New diffraction grating profiles in InP for DFB lasers and integrated optics

A bilevel processing technique has been used to obtain sub-micrometer-period InP diffraction gratings. Novel cross-sectional grating profiles with depths of up to 4000 ? have been obtained which should facilitate the fabrication of more efficient Bragg devices.     

Characterizing residual reflections within semiconductor lasers,integrated sources, and coupling optics

We describe a method for analyzing reflections within or near semiconductor lasers and more complicated integrated sources. Through Fourier transformation of an optical spectrum from the wavevector to the length domain, reflections are analyzed for strength, round-trip path length, and current or voltage dependence. Identification of reflections from within semiconductor lasers, integrated electro-absorption modulated lasers, and from coupling optics is presented. Spatial resolution in InP of ~5 μm with over two orders of magnitude in dynamic range is demonstrated. Inverse transformation of a spatially resolved feature in a transformed reflection spectrum provides an optical spectrum due to that individual feature of sufficient resolution to study wavelength dependence, for example, of coatings and gratings     

High-density integrated optics

This paper presents two dimensional (2-D) finite difference time domain (FDTD) simulations of low-loss right-angle waveguide bends, T-junctions and crossings, based on high index-contrast waveguides. Such structures are essential for the dense integration of optical components. Excellent performance characteristics are obtained by designing the waveguide intersection regions as low-Q resonant cavities with certain symmetries and small radiation loss. A simple analysis, based on coupled mode theory in time, is used to explain the operation principles and agrees qualitatively with the numerical results     

Ferroelectric integrated optics: recent developments

Advances in rare-earth-doped waveguide lasers in LiNbO₃, waveguided second harmonic generation through quasi-phase-matching in LiNbO₃ and LiTaO₃, and pulsed laser epitaxial growth of LiNbO₃ on Sapphire are reported. Efficient lasers operating in CW, Q-switch, and mode-lock modes were fabricated in Nd:LiNbO₃. In order to assess the potential of bulk-doped Er:LiNbO₃ samples, spectroscopic measurements have been carried out, the main limiting mechanism identified, the corresponding up-conversion coefficient evaluated, and a comprehensive gain model developed. First lasing action in this material, when pumped at 1.48 μm, is described. Quasi-phase-matched generation of blue light with conversion efficiencies up to 150%/Wcm² is also demonstrated, and finally we present the fabrication of low-loss LiNbO₃ single-crystal waveguiding layers     

Limits in integrated optics

A review is given of the characteristics and limits of integrated optics devices and circuits, with emphasis on size, speed, and power consumption. Performance limits and trade offs are discussed for semiconductor lasers, filters, switches and modulators, and bistable devices.     

Third order nonlinear integrated optics

The authors review progress in the application of nonlinear optical phenomena to integrated optics. Essentially all integrated optics devices such as directional couplers, Mach-Zehnder interferometers, prism couplers, etc., can be used for all-optical signal processing when at least one of the waveguiding media exhibits an intensity-dependent refractive index. Experimental and theoretical results on the operating characteristics and figures of merit of such devices, as well as a new class of phenomena based on large nonlinear changes in waveguide properties will be summarized. Also discussed are measurement techniques for evaluating waveguide nonlinearities. Progress in the implementation of other nonlinear third order interactions, such as degenerate four-wave mixing and nonlinear spectroscopy, will also be reviewed     

Device equivalence in integrated optics

The concept of device equivalence is introduced. In equivalent devices, the light propagation can be described by identically evolving modal expansions, resulting in identical power transfer ratios. By first applying this concept to a z-invariant structure with a low refractive-index contrast it is shown how a normalized coordinate space can be defined in which equivalent structures have exactly the same geometry. Subsequently it is shown how this normalized coordinate space can be defined for z-variant integrated optical devices, again provided that the lateral refractive-index contrast is small. This normalization makes it possible to perform numerical device simulations in normalized coordinate space, the results being applicable to a large set of equivalent devices. Furthermore, starting from a known design, it simplifies redesigning that device for use at another wavelength or using other materials significantly, the resulting device being equivalent to the original one     

Three-dimensional integrated optics using polymers

Some of the key components are demonstrated to make three-dimensional (3-D) optical integrated circuits possible using polymers. Fabrication techniques of shadow reactive ion etching, shadow photolithography, and gray-level photolithography to produce complex 3-D integrated optic structures are demonstrated. Vertical waveguide bends exhibit excess losses of <0.3 dB, and vertical power splitters possess predictable output splitting ratios between multiple core levels with excess losses of <0.5 dB. Vertical polarization splitters exhibit power extinction ratios of 15 dB between the output core layers. A 1×4 vertical-horizontal power splitter is also demonstrated. Additionally, these techniques are used to integrate different polymer materials into the same optical circuit while easily solving the mode mismatch problem. To show the technique, a polymer electrooptic modulator is vertically integrated with a low-loss waveguide     

Lensless integrated optics spectrum analyzer

An electrooptic integrated optics spectrum analyzer is investigated in which an electrode array with a spatially varying period performs the functions of the collimation and transformation lenses and of the signal introduction. The device yields a weighted discrete Fourier transform (DFT) of the voltages on the electrodes. An implementation of the device would be fully compatible with planar photolithographic processes.     

Integrated optics approach for advanced semiconductor lasers

Recent advances in the field of semiconductor integrated optics are reviewed from the point of view of monolithic integration of semiconductor lasers and other optical components and/or devices. Emphasis is placed on dynamic-single-mode (DSM) lasers, such as DFB and DBR lasers, intended for highly stable single-wavelength light sources for such monolithic integration. The realization of high-performance DSM lasers and the fabrication techniques of monolithically integrated optical devices and circuits are briefly reviewed. A variety of potential applications is discussed.     

Roughness, inhomogeneity, and integrated optics

Surface roughness (and more generally) inhomogeneity is a constraining factor on optoelectronics devices. Its more conspicuous effect is to scatter light thus leading to power attenuation. This effect partly explains the five orders of magnitude difference in attenuation between fibers and integrated waveguides. Less well known is the effect of roughness on back-coupling and mode coupling in devices such as couplers and gratings. I present here an overview of these effect analyzed from a heuristic approach based upon the length scales of the dominant physical mechanism present in such devices     

Telecommunications applications of integrated optics and optoelectronics

Integrated optics and optoelectronics will play key roles in the evolution of the telecommunications network. We briefly review the available and developing technologies for integrated optical and optoelectronic devices, and summarize their characteristics and their natural areas of application in telecommunications. We then describe the trends and developments in fiber communication systems, services, and architectures, and how they can benefit from these devices. Major areas in which these devices are expected to contribute are: lowering the costs of high-speed network termination equipment to aid in providing inexpensive wide-band services to the subscriber; increasing the fraction of the fiber's natural bandwidth that can be made available for network usage; and increasing the network flexibility to facilitate multiservice integration.     

Resonant cavity sensor for integrated optics

The design of interferometric sensors, fabricated on single integrated optic chips for use in a multiplexed system, is considered. A multiple-pass interferometer using a resonant cavity appears extremely attractive, since it has a large path imbalance which may easily be varied. Sensors may therefore be fabricated that are highly sensitive and easily individualized. The resonant cavity sensor is analyzed, and response curves are presented under a variety of conditions. Experimental results are presented for temperature sensors fabricated in LiNbO3.     

Vectorial beam-propagation method for integrated optics

A finite-difference beam-propagation method is derived directly from the vectorial Maxwell equations. The new approach allows the analysis of coupling between various components of the electric-field vector for optical beams propagating in dielectric waveguides as well as corresponding changes in the beam-polarisation state.<>     

Fibre optic interferometer using integrated optics

A fibre optic Mach-Zehnder interferometer has been constructed using channel waveguides in LiNbO3 as splitters and combiners and integrating the phase-tracking component on the LiNbO3 device. The results are discussed and improvements are suggested.     

Holographic interference lithography for integrated optics

In this paper, some of our recent work in the use of holographic interference lithography and various material removal techniques to corrugate thin-film optical waveguides are reviewed. The specific applications of these periodic thin-film devices in the distributed feedback and distributed Bragg reflector semiconductor laser, and as output grating couplers, are described. Recent results in the use and fabrication of chirped and curved-line gratings are also summarized.     

Optimization of multilayer integrated optics waveguides

A numerical method is described that provides the means for optimizing any objective function representing a general multilayer integrated optics waveguide. In this way, the physical parameters of the multilayer structure can be set so that the performance of the device is optimized. The method uses any standard numerical minimization algorithm in conjunction with the argument principle method. The method has been successfully applied for the optimization of a multilayer immunosensor and a TE-mode polarizer. The advantages of the method are its generality, its efficiency, its accuracy, and its applicability to a wide range of planar integrated optics devices     

Analysis of integrated optics parametric oscillators

An almost analytical model for the analysis of integrated optics parametric oscillators is proposed. A comprehensive discussion of the static device characteristics of a doubly resonant oscillator with varying parameters of the optical cavity which influence the operation conditions (single and double pass and resonant pump) is presented. A detailed discussion of the evolution towards the singly resonant condition and the possibility of hysteretic behavior is also included     

基于集成光学的波束形成以及误差分析

为了在系统设计中规避二维光子探测器(PD)阵列,基于集成光学对从空间光角度实现时延网络以及波束形成原理进行研究,通过集成光学空间棱镜组的方法进行光分束和合束,并利用空间光探测器的低通滤波效果实现射频波束的相干合成等关键技术。采用数值仿真对影响波束合成的误差因素进行分析,并与实测结果进行对比。仿真和实测结果相关误差会恶化波形质量和副瓣水平,但仍能够在±30°空域范围内和3:1的频域带宽内实现设计指向的同时四波束方向图。