Integrated Optics Technology Research Articles

Narrow-linewidth Q-switched DBR laser on Ytterbium-doped glass

In this paper, an integrated passively Q-switched DBR laser made in glass integrated optics technology is designed, fabricated and investigated. The laser, operating at 1030nm wavelength, is formed by an ion-exchanged single mode waveguide realized in an Ytterbium doped phosphate glass. The feedback is provided by a DBR structure made of a Fiber Bragg Grating and a dielectric mirror. The Q-switched behavior is obtained by hybridizing the saturable absorber on the waveguides, so that it interacts with the evanescent part of the guided field. The saturable absorber we use is a bis(4-dimethylaminodithiobenzil)nickel (BDN) dye incorporated in a polymeric film. Using this structure, we were able to demonstrate a Q-switched operation for several BDN concentrations, allowing to vary the pulse duration and the repetition rate of the device. Moreover, we report a very narrow 372MHz wide emission spectrum while in Q-switched regime.

FTTA System Demo Using Optical Fiber-Coupled Active Antennas

The convergence of optical and wireless systems such as Radio-over-Fiber (RoF) networks is the key to coping with the increasing bandwidth demands due to the increasing popularity of video and other high data rate applications. A high level of integration of optical technologies enables simple base stations with a fiber-to-the-antenna (FTTA) approach. In this paper, we present a complete full-duplex RoF–FTTA system consisting of integrated active fiber-coupled optical receiving and transmitting antennas that are directly connected to a standard single mode fiber optical link. Data rates up to 1 Gbit/s could be shown without advanced modulation formats on a 1.5 GHz carrier frequency. The antennas as well as the whole system are explained and the results of the system experiments are discussed.

Organo-erbium systems for optical amplification at telecommunications wavelengths

Modern telecommunications rely on the transmission and manipulation of optical signals. Optical amplification plays a vital part in this technology, as all components in a real telecommunications system produce some loss. The two main issues with present amplifiers, which rely on erbium ions in a glass matrix, are the difficulty in integration onto a single substrate and the need of high pump power densities to produce gain. Here we show a potential organic optical amplifier material that demonstrates population inversion when pumped from above using low-power visible light. This system is integrated into an organic light-emitting diode demonstrating that electrical pumping can be achieved. This opens the possibility of direct electrically driven optical amplifiers and optical circuits. Our results provide an alternative approach to producing low-cost integrated optics that is compatible with existing silicon photonics and a different route to an effective integrated optics technology.

The VLTi/PIONIER survey of southern TTauri disks

AbstractStudying the inner regions of protoplanetary disks (1-10 AU) is of importance to understand the formation of planets and the accretion process feeding the forming central star. Herbig AeBe stars are bright enough to be routinely observed by Near IR interferometers. The data for the fainter T Tauri stars is much more sparse. In this contribution we present the results of our ongoing survey at the VLTI. We used the PIONIER combiner that allows the simultaneous use of 4 telescopes, yielding 6 baselines and 3 independent closure phases at once. PIONIER's integrated optics technology makes it a sensitive instrument. We have observed 22 T Tauri stars so far, the largest survey for T Tauri stars to this date.Our results demonstrate the very significant contribution of an extended component to the interferometric signal. The extended component is different from source to source and the data, with several baselines, offer a way to improve our knowledge of the disk geometry and/or composition. These results validate an earlier study by Pinte et al. 2008 and show that the dust inner radii of T Tauri disks now appear to be in better agreement with the expected position of the dust sublimation radius, contrary to previous claims.

A quantum relay chip based on telecommunication integrated optics technology

We investigate an integrated optical circuit on lithium niobate designed to implement a teleportation-based quantum relay scheme for one-way quantum communication at a telecom wavelength. Such an advanced quantum circuit merges for the first time both optical–optical and electro-optical nonlinear functions necessary for implementing the desired on-chip single-qubit teleportation. On the one hand, spontaneous parametric down-conversion is used to produce entangled photon pairs. On the other, we take advantage of two photon routers, consisting of electro-optically controllable couplers, to separate the paired photons and to carry out a Bell state measurement, respectively. After having validated all the individual functions in the classical regime, we performed a Hong–Ou–Mandel experiment to mimic a one-way quantum communication link. Such a quantum effect, seen as a prerequisite towards achieving teleportation, has been obtained at one of the routers when the chip was coupled to an external single-photon source. The two-photon interference pattern shows a net visibility of 80%, which validates the proof of principle of a ‘quantum relay circuit’ for qubits carried by telecom photons. In the case of optimized losses, such a chip could increase the maximal achievable distance of one-way quantum key distribution links by a factor of 1.8. Our approach and results emphasize the potential of integrated optics on lithium niobate as a key technology for future reconfigurable quantum information manipulation.

Toward the Ultimate in Optical Integration Technology

Toward the Ultimate in Optical Integration Technology

Nonlinear silicon photonics

The phrase ‘silicon photonics’ has captured the excitement and dynamic growth of a powerful, new integrated-optics technology.1 Use of silicon (Si) and silicon dioxide (SiO2) as an integrated photonics platform employs the high-refractiveindex contrast between both materials to dramatically reduce the dimensions of an integrated circuit as well as the tools and advances of modern CMOS to fabricate complex but scatterfree shapes. These advances have, until recently, focused largely on linear Si photonics. However, equally exciting progress can be realized with nonlinear-optical Si photonics. Much work in this area is based on nonlinear effects in so-called Si-photonic wires.2–5 These have ‘wire’ cross sections of 2.5dB for 10Gb/s NRZ-to-RZ-OOK converted signal. RZ: Return-to-zero format. Div.: Division. Si: Silicon.

Two variable optical delay schemes based on polarization and interference

Variable optical delays have wide application in scientific research and optical communications. In this paper two different schemes to realize a variable optical delay are proposed, one based on polarization and the other on interference. A phase modulator is employed to restrict the signal pulse within an optical loop, and to release it when required. The delay time can be varied by adjusting the length of the loop and the number of cycles the pulse travels around it. Both types of delays are suitable for fiber systems, and can be made into a small package by means of integrated optics technology. The polarization scheme is also convenient for optical delays in free space.

Moving Polymer Waveguides and Latching Actuator for 2 $ \times$ 2 MEMS Optical Switch

We describe a novel type of MEMS optical switch based on moving waveguide which has merits inherited from both MEMS and integrated optics technologies. It provides an expandable 2 times 2 switching capability, a first in this category of switches. The switch is built by assembling independently optimized latching silicon actuator and soft polymer waveguides. The actuator is based on two new structures: a microhinge, dubbed the fork hinge, and a latching structure using a precompressed microspring. The mechanical switching speed was measured below 0.5 ms. The complex polymer waveguide structure was thoroughly characterized to obtain all the components of the optical loss. This analysis allowed us to estimate robustly the insertion loss of the assembled optical switch below 3 dB and to identify the possibilities to improve this figure.

An integrated optics beam combiner for the second generation VLTI instruments

The very recent years have seen a promising start in scientific publications making use of images produced by near-infrared long-baseline interferometry. The technique has reached, at last, a technical maturity level that opens new avenues for numerous astrophysical topics requiring milli-arcsecond model-independent imaging. The Very Large Telescope Interferometer (VLTI) is on the path to be equipped with instruments capable to combine between four to six telescopes. In the framework of the VLTI second generation instruments Gravity and VSI, we propose a new beam combining concept using Integrated Optics (IO) technologies with a novel ABCD-like fringe encoding scheme. Our goal is to demonstrate that IO-based combination brings considerable advantages in terms of instrumental design and performance. We therefore aim at giving a full characterization of an IO beam combiner to establish its performances and check its compliance with the specifications of an imaging instrument. Laboratory measurements were made in the H band with a dedicated testbed. We studied the beam combiners through the analysis of throughput, instrumental visibilities, phases and closure phases in wide band as well as with spectral dispersion. Study of the polarization properties is also done. We obtain competitive throughput, high and stable instrumental contrasts, stable but non-zero closure phases which we attribute to internal well calibrable optical path differences. We validate a new static and achromatic phase shifting IO function close to the nominal 90deg value. All these observables show limited chromaticity over the H band range. Our results demonstrate that such ABCD-like beam combiners are particularly well suited to achieve aperture synthesis imaging. This opens the way to extend to all near infrared wavelengths and in particular, the K band.

Integrated optical approach to trapped ion quantum computation

Recent experimental progress in quantum information processing with trapped ions have demonstrated most of the fundamental elements required to realize a scalable quantum computer. The next set of challenges lie in realization of a large number of qubits and the means to prepare, manipulate and measure them, leading to error-protected qubits and fault tolerant architectures. The integration of qubits necessarily require integrated optical approach as most of these operations involve interaction with photons. In this paper, we discuss integrated optics technologies and concrete optical designs needed for the physical realization of scalable quantum computer.

Quasi-Gaussian output from dual case I waveguide resonators with mirrors of step-index reflectivity profiles

There are three recognized low-loss configurations for waveguide laser resonators in which the waveguide is either closed at each end by a plane mirror (dual case I design) or one of the plane mirrors is replaced by a curved mirror at some distance from the guide exit. Some time ago, a variant of the latter design was proposed by exploiting the self-imaging properties of multimode waveguides. The resonator was predicted to produce a TEM(00)-like output with very low round-trip loss and excellent mode discrimination even though the curved mirror was placed much nearer to the guide exit (making the resonator more compact) than was conventional for achieving those results. In the present work, we show that the desirable features of the above design can be achieved even in a dual case I configuration by using end mirrors with suitable reflectivity profiles. Since there is no free space region between the waveguide and the mirrors, the resonator will have the additional advantages of being compact and portable. Furthermore, the absence of curved mirrors will also facilitate its realization in semiconductor integrated optics technology.

Optical Microsensors Integration Technologies for Biomedical Applications

This paper focuses on optical integration technology and its application in optical microsensors used in biomedical fields. The integration is based on the hybrid integration approach, achieving high performance, small size and weight, and lower cost. First, we describe the key technologies used in hybrid integration, namely passive alignment technology, low temperature bonding technology, and packaging technology for realizing advanced microsensors. Then, we describe an integrated laser Doppler flowmeter that can monitor blood flow in human skin.

Designing a next-generation waveguide by geometry

Planar lightwave circuits (PLCs) have broad application in areas ranging from space to telecommunications to sensing. For example, PLC technology can be used in optical true-time delays for phased array antennas. These delays make possible a simpler, less-expensive control system and improved performance that could benefit wireless communication in space and air.1 PLCs also have utility in integrated-optic network components, such as optical add-drop multiplexers (OADMs).2 These devices help achieve high system functionality in fiber-to-thehome networks. Finally, PLC techniques can be used for optical sensors and emerging visible applications, since they enable integration of mode filters, interferometric principles, and other optical functions required for compact, highly sensitive and selective devices. Figure 1 gives an overview of optical integration technologies. Integrating functions has several advantages over discrete solutions. Lower costs, mass production, stability, and form factor (footprint area and volume) are all well-known drivers for integration. Achieving integration in the field of optics will require meeting a number of specifications. First, to ensure tight bends and consequently small structures, the technology must offer high contrast in refractive index between the light-guiding layer and the surroundings. Second, there must be a way of correcting for additional losses owing to the greater number of functions. Third, because polarization is so important, there must be a way to control it. Finally, transparency for a large range of wavelengths is essential to guarantee the maximum flexibility required of an industrial standard for integration. We have developed the TriPleX waveguide technology, which is capable of meeting these requirements. It consists of alternating layers of silicon nitride (Si3N4) and silicon dioxide (SiO2) formed by CMOS-compatible low-pressure chemical vapor deposition (LPCVD). TriPleX is fully transparent for wavelengths Figure 1. Examples of optical integration: (from left to right) optical beam forming for phased array antennas, microring resonator filter for R-OADMs, and spiral waveguide for optical sensor. R-OADMs: Reconfigurable OADMs.

Study of deeply buried waveguides: A way towards 3D integration

Ion-exchange on glass is now a mature integrated optics technology. Indeed, many devices such as wavelength multiplexers, splitters, optical amplifiers, lasers or sensors have been already realized. The challenge now is to integrate all these functions on a single chip. Two different paths can be used to achieve this goal: the first one consists of a reduction of the waveguides’ dimensions by an increase of the refractive index change, whereas the second one, which is addressed in this paper, is based on the realization of multilayered devices. Because ion-exchange on glass allows manufacturing either surface or buried waveguides, this technology is well adapted for 3D integration. However, to realize integrated optical devices with two different layers, it is mandatory to prevent any parasitic light transfer between them. This condition can be fulfilled if the top and bottom waveguides are sufficiently separated. In this article, we present the development of ion-exchanged waveguides deeply buried into a glass substrate and their application to 3D integrated devices. Deeply buried waveguides have been realized by means of a two steps silver–sodium ion-exchange on a dedicated custom made silicate glass. First, a thermal ion-exchange has been carried out at 330 °C during 2 min in a 0.8NaNO 3–0.2AgNO 3 molten salt in order to create the core of the waveguide. Then, this core has been buried into the glass substrate by applying an electric field of 450 kV/m during 1 h 30 min in a sodium nitrate solution at 260 °C. The obtained waveguide has been measured to be 22 μm under the glass surface. It is singlemode at λ = 1.55 μm. In order to prove the good isolation between this waveguide and the surface, a top layer has been added to the device by the realization of surface channel waveguides through a thermal ion-exchange performed in a 0.8NaNO 3–0.2AgNO 3 molten salt at 330 °C during 2 min. The near-field observation of the device output has shown no coupling between the top and bottom layers demonstrating therefore the feasibility of 3D integrated optical devices by means of ion-exchange on glass.

Design and Characterization of Biophotonics Devices

In this paper we study the design and characterization of optical biosensors based on the integrated optics technology. The finite element based perturbation technique has been used to characterize the surface plasmon waveguide. The finite element based beam propagation method has been used to characterize the ring resonators. Some of the novel biosensor structures will be characterized and modal loss and sensitivity and selectivity of these biosensors are studied

Optimization of Low-Loss Al2O3 Waveguide Fabrication for Application in Active Integrated Optical Devices

In this paper we will present the fabrication and properties of reactively co-sputtered Al2O3 layers, being a very promising host material for active integrated optics applications such as rare- earth ion doped laser devices. The process optimization towards a reactive co-sputtering process, which resulted in stable, target condition-independent deposition of Al2O3 layers with high optical quality will be discussed in detail. The loss value of as- deposited optical waveguides sputtered by the optimized process has been measured. The loss in the near infrared wavelength range was 0.3 dB/cm. Furthermore, Al2O3 material hosts fabricated by sputtering techniques are compatible with Si-based integrated optical technology and allow for uniform deposition over a large substrate area.

Ming‐Sze Tong, Yinchao Chen, Qunsheng Cao, Mingwu Yang, and Ronan Sauleau, Design and analysis of on‐package dual‐mode band pass filters for highly integrated wireless transceivers, Microwave and Optical Technology Letters(2006) 48(4) 756‐760

AbstractThe original article to which this erratum refers was published in Microwave and Optical Technology Letters Microwave Opt Technol Lett (2006) 48(4) 756

Polymer optical waveguide vertically coupled to high-Q whispering gallery resonators

We report on a novel implementation of a polymer optical waveguide vertically coupled to the whispering gallery modes of a fused silica resonator disc. This is the first step in bringing high-Q silica discs close to the integrated optics technology. We obtained near-critical coupling and a loaded Q/spl ap/3.4/spl times/10/sup 6/.

Passive integrated optics elements based on long-range surface plasmon polaritons

Waveguides and passive integrated optics elements constructed from thin metal films of finite width embedded in a homogeneous background dielectric and propagating long-range surface plasmon polaritons (LRSPPs) have been characterized experimentally at free-space optical wavelengths near 1550 nm. Straight and curved waveguides, s-bends, four-port couplers, y-junctions, and Mach-Zehnder interferometers have been carefully characterized. Additionally, rigorous models based on modal decomposition have been proposed for all of these elements and validated via comparisons with the measurements. Excellent qualitative and quantitative agreement between theory and experiment is observed for all structures over all measurement wavelengths. It is hoped that this work will help further establish this new integrated optics technology, taking it beyond demonstrators.