Fabrication Of Waveguides Research Articles

Bringing Plasmonics Into CMOS Photonic Foundries: Aluminum Plasmonics on Si$_{3}$N$_{4}$ for Biosensing Applications

We present a technology platform supported by a new process design kit (PDK) that integrates two types of aluminum plasmonic waveguides with Si $_{3}$ N $_{4}$ photonics towards CMOS-compatible plasmo-photonic integrated circuits for sensing applications. More specifically, we demonstrate the fabrication of aluminum slot waveguide via e-beam lithography (EBL) on top of the Si $_{3}$ N $_{4}$ waveguide and an optimized fabrication process of aluminum plasmonic stripe waveguides within a CMOS foundry using EBL. Experimental measurements revealed a propagation length of 6.2 μm for the plasmonic slot waveguide in water at 1550 nm, reporting the first ever experimental demonstration of a plasmonic slot waveguide based on CMOS compatible metal materials in liquid environment. Propagation length in water for the aluminum stripe was measured equal to 66.8 μm which is, to the best of our knowledge, the highest value among all single-mode Al-based plasmonic waveguides presented so far at 1550 nm. Moreover, we evince with simulation data the sensing capabilities of the proposed structures when incorporated in a Si $_{3}$ N $_{4}$ -based interferometric configuration, yielding bulk sensitivity values up to 80 nm/RIU and 1300 nm/RIU, corresponding to an accumulated phase change per unit length of 0.77 π/RIU/μm and 1.26 π/RIU/μm for the aluminum slot and aluminum stripe waveguide, respectively.

Single-step fabrication of surface waveguides in fused silica with few-cycle laser pulses.

Direct laser writing of surface waveguides with ultrashort pulses is a crucial achievement towards all-laser manufacturing of photonic integrated circuits sensitive to their environment. In this Letter, few-cycle laser pulses (with a sub-10fs duration) are used to produce subsurface waveguides in a non-doped, non-coated fused-silica substrate. The fabrication technique relies on laser-induced microdensification below the threshold for nanopore formation. The optical losses of the fabricated waveguides are governed by the optical properties of the superstrate. We have measured losses ranging from less than 0.1dB/mm (air superstrate) up to 2.8dB/mm when immersion oil is applied on top of the waveguide.

Low-Loss Waveguide Fabrication by Inkjet Printing on Porous Silicon

We report fabrication of optical waveguides embedded in oxidised porous silicon in a mask-less process. Patterned pore-filling was attained by means of inkjet printing, enabling lateral modification of the waveguide's index of refraction and other optical properties thus providing full two-dimensional refractive index control of the optical waveguide. The waveguides were created by applying a KDP salt solution over a porous silicon film by means of a material printer. Light guiding was demonstrated at wavelengths 1.064 and 1.550 microns. Measured values of the intensity attenuation at these wavelengths were 2.5 dB/cm and below 1.3 dB/cm respectively

Fabrication and characterization of annealed proton exchanged long period waveguide grating in x-cut LiNbO3

In this paper, a long-period waveguide grating was fabricated in x-cut lithium niobate substrate by patterned annealed proton exchange waveguide fabrication process. The waveguide mode characteristic was evaluated using a charge-coupled device (CCD) camera. It shows that the waveguide is single mode transmission at a wavelength of 1 550 nm. The transmission spectra of the long period waveguide gratings were measured by optical spectrum analyzer (OSA) and show an extinction ratio of ~17 dB and a 3 dB bandwidth of ~10 nm at the resonant wavelength. The resonant wavelength moves toward to the long wavelength direction as the waveguide width-difference increases in the same period, and also shifts toward to the long wavelength direction with the increase of the period in the case of the same waveguide width-difference. The method of fabricating a long period waveguide grating based on a patterned annealed proton exchange technique simplifies the fabrication process, and at the same time, reduces the fabrication cost.

Spatial solitons in KTaxNb1-xO3 waveguides produced by swift carbon ion irradiation and femtosecond laser ablation

We report on the fabrication of planar waveguide and ridge waveguides in a KTN crystal by using swift heavy C5+ ions irradiation and femtosecond laser ablation. The reconstructed refractive index profile of the irradiated KTN waveguide illustrates an optical well and barrier distribution. The confocal Raman spectra suggest that the enhanced tetragonality and the lattice damage occurs in the waveguide region and the optical barrier area, respectively. The optical spatial solitons at 632.8 nm are observed from the planar waveguide and the ridge waveguides with a width of 60 μm and 20 μm, respectively, at room temperature.

Polarization mode converters in ZnO-diffused LiNbO3 waveguides

The linear electro-optic effect in lithium niobate is capable of realizing a variety of polarization transformations, including TE-to-TM and left-to-right circular polarization conversion. Several types of devices have been demonstrated in Ti-diffused waveguides. LiNbO3 devices have historically been based on either Ti-diffused or proton-exchanged waveguides. The proton-exchanged waveguides only guide light polarized along the optic axis, and therefore, are not applicable to polarization transforming devices. Zinc oxide diffusion is an alternative waveguide fabrication technology that guides both e- and o-waves with much higher power-handling capability than Ti : LiNbO3 waveguides. ZnO : LiNbO3 waveguides exhibit a highly circular mode field with lower anisotropy than Ti-diffused waveguides. We report the design, fabrication, and testing of ZnO : LiNbO3 devices for polarization mode conversion.

Ridge waveguides in magneto-optical glasses formed by combination of proton implantation and precise diamond blade dicing

We report on the fabrication of a ridge waveguide in the Tb3 + -doped aluminum borosilicate glass by combining the 550-keV proton implantation and the precise diamond blade dicing with a rotating speed of 20,000 rpm. The relative atom displacement of the original structure induced by the proton implantation is simulated by Stopping and Range of Ions in Matter 2013 in the Tb3 + -doped aluminum borosilicate glass. The morphology of the ridge waveguide is acquired by scanning electron microscopy. The near-field intensity distribution of the waveguide is recorded by the end-face coupling system, which indicates that the light can be well confined in the ridge waveguide region.

10‐2: Waveguide Manufacturing for AR Displays: Past, Present, and Future

Current AR waveguide fabrication processes, including Surface Relief Gratings (SRG), holographic and cascaded mirrors, are reviewed. We present DigiLens's Switchable Bragg Grating (SBG)‐based manufacturing process which transforms classical holographic contact copying into a versatile, cost‐effective printing process for AR waveguides of any size and field‐of‐view.

Simple one-step ion exchange enhanced Faraday rotation in heavy metal oxide diamagnetic glasses

Ion exchanges (IE) on silicate, tellurite, borate and phosphate glass have been extensively studied for different objectives such as changing glass refractive index, strengthening glass structure or realizing nanometal-glass systems, however, ion exchange on lead-bismuth-borate diamagnetic glass for Faraday rotation improvement is interesting and attractive for magneto optical glass and magneto optical waveguide devices. In this study, for the first time, we studied the one-step Ag+-Na+ ion exchange on diamagnetic Bi2O3-PbO-B2O3-Na2O (PBBN) glass for the aim of improving diamagnetic properties and providing an efficient route for magneto-optical waveguide. The Ag+-Na+ ions has been sucessfully exchanged at 270 °C for 20 min condition. And without any further heat or H2 treatment after IE, the Ag+ ions and Ag0 nanoparticles co-existed in glass. Heat treatment in H2 after IE not only greatly increased the Ag0 NPs size, but also produced the Bi0 crystals which were not helpful for glass properties. Ag nanoparticles showed characteristic surface plasmon resonance peak at 500–550 nm range. Raman spectra displayed the evolutions of Ag+ and Ag0 in functions of different ion exchange conditions. The UV–Visible and Faraday rotation measurements suggested that high polarizability and diamagnetic susceptibility properties of diamagnetic Ag+ ions and Ag0 nanoparticle induced surface plasmonic effects improved the optical refractive index and magneto optical Verdet constant. A simple linear optical waveguide also were obtained on PBBN glass surface using the optimized IE parameters. The proposed one-step ion exchange technique on diamagnetic glass will be an efficient method for glass properties enhancement and magneto optical waveguide fabrication.

Role of the high vacuum in the precise control of index contrasts and index profiles of LiNbO3 waveguides fabricated by high vacuum proton exchange

Precise control and reproducibility of optical waveguides fabrication are extremely important for efficient and compact devices for a wide range of applications in either classical or quantum photonics. In this way, waveguides fabricated in lithium niobate (LN) crystals offer one of the most established platforms in modern photonics. Here we experimentally validate the excellent control and reproducibility of the index contrast and index profile of optical waveguides fabricated on Z-cut lithium niobate (LN) substrates by the recently proposed High Vacuum Proton Exchange (HiVacPE) technique. Based on the known chemical reactions involved in the refractive index variation mechanism we explain why the high vacuum, having a drying effect, is the key feature to obtain highly reproducible HiVacPE waveguides.

Femtosecond direct laser writing of silk fibroin optical waveguides

Silk fibroin is an abundant natural polymer, which in the last years has been proposed as an attractive material for high-technological applications, offering also new opportunities for photonics and optoelectronics. In this context, the design of optical waveguides based on silk fibroin is of great interest because of their ability to direct light in a controlled manner. In this work, we demonstrate the use of femtosecond direct laser writing (fs-DLW) to fabricate silk fibroin waveguides. Such waveguides were characterized by coupling 632.8 nm light from a He–Ne laser. Our findings demonstrate the potential of fs-DLW as a novel approach for the fabrication of silk fibroin waveguides, which provides a versatile platform for optical and biomedical applications.

Theory and design of phase‐inverted balanced coupled‐line DC‐blocker

A planar DC-blocker suitable for differential mode signalling applications is designed and fabricated. The theory of this component is explained in a new form which utilises the wave scattering transfer matrix. The proposed interpretation of the transfer matrix is most suitable for series (cascade) elements like DC-blockers. In addition to the theoretical enhancement, design of a compressed balanced DC-blocker inserted through a shielded broadside coupled stripline (SBCSL) transmission line (TL) is presented. The return loss of better than 10 dB is obtained at 50-ohm differential-mode input ports of the fabricated DC-blocker in the entire frequency range of 5.6–8.4 GHz. The other achievement of this paper is design and fabrication of a wideband substrate-integrated waveguide (SIW)-mediated balun structure for single-ended measurement of a balanced SBCSL component. The fabricated balun exhibits a nearly perfect coaxial-mode to coupled-stripline differential-mode conversion in the full range of 5–9 GHz. The presented balun is successfully utilised to derive the scattering parameters (S-parameters) of the fabricated balanced SBCSL DC-blocker.

Circular Depressed Cladding Waveguides in Mechanically Robust, Biocompatible nc-YSZ Transparent Ceramics by fs Laser Pulses

We report on the fabrication of depressed cladding waveguides inscribed by direct femtosecond laser pulses irradiation in transparent nc-yttria stabilized zirconia (YSZ) polycrystalline ceramics. The waveguides consisted of two different circular structures with diameters of 30 and 100 $\mu \text{m}$ , and different lengths. Optical characterization at 633 $\text{}$ and 1568 nm was performed. The obtained modal profiles show dependence on the structure and size of the waveguides. We estimate a laser-induced refractive index contrast of nearly 10 $^{-2}$ , larger than can be explained by induced residual stresses alone. We conjecture that laser interactions lead to localized physical damage, i.e., microvoids cracks and possibly a decreased degree of crystallinity in the laser processed zones, which is supported by Raman measurements. Our results suggest a promising potential use of nc-YSZ in photonic bio-applications.

Characterization of Gas Absorption Modules Based on Flexible Mid-Infrared Hollow Waveguides.

A new gas absorption module, the substrate-embedded hollow waveguide (eHWG) model, is proposed. It consists of a substrate with a curved channel and a hollow waveguide. The hollow waveguide is curved into the channel and works as a gas absorption cell as well as a transmission medium for mid-infrared light. Owing to the low loss property of the hollow waveguide, the signal-to-noise ratio (SNR) was improved for the sensing system. A polycarbonate (PC) base tube was used to obtain flexibility in the fabrication of the hollow waveguide. A silver (Ag) layer and a silver iodide (AgI) layer were inner-coated to ensure a low loss property at the fingerprint wavelength of methane gas. A sensing system was established using a Fourier transform infrared spectrometer (FTIR), an external detector, and an eHWG. Experimental investigations were carried on the sensing performance of eHWGs with various channel shapes. Comparison studies were made on eHWGs embedded with Ag-coated or Ag- and AgI-coated hollow waveguides. The Ag- and AgI-coated hollow waveguides with inner diameters of 0.7, 1.4, and 2.0 mm were used in the eHWGs. The large bore waveguide had low loss but high bending additional loss. The large bore waveguide had a low detection limit due to high coupling efficiency with the light source. A limit of detection (LOD) as low as 2.7 ppm was attained for the system using the eHWG with the long and large bore waveguide.

Monolithic waveguide laser mode-locked by embedded Ag nanoparticles operating at 1 μm

Abstract Monolithic waveguide laser devices are required to achieve on-chip lasing. In this work, a new design of a monolithic device with embedded Ag nanoparticles (NPs) plus the Nd:YAG ridge waveguide has been proposed and implemented. By using Ag+ ion implantation, the embedded Ag NPs are synthesized on the near-surface region of the Nd:YAG crystal, resulting in the significant enhancement of the optical nonlinearity of Nd:YAG and offering saturable absorption properties of the crystal at a wide wavelength band. The subsequent processing of the O5+ ion implantation and diamond saw dicing of crystal finally leads to the fabrication of monolithic waveguide with embedded Ag NPs. Under an optical pump, the Q-switched mode-locked waveguide lasers operating at 1 μm is realized with the pulse duration of 29.5 ps and fundamental repetition rate of 10.53 GHz, owing to the modulation of Ag NPs through evanescent field interaction with waveguide modes. This work introduces a new approach in the application of monolithic ultrafast laser devices by using embedded metallic NPs.

Flexible and low-cost fabrication of optical waveguides by UV laser resist-mask writing

We report on UV laser photoresist mask writing as a tool for fabricating integrated optical waveguides and devices. Using 375 nm laser light and a pneumatically controlled direct writing stage, we defined mask features into a 250-nm-thick negative photoresist layer on a silicon nitride film on an oxidized silicon substrate. We investigated the feature size and edge roughness for different laser powers. Using the photoresist mask layer and reactive ion etching, we patterned high-refractive-index-contrast silicon nitride strip waveguides and devices with varying waveguide widths and gaps. We report on the structural and transmission characteristics of a directional coupler, Sagnac interferometer, and ring resonator and demonstrate 50/50 coupling at 1510 nm, 20 dB transmission drop at 1580 nm, and a Q factor of ∼13,000 at 1576 nm, respectively. These results demonstrate that this technique can be applied to a variety of thin film materials and substrates for inexpensive and rapid prototyping of integrated photonic devices.

Optical properties of an Er3+-doped phosphate glass waveguide formed by single-energy H+ ion implantation

In this work, we report the fabrication of an optical waveguide by single-energy H+ ion implantation in the Er3+-doped phosphate glass. The ion implantation conditions are with energy of 0.4 MeV and a fluence of 8.0×1016 ions/cm2. The dark mode spectrum of the waveguide structure was measured by the prism coupling experiment. The refractive index change along with the penetration depth was fitted by using the reflectivity calculation method (RCM). Finally, the calculated near-field light intensity distribution shows superior waveguide properties, which demonstrates its promising potentials for compact optical integrated devices.

Design and fabrication of a linear broadband non-reciprocal acoustic waveguide using feedforward control

Acoustic metamaterials that exhibit non-reciprocal transmission have received substantial attention due to their wide range of applications such as noise control, diagnostic imaging, communications, and acoustic cloaking. Passive metamaterials achieve non-reciprocity through system resonances combined with nonlinearities or manipulation of phononic bandgap and are usually effective over a narrow band of frequencies. In this study, we describe the development of a new class of acoustic waveguides that exhibit linear non-reciprocal sound transmission over a wide range of frequencies. We use an open loop feedforward control mechanism where the measured local pressure is passed through an electronic controller and transmitted downstream to actuate an acoustic source. Analysis of the idealized one-dimensional model with a continuous distribution of probes and sources shows spatial asymmetry with attenuation in one direction and amplification in the other for frequencies ranging from one-half to five times the ratio of the active length of the segment to the acoustic wavelength. We show that such behavior can be replicated in a physical system with a finite array of acoustic probes and sources and develop the framework to compute the stability of this class of active waveguides. The experimental results for a simple feedforward model system are presented.

Ion irradiated magneto-optic waveguide based on TGG crystal

Here we report the fabrication of a magneto-optic waveguide based on TGG crystal via 15 MeV C3+ ion irradiation. The ion irradiation process leads to the optical anisotropy in the as-irradiated TGG waveguide, which hinders the magneto-optical rotation in the waveguide. To remove the irradiation-induced optical anisotropy, we annealed the as-irradiated TGG waveguide under different conditions. After annealing at 400 °C for one hour, the magneto-optical rotation of 14° per centimeter is observed in the waveguide at the wavelength of 632.8 nm, under the magnetic field of 0.24 T, which is comparable to that observed in the TGG crystal under the same magnetic field. This work paves the way for applications of TGG waveguides as integrated optical rotators and isolators.

Design and fabrication of optical waveguide as directional coupler using laser cutting CO2 on acrylic substrate

CO2 laser cutting machine can provide convenience on making various souvenirs and decorations and billboards. CO2 Laser cutting machines are widely used for cutting and grafting in some materials such as polymer, glass, paper, fabric and some non metallic materials. In this study using CO2 laser cutting to create a directional coupler channel. In the process of making the canal done with engraving on acrylic substrate with 4.2 mW laser power and speed 10 mm/seconds and then repeated three times. Directional coupler fabrication is done variation of interaction length 20 mm, 25 mm, 30 mm, 35 mm and 40 mm. The result of directional coupler fabrication resulted in a coupling ratio of 49.8: 50.2 at 25 mm interaction length with input A2. Directional coupler fabrication with CO2 laser cutting machine provides easy interaction length setting as it can be made with the engine and the results are in accordance with the desired design.