-precision molds is a vital process for the roll-to-roll-based ultraviolet resin imprinting process in fabricating subwavelength gratings. The effects of the grating shape and grating period on diffraction efficiencies and diffraction angles were simulated. Experiments were then conducted to examine the effects of shape design, grating period, and cutting speed on machinability of the mold. According to the optical measurement results, the performance of the subwavelength gratings matched the design well at various incident angles. The results confirm that diamond turning of high-precision molds is a feasible approach for ensuring the continual mass production of subwavelength gratings. [ABSTRACT FROM AUTHOR]

We have developed a compact dual-view endoscopic probe without field obscuration to address the need of simultaneously observing forward and backward fields of view (FOVs) in the colon. The objective is compact with the forward-view and rear-view optical paths sharing the same optical elements. The compact objective is new in that no FOV is blocked. The illumination for forward-view imaging is provided by the cylindrical light guide and backward illumination is achieved with a reflector. We have designed, prototyped, and tested the endoscope by comparing it to a standard clinical colonoscope. We will discuss the system concept, objective design, fabrication of the freeform lens, and test results. [ABSTRACT FROM AUTHOR]

Abstract: Current results of the development of a process chain for optics manufacturing with laser radiation are presented. The process chain consists of three process steps: High Speed Laser Ablation creates the surface geometry by material ablation, Laser Polishing reduces the surface roughness by material remelting and High Precision Laser Ablation applies a form correction by removing redundant material. Compared to conventional optics manufacturing methods, this process chain benefits from its high flexibility concerning the optics geometry and its processing speed, which is independent from the processed geometry. [Copyright &y& Elsevier]

This paper proposes an effective approach for spectrum shaping in the optical modeling of phosphor-converted white light-emitting diodes (LEDs) in which overlapping of the absorption and emission spectra of the phosphor are considered. The spectrum shaping method was applied to explore the wavelength-dependent absorption effect and reabsorption by the green phosphor. The experimental results indicated that the adjustment factor for blue light can enable the blue light spectrum to fit well with the measured spectrum. The adjustment factor was linearly related to the transmission ratio of the blue light. The blue light emitted by the blue die and the green light emitted by the phosphor were simulated and predicted in an accurate way as compared with the experimental measurements. The enhanced accuracy in assessing the spectra resulted in enhanced precision of chromaticities. In the experiments, the color differences were one order smaller in CIE 1931 chromaticity (Δx, Δy) than in models without spectrum shaping and were almost imperceptible to the human eye. The novel optical modeling of green phosphor pumped by a blue die facilitates the application of these materials in high-color rendering in white LEDs and projection displays. [ABSTRACT FROM PUBLISHER]

Abstract: An analysis model to optimize the materials selected for multilayer diffractive elements (MLDOEs) is presented with approximate Cauchy dispersion formula of refractive index and the maximum polychromatic integral diffraction efficiency (PIDE). The analysis model presents that the maximum PIDE of MLDOEs consisting of two materials with large Abbe number difference and small partial dispersion difference can be generated. The scope of application and the relationship between diffraction efficiencies of MLDOEs with different material pairs and different design wavelength pairs are presented and simulated with the analysis model of MLDOEs. [Copyright &y& Elsevier]

For high performance imaging and focusing applications, figure errors can degrade the performance of lenses, especially in catoptric and catadioptric lenses. An automatic figure errors balancing method is proposed. By using geometrical optics, the linear relationships between the figure errors and wavefront error (WFE) of lens for three kinds of optical surfaces are established and verified. The WFE sensitivity to figure errors based on this linear relationship is analyzed before clocking optimization to improve the efficiency of optimization. The clocking procedure indirectly optimizes the rotation angle of individual WFE map induced by figure error and performs a 360-deg tour to determine which the best position is. Using this method, the optimal combination of rotation angle of components would be acquired fleetly, especially for optical system included an optical component which figure errors is remarkable influence on WFE. The method is implemented on two manufactured optical systems: a Schwarzschild projection lens and a collimator lens. Simulation experiment proves our method can greatly reduce the aberration caused by figure errors. Compared with conventional randomly assembling method, WFE of the projection lens can be reduced by 40% and WFE of the collimator lens can be reduced by 51%. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a novel triple-layer diffraction optical element (TLDOE) composed of the optical materials with different indices and dispersion in each layer has been designed and investigated, the principle of selecting optical materials is discussed as well. The diffraction efficiency of the TLDOE at each wavelength in designed band is larger than 90% and the field of view (FOV) can even reach 110°, which can effectively improve energy utilization ratio and image quality of the hybrid refractive–diffractive optical system. [Copyright &y& Elsevier]

Applications of anamorphic diffractive lenses, or in other words elliptical zone plates, are growing in number and diversity. Following this progress, the manufacturing methods of anamorphic diffractive lenses are also a subject of continuous improvement. On the other hand, their design is still based mainly on the paraxial approximation. In the present paper nonparaxial elliptical zone plates are presented and their difference from the paraxial version, termed as the elliptical aberration is shown. A comparison of their focusing quality was performed based on results of numerical modelling as well as experiments. [ABSTRACT FROM AUTHOR]

A glass-based substrate technology that fills the gap between a truly flexible extended length distributed sensor medium and the multifunctionality of optical chips is demonstrated. Flat fiber chips will open further degrees of freedom to control the behavior of light via mechanical manipulation. A flexible flat format will also allow straightforward incorporation into smart structures. Coupled with low manufacturing costs, these flexichips can also be a key enabler to disposable high-end sensing devices or fully distributed point sensors. In this study, Bragg gratings were used to demonstrate the optical flatness of the flat fiber core layer. Furthermore, the effective index values obtained from the grating experiment were input into a dynamic model, subsequently proving the influence of the dumbbell-shaped flat fiber cross section on the resultant UV written waveguides. Evanescent field sensing was also demonstrated by adopting a stepped Bragg approach. [ABSTRACT FROM PUBLISHER]

Abstract: An ultra-low-loss coupler for interfacing a silicon-on-insulator ridge waveguide and a single-mode fiber in both polarizations is presented. The inverted taper coupler, embedded in a polymer waveguide, is optimized for both the transverse-magnetic and transverse-electric modes through tapering the width of the silicon-on-insulator waveguide from 450nm down to less than 15nm applying a thermal oxidation process. Two inverted taper couplers are integrated with a 3-mm long silicon-on-insulator ridge waveguide in the fabricated sample. The measured coupling losses of the inverted taper coupler for transverse-magnetic and transverse-electric modes are ∼0.36dB and ∼0.66dB per connection, respectively. [Copyright &y& Elsevier]

The article examines the effects of seidel and mono-axial comatic aberration on the deformation of the Laguerre-Gaussian (LG) beam. Similar to astigmatism, both aberrations can also be caused by misalignment and imperfection of optical elements as seen in quadratic deflection errors in the fabrication system of the lens and induces high-charge phase singularity to split. LG beam transformations were studied through numerical simulation based on the angular spectrum method.

Going to shorter wavelengths beyond the deep ultraviolet involves the development of dedicated optics for FEL with devoted coating techniques and characterizations. Low loss, high reflectivity dielectric mirrors with a long lifetime in a strongly harsh synchrotron radiation environment are required. In February 2001, lasing at 189.7 nm was obtained with Al2O3/SiO2 Ion Beam Sputtering mirrors, the shortest wavelength obtained so far with FEL oscillators. In July 2001, 330 mW extracted power was measured with optimized transmission mirrors. Coating research and development correlated to lasing performance obtained so far is reported. [Copyright &y& Elsevier]

The advanced understanding of the complete degradation phenomena is crucial in order to develop robust optics for FEL. Under very harsh Synchrotron Radiation conditions, results show that multiscale wavelength damages could be observed, inducing local crystalline structure modifications of the high optical index material with a severe increase of the surface roughness. [Copyright &y& Elsevier]