Polymer Waveguide Research Articles

Optical Gain at 637 nm Wavelength in Polymer Waveguide Amplifier Under Commercial LED Pumping for Planar Photonic Integration

AbstractOptical gains at 637 nm wavelength using light‐emitting diodes (LEDs) instead of traditional semiconductor lasers as pumping sources are demonstrated in the organic molecule 2,6‐bis[4‐(diphenylamino)phenyl]‐9,10‐anthracenedione (AQ(PhDPA)2)‐doped polymethylmethacrylate (PMMA) and SU‐8 polymer waveguides. Under excitation of four blue‐violet LEDs with different central wavelengths, fluorescence in the red band is observed owing to the transition of AQ(PhDPA)2 from the excited states to the ground state based on the thermally activated delayed fluorescence (TADF) mechanism. Channel waveguides with a cross‐section of 6 µm × 5 µm are fabricated. The relative gains of 5.0 and 4.0 dB cm−1 are obtained in rectangular waveguides with active core layers as AQ(PhDPA)2 doped PMMA and SU‐8, respectively. Optical gains have also been achieved in waveguides based on evanescent‐wave coupling. By using the vertical top pumping mode of a 450 nm LED, a gain of 2.6 dB cm−1 is obtained in a passive SU‐8 waveguide with AQ(PhDPA)2 doped PMMA as the upper cladding. In contrast, the replacement of SU‐8 with AQ(PhDPA)2 doped SU‐8 as the active material, triples the optical gain, which reaches to 7.8 dB cm−1 owing to the presence of stimulated excitation in both channel waveguide and upper cladding.

Frequency Response of Thermo-Optic Phase Modulators Based on Fluorinated Polyimide Polymer Waveguide.

Polymer waveguide phase modulators exhibit stable low-power phase modulation owing to their exceptional thermal confinement and high thermo-optic effect, and thus, have the merit of thermal isolation between channels, which is crucial for an optical phased array (OPA) beam scanner device. In this work, a waveguide phase modulator was designed and fabricated based on a high-refractive-index fluorinated polyimide. The propagation loss of the polyimide waveguide and the temporal response of the phase modulator were characterized. Moreover, the transfer function of the phase modulator including multiple poles and zeros was obtained from the measured frequency response. The polyimide waveguide modulator device demonstrated a fast response time of 117 μs for 1 kHz input signal, however, for 1 mHz step-function input, it exhibited an additional 5% phase change in 5 s.

Thermally resettable laser transmission induced transparency in polymer waveguides at 635 nm.

Laser transmission induced transparency (LTIT) has been observed in a polymer waveguide using commercial perfluorinated acrylate-based materials when a continuous-wave laser at 635 nm is injected. The transmitted optical power increases continuously and follows a non-linear curve with respect to the laser injection time. Loss reduction over 13 dB is observed within 60 min at a moderate laser power of 5 mW. While higher injection power leads to a quicker change of the waveguide transparency, this loss reduction tends to saturate at a level irrelevant to the injection power. Further experiments demonstrate that a laser injection at 635 nm can also slightly improve the transparency at near-infrared wavelengths from 1500 nm to 1600 nm which is also the target wavelength range for this material. The state after a certain laser injection dose of 635 nm proves to be stable and the transmission characteristics of the polymer waveguide can be maintained and will continue after being stored at room temperature over a long period of time. By baking the waveguide at 200 °C for 20 min, the transparency property can be reset and the waveguide will return to the original high-loss state of 635 nm. These unique properties can be attributed to the photo-induced generation and thermally induced recombination of free radicals in the organic material. Our discovery may trigger interesting applications of polymer waveguides in the development of optical memory, clock, and encryption devices, beyond their target applications in optical communication.

All-optical mode switching with a graphene-buried polymer waveguide directional coupler.

We demonstrate all-optical mode switching with a graphene-buried polymer waveguide asymmetric directional coupler (DC) by using the photothermal effect of graphene, where TE-polarized pump light and TM-polarized signal light are employed to maximize pump absorption and minimize graphene-induced signal loss. Our experimental device, which uses a graphene length of 6.2 mm, shows a pump absorption of 3.4 dB (at 980 nm) and a graphene-induced signal loss of 0.1 dB. The device can spatially switch between the fundamental mode and the higher-order mode with extinction ratios larger than 10 dB (at 1580 nm) and switching times slightly shorter than 1 ms at a pump power of 36.6 mW. Graphene-buried polymer waveguides offer many new possibilities for the realization of low-power all-optical control devices.

Broadband Optical Amplification of Waveguide Cut‐Off Mode in Polymer Waveguide Doped with Graphene Quantum Dots

AbstractGraphene quantum dots (GQDs) showing a wide‐range tunability in their emission wavelength are promising materials for next‐generation optoelectronic applications. However, there are few studies on optical amplification functionalities for broadband emission of GQDs. Here, the authors demonstrate a broadband optical amplification of GQDs mixed with a polymer matrix. The GQD particles prepared by microwave‐assisted hydrothermal method show a large variation in their dimension and a broadband emission with a large Stokes shift. In a form of polymeric thin film, the GQDs exhibit amplified spontaneous emission (ASE) signal showing the broadband gain of ≈370–650 nm and the gain coefficient up to ≈4 cm–1. Cut‐off mode propagation is the origin of ASE signal generation. The optical amplification performance is found to be associated to the photoluminescence quantum yield, which is improved by the GQDs passivation with the polymer matrix. These results demonstrate that the GQDs are a promising active material as a wideband optical amplification medium.

Fabrication of Y-Branched GI Core Polymer Waveguide and its Application to CWDM MUX Device for Multimode Fiber

This paper describes the characteristics of graded-index (GI) core Y-branched polymer optical waveguides as optical couplers for multimode fibers (MMFs) in coarse wavelength division multiplexing links with a restricted mode launch function. In this paper, we compare two GI-core Y-branched waveguides fabricated using different methods: the Mosquito method and the imprint method. Error free transmission is confirmed when transmitting a 25.6125-Gbps NRZ optical signal (PRBS31) at 850-nm wavelength through a 100-m long OM3 fiber using the waveguide as an optical coupler. We also discuss the function of a restricted mode launch exciter for a 1-km long MMF. From the effective modal bandwidth analysis, realizing higher bandwidth-distance product in long MMFs should be possible by reducing the core size of the waveguide coupler.

Tunable Filters Based on Cascaded Long-Period Polymer Waveguide Gratings

Long-period waveguide grating based filters have attracted attention due to their flexible fabrication, a variety of materials and structures, low back reflection, low insertion loss, and excellent performance in the tuning range and temperature sensitivity. To our knowledge, for the first time, a two-segment polymer long-period waveguide grating was cascaded to implement a filter with a narrower bandwidth. Experimental results showed that the device had a maximum extinction ratio of 24 dB at 1 577 nm, and the 12 dB bandwidth was 10 nm. The temperature sensitivity of the fabricated device was 1.79 nm/°C.

Identification of dyes and matrices for dye doped polymer waveguide emitters covering the visible spectrum

Polymer based photonic devices offer the possibility cost effective roll-to-roll manufacture of photonic devices. The incorporation of luminescent dopants within a solid polymer waveguide allows for the generation of light within the device avoiding tedious mechanical light coupling. However, when a dopant is embedded in a solid matrix, depending on its concentration and the nature of materials involved, the emitted light may be quenched due to aggregation effects. In this work, thin films and ridge waveguides processed by UV-photolithography have been successfully obtained from a selection of standard photopolymerizable organic monomers, SU8, EpoCore and OrmoStamp doped with a selection of standard dyes like Rhodamine-B, Coumarin-540A and Pyrromethene-580. All structures were manufactured on glass substrates. An analysis of the solubility and optical properties including band gap energy, absorption coefficient (alpha ) and fluorescence of the doped photoresists at different concentrations has been performed. Photoresists doped with Rhodamine-B shows a higher energy of indirect allowed band gap transition (2.04–2.09 eV) compared to previously reported pure Rhodamine-B thin films (1.95–1.98 eV). Fabrication protocols of dye doped photoresists covering the entire visible spectrum is established.

Ultra-Broadband and Compact TM-Pass Polarizer Based on Graphene-Buried Polymer Waveguide.

We report an ultra-broadband and compact TM-pass polarizer based on graphene-buried polymer waveguides. The characteristic parameters of the polarizer were carefully designed and optimized. The standard microfabrication processes were employed to fabricate the device. The presented polarizers exhibit high polarization-dependent transmission imposing a TE mode cutoff while leaving the TM mode almost unaffected. We experimentally demonstrated the polarizer that has an ultra-high extinction ratio of more than 22.9 dB and 41.9 dB for the monolayer graphene film placed on the surface of core layer and buried in the center of core layer, respectively, and as low insertion loss as ~4.0 dB for the TM mode with the bandwidth over 110 nm. The presented polarizer has the advantages of high extinction ratio, ultra-broadband, low cost, and easy integration with other polymer-based planar lightwave devices.

Selective and sensitive detection of miRNA-198 using single polymeric microfiber waveguide platform with heterogeneous CHA amplification strategy.

Pancreatic cancer (PC), which has a high fatality rate, is a kind of cancer with poor diagnosis and poor prognosis. Development of selective and sensitive detection platform to diagnose and prognostic of PC has attracted considerable attention. The miRNA-198 has been reported a potential prognostic and early diagnostic marker signature of PC. Herein, we report a novel sensitive detection of miRNA-198 in buffer and serum based on one dimensional chitosan/fluorescein isothiocyanate (CS/FITC) fluorescent microfiber waveguide system combined with the catalytic hairpin assembly amplification strategy. By combination with condensing enrichment effect, the proposed detection platform exhibited high specificity and sensitivity to miRNA-198 target, giving a detection limit as low as 2fM. More importantly, the proposed detection platform can be applied directly to distinguish the expression of miRNA-198 in clinical serum, affording the ability to distinguish pancreatic cancer patients from those of healthy human beings, and quantify the expression variation of miRNA-198 for the pancreatic cancer patients before and after resection, which may pave the way to develop novel clinical diagnostic equipment for cancer diagnosis and therapeutic evaluation.

ポリマー光導波路を用いた光電コパッケージ

ポリマー光導波路を用いた光電コパッケージ

Latest Trends of Polymer Waveguide Material for Co-Packaged Optics

Latest Trends of Polymer Waveguide Material for Co-Packaged Optics

125 GHz Frequency Doubler Using a Waveguide Cavity Produced by Stereolithography

This article reports on the first Schottky diode frequency doubler with a split-block waveguide structure fabricated by a high-precision stereolithography (SLA) printing process. The printed polymer waveguide parts were plated with copper and a thin protective layer of gold. The surface roughness of the printed waveguide parts has been characterized and the critical dimensions measured, revealing good printing quality as well as a dimensional accuracy that meets the tight tolerance requirements for subterahertz active devices. The 62.5 to 125 GHz frequency doubler circuit comprises a 20 μm thick GaAs Schottky diode monolithic microwave integrated circuit (MMIC) in the waveguide. The measured doubler provides a maximum output power of 33 mW at 126 GHz for input power of 100 mW. The peak conversion efficiency was about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$32\% $</tex-math></inline-formula> at input powers from 80 to 110 mW. This doubler performance is compared with and found to be nearly identical to the same MMIC housed in a CNC-machined metal package. This work demonstrates the capability of high-precision SLA techniques for producing subterahertz waveguide components.

Low-power all-optical switch based on a graphene-buried polymer waveguide Mach-Zehnder interferometer.

We propose a low-power all-optical switch based on the structure of a graphene-buried balanced Mach-Zehnder interferometer (MZI), where the signal light is switched between the two output ports of the MZI by the heat generated from graphene's absorption of the pump light. We use orthogonal polarizations for the pump and the signal light to maximize pump absorption and minimize graphene-induced signal loss. Our experimental device fabricated with polymer waveguides buried with 5-mm long graphene shows a pump absorption of 10.6 dB (at 980 nm) and a graphene-induced signal loss of 1.1 dB (at 1550 nm) and can switch the signal light with a pump power of 6.0 mW at an extinction ratio of 36 dB. The actual pump power absorbed by graphene for activating switching is estimated to be 2.2 mW. The rise and fall times of the switch are 1.0 and 2.7 ms, respectively. The switching characteristics are weakly sensitive to ambient temperature variations. Our device can be butt-coupled to single-mode fibers and could find applications in fiber-based and on-chip all-optical signal processing.

Recording of Long Low-Amplitude Bulk Elastic Waves in Transparent Solid Waveguides by Digital and Classical Holography

In this paper we compare two implementations of the holographic technique for recording long, nonlinear, elastic waves of low amplitude in solid polymer waveguides: classical holographic interferometry and digital holography. Both implementations are realized in transmission configuration, with recording in the off-axis schematic. The advantages and disadvantages of these implementations are discussed as applied to the investigation of the evolution of shock waves and strain solitons in transparent solid waveguides.

Evolution of System Embedded Optical Interconnect in Sub-Top-of-Rack Data Center Systems

In this paper we review key technological milestones in system embedded optical interconnects in data centers that have been achieved between 2014 and 2020 on major European Union research and development projects. This includes the development of proprietary optically enabled data storage and switch systems and optically enabled data storage and compute subsystems. We report on four optically enabled data center system demonstrators: LightningValley, ThunderValley2, Pegasus and Aurora, which include advanced optical circuits based on polymer waveguides and fibers and proprietary electro-optical connectors. We also report on optically enabled subsystems including Ethernet-connected hard disk drives and microservers. Both are designed in the same pluggable carrier form factor and with embedded optical transceiver and connector interfaces, thus allowing, for the first time, both compute and storage nodes to be optically interchangeable and directly interconnectable over long distances. Finally, we present the Nexus platform, which allows different optically enabled data center test systems and subsystems to be interconnected and comparatively characterized within a data center test environment.

Effective electromagnetic interference shielding properties of micro-truss structured CNT/Epoxy composites fabricated based on visible light processing

In this work, a novel self-writing visible light processing method is employed to fabricate self-propagating polymer waveguide based porous epoxy matrix, which subsequently turns into micro-truss structured carbon nanotube (CNT)/epoxy conductive composites through CNT dip-coating. It is discovered that, by illuminating a photosensitive epoxy pre-polymer with intersecting blue LED beams simultaneously for only 15 min, 3D micro-truss structured epoxy matrix with thickness of ∼1.8 mm is obtained. When incorporating CNTs with a low content of 1.20 vol%, the micro-truss structured CNT/epoxy composites exhibit high electrical conductivity of 62.93 S/m. These composites show absorption-dominated shielding mechanism, and high electromagnetic interference (EMI) shielding efficiency (SE) of 34.5 dB is obtained in the X band with 1.20 vol% of CNT. The specific shielding efficiency (SSE) of the CNT/epoxy composites is up to 100 dB cm3 g−1, and the corresponding SSE/t eliminating the effect of thickness is up to 535 dB cm2 g−1, which is much higher than that reported in other studies with the same CNT contents. This work provides a quick and scalable technique to prepare polymer matrix with ordered porous structures, and would also inspire and guide the fabrication of well-ordered porous conductive polymer composites with superior EMI shielding performances.

90°-bent graded-index core polymer waveguide for a high-bandwidth-density VCSEL-based optical engine.

In this paper, we present a low-loss optical assembly utilizing a 90°-bent graded-index (GI) core polymer optical waveguide on vertical cavity surface emitting laser (VCSEL) based optical transceivers. The proposed assembly can replace conventional components such as mirrors and lenses for realizing subminiature optical engines applicable to on-board integration. To minimize the total insertion loss of the waveguide when connected to a high-speed VCSEL and a GI-core multimode fiber (MMF) at each end, the characteristics of the beam emitted from VCSELs are measured and taken into consideration for the waveguide design. In order to confirm the effect of insertion loss reduction by the waveguide numerical aperture control, 90°-bent GI-core polymer waveguides are fabricated applying the Mosquito method. The fabricated waveguide exhibits a total insertion loss as low as about 2 dB at 850-nm wavelength, which includes the coupling losses at both ends, bending, and propagation losses. We also investigate a way to reduce the insertion loss when a gap exists between the waveguide and VCSEL chip. We theoretically and experimentally confirm that filling the gap with a high index resin can reduce the coupling loss by 5 dB.

Compact and efficient three-mode (de)multiplexer based on horizontal polymer waveguide couplers.

A compact and efficient polymer three-mode (de)multiplexer with two cascaded waveguide directional couplers fabricated on the same substrate along the horizontal direction is proposed. Three waveguides formed two couplers, where two narrower waveguides were placed on either side of the central waveguide. By optimizing the core height and width, the two couplers can ensure that the E11x mode of the two narrower waveguides are highly coupled into the E21x and E31x modes of the central waveguide at a wavelength of 1310 nm. The structural size of the fabricated three-mode (de)multiplexer using ultraviolet (UV) lithography technology is in agreement with the designed value. The fabricated device, which is 35 mm long, exhibits coupling ratios of 98.07% and 95.43% for the two couplers, respectively. The insertion losses of the three waveguides are 5.23 dB, 8.58 dB, and 14.39 dB, respectively. The device can achieve the multiplexing of three modes in two dimensions, which can increase the channel capacity of optical communication.

Polarization-independent electro-absorption optical modulator based on trapezoid polymer-graphene waveguide

A polarization-independent electro-absorption modulator based on the trapezoid polymer-graphene waveguide (PGW) was proposed. The modulator was constructed on a trapezoid polymer waveguide, and the insulting dielectric spacer sandwiched in the two graphene layers was placed on the surface of the trapezoid polymer waveguide core. The simulation results show that by applying different gate voltages on the graphene layers, effective mode index of the TE and TM modes in the PGW can realize the similar changes in the C-band, which provides the possibility for realizing the polarization-independent modulation. Here, through simulation and optimization, the presented modulator has a compact size and the extinction ratio (ER) of 37 dB can be achieved by reasonably setting working points of “OFF” and “ON” states with 800 μm long active graphene length. The ER variation between the two operating modes is about 0.46 dB. The corresponding power consumption of the modulator is about 23.6 pJ/bit.