Laser-based, on-chip fabrication of glass-based core-cladding waveguidesKranert, Fabian; Fawaz, Hussein; Hinkelmann, Moritz; Neumann, Jörg; Kracht, Dietmar
doi: 10.1117/12.2649880pmid: N/A
Photonic integrated circuits (PIC) have been established for miniaturized, on-chip optical systems. Current approaches for producing PICs mostly rely on semiconductor processing technologies, which are complex and costintensive. A promising alternative with the potential to revolutionize PIC fabrication is additive manufacturing (AM), which offers the opportunity to develop tailored and customized waveguide designs for functionalities needed in fast-evolving modern applications like the Internet of Things. Here, an AM technology called laser glass deposition (LGD) is presented for the production of on-chip core-cladding waveguides based on fused silica. Commercially available glass fibers with a diameter of 125 μm are fused onto a quartz glass substrate using a CO2-laser in a 2.5D-printing process. Test series are performed to determine the process window to reach a stable connection between fiber and substrate while maintaining the fiber´s optical functionality. To enable efficient light coupling into the waveguide, the fiber end facets are laser cleaved after the deposition within the same process environment. Again, parameter studies are performed to reach a high surface quality. Both the waveguides and the cleaved surfaces are characterized using different imaging techniques. In addition, the optical properties of the generated waveguides are analyzed.
Characterization of mid-infrared optical loss and nonlinear refractive index in InP based waveguidesZhang, K.; Boehm, G.; Belkin, M. A.
doi: 10.1117/12.2647891pmid: N/A
We report experimental measurements of optical loss and n2 nonlinearity in two possible InP-based mid-IR waveguiding platforms with waveguide cores made of In0.53Ga0.47As and GaAs0.51Sb0.49, both lattice-matched and grown on InP. We report the first broadband (5-11 μm) characterization and optimization of optical losses within InP/InGaAs and InP/GaAsSb based waveguides with losses as low as 0.5 dB/cm at shorter wavelengths and 4-5 dB/cm at longer wavelengths of this wavelength range. In addition, we measure the values of Kerr nonlinearity in these waveguides to be approximately an order of magnitude higher than that reported for Si- and SiGe-based waveguides in mid-IR.
Miniaturized photonic sensors based on micro-interferometersOton, C. J.; Elaskar, J.; Bontempi, F.; Piretta, F.; Ayaz, R. M. A.; Faralli, S.; Di Pasquale, F.
doi: 10.1117/12.2655436pmid: N/A
It is well known that interferometers make great sensors. This is because phase is a magnitude that can be measured with very accurate precision and with a great dynamic range at the same time. Integrating these devices on a chip is very appealing because it can make the device much smaller, lighter, and affordable. However, this technology also poses some challenges, which can degrade performance with respect to free-space or fiber-based devices. In this work we overview these challenges and possible strategies to tackle them.
Dispersion engineered SiON ring resonators for integrated photon sourcesPiccoli, Gioele; Ghulinyan, Mher
doi: 10.1117/12.2648993pmid: N/A
The interest in integrated photonic processors is growing rapidly, with the perspective of the realization of devices capable to provide single photon qubits for efficient and scalable quantum computation. While the on-chip single photon manipulation is well developed in quantum photonics circuits, the integration of photon generation and photon detection stages on the same chip is currently far from being established. In this work we present a potentially scalable, integrated source of near-infrared photon pairs based on ring resonators, realized with dispersion-engineered silicon oxynitride waveguides. The use of high-index silicon oxynitride as core material gives the possibility to engineer the optical properties of waveguides by adapting the ratio between oxygen and nitrogen gases in the deposition chamber and allows the realization of films with thicknesses over 500nm without the formation of cracks. An efficient photon generation process via nonlinear Four-Wave-Mixing (FWM) in a ring resonator requires a zero group-velocity-dispersion in order to have energy equidistant resonances. Here we show that, while it is almost impossible to achieve such a condition with oxide-cladded SiON waveguides, the zero-dispersion-point in the red and near-infrared wavelengths can be engineered if the waveguides are in direct contact with air. This can be achieved through a selective removal of the top oxide cladding from the ring resonators by the means of wet chemical etching and a silicon nitride etch-stop layer. We show that the realized devices are characterized by a constant Free Spectral Range at the engineered wavelengths and are thus feasible devices for nonlinear photon generation via FWM.
Production of dielectric filters with low defect levels for integrated optical devicesMingels, Stephan; Kutty, Navas; Tack, Nicolaas; Bangels, Dries; Janssens, Elias; Hagedorn, Harro
doi: 10.1117/12.2667774pmid: N/A
We have assessed and reduced the particle count in coatings from a magnetron sputter coater used for production of optical coatings for applications in photonics and semiconductor industry. Results for particle levels in single layers from Al2O3, SiO2, Nb2O5, Ta2O5, and TiO2 showed semiconductor grade particle levels for the upgraded deposition system. Moreover, particle levels were also investigated for optical filter stacks deposited on bare Si, glass substrates and actual CMOS device wafers, which were used for the manufacturing of hyperspectral imaging (HSI) sensors. In all cases, low particle counts were detected in the optical filters as expected from the results obtained for the single layer. It could be shown that the coating on the device wafers had no negative impact on the production yield of the HSI sensors.
Hybrid lithium niobate-on-silicon nitride platform for mid-IR supercontinuum generationLafforgue, C.; Churaev, M.; Kippenberg, T. J.; Brès, C.-S.
doi: 10.1117/12.2649971pmid: N/A
Integrated optics has shown itself very convenient for exploiting nonlinear processes as it results in high confinement factor, freedom of dispersion engineering and compactness. However, the choice of materials is crucial for the development of nonlinear systems. Ideally, one looks for a platform that offers high second and/or third order nonlinearities, low loss and ease of fabrication. Silicon nitride (Si3N4) is now proven to be a good platform for frequency conversion based on third order nonlinearity. Supercontinuum generation (SCG) was obtained in the near-IR and mid-IR regions by pumping waveguides with common fiber lasers. It resulted in broadband coherent combs extending in the mid-IR thanks to dispersive wave generation. Yet, Si3N4 does not exhibit any second order nonlinearity desirable for comb self-referencing via second-harmonic generation (SHG). On the other hand, lithium niobate (LiNbO3) is widely used in integrated photonics for second order nonlinear processes. In our work, we exploit a hybrid Si3N4-LiNbO3 photonic integrated platform that combines maturity and dispersion engineering capabilities of Si3N4 integrated photonics with second-order nonlinear properties of LiNbO3 bypassing challenging lithium niobate etching. We study numerically and experimentally the potential of SCG and SHG for frequency comb self-referencing on this platform when pumping with a fiber laser operating at 2 μm for mid-IR operation, a window useful for sensing as it contains many molecular signatures.
Cascaded ring resonator based wide stop-band filter fabricated in AIM photonics technology at Albany Nanotech ComplexUddin, M. Rakib; Wallner, Jin; Dikshit, Amit; Hossain, M. Jobayer; Timalsina, Yukta; Fahrenkopf, Nicholas M.; Harame, David L.
doi: 10.1117/12.2649056pmid: N/A
In this work, we demonstrate a cascaded ring resonator based wide stop-band filter. The filter consists of four cascaded rings and a bus waveguide. The first ring has a radius of 7μm, the second, third and the fourth rings have radius of 7.01 μm, 7.02 μm, and 7.03 μm, respectively. The radius varion is designed for a small shift of resonant wavelength so that the combined resonance effect of four ring resonators exhibits a wide stop-band filter function compare to a single ring resonator. Both the bus and ring waveguides have a width of 480 nm. The thickness of the waveguides were 220 nm which is a standard silicon-on-insulator (SOI) wafer available in the market. A 100-nm gap is designed between the ring and the bus waveguide to provide optimum filtering. The device is fabricated using the American Institute for Manufacturing integrated Photonics (AIM Photonics) 300mm Multi-Project Wafer (MPW) service. It is tested using the AIM Photonics inline vertical grating coupled automated measurement tool with a tunable light source that has wavelengths ranging from 1485 nm to 1590 nm and a wavelength resolution of 60 pm. The fabricated cascaded ring filter exhibits a 3-dB stop-band about 6 nm wide with an extinction ratio of ~30 dB in across the S, C and L-bands. It is noted that the desired width of the stop-band is achievable by cascading required number of rings with slight radius variation.