High Performance Optical Systems Research Articles

Investigation of the spatial structure of a high-power fiber laser beam

Analysis of experimental results and theoretical studies has confirmed that the free- space propagation and the transformation of a high-power fibre laser beam by an optical system can be described by the theory of laser optics. The need to use the theory of laser optics to develop modern high-performance optical systems of laser processing heads, which form the beam of the high-power fibre laser, is discussed.

High-performance optical modulators bias control system without dither

A software-based bias control system of push–pull Mach–Zehnder modulators (MZMs) without dither tone is described in this paper. The slope of the average optical output power respect to the bias voltage is used to control the operating bias points in the automatic control system. The paper analyses the theory of automatic bias control intensively and verifies the effectiveness of the proposed technique which is a modulation-format-free method under the RF signal through testing and contrasting the BER (bit error rate) between the new technique and manual measure on the experimental platform. Based on this, an automatic bias control system set up by an optical QPSK composed by double MZMS on the LabVIEW platform is described.

Threshold Characteristics Enhancement of a Single Mode 1.55 µm InGaAsP Photonic Crystal VCSEL for Optical Communication Systems

In the present work, we investigate threshold characteristics of a single mode 1.55 μm InGaAsP vertical cavity surface emitting laser (VCSEL) with two different optical confinement structures. The device employs InGaAsP active region, which is sandwiched between GaAs/AlGaAs and GaAs/AlAs distributed Bragg reflectors (DBRs). The optical confinement introduced by the oxide aperture or a single defect photonic crystal design with holes etched throughout the whole structure, is compared with previous work. Photonic crystal VCSEL shows 30.86% and 57.02% lower threshold current than that of the similar oxide confined VCSEL and previous results, respectively. This paper provides key results of the threshold characteristics, including the threshold current and the threshold power. Results suggest that, the 1.55 μm InGaAsP photonic crystal VCSEL seems to be the most optimal one for light sources in high performance optical communication systems.

Transmission behavior improvement of electro‐optic modulators for integrated photonic systems in the present communication technology

SummaryThis paper has presented the transmission performance evaluation of different electro‐optic modulators (EOM) for ultra high switching speed operations and applications. As well as the optimization design parameters for different EOMs have been investigated, where the effective refractive index plays an essential role in the evaluation of the bandwidth structure. The effects of the operating parameters on the switching, modulating voltage, device performance index, and optical bandwidth are also investigated for different material‐based EOMs, where the transmission bit rate is evaluated by using non‐return‐to‐zero coding transmission technique. As well as lithium niobate, gallium arsenide, and poly methyl metha acrylate polymer EOMs have been developed for extensive use in high speed and high transmission performance optical fiber transmission systems. Copyright © 2013 John Wiley & Sons, Ltd.

Design of a new broadband monopole optical nano-antenna

In this paper, we propose a novel design of broadband monopole optical nano-antennas. It is consisted of a corrugated half elliptical patch inside an elliptical aperture. By adjusting the dimensions of the elliptical patch and the elliptical aperture, the overall performance of the proposed monopole nano-antenna can be made remarkable broadband. Full wave electromagnetic simulations have been used to investigate the effects of different parameters on the nano-antenna performance. Moreover, the proposed broadband nano-antenna can support light waves with different polarizations. It is expected that the new optical antenna will pave the way towards the development of high performance optical antennas and optical systems.

Lensless optical data hiding system based on phase encoding algorithm in the Fresnel domain

A novel and efficient algorithm based on a modified Gerchberg-Saxton algorithm (MGSA) in the Fresnel domain is presented, together with mathematical derivation, and two pure phase-only masks (POMs) are generated. The algorithm's application to data hiding is demonstrated by a simulation procedure, in which a hidden image/logo is encoded into phase forms. A hidden image/logo can be extracted by the proposed high-performance lensless optical data-hiding system. The reconstructed image shows good quality and the errors are close to zero. In addition, the robustness of our data-hiding technique is illustrated by simulation results. The position coordinates of the POMs as well as the wavelength are used as secure keys that can ensure sufficient information security and robustness. The main advantages of this proposed watermarking system are that it uses fewer iterative processes to produce the masks, and the image-hiding scheme is straightforward.

Design of High-Performance Vehicle Multi-Axis Optical Encoder Data Acquisition System Based on PC104 Bus

A high-performance vehicle multi-axis optical encoder data acquisition system based on PC104 bus is introduced. The paper puts emphases on the main function of the system module. VHDL hardware description language is used to design the modules, and ModelSim is introduced to implement logic and sequential simulation. An experiment is carried on in Altera EPF10K40 chip. Both the simulation and experimental results verify the correctness and validity of the method.

Morphology evolution of fused silica surface during ion beam figuring of high-slope optical components

Ultra-precision and ultra-smooth surfaces are vitally important for some high performance optical systems. Ion beam figuring (IBF) is a well-established, highly deterministic method for the final precision figuring of extremely high quality optical surfaces, whereas ion sputtering induced smoothing, or roughening for nanoscale surface morphology, strongly depends on the processing conditions. Usually, an improper machining method would arouse the production of nanoscale patterns leading to the coarsening of the optical surface. In this paper, the morphology evolution mechanism on a fused silica surface during IBF of high-slope optical components has been investigated by means of atomic force microscopy. Figuring experiments are implemented on two convex spherical surfaces by using different IBF methods. Both of their surface errors are rapidly reduced to 1.2 nm root mean square (RMS) after removing similar deep material, but their surfaces are characterized with obviously different nanoscale morphologies. The experimental results indicate that the ion incidence angle dominates the microscopic morphology during the IBF process. At near-normal incidence, fused silica achieves an ultra-smooth surface with an RMS roughness value R(q) down to 0.1 nm, whereas nanoscale ripple patterns are observed at a large incidence angle with an R(q) value increasing to more than 0.9 nm. Additionally, the difference of incidence angles on various machined areas would influence the uniformity of surface quality, resulting from the interplay between the smoothing and roughening effects induced by ion sputtering.

Current Trends of High capacity Optical Interconnection Data Link in High Performance Optical Communication Systems

Optical technologies are ubiquitous in telecommunications networks and systems, providing multiple wavelength channels of transport at 2.5 Gbit/sec to 40 Gbit/sec data rates over single fiber optic cables. Market pressures continue to drive the number of wavelength channels per fiber and the data rate per channel. This trend will continue for many years to come as electronic commerce grows and enterprises demand higher and reliable bandwidth over long distances. Electronic commerce, in turn, is driving the growth curves for single processor and multiprocessor performance in data base transaction and Web based servers. Ironically, the insatiable taste for enterprise network bandwidth, which has driven up the volume and pushed down the price of optical components for telecommunications, is simultaneously stressing computer system bandwidth increasing the need for new interconnection schemes and providing for the first time commercial opportunities for optical components in computer systems. The evolution of integrated circuit technology is causing system designs to move towards communication based architectures. We have presented the current tends of high performance system capacity of optical interconnection data transmission link in high performance optical communication and computing systems over wide range of the affecting parameters.

Dynamics in lithographic projection objectives

High-performance optical systems like lithography objectives are very sensitive to external dynamic excitations, which may occur both during operation and out of operation, i.e., during handling and transport. Lithography objectives are typical opto-mechanical systems. For the non-operating state, the focus of dynamical investigations is on avoiding damage, whereas during operation, the preservation of a good imaging behavior is of interest. In the first part, some out-of-operation situations are introduced, namely handling, transport, and earthquakes. In this context, excitation models are discussed and also applied to a nonlinear model. In the second part, an overview of techniques for modeling interfaces between dynamics and optics is given regarding lens systems. The interfaces are summarized in the lens kinematics. Lens kinematics is comprised of rigid lens motion, surface deformations, and refraction index variations due to stresses. According to these issues, some examples are provided.

高成像质量光学系统的元件旋转补偿

高成像质量光学系统的元件旋转补偿

Development of a High-performance Optical System and Fluorescent Converters for High-resolution Neutron Imaging

Abstract Two novel devices for use in neutron imaging technique are introduced. The first one is a high-performance optical lens for video camera systems. The lens system has a magnification of 1:1 and an F value of 3. The optical resolution is less than 5 μm. The second device is a high-resolution fluorescent plate that converts neutrons into visible light. The fluorescent converter material consists of a mixture of 6 LiF and ZnS(Ag) fine powder, and the thickness of the converter is material is as little as 15 μm. The surface of the plate is coated with a 1 μm-thick gadolinium oxide layer. This layer is optically transparent and acts as an electron emitter for neutron detection. Our preliminary results show that the developed optical lens and fluorescent converter plates are very promising for high-resolution neutron imaging.

High reliability optical interconnections for short range applications in high performance optical communication systems

This paper has proposed a new progress of optical interconnections, taking into account the following items such as its ultimate device bandwidth, its available transmission bit rates based on soliton transmission technique, its ultimate transmission link bandwidth, and the product of the link bandwidth and its transmission length. Two items of special emphasis in the basic design of optical interconnection are polymethyl metha acrylate (PMMA) and barium fluoride (BaF2) waveguides, and the optical source cast as vertical cavity surface emitting laser diode (VCSELD), made of either AlGaAs at operating wavelength of 1.3μm or aluminum gallium indium phosphors (AlGaInP) at operating wavelength of 1.55μm; special emphasis is focused on both the above two items under different operating conditions including both thermal and electrical effects. The optical interconnect is built up on the bases of two VCSELD and one optical link where thermal effects of both diodes and links are included. The good performance of the optical interconnect is deeply and parametrically investigated under wide ranges of the affecting parameters. The high speed performance is processed through three different effects, namely the device 3-dB bandwidth, and the link dispersion characteristics.

An Equivalent Circuit Model for Separate Absorption Grading Charge Multiplication Avalanche Photodiode

With the scale of microwave photonics system getting larger and the structure of it getting more complex, the CAD tools and accurate circuit models have become essential for designers, since difficulty for system design increases greatly. In this work, an equivalent circuit model for separate absorption grading charge multiplication avalanche photodiode (SAGCM APD) has been proposed. The model is applied to simulate the device performance and the simulating results show a well reasonable agreement with the physical model calculation and experimental data. A detailed comparison has been made for InP/InGaAs, InAlAs/InGaAs and Si/Ge APD with different structures. Our results show that Si/Ge APD is the most promising candidate for high performance optical communication system.

Time-resolved, local temperature measurements during pulsed laser heating

To analyse processes during laser heating, one needs to be able to measure temperatures of about 1000 K within one microsecond and with micrometre resolution. To achieve this accuracy, we set up a high-performance optical detection system with a microsecond gated camera in combination with selected interference filters to detect the thermal emission spectrum in the visible range. By fitting the emission spectrum to Planck's law, we are able to collect an area temperature profile for time intervals as short as one microsecond. Thus we can show that a polymer film, which is doped with an organic dye for energy conversion, can reach temperatures of at least 900 K, which is high above its ‘normal’ decomposition temperature. It is, furthermore, possible to relate the temperature to the effect of the laser beam on the polymer film.

Dimensional Stability Testing on a Space Optical Bench Structure

High-performance space-based optical systems typically require structures that exhibit high levels of dimensional stability over their lifetimes. To better understand the mechanisms for dimensional instability, a novel series of tests were carried out at Rutherford Appleton Laboratory on a breadboard high-stability optical bench structure. Goals of the testing were to assess the relative stability of a pair of reference surfaces and to determine the contributions of various structural elements and joints to dimensional instability. The breadboard was subject to an intensive environmental test campaign that included thermal cycling under vacuum and random vibration testing. Metrology was performed throughout the campaign to assess the dimensional stability response to the various environmental loads. The metrology requirement was challenging, with measurements of micron-level displacement and arcsecond- level tilt over 1-meter distances being necessary in situ during environmental testing. This issue was resolved using a combination of techniques: a contacting coordinate measurement machine, laser interferometry, and optical autocollimation. The greatest levels of instability were produced by random vibration testing, though evidence of a bedding-in process implies that vibratory conditioning could be used to improve stability.

REPLICATION OF NANO/MICRO QUARTZ MOLD BY HOT EMBOSSING AND ITS APPLICATION TO BOROSILICATE GLASS EMBOSSING

Glass hot-embossing is one of essential techniques for the development of high-performance optical, bio, and chemical micro electromechanical system (MEMS) devices. This method is convenient, does not require routine access to clean rooms and photolithographic equipment, and can be used to produce multiple copies of a quartz mold as well as a MEMS component. In this study, quartz molds were prepared by hot-embossing with the glassy carbon (GC) masters, and they were applied to the hot-emboss of borosilicate glasses. The GC masters were prepared by dicing and focused ion beam (FIB) milling techniques. Additionally, the surfaces of the embossed quartz molds were coated with molybdenum barrier layers before embossing borosilicate glasses. As a result, micro-hot-embossed structures could be developed in borosilicate glasses with high fidelity by hot embossing with quartz molds.

Tight focusing of plane waves from micro-fabricated spherical mirrors

We derive a formula for the light field of a monochromatic plane wave that is truncated and reflected by a spherical mirror. Within the scalar field approximation, our formula is valid even for deep mirrors, where the aperture radius approaches the radius of curvature. We apply this result to micro-fabricated mirrors whose size scales are in the range of tens to hundreds of wavelengths, and show that sub-wavelength focusing (full-width at half-maximum intensity) can be achieved. This opens up the possibility of scalable arrays of tightly focused optical dipole traps without the need for high-performance optical systems.

Disposable Microscope Objective Lenses for Fluorescence Correlation Spectroscopy Using Latex Microspheres

We explore the combination of a latex microsphere with a low NA lens to form a high performance optical system, and enable the detection of single molecules by fluorescence correlation spectroscopy (FCS). Viable FCS experiments at concentrations 1-1000 nM with different objectives costing less than $40 are demonstrated. This offers a simple and low-cost alternative to the conventional complex microscope objectives.

90$^{\circ}$ Light Beam Deflection Technology for Single-Mode Optical Interconnection Systems

In this letter, we demonstrate an extremely low loss (<0.06 dB) 1-mm bending radius 90deg light deflection by using a 12-single-mode-fiber ribbon for optical interconnection systems. This technology is easy to be adopted for optical surface mount assemblies that need light beam deflection between the vertical surface-emitting lasers or surface-receiving photodiodes and optical paths parallel to an electric circuit board. We have chosen single-mode fiber (SMF) for the 90deg-bent fiber expecting the single-mode transmission will be applied for high-performance optical interconnection systems because of its wide bandwidth and stability in transmission characteristics. In order to minimize the bending loss and accomplish a small bending radius, we have developed a new optical fiber having higher refractive index of the core (high delta n fiber) than that of conventional fiber and 80-mum-cladding 125-mum spacing 12-fiber ribbon for dense packaging and easy handling in narrow spaces. It is bent at a radius of 1 mm by heating process with a ceramic heater.