Recent advances in integration technologies enable constructing novel, highly complex and miniaturized photonic systems for a large variety of applications. A constantly increasing interest can be observed in implementing application specific photonic integrated circuits (ASPICs) in a new generation of optical sensing systems.
The InP platform allows to realize complete interrogators of sensing systems, comprising the light sources and photodetectors. An InP PIC can also be used as a sensing element itself. In this work we discuss the sensing systems addressing two different application fields, which can benefit from the recent developments of InP platforms - optical gyroscopes and interrogators of fiber Bragg gratings.
The principle of work of optical gyroscope is based on the Sagnac effect. Two typical configurations can be identified – interferometric fiber-optic gyroscope (IFOG) and ring laser gyroscope (RLG). An integrated interrogator unit of an IFOG system presented here was realized using a DBR laser, passive couplers and PIN photodiodes. Characterization results have proven the possibility of detection of the Sagnac signal for the length of the fiber loop of 1 km. We also discuss monolithic single-frequency lasers, which were realized in the framework of the development of an integrated optical gyro.
Also, the integrated interrogators of fiber Bragg gratings are presented and discussed. The investigated solutions are based on the interrogation scheme in which a broadband signal is coupled to a network of FBGs, and the reflected signals are analyzed using a spectrometer based on an arrayed waveguide grating. Several realized circuits are discussed with respect to their design, characterization results and potential for application in sensing systems.
Studies were funded by FOTECH-1 project granted by Warsaw University of Technology under the program Excellence Initiative: Research University (ID-UB). This work was partially supported by National Centre for Research and Development (PBS3/B9/41/2015).
In this paper we analyze the possibilities of developing efficient and low-cost multichannel photonic sensor system using SiO2:TiO2 photonic integrated circuit (PIC) technology. We examine numerically the possibility of using optical ring resonator as a fundamental building block of the system. The most convenient ring resonator configuration is shown providing both relatively high sensitivity (125 nm/RIU) and relatively wide free spectral range (9.6 nm) large enough for serial connection of multiple rings. Our study is completed by the report of recent advances in fabrication technology obtained in our project.
In this paper we discuss the technology of SiO2:TiO2 waveguide films produced via sol-gel method and dip-coating technique, mastered at Silesian University of Technology. The technology allows fabrication of 150–300 nm thick waveguide films in single step deposition process and up to 500 nm thick with multiple step deposition process. The typically fabricated waveguide films have refractive index of ~1.8, however this value can be arbitrary altered from 1.45 to 1.94. The developed technology allows fabrication of waveguides having propagation losses below 0.2 dB/cm. The up-to-now fabricated waveguide films seem to be very promising. However biggest stumbling block in their application lays in elaboration of efficient patterning techniques. Currently the technology is developed towards an efficient way of waveguide layers patterning and introducing rare earth ions into the waveguide layers. The patterning technology will be developed in a twofold way, including mainly deep and shallow strip waveguide structures. The deeply patterned waveguide structures will be fabricated either with the direct nanoimprint of waveguide layer or in a more conventional way by using electron beam lithography and dry plasma etching. The fabrication of shallowly patterned waveguide structures will be carried out using also direct nanoimprint or alternatively photolithography combined with wet chemical etching.
The magnetic resonance imaging (MRI) technique is a powerful diagnostic tool which is nowadays commonly used in many fields of medicine. In some cases, especially of the patients of intensive care units, it is highly recommended or even necessary to provide continuous monitoring of basic physiologic parameters, mainly the heart rate and the respiratory rate, during the MRI scan procedure. The presence of a strong magnetic field within the MRI chamber requires application of non-standard devices and solutions. The monitoring system needs to be immune to the strong magnetic field and simultaneously cannot negatively influence on the results of the scan. Therefore, application of optical sensing technologies could be potentially advantageous to fulfil these requirements. In this work we propose a novel optoelectronic measurement system, dedicated to monitoring of the patient during an MRI scan, immune to strong magnetic field and compatible with the MRI apparatus.
Fiber Bragg gratings (FBGs) are used as the sensing elements – the strain induced by the patient’s respiration and cardiac activity cause a change of the Bragg wavelength. These changes can be accurately measured and monitored in the time domain. The respiratory and heart rate can be extracted by further processing of the measured signal by dedicated software. The gratings are organized in a network to maximize the effective sensing area. Each of the FBGs has a different Bragg wavelength so that they can be connected in series.
The information from the sensors is read out using an interrogator based on an application specific photonic integrated circuit (ASPIC), designed and fabricated in an InP-based generic integration technology. The interrogator comprises a 36-channel arrayed waveguide grating wavelength demultiplexer, which outputs are connected to PIN photodiodes. Such a photonic circuit acts as a spectrometer and allows to reconstruct the reflection spectrum of many gratings simultaneously. An external superluminescent LED is used as the light source, however in the target configuration the source could be monolithically integrated with the interrogator. The Bragg gratings, the interrogator and the SLED are connected with each other using an optical circulator.
Initial tests of the monitoring system have been performed using a single fiber Bragg grating as the strain sensor and a commercially available optoelectronic interrogator. The fiber with an inscribed FBG was mounted using an epoxy glue on a PMMA board and deployed under the patient. Two signals can be distinguished out of the measured waves. The first one, with strong and slowly-varying peaks, reflects the respiration of the patient. The second signal, characterized by low-intensity and fast-varying peaks is a result of the cardiac activity. No influence of the magnetic field of the MRI instrument on the sensing system has been observed. The first results have confirmed both the correctness of the approach and the applicability of the system to monitoring the patient’s physical condition during MRI diagnosis.
This work was supported by the National Centre for Research and Development, project OPTO-SPARE, grant agreement PBS3/B9/41/2015.
The objective of this research is to design, develop and test the InP based multichannel transceivers dedicated for application in WDM access systems. The transmitters are making use of DBR lasers and Mach-Zehnder modulators. The satisfying parameters of transceivers were obtained like low threshold current and good side mode suppression ratio.
Together with the development of fiber optic sensor networks the accurate and reliable operation of dedicated readout instruments became a critical issue. After years of optimizing the interrogating devices the use of photonic integrated circuits (PICs) has opened a new era of highly reliable, compact and versatile devices offering additionally advantages of low power consumption and cost-optimized design.
Considering the most commonly deployed fiber Bragg grating (FBG) based sensor systems/networks, typically two PICs-based solutions for interrogators may be used: an arrayed waveguide grating (AWG) spectrometer with a broadband SLED source or a set of tunable laser sources with a photodiode detector. Among commercially available PIC technologies the InP platform has a substantial advantage as it allows fabrication of both passive devices (waveguide circuitry) as well as active devices (photodiodes and light sources) in the same technological process.
In this work we investigate two different layouts of AWG-based integrated interrogators fabricated in generic technology of indium phosphide. We analyze the influence of crosstalk between AWG channels on operation of the device and possibility of interrogating narrow-band FBG reflection peaks as well as the influence of input polarization state on the AWG response, which is of fundamental importance for proper operation of an integrated FBG interrogator. As there is no polarization control elements available at present in the offer of generic InP technology providers we discuss the possibility of using off-chip solutions exploiting additional fiber-optic components. As a possible alternative to AWGbased interrogators, we discuss also the possibility of using integrated tunable lasers for FBG interrogation.
In this work a study on three different concepts of photonic integrated multichannel transmitters for applications in WDM-PON access systems is presented. The devices differ in design of the main components of the chip – the lasers and modulators are optimized for different technology platforms. All are compared and analyzed with respect of the fundamental parameters like spectral and power characteristics of the lasers and performance of the amplitude modulators. The transmitters were designed in a generic approach and fabricated in multi-project wafer runs as InP-based monolithic photonic integrated circuits.
Recently observed dynamic development of photonic integrated circuits (PICs) technology enabled significant broadening of potential application area, initially focused on high speed optical communication. One of the prospective and emerging fields is optical sensing, where photonic chips can play twofold role of an optical interrogator and an optical transducer itself. In this paper we discuss the possibilities and perspectives of deploying PIC-based solutions for both these applications.
The research aims to design and manufacture of wireless optogenetics devices for freely moving animals in cages IntelliCage system. The purpose of the device is to stimulate specific brain regions using light. The constructed device consists of a light source and optical fibre structure responsible for delivering light into the corresponding region of the brain of the animal. The size of the animal (mouse) and the fact that it is freely moving imposes substantial limitations with respect to the size and weight of the optoelectronic device. The present paper describes research on optical fibre structure fabrication, assembling it to the small size (less than 500 × 500 μm2 top surface) LED chip and experimental validation of the optoelectronic stimulator.
We present here research work on two optical biosensors which have been developed within two separate European
projects (6th and 7th EU Framework Programmes). The biosensors are based on the idea of a disposable biochip,
integrating photonics and microfluidics, optically interrogated by a multichannel interrogation platform. The objective is
to develop versatile tools, suitable for performing screening tests at Point of Care or for example, at schools or in the
field.
The two projects explore different options in terms of optical design and different materials. While SABIO used
Si3N4/SiO2 ring resonators structures, P3SENS aims at the use of photonic crystal devices based on polymers, potentially
a much more economical option. We discuss both approaches to show how they enable high sensitivity and multiple
channel detection.
The medium term objective is to develop a new detection system that has low cost and is portable but at the same
time offering high sensitivity, selectivity and multiparametric detection from a sample containing various components
(e.g. blood, serum, saliva, etc.). Most biological sensing devices already present on the market suffer from limitations in
multichannel operation capability (either the detection of multiple analytes indicating a given pathology or the
simultaneous detection of multiple pathologies). In other words, the number of different analytes that can be detected on
a single chip is very limited. This limitation is a main issue addressed by the two projects. The excessive cost per test of
conventional bio sensing devices is a second issue that is addressed.
We analyze a highly compact optical add-drop filter topology based on a pair of microdisk resonators and a bus waveguide intersection. The filter is further assessed on an integrated optical 4×4 network for optical on-chip communication. The proposed network structure, as compact as 50×50 µm, is fabricated in a CMOS-compatible process on a silicon-on-insulator (SOI) substrate. Finally, the experimental results demonstrate the proper operation of the fabricated devices.
We present an efficient and highly alignment-tolerant light coupling and distribution system for a multichannel Si3N4/SiO2 single-mode photonics sensing chip. The design of the input and output couplers and the distribution splitters is discussed. Examples of multichannel data obtained with the system are given.
We present a compact passive optical add-drop filter which incorporates two microring resonators and a waveguide intersection in silicon-on-insulator (SOI) technology. Such a filter is a key element for designing simple layouts of highly integrated complex optical networks-on-chip. The filter occupies an area smaller than 10μm×10μm and exhibits relatively high quality factors (up to 4000) and efficient signal dropping capabilities. In the present work, the influence of filter parameters such as the microring-resonators radii and the coupling section shape are analyzed theoretically and experimentally
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