Add-drop multiplexer with UV-written Bragg gratings and directionalcoupler in SiO2-Si integrated waveguides

The needs of wavelength multiplexers is growing and therefore optical add-drop multiplexers (OADMs) become key components for the advanced high bit rate telecommunication networks. Currently, one of the solutions to make OADMs use fiber Bragg gratings and circulators. In order to take advantage of integrated optics and to avoid the use of expensive circulators, we perform this kind of OADM in ridge silica waveguide on silicon. This technology makes possible short based directional coupler (DC) device. In previous work, we firstly realized an OADM which involves a symmetrical directional coupler combined with two Bragg gratings inside the coupling zone. The results meet difficult tradeoff between a high extinction ratio and a narrow spectral width of the rejection band. This paper reports some fabrication improvements for DC-OADM that lead to more efficient components, progress results from a lot of works concerning both the photo-writing process of Bragg gratings and the lowering of the waveguide internal stresses. Thus, we show that apodization of gratings and low birefringence in the waveguides enables us to achieve DC-OADM with an extinction ratio of 30 dB and a spectral bandwidth less than 1.5 nm     

Low-loss planar lightwave circuit OADM with high isolation and nopolarization dependence

A passive optical add-drop multiplexer with 1 dB of insertion loss and 36 dB of isolation is fabricated by writing Bragg gratings in a waveguide Mach-Zehnder interferometer using ArF excimer laser light. The spectral properties and bit-error-rate performance of the device are fully characterized using polarized light     

Simple Reconfigurable Photonic Microwave Filter Using an Arrayed Waveguide Grating and Fiber Bragg Gratings

We demonstrate a photonic microwave finite impulse response filter with reconfiguration and tuning capabilities. The filter is based on spectral slicing of a broadband source and optical fiber as a wideband dispersive medium. An arrayed waveguide grating and fiber Bragg gratings are used to select and vary the weight of the optical taps to achieve reconfiguration and tuning     

Optical cross-connect structures for interleaved multiwavelengthbidirectional ring networks

Novel bidirectional optical cross-connect structures using a single arrayed waveguide grating router and tunable fibre Bragg gratings have been proposed for interleaved multiwavelength ring networks. In the proposed structures, each wavelength channel is independently switched by tuning the centre wavelength of the gratings. The feasibility of the cross-connectors has been experimentally demonstrated. A homodyne crosstalk less than -26 dB and a backscattering suppression ratio of -35 dB have been obtained     

Fabrication of ultra high aspect ratio Bragg gratings for optical filter

In this paper a novel process for fabrication of high finesse and large spectral range integrated optics filtering structure for optical communication applications is presented.The technology approach used in the fabrication make use of glass-on-silicon substrates and comprise deep submicron ultra-high aspect ratio Bragg gratings which are deeply buried into the waveguide glass materials.     

Optical arbitrary waveform generation based on an array of tunable apodized waveguide Bragg gratings

A structure of optical arbitrary waveform generation (OAWG) based on an array of tunable apodized waveguide Bragg gratings (WBGs) is proposed. The WBGs array on lithium niobate (LN) consists of several apodized gratings, waveguides and electrodes deposited on both sides of gratings and waveguides. The properties of OAWG are analyzed using transfer matrix method. Due to the electro-optic effect of LN, the amplitude and phase of incident light source are controlled via adjusting the voltages on electrodes. Consequently, the optical pulses with different waveforms are obtained and the amplitude is linearly tuned. In addition, voltages compensating amplitude and phase distortion are demonstrated.     

Electrooptic Bragg-diffraction modulators in GaAs/AlGaAsheterostructure waveguides

Reports theoretical and experimental results on electrooptic Bragg-diffraction modulators in GaAs/GaAlAs heterostructure waveguides. The devices utilize the linear electrooptic effect in periodic structures to facilitate spatial modulation of the refractive index in the waveguide. A numerical method was established to solve the waveguide equation and quantify the induced changes in the effective index of the waveguide as a result of reverse bias. The numerical calculation has established the guidelines for an optimum design of the modulator that operates in the Bragg regime. The measured diffraction efficiency of the single-grating Bragg modulator was as high as 90 percent at a driving voltage of 15 V. A device consisting of four such basic diffraction gratings was also fabricated and used to demonstrate the function of scalar addition. The highest bandwidth of the devices that have been measured exceeds 1 GHz. The planar waveguide Bragg modulators offer advantages including lower optical propagation loss, greater fabrication tolerance, and spatial separation between the diffracted and the undiffracted light beams     

Mode control in integrated optical devices via photoinducedbirefringence

Photoinduced birefringence is proposed as a tool for mode-control applications in integrated optical devices such as waveguides, fibers, etc. Various geometries of photoexposure are theoretically considered for the example of a planar waveguide. Analytical solutions are obtained that provide information about the resulting polarizational behavior of the guide. The presence of birefringent Bragg gratings is then considered and conditions are identified to obtain polarization-insensitive spectral filters     

UV-induced surface-relief gratings on LiNbO3 channelwaveguides

We report a new technique for fabricating Bragg gratings in LiNbO ₃ channel waveguides. This technique involves the irradiation of the waveguide by means of an ultraviolet beam. We also demonstrate the applications of these gratings as tunable input couplers and as Bragg reflectors     

Integrated III–V Bragg Gratings for Arbitrary Control Over Chirp and Coupling Coefficient

In this work, integrated chirped Bragg gratings based on tapered waveguide sidewall gratings are presented, along with the method by which arbitrary variations of Bragg condition and coupling coefficient may be achieved. Fabricated devices with constant Bragg condition, linear, and nonlinear chirp are exhibited with and without apodized coupling coefficient profiles. Finally, an integrated Michelson interferometer setup is used to confirm the grating phase characteristics.      

Design of polarization-insensitive Bragg gratings inzero-birefringence ridge waveguides

Addresss the problem of designing polarization-insensitive Bragg gratings in zero-birefringence ridge waveguides. It is known that the reflection spectrum of a Bragg grating is be polarization-independent if both the phase-matching condition and the coupling coefficient are polarization-independent. While the use of a zero-birefringence waveguide can guarantee a polarization-independent phase-matching condition, it does not in general lead to a polarization-independent coupling coefficient. Our theoretical analysis indicates, however, that a strictly polarization-independent coupling coefficient is not essential for the achievement of a polarization-insensitive Bragg grating. Our detailed calculations on both corrugation and phase gratings in zero-birefringence ridge waveguides reveal some general design principles. Our results should be useful for the design of a wide range of Bragg-grating-based waveguide devices     

A compact Cherenkov laser with a Bragg cavity composed ofdielectric gratings

The growth and saturation characteristics of a Cherenkov laser with a Bragg cavity composed of dielectric gratings are investigated in detail with the aid of numerical simulation based upon the fluid model of the electron beam, For the analysis of the problem, a two-dimensional (2-D) model of the Cherenkov laser is considered which consists of a planar relativistic electron beam and a parallel plate waveguide, one plate of which is loaded with a dielectric sheet. For confinement and extraction of the electromagnetic wave, a Bragg cavity is formed by dielectric gratings fabricated at both ends of a dielectric-loaded parallel plate waveguide. The result of numerical simulation shows that a compact Cherenkov laser, the longitudinal dimension of which is about one order of magnitude smaller than that of the corresponding single-pass Cherenkov laser, can be realized by using a Bragg cavity composed of dielectric gratings     

Surface Plasmon Bragg Gratings Formed in Metal-Insulator-Metal Waveguides

We propose and numerically analyze surface plasmon Bragg gratings formed by a periodic variation of the width of the insulator in a metal-insulator-metal waveguide. The results indicate that very good filtering characteristics can be achieved in these plasmonic Bragg gratings. To suppress the sidelobes in the transmission spectrum, we further propose S-shaped Bragg cells and find better performance. By introducing a defect into the grating, a defect state with high Q-value is introduced into the bandgap and a Fabry-Peacuterot-like structure is formed     

从亚波长光栅到超构光栅:原理、设计及应用

随着纳米光子学的发展,光学结构如光学微腔、波导结构、光子晶体、亚波长光栅、超构表面等能够在微纳尺度实现对光的传输与调控,推动了光学集成化的发展。亚波长光栅由于其结构简单、成本低廉等特点得到了科学家们广泛的研究,应用在各种光学器件,逐渐形成了光栅分析模型的成熟理论体系。结合周期性结构耦合行为及超构表面中超构原子的散射调制特性,从亚波长光栅衍生出的超构光栅能够利用周期性布拉格散射提高调控光束的效率,从而避免了超构表面相位离散化带来的效率降低和能量损失。科学家们研究并设计了超构光栅,更多的物理现象及应用被探究和挖掘。文中对亚波长光栅以及超构光栅的基本理论、设计和应用进行了概述。从基本原理出发,论述了亚波长光栅和超构光栅的特性,综述了二者的理论设计及单元设计方法,并介绍了在生物传感、滤光片光谱调控和吸收薄膜等方面的应用。最后,展望了未来的发展方向。     

Optical Refractive-Index Sensor Based on Dual Fiber-Bragg Gratings Interposed With a Multimode-Fiber Taper

A new type of optical refractive-index (RI) sensor is proposed and experimentally demonstrated by using a structure of two single-mode fiber (SMF) Bragg gratings with a multimode fiber (MMF) taper in-between. The loss induced by a mismatch of waveguide structure between SMFs and MMFs is amplified by a tapering process, and is utilized for RI sensing through evanescent field. Experimental results show that the sensor possesses a tailorable sensitivity to the change of external RI and has a good linear response in the simultaneous measurement of external RI and temperature     

A distributed feedback ridge waveguide quantum well heterostructurelaser

A method for incorporating distributed feedback in a ridge waveguide laser by means of lateral gratings and a single growth step is discussed. The necessary Bragg condition for distributed feedback is satisfied by etching gratings along the ridge in the top confining layer of the laser on either side of the contact stripe. Both Fabry-Periot modes and a single emission peak away from the peak of the gain profile are observed in lasers with cleaved facets. The Bragg reflection emission peak does not shift with increasing drive current, which is characteristic of a distributed-feedback (DFB) laser     

Applications of ultrashort pulse propagation in Bragg gratings forwavelength-division multiplexing and code-division multiple access

We discuss theoretical and experimental studies on the propagation of ultrashort pulses through fiber Bragg gratings. We also consider several applications in optical communications to be found by combining ultrashort pulses and fiber Bragg gratings: a multiwavelength source for wavelength-division-multiplexed systems and a means for implementing optical code-division multiple access     

Fabrication of High Quality Broadband Type IIA Chirped Fiber Bragg Gratings

Chirped fiber Bragg gratings have found many applications in optical communication and sensing systems. High quality filters based on chirped fiber Bragg gratings with reflection bandwidth of 2.6 and 32nm and high reflectivity are demonstrated experimentally with 2 and 4cm long phase masks, respectively. These filters with flat reflection band and high reflectivity are achieved by writing type IIA chirped Bragg gratings.     

Fabrication and Evaluation of Bragg Gratings on Optimally Designed Silicon-on-Insulator Rib Waveguides Using Electron-Beam Lithography

报道了一种用电子束曝光的方法在绝缘体上硅的脊状光波导上制做布拉格光栅的技术.考虑到实际的光子学集成的应用,讨论了这个带有布拉格光栅的脊状光波导的优化设计,给出了该布拉格光栅的测试和理论模拟结果.通过薄化绝缘体上硅的波导层的厚度和光栅的深腐蚀加工,获得了高达30cm-1的光栅耦合系数.     

用电子束曝光方法在优化设计的绝缘体上硅脊状波导上实现布拉格光栅的制作和评价

报道了一种用电子束曝光的方法在绝缘体上硅的脊状光波导上制做布拉格光栅的技术.考虑到实际的光子学集成的应用,讨论了这个带有布拉格光栅的脊状光波导的优化设计,给出了该布拉格光栅的测试和理论模拟结果.通过薄化绝缘体上硅的波导层的厚度和光栅的深腐蚀加工,获得了高达30cm-1的光栅耦合系数.