Organic Waveguide Research Articles

Ultra‐Wide Modulation and Reversible Reconfiguration of a Flexible Organic Crystalline Optical Waveguide Between 645 and 731 nm

Flexible organic crystalline optical waveguides, i.e., delivering input or self‐emit lights through various dynamic organic crystals, have attracted increasing attentions in the past decade. However, the modulation of waveguide outputs relies on chemical design and substituent modification, being time‐consuming and laborious. Here we report an elastic organic crystal that displays long‐distance light transducing capability up to 2.0 cm and ultra‐wide modulation of crystalline optical waveguides between red (645 nm) and near infrared (731 nm) in both the pristine and the elastically bent states based on a pre‐designed self‐absorption effect. The flexible organic crystalline optical waveguides can be precisely and reversibly reconfigured by controlling irradiation point. In addition, deep red amplified spontaneous emissions (ASE) that are able to transduce through a 5.0 mm bent crystal with an ultra‐low optical loss coefficient of 0.092 dB/mm has been attained. To the best of our knowledge, this is the first report of flexible organic ASE waveguides. The present study not only provides a simple yet effective strategy to remarkably modulate flexible organic crystalline optical waveguides but also demonstrates the superiority of laser over normal emission as flexible optical communication elements.

The New Era of Organic Field-Effect Transistors: Hybrid OECTs, OLEFETs and OFEWs

Advancements in electronic device technology have led to an exponential growth in demand for more efficient and versatile transistors. In this context, organic field-effect transistors (OFETs) have emerged as a promising alternative due to their unique properties and potential for flexible and low-cost applications. However, to overcome some of the inherent limitations of OFETs, the integration of organic materials with other materials and technologies has been proposed, giving rise to a new generation of hybrid devices. In this article, we explore the development and advances of organic field-effect transistors and highlight the growing importance of hybrid devices in this area. In particular, we focus on three types of emerging hybrid devices: organic electrochemical transistors (OECTs), organic light-emitting field-effect transistors (OLEFETs) and organic field-effect waveguides (OFEWs). These devices combine the advantages of organic materials with the unique capabilities of other technologies, opening up new possibilities in fields such as flexible electronics, bioelectronics, or optoelectronics. This article provides an overview of recent advances in the development and applications of hybrid transistors, highlighting their crucial role in the next generation of electronic devices.

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.

High-quality on-chip entangled photon source with broad tunable range based on coupling compensation

This paper introduces a tunable and high-quality photon source that utilizes evanescent-wave coupling phase matching. By adjusting the coupling gap, the signal light can be tuned from 1307 nm to 1493.9 nm, and the idler light can be tuned from 1612.8 nm to 1907 nm. Throughout the entire tuning range, the purity of the photon pairs remains above 92%. In specific tuning ranges (signal photons from 1307 nm to 1421.7 nm and idler photons from 1706.4 nm to 1907 nm), the purity exceeds 99% and the full width at half-maximum of the generated photon spectra is less than 1.85 nm. The photon source is designed using a silicon–organic hybrid waveguide, which effectively minimizes the impact of two-photon absorption and achieves a 15 dB enhancement in four-wave mixing conversion efficiency compared to a strip waveguide. This design may promote efficient and precise generation of high-quality photons at desired frequencies, offering promising potential for various applications in quantum technologies.

Mechanically controlled multifaceted dynamic transformations in twisted organic crystal waveguides

This study introduces mechanically induced phenomena such as standing, leaning, stacking, and interlocking behaviors in naturally twisted optical waveguiding microcrystals on a substrate. The microscale twisted crystal self-assembled from 2,4-dibromo-6-(((2-bromo-5-fluorophenyl)imino)methyl)phenol is flexible and emits orange fluorescence. Mechanistic analysis reveals the strain generated by the intergrowing orientationally mismatched nanocrystallites is responsible for the twisted crystal growth. The crystal’s mechanical flexibility in the perpendicular direction to (001) and (010) planes can be attributed to intermolecular Br···Br, F···Br, and π···π stacking interactions. Through a systematic process involving step-by-step bending and subsequent optical waveguiding experiments at each bent position, a linear relationship between optical loss and mechanical strain is established. Additionally, the vertical standing and leaning of these crystals at different angles on a flat surface and the vertical stacking of multiple crystals reveal the three-dimensional aspects of organic crystal waveguides, introducing light trajectories in a 3D space. Furthermore, the integration of two axially interlocked twisted crystals enables the coupling of polarization rotation along their long axis. These crystal dynamics expand the horizons of crystal behavior and have the potential to revolutionize various applications, rendering these crystals invaluable in the realm of crystal-related science and technology.

Low temperature PECVD processes for the fabrication of integrated symmetrical resonant UV210 organic/semiconductor structures

The resonant structures used as sensors for investigating specific dark and opaque substances may pose difficulties due to their potential aggressiveness towards photonic chips and the risk of destruction upon contact. To avoid it, this study presents a detailed description of a novel symmetrical waveguide structure with UV210 enclosed between Si/SiO2 bi-layers implemented for integrated photonics. The fabrication process is thoroughly explained, accompanied by various analyses conducted for characterizations purposes. The structure is composed of an organic UV210 material developed using deep UV lithography at 248 nm and fabricated onto an oxidized silicon layer, resulting in a Si/SiO2 bi-layer configuration. This process enables the fabrication of µm-scale access waveguides and racetrack Micro-Resonators (MRs) with a 400-nanometers gap. Several multilayer families have been produced using various low-temperature PECVD processes to obtain symmetrical Si/SiO2/UV210/Si/SiO2 structures and then properly characterized using non-destructive analyses and imaging techniques. The advantage of structural symmetry is primarily related to the electromagnetism and guidance equations, which eliminate the requirement for a cut-off thickness (or frequency), enabling significant miniaturization. Additionally, the upper cladding composed of a Si/SiO2 bi-layer offers protection against potentially aggressive substances directly in contact with the organic waveguide core and MRs. Different bi-layer upper cladding families, produced under various PECVD conditions, were characterized using XPS to understand the bonding mechanism between the silicon and UV210 organic. In addition, ellipsometric analyses were conducted to determine the real and imaginary components of the refractive index of the global structure and the upper cladding bi-layer. Structure imaging were obtained by Raman analyses and optical statistical measurements were conducted on four different types of heterostructures, with silica temperatures ranging from 120°C to 150°C during the second PECVD process. The resonance analysis, performed through Free Spectral Range (FSR) measurements, allowed us to draw conclusions regarding the stability and reproducibility of the fabrication process, as well as the impact of PECVD processes conditions on the optical measurements. Such optoelectronic resonant elements and hybrid heterostructures enable the investigation of aggressive substances in direct contact.

Tunable Unexplored Luminescence in Waveguides Based on D-A-D Benzoselenadiazoles Nanofibers.

A set of novel Donor-Acceptor-Donor (D-A-D) benzoselenadiazole derivatives has been synthesized and crystallized in nanocrystals in order to explore the correlation between their chemical structure and the waveguided luminescent properties. The findings reveal that all crystals exhibit luminescence and active optical waveguiding, demonstrating the ability to adjust their luminescence within a broad spectral range of 550-700 nm depending on the donor group attached to the benzoselenadiazole core. Notably, a clear relationship exists between the HOMO-LUMO energy gaps of each compound and the color emission of the corresponding optical waveguides. These outcomes affirm the feasibility of modifying the color emission of organic waveguides through suitable chemical functionalization. Importantly, this study marks the first utilization of benzoseleniadiazole derivatives for such purposes, underscoring the originality of this research. In addition, the obtention of nanocrystals is a key tool for the implementation of miniaturized photonic devices.

A Pick‐and‐Place Technology Enabled, Mechanically Programmable, Spiral Optical Waveguides Integrated Hybrid Circuits from Four Extremely Pseudo‐Plastic Organic Crystals for Visible Spectral Band Tunability

AbstractIn the field of silicon photonics, highly compact and miniature high‐density circuits are achieved by precisely shaping millimeter‐long waveguides into spiral configurations. Organic photonics, on the other hand, takes advantage of mechanically flexible crystal spiral waveguides (SWs) within organic photonic circuits. These SWs offer versatility, enabling precise control over light paths and mechanical programmability. This study introduces an innovative pick‐and‐place technique for constructing various organic spiral waveguides (OSWs) with different geometries, such as Cornu, Archimedean, elliptical, rectangular, four‐sided polygons, and three‐sided polygons. Additionally, this method allows for the creation of optically reprogrammable photonic circuits. Custom‐synthesized flexible crystals are used, including blue‐emitting (Z)−3‐(4‐(9H‐carbazol‐9‐yl)phenyl)−2‐(3,5‐bis(trifluoromethyl)phenyl)acrylonitrile (Cz‐2CF3), green‐emitting (E)−1‐(((5‐bromopyridin‐2‐yl)imino)methyl)naphthalene‐2‐ol (BPyIN), cyan‐emitting 9,10‐dibromo anthracene (DBA), and red‐emitting 4,7‐bis(4‐octylthiophen‐2‐yl)benzo[c][1,2,5]thiadiazole (BTD). Systematically integrating a Cz‐2CF3 OSW (with two ports for optical signal routing in clockwise/counterclockwise directions) with DBA and BTD waveguides produces multi‐color hybrid photonic circuits with customizable optical functions, tailored to specific design needs. The number of output ports can be dynamically adjusted through mechanical programming by coupling crystals tip‐to‐tip when replacing the DBA waveguide with a BPyIN waveguide using the pick‐and‐place technology. This mechanically programmable hybrid spiral photonic circuit seamlessly operates across the entire visible spectral bandwidth, making it valuable for various applications, including high‐fidelity sensing, spectrometer components, and intelligent circuitry.

Rational Design of a Multifunctional Benzothiadiazole Derivative in Organic Photonics and Electronics.

In order to achieve a multifunctional compound with potential application in organic photonics and electronics, a multidonor benzothiadiazole derivative was rationally designed and synthesized employing microwave irradiation as energy source, increasing the process efficiency about yields and reaction times in comparison with conventional conditions. This powerful compound displayed solvatochromism and showed efficient behavior as red optical waveguide with low OLC around 10-2 dB μm-1 and with the capacity of light transmission in two directions. In addition, the proposed derivative acted as efficient p-type semiconductor in organic field-effect transistors (OFETs) with hole mobilities up 10-1 cm2 V-1 s-1 . This corroborates its multifunctional character, thus making it a potential candidate to be applied in hybrid organic field-effect optical waveguides (OFEWs).

Luminescence colour modulation in benzotriazole-derived waveguides

A series of new Donor-Acceptor-Donor (D-A-D) benzotriazole derivatives have been synthesized and processed into crystals with the aim to establish a relationship between their chemical structure and waveguided luminescent properties. The outcomes show that all crystals display luminescence and active optical waveguiding with optical loss coefficients in the 10−2 dB/μm range, with the capability to tune their luminescence across a wide spectral range of 500–700 nm upon substitution at the benzotriazole moiety. There is also an evident relationship between the HOMO-LUMO energy gaps and the color emission of the corresponding waveguides. These results support the possibility of modulating the emission color of organic waveguides by appropriate chemical functionalization.

Dimension Engineering of Stimuli‐Responsive 1D Molecular Crystals into Unusual 2D and 3D Zigzag Waveguides

AbstractWe demonstrate an innovative technique to achieve organic 2D and 3D waveguides with peculiar shapes from an acicular, stimuli‐responsive molecular crystal, (2Z,2′Z)‐3,3′‐(anthracene‐9,10‐diyl)bis(2‐(3,5‐bis(trifluoromethyl)phenylacrylonitrile), Ant‐CF3. The greenish‐yellow fluorescent (FL) Ant‐CF3 molecular crystals exhibit laser power‐dependent permanent mechanical bending in 2D and 3D. Investigation of a single‐crystal using spatially‐resolved Raman/FL/electron microscopy, and theoretical calculations revealed photothermal (Z,E)/(E,E) isomerization‐assisted transition from crystalline to amorphous phase at the laser‐exposed regions. This phenomenon facilitates the dimension engineering of a 1D crystal waveguide into 2D waveguide on a substrate or a 3D waveguide in free space. The bends can be used as interconnection points to couple different optical elements. The presented technique has broader implications in organic photonics and other crystal‐related photonic technologies.

Dimension Engineering of Stimuli-Responsive 1D Molecular Crystals into Unusual 2D and 3D Zigzag Waveguides.

We demonstrate an innovative technique to achieve organic 2D and 3D waveguides with peculiar shapes from an acicular, stimuli-responsive molecular crystal, (2Z,2'Z)-3,3'-(anthracene-9,10-diyl)bis(2-(3,5-bis(trifluoromethyl)phenylacrylonitrile), Ant-CF3 . The greenish-yellow fluorescent (FL) Ant-CF3 molecular crystals exhibit laser power-dependent permanent mechanical bending in 2D and 3D. Investigation of a single-crystal using spatially-resolved Raman/FL/electron microscopy, and theoretical calculations revealed photothermal (Z,E)/(E,E) isomerization-assisted transition from crystalline to amorphous phase at the laser-exposed regions. This phenomenon facilitates the dimension engineering of a 1D crystal waveguide into 2D waveguide on a substrate or a 3D waveguide in free space. The bends can be used as interconnection points to couple different optical elements. The presented technique has broader implications in organic photonics and other crystal-related photonic technologies.

Phase regeneration of star-16QAM using phase-sensitive amplification in graphene silicon-based organic hybrid waveguide

We theoretically demonstrate the phase regeneration of the star-16-quadrature-amplitude-modulation(star-16QAM) signal in a graphene-graphene oxide hybrid waveguide. The multi-order dispersion properties of this waveguide are tuned by graphene, where the near-zero-dispersion-point moves to right with increasing applied electrochemistry. The waveguide nonlinearity coefficient is 1.534×106/m/W and the dispersion is flat in the ultra-wide wavelength range of 1310 nm to 1860 nm by filling the waveguide with the high kerr coefficient organic material graphene oxide. The phase regeneration of the star-16QAM signal is achieved by using a dual-conjugate-pump degenerate four-wave mixing (FWM) technique, and the results show that the error-vector -magnitude (EVM) is reduced from 39.25% to 2.14%, the phase noise is effectively compressed.

Self‐Amplified Photon Guiding in the Luminescent Organic Semiconductor Nanowires

AbstractOrganic semiconductor nanocrystals are important building blocks for miniaturized room‐temperature optoelectronic and excitonic devices, benefitting from their large oscillator strength, high quantum yield, and large exciton binding energy. Specifically, 1D organic semiconductor nanowires have been widely studied with promising applications such as nanoscale light sources and optical waveguides. Although both amplified spontaneous emission and lasing have been well demonstrated in organic semiconductor nanowires under pulsed laser excitation, amplification of guided photons during propagation along the nanowire has been rarely investigated. Here, a highly polarized luminescent organic semiconductor nanowire with self‐amplified photon guiding capability under continuous‐wave laser excitation is reported. The nanowire waveguide itself functions as a gain medium to provide optical gain during its photoluminescence propagation, with the value of gain depending on temperature and excitation laser power. This research reveals the optical gain effect in the organic semiconductor waveguide system, which paves the way for on‐chip energy‐efficient photonic communications.

Race‐Track Type Resonator Integrated Active Add‐Drop Filter from Flexible Organic Crystals: Experiments and Numerical Calculations

AbstractThe success of silicon photonics stems from the ability to design, simulate, and construct optical components and their optical performance simultaneously. However, poor mechanical compliance of Si‐based materials demands alternative photonic materials. The recent development of mechanically flexible organic waveguides as reliable photonic material platform is quite promising. Herein, the design and fabrication of a race‐track type resonator based add‐drop filter (ADF) from elastically bendable 9,10‐dibromoanthracene (DBA) crystals are reported. The elastic DBA microcrystals exhibit pseudo‐plasticity on a substrate facilitating the fabrication of race‐track type resonator and ADF via mechanophotonics technique. Photonic investigations of the circuit reveal its spectral filtering ability. These experimental observations confirmed by FDTD modelling support the unique abilities of organic optical elements for photonic device applications.

A Broadband, Multiplexed-Visible-Light-Transport in Composite Flexible-Organic-Crystal Waveguide.

We report the construction of an organic crystal multiplexer using three chemically and optically different acicular, flexible organic crystals for a broadband, visible light signal transportation. The mechanical integration of a highly flexible crystal waveguide of (Z)-2-(3,5-bis(trifluoromethyl)phenyl)-3-(7-methoxybenzo[c][1,2,5]thiadiazol-4-yl)acrylonitrile (BTD2CF3 ) displaying bright yellow (λ1 ) fluorescence with blue-emitting (λ2 ) BPP and cyan emitting (λ3 ) DBA crystals using AFM-tip provides a composite organic crystal multiplexer. The constructed hybrid single crystal multiplexer effectively transduces three optical signals (λ1 +λ2 +λ3 ) covering the 420-750 nm region as a composite output signal. The presented proof-of-principle experiment demonstrates the real potential of organic flexible crystal waveguides for visible light communication technologies.

A Broadband, Multiplexed‐Visible‐Light‐Transport in Composite Flexible‐Organic‐Crystal Waveguide

AbstractWe report the construction of an organic crystal multiplexer using three chemically and optically different acicular, flexible organic crystals for a broadband, visible light signal transportation. The mechanical integration of a highly flexible crystal waveguide of (Z)‐2‐(3,5‐bis(trifluoromethyl)phenyl)‐3‐(7‐methoxybenzo[c][1,2,5]thiadiazol‐4‐yl)acrylonitrile (BTD2CF3) displaying bright yellow (λ1) fluorescence with blue‐emitting (λ2) BPP and cyan emitting (λ3) DBA crystals using AFM‐tip provides a composite organic crystal multiplexer. The constructed hybrid single crystal multiplexer effectively transduces three optical signals (λ1+λ2+λ3) covering the 420–750 nm region as a composite output signal. The presented proof‐of‐principle experiment demonstrates the real potential of organic flexible crystal waveguides for visible light communication technologies.

21‐2: Invited Paper: Improve OLED Light Outcoupling Efficiency by Eliminating Waveguide Mode using Ultrathin Metal Electrode

Extracting light from the waveguide mode in organic light‐emitting diodes (OLED) is most challenging as such optical mode is intrinsic in traditional OLED due to materials and layered structure used in the device. This work intends to address the root cause of the light trapping problem. We systematically analyzed OLEDs made with an ultrathin Ag anode and found that waveguide modes can be completely eliminated by designing a structure to below the cutoff thickness of waveguide modes. We also experimentally verified the waveguide mode elimination in organic waveguides. In principle such a scheme can be extended to tandem cells, and in making transparent OLED. A further benefit is the ductility of the ultrathin metal allows foldable OLED to be realized.

Enhanced optical nonlinearity in a silicon–organic hybrid slot waveguide for all-optical signal processing

Silicon photonic integrated devices used for nonlinear optical signal processing play a key role in ultrafast switching, computing, and modern optical communications. However, current devices suffer from limited operation speeds and low conversion efficiencies due to the intrinsically low nonlinear index of silicon. In this paper, we experimentally demonstrate enhanced optical nonlinearity in a silicon–organic hybrid slot waveguide consisting of an ultranarrow slot waveguide coated with a highly nonlinear organic material. The fabricated slot area is as narrow as 45 nm, which is, to the best of our knowledge, the narrowest slot width that has been experimentally reported in silicon slot waveguides. The nonlinear coefficient of the proposed device with a length of 3 mm is measured to be up to 1.43 × 10 6 W − 1 km − 1 . Based on the nanostructure design, the conversion efficiencies of degenerate four-wave mixing showed enhancements of more than 12 dB and 5 dB compared to those measured for an identical device without the organic material and a silicon strip waveguide, respectively. As a proof of concept, all-optical canonical logic units based on the prepared device with two inputs at 40 Gb/s are analyzed. The obtained logic results showed clear temporal waveforms and wide-open eye diagrams with error-free performance, illustrating that our device has great potential for use in high-speed all-optical signal processing and high-performance computing in the nodes and terminals of optical networks.

Improved light coupling efficiency of organic light-emitting diode and polymer optical waveguide integrated device by grating coupler

Improved light coupling efficiency of organic light-emitting diode and polymer optical waveguide integrated device by grating coupler