Number Of Optical Components Research Articles

Multifunctional binary diffractive optical elements for structured light projectors.

A set of diffractive optical elements for multiple-stripe structured illumination was designed, fabricated and characterized. Each of these elements with a single layer of binary surface relief combines functions of a diffractive lens, Gaussian-to-tophat beam shaper, and Dammann beam splitter. The optical investigations of laser light patterns at 20° fanout angle reveal up to 88% diffraction efficiency, high contrast, and nearly diffraction limited resolution. The developed technology has the potential for reducing complexity, number of optical components, power consumption and costs of structured light projectors in mobile and stationary 3D sensors.

Opportunities in laser cutting with direct diode laser configurations

This paper explores the opportunities associated with the use of well-designed direct diode laser configurations for cutting of metal sheets. Continuously improving diode stacking, and consequently greater brightness, allow the requirements for laser cutting to be met without the use of further brightness converters (diode-pumped solid state lasers). This contributes to a reduction in the number of optical components and increased energy efficiency. Furthermore, laser architecture related degrees of freedom for tailoring the wavelength, beam polarization and beam shape are instrumental to increase the cutting performance. Different stacking configurations, optical structures and related cutting strategies are discussed, with performance validation through experimental verification.

Combined spontaneous Stokes and coherent anti-Stokes Raman scattering spectroscopy

The simultaneous determination of multiple parameters is the key in the characterization of processes and materials that change with time. In combustion environments, the combined measurement of temperature and chemical composition is particularly desirable. In the present work, possible approaches for the simultaneous application of spontaneous Raman scattering (RS) and coherent anti-Stokes Raman scattering (CARS) spectroscopy are proposed and analyzed. While RS provides concentration information of all major species, vibrational CARS is a highly accurate thermometry tool at flame conditions. Five experimentally feasible CARS–RS schemes are identified and discussed with respect to signal intensity, measurement volume, and experimental complexity. From this analysis, one scheme was found to be the best option. It utilizes a broadband dye laser centered at 852 nm as a pump and the fundamental 1064-nm radiation of the Nd:YAG as Stokes laser. The third harmonic is used as CARS probe and RS laser. The experimentally most elegant scheme replaces the third harmonic in the above scheme by the second harmonic hence involving the smallest number of optical components in the setup.

Optical chirp z-transform processor with a simplified architecture.

Using a simplified chirp z-transform (CZT) algorithm based on the discrete-time convolution method, this paper presents the synthesis of a simplified architecture of a reconfigurable optical chirp z-transform (OCZT) processor based on the silica-based planar lightwave circuit (PLC) technology. In the simplified architecture of the reconfigurable OCZT, the required number of optical components is small and there are no waveguide crossings which make fabrication easy. The design of a novel type of optical discrete Fourier transform (ODFT) processor as a special case of the synthesized OCZT is then presented to demonstrate its effectiveness. The designed ODFT can be potentially used as an optical demultiplexer at the receiver of an optical fiber orthogonal frequency division multiplexing (OFDM) transmission system.

High-Splitting-Ratio PON Systems Using a PLC-Based Funnel-Shaped Waveguide With Dual-Mode Fiber [Invited

This paper increases the splitting ratio of 10 Gb/s-class passive optical network (PON) systems by using a novel low-loss optical splitter based on single-mode (SM) to multimode (MM) coupling. It consists of a planar lightwave circuit (PLC)-based funnel-shaped waveguide (FW) and a dual-mode fiber (DMF) that supports both SM and MM propagation through its dual core configuration. While conventional low-loss splitters based on a similar principle, called mode couplers or mode combiners (MCs), pass through only upstream signals, the proposed FW-DMF acts as a low-loss splitter for upstream and a conventional splitter for downstream despite its simple configuration. Compared to conventional MCs, it greatly reduces the number of optical components required for an optical line terminal. Considering the more efficient use of existing infrastructures, we develop two types of FW-DMFs with branching ratios of 4 and 16. Bit error rate measurements assuming 10 G-EPON systems show the ability of our prototypes to realize 128-split 10 Gb/s-class PON systems.

Propagation of vector solitons in a quasi-resonant medium with stark deformation of quantum states

The nonlinear dynamics of a vector two-component optical pulse propagating in quasi-resonance conditions in a medium of nonsymmetric quantum objects is investigated for Stark splitting of quantum energy levels by an external electric field. We consider the case when the ordinary component of the optical pulse induces σ transitions, while the extraordinary component induces the π transition and shifts the frequencies of the allowed transitions due to the dynamic Stark effect. It is found that under Zakharov-Benney resonance conditions, the propagation of the optical pulse is accompanied by generation of an electromagnetic pulse in the terahertz band and is described by the vector generalization of the nonlinear Yajima-Oikawa system. It is shown that this system (as well as its formal generalization with an arbitrary number of optical components) is integrable by the inverse scattering transformation method. The corresponding Darboux transformations are found for obtaining multisoliton solutions. The influence of transverse effects on the propagation of vector solitons is investigated. The conditions under which transverse dynamics leads to self-focusing (defocusing) of solitons are determined.

Objective speckle velocimetry for autonomous vehicle odometry

Speckle velocimetry is investigated as a means of determining odometry data with potential for application on autonomous robotic vehicles. The technique described here relies on the integration of translation measurements made by normalized cross-correlation of speckle patterns to determine the change in position over time. The use of objective (non-imaged) speckle offers a number of advantages over subjective (imaged) speckle, such as a reduction in the number of optical components, reduced modulation of speckles at the edges of the image, and improved light efficiency. The influence of the source/detector configuration on the speckle translation to vehicle translation scaling factor for objective speckle is investigated using a computer model and verified experimentally. Experimental measurements are presented at velocities up to 80 mm s(-1) which show accuracy better than 0.4%.

A multiline spectrometer for the analysis of solar atmospheric oscillations and flows at the VTT, Tenerife

Context. Despite longstanding observational efforts, the origins of the chromospheric temperature rise and the coronal heating are still not well understood. There is reason to believe that the limitations of existing observational devices might be contributing to this lack of experimental evidence. Aims. We intended to develop a multiline spectrometer capable of observing velocity fields simultaneously at more height levels of the solar atmosphere than previously possible. System design and handling would be optimized for the 3D-analysis of atmospheric waves and flows. Methods. The number of optical components was kept to a minimum in order to achieve high optical throughput and short scanning times. A new type of bandpass preselection unit was developed. We successfully tested this Fabry-Perot based multiline device at the Vacuum Tower Telescope (VTT). Results. During a proof-of-concept run we were able to observe 16 spectral lines at a cadence of 60 s sustained over several hours. The field of view was 100-by-100 arcsecs. Multiple diagnostic diagrams from closely spaced height levels were derived. Conclusions. A new instrument of this type will be installed permantently at the VTT. We expect to be able to collect new 3Dinformation about atmospheric waves and flows.

Performance analysis of multiple interference suppression over asynchronous/synchronous optical code-division multiple-access system based on complementary/prime/shifted coding scheme

A complete complementary/prime/shifted prime (CPS) code family for the optical code-division multiple-access (OCDMA) system is proposed. Based on the ability of complete complementary (CC) code, the multiple-access interference (MAI) can be suppressed and eliminated via spectral amplitude coding (SAC) OCDMA system under asynchronous/synchronous transmission. By utilizing the shifted prime (SP) code in the SAC scheme, the hardware implementation of encoder/decoder can be simplified with a reduced number of optical components, such as arrayed waveguide grating (AWG) and fiber Bragg grating (FBG). This system has a superior performance as compared to previous bipolar-bipolar coding OCDMA systems.

Multifiber Shared-Per-Wavelength All-Optical Switching: Architectures, Control, and Performance

A new wavelength converter sharing strategy for multifiber optical switches, namely shared-per-wavelength (SPW), which employs wavelength converters with fixed input wavelengths is presented. The aim is to reduce switch costs by using simpler optical components and low complexity space switching matrices. Practical implementations of both the well-known shared-per-node (SPN) and the new SPW schemes are presented, as well as the related scheduling algorithms to manage optical packet forwarding in synchronous scenario. An analytical model to evaluate blocking performance of the SPN architecture is also provided. Results show the accuracy of the model in the range of interest for switch design. The proposed architectures are compared in terms of performance and number of optical components employed. The SPW approach is shown to save a large number of semiconductor optical amplifier gates with respect to the SPN one when the number of fibers per interface is suitably not too high. In these cases, the SPW architecture requires a number of wavelength converters higher than the SPN, but simpler, being their inputs tuned on a single wavelength.

Heterodyne interferometer with unequal path lengths

Laser interferometry is an extensively used diagnostic for plasma experiments. Existing plasma interferometers are designed on the presumption that the scene and reference beam path lengths have to be equal, a requirement that is costly in both the number of optical components and the alignment complexity. It is shown here that having equal path lengths is not necessary, instead, what is required is that the path length difference be an even multiple of the laser cavity length. This assertion has been verified in a heterodyne laser interferometer that measures typical line-average densities of ∼1021∕m2 with an error of ∼1019∕m2.

Analysis of a combined tip-tilt and deformable mirror

A deformable mirror mounted on a two-axis tilt platform can provide wavefront compensation at a single location in an adaptive optics system, resulting in a significant reduction in the number of optical components in the system and in a simplification of the alignment. However, the moment of inertia of a deformable mirror is significantly different from that of the monolithic mirror commonly mounted on a tilt platform. We report on what are to our knowledge the first experimental results of mounting a microelectromechanical deformable mirror onto a fast steering platform and the first observation that at low operating frequencies high-order deformation of the deformable mirror membrane was not recorded.

Triple-wavelength optical pickup head designs for compact disk, digital versatile disk and high-density digital versatile disk devices

We present a triple-wavelength design for a compact optical pickup head which uses two rhomboid prisms in parallel with three laser diodes. The design can be used for compact disk, digital versatile disk and high-density digital versatile disk devices. The specific prism lens used decreases the geometrical size and reduces the total number of optical components. The trade-off between tolerance and fabrication is also presented.

Simplified receiver implementation for optical differential 8-level phase-shift keying

A simplified receiver implementation for optical differential 8-level phase-shift keying using direct detection is proposed. This implementation reduces the number of optical components in the receiver to half. The impact of non-ideal receiver parameters is analysed and quantified for a 1 dB OSNR penalty.

Experimental scheme of quantum cryptography on the nonorthogonal states with time shift and a minimum number of optical components

A new scheme of experimental quantum cryptography on the nonorthogonal states is described. Nonorthogonality is achieved by the time shift of states in different messages. For this scheme to be efficient, it is sufficient to balance the arms of an interferometer at the receiver and transmitter ends to an accuracy of 1–2 cm. This is a fundamental advantage of this scheme over, e.g., the most developed cryptosystem based on phase coding, where the maximum transmission distance has been achieved. In the latter system, the arms of the interferometer need to be balanced with an accuracy of fractions of a micron for a distance of several tens of kilometers.

Optical Pickup Employing a Hologram-Laser-Photodiode Unit

In this paper we review the holographic optical element technology applied to compact disc (CD), digital versatile disc (DVD) and mini disc (MD) pickups. Using this technology, the number of optical components and the size and weight of a CD pickup are successfully reduced and its reliability is improved, because many functions of the optical components are integrated into a hologram-laser-photodiode unit. For DVD application, the focus detection for a dual-layer disk and the differential phase detection (DPD) method are realized by the hologram technology. Our unique two-segment DPD method shows more stable characteristics than the conventional DPD method. An integrated MD hologram pickup is also developed with an optical waveguide device that functions in magneto optical (MO) signal detection.

Detection of Riboflavin Based on Fluorescence Enhancement of Evanescent-Wave Excited β-Cyclodextrin Complex in Sol-Gel-Derived Porous Coatings

A sol-gel-derived film doped with β-cyclodextrin was used to construct a fiber-optic evanescent-wave fluorosensor. In this sensing configuration, the fluorescence emitted was detected from the side surface of the fiber, where the cladding at the distal end was removed. For detection of riboflavin, the fluorescence enhancement by the film coated at the distal end of an optical fiber is 10.6 times than that of an unmodified optical fiber. The enhancement is due to the accumulation of riboflavin in the sol-gel cladding and the more constrained microenvironment for riboflavin. The linear dynamic range of this sensor extends well over 2 orders of magnitude. Detection limit (signal-to-noise ratio = 3) is as low as 80 nM. The sensor is easy to operate, simple to construct, and requires a minimal number of optical components.

A Rigorous Two-Dimensional Field Analysis of Dfb Structures - Abstract

It is the aim of this work to develop a two-dimensional (2-D) analysis for the electromagnetic field distribution in distributed feedback (DFB) structures. This analysis is based on an equivalent network for the 2-D wave equation which must be satisfied by the components of both electric and magnetic field. The parameters of the equivalent network are determined from the physical parameters of the DFB structure in a straightforward manner. The zero-input response of this equivalent network leads to the dispersion relation for the modes guided by the DFB structure. The method has been applied to a number of optical components utilizing a DFB structure like DFB lasers, optical filters, and multi quantum well DFB lasers. A comparison with common methods of analysis shows that the network modeling yields accurate numerical results. At the same time its computational efficiency can be maintained quite high.

Compensating pulse-to-pulse fluctuations and increasing spectral reproducibility of phase-matched CARS measurements

The compensation of pulse-to-pulse fluctuations and the improvement of spectral reproducibility of scanned coherent anti-Stokes Raman scattering (CARS) spectra of dispersing media are discussed. A simple reference CARS setup is presented that needs a minimum number of optical components as a result of using the same optical path for both signals. Variations in spectral profile were found to be caused by mechanical play in the translation stage, which is used to adjust the matching angle. Using retroreflection, the matching angle adjustment is made insensitive to these mechanical imperfections. The multiple interference of probe and signal beam that may occur in thin cuvette walls and its effect on the detected CARS signals are shown, and possible solutions are discussed.

Picosecond semiconductor laser radar with optical amplifier

An optical range finder, which uses the same semiconductor laser as both an optical pulse source and an optical preamplifier of the reflected pulse, is reported. This method has the advantage of reducing the number of optical components that must be aligned, which makes it suitable as a picosecond laser radar in aerospace applications. The device showed a maximum optical gain of 17 dB with a dynamic range of 33 dB, and the obtained resolution was of the order of 1 mm.