Polymer-based Optical Waveguide Research Articles

Effect of inorganic compound size on the relative gain of polymer-based optical waveguide amplifiers

Polymer based waveguide amplifiers are the key devices to improve the performance of integrated communication systems. However, due to their comparatively low relative gain, their widespread practical application has been limited. In polymer based optical waveguide amplifiers, the size of inorganic compounds in the composite gain media has a significant impact on the gain performance of the amplifier. Up to now, there has been limited research on the size influence of inorganic compound on the gain variation in organic polymer based optical waveguide amplifiers. In this study, a series of NaLu0.8-xYxF4: Yb, Er-PMMA composite polymer were used as gain media to prepare organic waveguide amplifiers working in the C-band (1530–1565 nm). The size of NaLu0.8-xYxF4: Yb, Er compounds varies between 20 nm and 150 nm. In the polymer based optical waveguide amplifiers, variations in the size of the inorganic NaLu0.8-xYxF4:Yb,Er compound affects not only the C-band emission intensity but also the relative gain. When the size of the inorganic compound is 65 nm, the composite gain media exhibits the maximum emission peak intensity at 1550 nm and the corresponding device achieves a maximum relative gain of 19.3 dB/cm. Our results show that the size of inorganic compounds affects the variation of luminescence intensity and ultimately the gain of waveguide amplifiers. The gain of future polymer optical waveguide amplifiers can be improved by this method.

Thin films with implemented molecular switches for the application in polymer-based optical waveguides

Complexes like iron (II)-triazoles exhibit spin crossover behavior at ambient temperature and are often considered for possible application. In previous studies, we implemented complexes of this type into polymer nanofibers and first polymer-based optical waveguide sensor systems. In our current study, we synthesized complexes of this type, implemented them into polymers and obtained composites through drop casting and doctor blading. We present that a certain combination of polymer and complex can lead to composites with high potential for optical devices. For this purpose, we used two different complexes [Fe(atrz)3](2ns)2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$[\ ext {Fe}(\ ext {atrz})_{3}](2\\, \ ext {ns})2$$\\end{document} and [Fe(atrz)3]Cl1.5(BF4)0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$[\ ext {Fe}(\ ext {atrz})_{3}]\ ext {Cl}_{1.5}(\ ext {BF}_{4})_{0.5}$$\\end{document} with different polymers for each composite. We show through transmission measurements and UV/VIS spectroscopy that the optical properties of these composite materials can reversibly change due to the spin crossover effect.

Fabrication and characterization of polymer optical waveguide Bragg grating for pulse signal sensing.

Polymer materials have the advantages of a low Young's modulus and low-cost preparation process. In this paper, a polymer-based optical waveguide pressure sensor based on a Bragg structure is proposed. The change in the Bragg wavelength in the output spectrum of the waveguide Bragg grating (WBG) is used to linearly characterize the change in pressure acting on the device. The polymer-based WBG was developed through a polymer film preparation process, and the experimental results show that the output signal of the device has a sensitivity of 1.275 nm/kPa with a measurement range of 0-12 kPa and an accuracy of 1 kPa. The experimental results indicate that the device already perfectly responds to a pulse signal. It has significant potential application value in medical diagnostics and health testing, such as blood pressure monitoring, sleep quality monitoring, and tactile sensing.

Polymer-Based Optical Waveguide Tactile Sensing Method for 3-D Surfaces

At present, most tactile sensors are fabricated based on the flat surface, which greatly limits their applications in the 3-D scenario. To deal with the bottleneck, this article proposes a polymer-based optical waveguide sensing method. The waveguide can be integrally formed along a channel within a 3-D surface. Microbending light loss of a waveguide is the sensing principle. By studying the linearity between the degree of microbending and light loss, the feasibility analysis of spherical tactile sensing element (tactile) was completed, as well as the basis for size selection of it. In addition, the key to layout on 3-D surface of the proposed sensing method is that the bending radius of the waveguide is within the critical angle of total internal reflection (TIR). By normalizing the ratio of the side length of the cross Section to the bending radius, it is shown that the light loss does not increase when the proportionality coefficient is less than 0.3. The experiment is validated by embedding four tactiles in a 3-D surface. The cross Section of the waveguide is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.5\times1.5$ </tex-math></inline-formula> mm. We demonstrated that the static hysteresis error for a tactile is less than 16% within 595 kPa, the best sensing sensitivity is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}.{42} \times {{10}}^{-{5}} {}{\text {kPa}}^{-{1}}$ </tex-math></inline-formula> , and the maximum measurement range is from 0 to 850 kPa. As for the dynamic measurement, the tactile can rapidly response the signal change with given frequencies (the maximum is 10 Hz). The average delay time is around 12 ms.

Light-Induced Waveguide With Directional Transmission

Herein, we propose and demonstrate that the light-induced optical polymeric waveguides can function as the fully online optical connectors with directional transmission characteristics. The light-induced optical waveguides, which can be used for the optical couplings between single-mode fibers, are fabricated by using a photopolymerizable resin system formed by a 405-nm laser. Subsequently, the transmission characteristics of the light-induced waveguides with different parameters are investigated, and the experimental results reveal that the (directional) transmission characteristics can be modified by controlling the structure of the light-induced waveguides by controlling the illumination time (single-side) or the ratio of the illumination intensity (dual-side). Additionally, the preliminary experimental results reveal that the light-induced optical waveguides can function as the optical connectors. The light-induced waveguide build-up process, which is simple and effective, can be applied to the fabrication of polymer-based optical waveguide modules and for optical interconnections. Simultaneously, this present technique could be a feasible method of incorporating devices such as filters, isolators, and polarizers into fibers, which can potentially contribute to further expansion of integrated optoelectronic system.

Controllable synthesis of β-NaLuF4:Yb3+, Er3+ nanocrystals and their application in polymer-based optical waveguide amplifiers

Abstract Hexagonal structured NaLuF4 (β-type) nanocrystals (NCs) with controllable particle size were prepared by thermal decomposition approach. The as-prepared NCs possessed good dispersibility in organic solvents. Under a 980 nm laser excited, these Er3+ and Yb3+ co-doped β-NaLuF4 NCs demonstrated emission around 1530 nm. These β-NaLuF4:Yb3+, Er3+ NCs were dispersed into SU-8 polymer to fabricate polymer waveguides, and the results showed that their crystal size influenced greatly on the performance of polymer waveguides. The relative optical gain of 2.413 dB, 1.653 dB and 0.481 dB at 1530 nm was achieved when the particle size was about 8 nm, 15 nm, and 23 nm, respectively. These results show that β-NaLuF4:Yb3+, Er3+ NCs with small particle size were promising materials for building Er3+-doped polymer-based optical waveguide amplifiers.

Oleic acid-modified LiYF4:Er,Yb nanocrystals for potential optical-amplification applications.

LiYF4:18%Yb, 2%Er nanocrystals and NaYF4:18%Yb,2% Er nanoparticles (NCs) were synthesized by a solvothermal approach using oleic acid (OA) as the surfactant. With the excitation of a 980 nm diode laser, LiYF4:18%Yb, 2%Er NCs exhibit more strong emission than alpha-NaYF4:18%Yb, 2%Er at around 1530 nm. The TEM images showed that the LiYF4:18%Yb, 2%Er NCs have a nearly spherical shape and the size is about 15 nm. The OA-capped LiYF4 NCs have excellent dispersibility in organic solvents. These results showed that LiYF4:18%Yb, 2%Er NCs are a promising material for polymer-based optical waveguide amplifiers.

Enhancement of 153 μm emission band in NaYF_4:Er^3+,Yb^3+,Ce^3+ nanocrystals for polymer-based optical waveguide amplifiers

NaYF4:Er3+,Yb3+,Ce3+ nanocrystals (NCs) were synthesized by using a solvothermal approach. Under the excitation of a 980 nm laser, the 1.53 μm emission band of Er3+ ions in the NCs was enhanced by 6 times after codoping Ce3+ ions owing to the efficient energy transfer between Ce3+ and Er3+: 4I11/2 (Er3 +) + 2F5/2 (Ce3+) → 4I13/2 (Er3+) + 2F7/2 (Ce3+). By dispersing the NaYF4:Er3+,Yb3+,Ce3+ NCs into SU-8 2005 polymer matrix, we constructed Er3+-doped polymer-based optical waveguide amplifiers (EDPOWAs) and measured their performances. The measured optical gain of the EDPOWA doped with NaYF4: Er3+,Yb3+,Ce3+ NCs was enhanced by ~2dB in comparison with that doped with NaYF4:Er3+,Yb3+ NCs. These results showed that NaYF4:Er3+,Yb3+,Ce3+ NCs are promising candidates for building high gain EDPOWAs.

Sub-10 nm BaYF5:Yb3+,Er3+ core–shell nanoparticles with intense 1.53 μm fluorescence for polymer-based waveguide amplifiers

Sub-10 nm BaYF5:Yb3+,Er3+ core–shell nanoparticles (NPs) were synthesized by a high boiling solvent process. Under a 980 nm laser excitation, up- and down-conversion fluorescence spectra from BaYF5:Yb3+,Er3+ NPs were recorded and analyzed. After coating the active-shell (containing Yb3+ ions) around the BaYF5:Yb3+,Er3+ NPs, the intensity of the 1.53 μm fluorescent band was enhanced by 11 times owing to surface passivation effect and efficient energy transfer between Yb3+ ions in active-shell and Er3+ ions. Furthermore, the NPs showed excellent redispersibility in common nonpolar solvents. By dispersing BaYF5:Yb3+,Er3+ active-core–active-shell NPs into an SU-8 2005 polymer, we constructed polymer-based optical waveguide amplifiers and measured their performance. For an input signal power of 0.1 mW and a pump power of 200 mW, a relative optical gain of ∼6.3 dB was obtained at 1535 nm in a 13 mm-long waveguide.

Control of Refractive Index of Fluorinated Polyimide by Proton Beam Irradiation

To clarify the feasibility of controlling the refractive index of a polymer by proton beam irradiation, we irradiated 1.0 MeV protons to a fluorinated polyimide film. Before and after the proton irradiation at a fluence between 1×1014 and 7×1016 cm-2, the film surface was scanned by a profilometer. It was found that the depth of a dent, which increases with fluence, was induced by the irradiation. The refractive index of the ion-irradiated region was calculated using the Lorentz–Lorenz equation, substituting the depth of the dent and the projected range of the protons. When the fluorinated polyimide was irradiated at a fluence of 7×1016 cm-2, the refractive index increased by about 3.3%, which agrees with the increment in refractive index measured by spectroscopic ellipsometry. The increment in refractive index (0.21%) induced by the irradiation of protons at the fluence of 1×1015 cm-2 is comparable to the value (0.35%) observed when protons were irradiated to SiO2 glass at a similar fluence. Therefore, it is reasonable to assume that the ion irradiation to a polymer can be a good method for fabricating a high-performance polymer-based optical waveguide.

Long aliphatic chain coated rare-earth nanocrystal as polymer-based optical waveguide amplifiers

Oleic acid-coated erbium–ytterbium co-doped NaYF4 nanocrystals, NaY78%F4:Yb20%Er2%, have been synthesized. The cubic nanocrystals were of an average size of 10 nm. The nanocrystals showed excellent redispersibility in common organic solvents and the KMBR® polymer matrix. An optical waveguide amplifier was fabricated by doping 0.1 wt% of the nanocrytals into the KMPR® polymeric host. At a small input signal power of 150 nW and a pump power of 150 mW, an optical gain of 4.81 dB cm−1 at 1535 nm was achieved.

Oleic acid (OA)-modified LaF3 : Er,Yb nanocrystals and their polymer hybrid materials for potential optical-amplification applications

Oleic acid (OA)-modified LaF3 : Er,Yb nanocrystals (NCs) have been prepared and investigated. The OA-capped nanocrystals have a nearly spherical shape with a mean diameter of 7 nm and show excellent dispersibility in common organic solvents and a PMMA matrix. A 0.25 g ml−1 transparent colloidal solution in toluene can be obtained. The resulting nanocrystal–polymer hybrid materials exhibit strong emission around the 1550 nm telecommunication window when excited at 980 nm and are promising materials for polymer-based optical waveguide amplifiers.

O/E Integration of Polymer Waveguide Devices by Using Replication Technology

The simple optoelectronic integration of polymer-based optical waveguide devices and the development of the realization processes have been critical issues for cost-effective, high-volume manufacturing of a next-generation optoelectronic integrated circuit (OEIC). We demonstrated the replication technology as a means of implementing the polymer microoptoelectromechanical system (MOEMS)-based packaging structure providing the optical/electrical (O/E) integration of the functional polymer waveguide device. To achieve this, a micromechanical packaging structure consisting of an electric-circuit-embedded polymer optical bench and planar-lightwave-circuit (PLC)-type waveguide chip with alignment microstructure was designed, and the realization process incorporating the UV imprint technique was investigated. To improve optical coupling efficiency, the electric circuit was embedded under the optical bench and the contact pads were opened at the bottom of the alignment pits. In addition, a conductive adhesive-fill space was created at the alignment pits to accommodate the surplus conductive adhesive. Efficient fiber-chip coupling and good electrical contact of upside-down mounted single-mode waveguide chip was accomplished by the simple joining of the electric-circuit patterned micropedestals on the waveguide chip and the alignment pits on the bench. A coupling loss of 0.9 dB per coupling face was measured with a single-mode fiber at a wavelength of 1.5 mum. It was concluded that the replication technology has versatile application capabilities in manufacturing next generation optical interconnect systems

Investigation of environmental reliability of optical polymer waveguides embedded on printed circuit boards

In this paper, the effects of environmental stresses on the properties of polymeric optical waveguides were investigated. Optical multimode waveguides were embedded on printed circuit boards by employing commercial polymers. Three optical-PCB constructions varying in board structure and in optical build-up materials were compared. The guide systems were subjected to four different tests: damp heat-high humidity, isothermal annealing, thermal shock and environmental flowing multigas test. Isothermal annealing reduced the refractive index to greatest extent. The optical-PCB structure with optical surface build-up layer was observed to be more vulnerable under temperature shock when compared with the O-PCB with optical inner layer. The buffer layer beneath the optical build-up was found to improve the stability of the optical waveguides significantly. The results indicated of a wavelength dependence to the aging factor with a failure mechanism. The factors affecting the performance and reliability of polymer-based optical waveguides on PCBs were discussed.

Polymer-based materials for amplification in the telecommunication window: Influence of erbium complex concentration on relevant parameters for the elaboration of waveguide amplifiers around 1550 nm

Erbium-doped polymer-based optical waveguides offer an attractive alternative for inorganic amplifiers in the eye-safe telecommunication window at 1550nm. We are succeeded in doping a standard polymethyl-methacrylate (PMMA) matrix with an octupolar erbium complex designed to display quadratic nonlinear optical response and IR luminescence in the same time. We have investigated the influence of erbium complex concentration on various parameters such as spun coated thickness, reactive ionic etching rate, refractive index and near infrared luminescence. The optimal erbium concentration for emission at 1550nm reaches 1wt.%. These carefully optimized processing and optical parameters are of great relevance for a further design and elaboration of polymer-based single mode waveguide amplifiers.

Fabrication and integration of VLSI micro/nano-photonic circuit board

We report on the design, fabrication and integration of a modular system that we newly propose as “optical printed circuit board (O-PCB).” The O-PCB is designed to provide micro/nano-scale optical waveguides to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards or substrates that can lead to a platform for VLSI micro/nano-photonic integration. We fabricated and assembled O-PCBs using polymer-based optical waveguides, which we fabricated by thermal or ultra-violet (UV) imprinting using silicon masters. For nano-scale VLSI photonic integrated circuit applications, we used photonic crystal devices and plasmonic devices. We present the use of near-field scanning optical microscopy (NSOM) for optical characterization of micro/nano-scale photonic devices and also examine the effect of the waveguide surface roughness on the transmission characteristics of the waveguides. We present the results of calculation and simulation study that we pursue in search of scaling rules for the miniaturization and integration of waveguide devices, which we use as a guide for our design of VLSI waveguide circuits.

Direct milling and casting of polymer-based optical waveguides for improved transparency in the visible range

Polymer waveguides fabricated from photoresist have an inherent high propagation loss in the short visible wavelength range caused by absorption due to the added photosensitizers. We have addressed this problem by development of two novel methods for the fabrication of microfluidic systems with integrated optical waveguides. Polymethylmethacrylate (PMMA) is dissolved in anisole and ‘doped’ with styrene-arcylonitrile copolymer to vary the refractive index. The doped PMMA with a higher refractive index is then spin coated onto a PMMA substrate with a lower refractive index to provide waveguide properties. Direct micromilling enabled us to fabricate 100 µm wide optical waveguides. Propagation losses of less than 1 dB cm−1 could be achieved throughout the entire visual range down to a wavelength of 400 nm. A casting process amenable to high number production of such devices was furthermore developed.

Polymer-Based Optical Waveguides: Materials, Processing, and Devices

Polymer optical waveguide devices will play a key role in several rapidly developing areas of broadband communications, such as optical networking, metropolitan/access communications, and computing systems due to their easier processibility and integration over inorganic counterparts. The combined advantages also makes them an ideal integration platform where foreign material systems such as YIG (yttrium iron garnet) and lithium niobate, and semiconductor devices such as lasers, detectors, amplifiers, and logic circuits can be inserted into an etched groove in a planar lightwave circuit to enable full amplifier modules or optical add/drop multiplexers on a single substrate. Moreover, the combination of flexibility and toughness in optical polymers makes it suitable for vertical integration to realize 3D and even all-polymer integrated optics. In this review, a survey of suitable optical polymer systems, their processing techniques, and the integrated optical waveguide components and circuits derived from these materials is summarized. The first part is focused on discussing the characteristics of several important classes of optical polymers, such as their refractive index, optical loss, processibility/mechanical properties, and environmental performance. Then, the emphasis is placed on the discussion of several novel passive and active (electro-optic and thermo-optic) polymer systems and versatile processing techniques commonly used for fabricating component devices, such as photoresist-based patterning, direct lithographic patterning, and soft lithography. At the end, a series of compelling polymer optical waveguide devices including optical interconnects, directional couplers, array waveguide grating (AWG) multi/demultiplexers, switches, tunable filters, variable optical attenuators (VOAs), and amplifiers are reviewed. Several integrated planar lightwave circuits, such as tunable optical add/drop multiplexers (OADMs), photonic crystal superprism waveguides, digital optical switches (DOSs) integrated with VOAs, traveling-wave heterojunction phototransistors, and three-dimensionally (3D) integrated optical devices are also highlighted.

10 Gb/s data transmission with TO-packaged multimode GaAs VCSELs over 1 m long polymer waveguides for optical backplane applications

TO-packaged GaAs vertical-cavity surface-emitting lasers (VCSELs) are being investigated for high-bit-rate data transmission over 103 cm of a 250×200 μm 2 core size polymer-based optical waveguide to be employed in optical backplanes. The bit-error rates for 5 and 10 Gb/s transmission over the waveguides incorporating 45° deflection mirrors are better than 10 −12. For the first time, the measured bandwidth-length-product for a polymer-based optical backplane exceeds 10 GHz× m .