Seamlessly integrating stimulated Brillouin scattering (SBS) in a low-loss and mature photonic integration platform remains a complicated task. Virtually all current approaches fall short in simultaneously achieving strong SBS, low losses, and technological scalability. In this work we incorporate stong SBS into a standard silicon nitride platform by a simple deposition of a tellurium oxide layer, a commonly used material for acousto-optic modulators. In these heterogeneously integrated waveguides, we harness novel SBS interactions actuated by surface acoustic waves (SAWs) leading to more than two orders of magnitude gain enhancement. Three novel applications are demonstrated in this platform: (i) a silicon nitride Brillouin amplifier with 5 dB net optical gain, (ii) a compact intermodal stimulated Brillouin laser (SBL) capable of high purity radio frequency (RF) signal generation with 7 Hz intrinsic linewidth, and (iii) a widely tunable microwave photonic notch filter with ultra-narrow linewidth of 2.2 MHz enabled by Brillouin induced opacity. These advancements can unlock an array of new RF and optical technologies to be directly integrated in silicon nitride.

Europium doped silicon (oxy)carbonitride (Si(O)CN) thin films were fabricated using an integrated electron cyclotron resonance plasma-enhanced chemical vapor deposition system combined with in situ magnetron sputtering. Post-deposition annealing was performed from 800 degrees C to 1200 degrees C to investigate europium activation within the Si(O)CN matrix. Room-temperature photoluminescence revealed visible bright red emission attributed to the intra 4 f transition of Eu3+ ions, prominently observed in films annealed at 1100 degrees C and 1200 degrees C. A detailed compositional analysis was performed with a combination of Rutherford backscattering spectrometry and elastic recoil detection analysis showing nearly 7 at% of europium in the luminescent film. The presence of crystalline phases from the high temperature annealed samples was confirmed by X-ray diffraction analysis. These investigations were conducted to assess the feasibility of amorphous Si(O)CN as a thermally and chemically stable, silicon-compatible host for rare-Earth doping. Europium doped Si(O)CN can offer promising potential for visible light emission in next generation integrated photonic and optoelectronic devices.

In this paper, we demonstrate erbium ion implantation and signal enhancement in tellurium oxide hybrid waveguides. Silicon nitride strips with a width of 2 μm and a height of 100 nm were clad with a 110-nm-thick tellurium oxide layer to form hybrid waveguides, followed by erbium ion implantation at an energy of 200 keV and a dose of 1×10^15 ions/cm^2, with a projected peak implantation depth of approximately 50 nm into the tellurium oxide layer. After low-temperature annealing at 150 °C for 30 minutes, the propagation loss decreased from 1.7 to 0.9 dB/cm, while the erbium lifetime increased from 40 μm to over 800 μm. We measure a small-signal enhancement of 9 dB in an 11-cm-long waveguide at a wavelength of 1550 nm. These results demonstrate progress towards a low-temperature post-ion implantation process for incorporating erbium and other rare earth ions into tellurium oxide films for integrated photonic applications.

Down-conversion improves photon conversion in silicon-based systems by converting high-energy photons into usable wavelengths. In this work, europium terbium cerium-doped oxygen-rich silicon oxide (ORSO:EuTbCe) thin films were fabricated and analyzed to examine the effect of deposition parameters on rare-earth incorporation, film structure, and emission behavior. Structural analysis indicates that the resulting films exhibit a previously unreported structure not found in available databases. The films show broad visible emission under UV excitation, which shows potential for silicon-based photonic applications.

In this work we demonstrate thermo-optic measurement and compositional analysis for nitrogen-rich silicon nitride films. The thermo-optic effect is measured using temperature-dependent spectroscopic ellipsometry, while the silicon and nitrogen content of the films were determined using Rutherford backscattering spectrometry. Increasing the nitrogen content of the film reduced both the refractive index and thermooptic coefficient.

This study characterizes the optical and structural properties of terbium-doped oxygen-rich silicon oxide (ORSO:Tb) thin films and investigates focused ion beam (FIB)-induced damage on transmission electron microscopy (TEM) lamellae prepared from these films. While there are significant advantages to the FIB technique, there is a potential that energetic ions used during the FIB process can damage the lamellae. A comparative analysis of TEM images obtained using FIB and conventional mechanical preparation methods was performed. The results indicate that TEM images of FIB-prepared lamellae exhibit higher resolution, allowing for a more detailed examination of nanocrystal structures and quantum dots. In contrast, the lack of sufficient clarity of the mechanically prepared TEM images reduces the number of nanocrystals visible in the field of view, resulting in a less effective and detailed study of the thinned films. We found no evidence of Ga implantation or mixing into the thinned film, and no observable FIB-induced damage such as recrystallization, or amorphization. Photoluminescence spectra exhibited red and blue shifts with increasing annealing temperature at blue and green emissions, respectively. X-ray diffraction patterns verify that the formation of crystalline nanostructures begins at 1100 degrees C, and at least at 1200 degrees C, two phases of Tb4Si3(SiO4)O10 and Tb2O3 in the sample are recognized.

This work reports tunable emission of Eu 3+ and Eu 2+ from SiO x N y films fabricated by integrated electron cyclotron plasma enhanced chemical vapor deposition and magnetron sputtering. The photoluminescence (PL) spectra of intense red emission from Eu 3+ around 600 nm and blue broadband emission from 400 to 750 nm of Eu 2+ are observed under daylight conditions with the naked eye. The findings of this work are promising toward the realization of europium doped Si-based materials for photonics and lighting technologies. Silicon (Si) based optoelectronic components are becoming very important for the advanced silicon photonic industry 1 . These optoelectronics components are also highly desirable for biochemical sensor applications in medicine and environmental control 2 . 3,4 However, the indirect band gap of bulk Si has limited its light emission efficiency . Several methods have been developed to engineer Si into an efficient light emitter, and among them, doping Si with rare earth ions has earned significant interest due to their excellent luminescent and chemical stability. Europium (Eu) is one of the promising rare earths that exhibits two optically active states, Eu 2+ and Eu 3+ , making it suitable for a wide range of color emission from the blue to the red spectral region 5 . The emission lines of Eu 3+ correspond to the transitions from the excited 5 D 0 level to the 7 F J (J= 0 to 6) level of the 4f n configuration and generate sharp peaks in the red spectral range. On the other hand, the emission from Eu 2+ occursdue to the electronic transitions from the 4f 6 5d 1 level to the 4f 7 shell, and emission happens between 400 to 800 nm 6 . Thus, Eu is very attractive in the fields of silicon photonics, along with solid state lighting, display, senor and photovoltaic applications 7 . In this study, we have investigated the optical properties and compositions of Eu-doped Si oxynitride thin films prepared by integrated electron cyclotron resonance plasma enhanced chemical vapor deposition and magnetron sputtering (ECR–PECVD) on p-type Si substrates. Different samples were fabricated by varying nitrogen and oxygen flow to understand the effect of the surrounding matrix on the luminescence. Post-deposition annealing was performed at different temperatures ranging from 600 to 1200 O C. The dependencies of the PL properties on Eu concentrations and annealing temperatures were investigated in detail. It is found that films annealed at a temperature higher than 1000 O C produced bright red emission from Eu 3+ and bright blue emission from Eu 2+ , which can be seen under daylight conditions with the naked eye. Furthermore, the existence of Eu-containing phases is confirmed by high-resolution X-ray diffraction spectroscopy (XRD). The stoichiometry of the films is analyzed by Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA). The optical constants and thickness of the films are analyzed by variable angle spectroscopic ellipsometry (VASE). This work highlights the tunable luminescence property of Eu doped SiO x N y thin films, making them promising candidates in light emission systems for optoelectronic platforms. Acknowledgements: This work is funded by NSERC Discovery Grant RGPIN-2019-06023 and ORF Grant ORF-RE 09-051. References Wang Z, Abbasi A, Dave U, et al., Laser Photon Rev . 2017;11(4). doi:10.1002/lpor.201700063 Germer S, Cherkouk C, Rebohle L, Helm M, Skorupa W., SPIE 8767, Integrated Photonics: Materials, Devices, and Applications II . 2013;8767:1-13. doi:10.1117/12.2017275 Tian Y, Chen B, Hua R, et al., J. Appl. Phys . 2011; 109 (5): 53511. doi:10.1063/1.3551584 Tian Y, Chen B, Hua R, et al., Cryst. Eng. Comm . 2012; 14 (5): 1760-1769. doi:10.1039/C1CE06232H Lin Z, Huang R, Wang H, et al., J. Alloys Compd . 2017; 694: 946-951. doi:10.1016/j.jallcom.2016.10.132 Azmi F, Gao Y, Khatami Z, Mascher P., J. Vac. Sci. Technol. A 2022; (043402). doi:10.1116/6.0001761 Bellocchi G, Franzò G, Iacona F, et al., Opt. Express . 2012; 20 (5): 5501-5507. doi:10.1364/OE.20.005501

Optical and mechanical properties of europium (Eu)-doped silicon nitride (SixNy) films were investigated as a function of the sputtering power applied to the Eu metal target and argon flow into the deposition chamber. Films were fabricated by an electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) system combined with magnetron sputtering for in-situ rare-earth doping. Results show that Eu-doped SixNy films fabricated with higher sputtering power exhibit intense red emission when annealed above 1000°C, making the luminescence visible under daylight conditions. Variable-angle spectroscopic ellipsometry analysis shows that the refractive index and film thickness are strongly dependent on the sputtering power; however, argon (Ar) flow has minimal influence. High-resolution X-ray diffraction reveals that the crystalline phases in the films play a crucial role in efficient Eu emission. Additionally, the films show increased hardness, up to 18 GPa, and an elastic modulus of 160 GPa, ensuring their durability and performance as cladding layers in photonic devices. These mechanical properties are essential for maintaining structural integrity and preventing defects, which are critical for the reliability of optoelectronic devices. The combination of strong emissions and good mechanical properties make Eu-doped SixNy films suitable for optoelectronic and solar cell applications, where both efficient light emission and material stability are essential.

Electric vehicles’ usage can reduce greenhouse gas emissions and their adverse health effects on humans. But we can only utilize the full environmental benefits of them when charging is done using renewable energy sources with zero or low carbon emissions. Researchers have suggested integrating low-cost, flexible, and thin-film copper indium gallium selenide solar cells directly onto all the upward-facing body parts of electric vehicles [1]. However, this integration comes with an aesthetic drawback. We are proposing replacing the anti-reflective coating present in standard solar cells with a notch filter (a narrow high-reflection region in the visible range along with high transmission for the rest of the solar spectrum) to give a distinct color rendering to solar-charged electric vehicles. Notch filters can be designed using a rugate filter structure consisting of continuously modulated refractive indices or using a repetitive two-material stack of alternating high (H) and low (L) refractive index materials with precise thickness, also known as the standard two-material technology (S2MT). Using OptiLayer and MATLAB, we designed our S2MT thickness modulated structures to obtain blue (400 nm), green (550 nm), and red (632 nm) colors with minimum number of layers. Layer numbers in each design range between 2 – 12 depending on the chosen material pair and the targeted color, thus achieving simplicity and effectiveness. We used gradual evolution method followed by thin layer removal to obtain our thickness modulated multilayer optical filter designs. We simulated our optical filter structures for various high and low refractive index material pairs, and a detailed analysis of our findings will be presented. In this analysis, we studied the effect of refractive index ratios (high refractive index to low refractive index) on the current response of the colorful solar cells and our merit function. This study helped us to understand the optimal material pair range suitable to our application. Our designs were fabricated using magnetron sputtering and electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) and validated through variable angle spectroscopic ellipsometry and reflectance spectroscopy, showing strong agreement with our simulations. We fabricated these optical filters with three different material pairs using ECR-PECVD (SiN-SiON, refractive index ratio of 1.38 [2]) and magnetron sputtering (Nb2O5-SiO2, with refractive index ratio of 1.71 [3] and Al2O3-SiO2, with a refractive index ratio of 1.21). With a minimal trade-off in the functionality and efficiency of solar cells, we were successfully able to transform standard solar cells into aesthetically pleasing components, broadening their appeal and potential applications in consumer products. A detailed comparison of our simulation and fabrication results will be presented. Figure 1: Observed color of the fabricated (a) blue, (b) green, and (c) red filter on silicon wafer using a solar simulator under 1 sun condition. [3] References: [1] M. H. Mobarak, R. N. Kleiman, and J. Bauman, “Solar-Charged Electric Vehicles: A Comprehensive Analysis of Grid, Driver, and Environmental Benefits,” IEEE Transactions on Transportation Electrification , vol. 7, no. 2, pp. 579–603, Jun. 2021, doi: 10.1109/TTE.2020.2996363. [2] P. Bhattacharyya, B. Ahammou, F. Azmi, R. Kleiman, and P. Mascher, “Design and fabrication of color-generating nitride based thin-film optical filters for photovoltaic applications,” Journal of Vacuum Science & Technology A , vol. 41, no. 3, May 2023, doi: 10.1116/6.0002357. [3] P. Bhattacharyya et al. , “Design method for generating multiple colors with thickness-modulated thin-film optical filters for silicon solar cells,” Journal of Vacuum Science & Technology A , vol. 43, no. 1, Jan. 2025, doi: 10.1116/6.0003977. Figure 1

This study explores an innovative approach to enhance the esthetic appeal while having minimal impact on the functional performance of solar-charged electric vehicles. We propose replacing the standard antireflective coating on solar cells with a custom-designed notch filter. This optical filter ensures high transmission across the solar spectrum and creates a distinct color rendering effect in the visible range, thereby making the cells more visually appealing. We utilized niobium pentoxide and silicon dioxide for their excellent optical, mechanical, and corrosive properties to fabricate filters reflecting at specific wavelengths, producing vibrant blue, green, and red color renderings at 400, 550, and 632 nm, respectively. Theoretical relative photocurrent density losses of only similar to 7 % , similar to 10 % , and similar to 14 % were observed for blue, green, and red colors, respectively, due to the presence of these filters when compared to a silicon solar cell with a standard antireflective coating. Using optilayer and matlab software, we precisely designed filters with just two to four layers, achieving simplicity and effectiveness. Gradual evolution optimization followed by thin layer removal optimization produced automated and consistent thickness-modulated multilayered optical filter designs over a wide range of user inputs. Our designs were fabricated using magnetron sputtering and validated through variable angle spectroscopic ellipsometry and reflectance spectroscopy, showing strong agreement with our simulations. With a minimal trade-off in the functionality and efficiency of solar cells, this method transforms standard solar cells into esthetically pleasing components, broadening their appeal and potential applications in consumer products.

The monolithic fabrication of passive, nonlinear, and active functionalities on a single chip is highly desired in the wake of the development and commercialization of integrated photonic platforms. However, the co-integration of diverse functionalities has been challenging as each platform is optimized for specific applications, typically requiring different structures and fabrication flows. In this article, we report on a monolithic and complementary metal-oxide- semiconductor CMOS-compatible hybrid wafer-scale photonics platform that is suitable for linear, nonlinear, and active photonics based on moderate confinement 0.4-mu m-thick Si3N4 waveguiding layer coated with a '0.4-mu m thick TeO2 film. This platform offers four main advantages, which are (1) ensuring reduced stress and film cracking for scalable fabrication by using thin Si3N4, (2) allowing polarization-insensitive single-mode operation at telecom wavelengths, (3) enhancing waveguide nonlinearity and allowing dispersion engineering by adding the TeO2 film coating, and (4) achieving amplification and lasing through incorporation of rare-earth dopants during the TeO2 film deposition step. We present the design and experimental measurement of TeO2-coated '0.4-mu m-thick Si3N4 microring resonators with internal Q factors of 7.5 x 105 and 5.2 x 105 for TE and TM polarizations, respectively. The experimental results show that the dispersion of TeO2-coated '0.4-mu m-thick Si3N4 waveguides can be engineered between normal and anomalous by adjusting the thickness of the TeO2 layer. For a 1.6-mu m wide, 500 mu m bend radius ring resonator with a '0.4-mu m-thick TeO2 coating, anomalous dispersion values of 25 and 78 ps/nm km were measured at 1552 nm wavelength for the TE and TM-modes, respectively, and the onset of Kerr comb generation was observed. Also, by applying an Er-doped TeO2 coating, an optical amplifier with TE and TM net gain and 5.5 dB net internal gain at 1533 nm in a 6.7-cm-long waveguide and a microdisk laser were demonstrated. These results show a promising route to monolithic integration of passive, nonlinear, and active functionalities via hybrid waveguides on standard silicon photonic platforms. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Silicon photonics (SiP) has emerged as a leading platform in integrated photonics enabling a variety of applications including high-speed communications, quantum photonics, gyroscopes, and light detection and ranging (LIDAR)[1]. SiP is well suited for operation in the O, S, and C telecommunications bands. However, silicon has fundamental material limitations that restrict its uses in visible (VIS) and near-infrared (NIR) applications, such as microscopy, augmented reality, and biological sensing [2]. As an alternative to silicon-on-insulator (SOI), silicon nitride (SiN)-based platforms have gained success in recent years and are now being offered by foundries through multi-project wafer (MPW) fabrication runs [2], [3].

Photoconductive amorphous selenium (a-Se) layers are utilized in flat panel X-ray imaging detectors as a direct conversion medium, converting X-ray photons directly into electric charge. Commercial a-Se direct conversion Active Matrix Flat Panel Imagers (AMFPIs) have demonstrated superior image quality in mammography, showcasing the potential of this X-ray imaging technology [1-2]. The use of a-Se is limited, however, by its low Z, resulting in low stopping of high energy X-rays [2]. This limitation is not shared by PbO thin films. Earlier PbO films consisted of small poly-crystalline platelets with low film density and suffered from the presence of both oxygen vacancies and impurity phases (PbO 2 ). Recent advances [3-4] have yielded dense amorphous PbO (a-PbO) films with apparently uniform stoichiometry, as confirmed by X-ray photoelectron spectroscopy (XPS). More careful analysis [5] using X-ray absorption spectroscopy (XAS) indicated some tailing of the conduction band, which was attributed to suspected O-vacancies. An annealing study on a-PbO [3] indicated a transition to β-PbO around 500 C. X-ray diffraction (XRD) data of the β-PbO (annealed a-PbO) film matched that of a β-PbO reference, while XAS data did not. This was attributed to the different depths of the sample volumes probed by the two techniques. Doppler-broadened positron annihilation spectroscopy (DBPAS) was conducted on several a-PbO samples synthesized under different conditions using the McMaster Variable-Energy Positron Beam (MVEPB) and the results were modelled using VEPFIT [6]. All samples were found to have a three-layer structure, with the bulk S-parameters between 0.4725 and 0.4753. The two other layers were contained within the first 300nm of the film and varied in thickness, diffusion length and S-parameter value. This confirms the suitability of DBPAS, as a sensitive probe of vacancy-type defects and the layer structure of thin films, to guide the optimization of a-PbO synthesis for photoconductive detectors. Work is underway to produce a series of samples which vary systematically in their synthesis conditions to establish synthesis-structure relationships.

We show a distributed Bragg reflector laser operating at 1875 nm, using a hybrid silicon nitride photonic chip coated with thulium-doped tellurite glass. The passive laser cavity consists of nominally 50-nm-wide sidewall Bragg gratings directly patterned in a 1.2-μm-wide, 0.2-μm-thick, and 22-mm-long silicon nitride waveguide on a thermally-oxidized silicon substrate fabricated using a standard foundry process. A 0.39-μm-thick thulium-doped tellurium dioxide optical gain layer was deposited onto the chip by reactive radio frequency magnetron co-sputtering. The resulting hybrid laser includes 6- and 4-mm-long gratings separated by a 11-mm gap to form an asymmetrical cavity and promote directional lasing off the shorter reflector. We obtain a maximum on-chip output power of 4.5 mW and lasing threshold of 20 mW when pumping at 1610 nm. A total slope efficiency of 5% was achieved, as well as a thermal tunability of the laser wavelength of 32.3 pm/°C. These results are a step towards simple, compact, and high-power on-chip thulium-based tellurite lasers for silicon-based photonic integrated circuits.

We describe a rapid prototyping process for silicon nitride photonic integrated circuits operating at wavelengths around 1.3 and 1.5 μm. Moderate confinement silicon nitride waveguides and other essential integrated photonic components, such as fiber-chip couplers, microring resonators, multimode interference-based 3-dB power splitters, and subwavelength grating metamaterial waveguides, were fabricated and characterized and are reported. The prototyping platform features a 400-nm-thick layer of silicon nitride grown via low-pressure chemical vapour deposition onto 4” silicon thermal oxide wafers and uses direct-write electron beam lithography to define single mode waveguide structures that exhibit losses of < 1.3 dB/cm across the O-band (1260–1360 nm), < 1.8 dB/cm across the S-band (1460–1530 nm), < 1.6 dB/cm across the C-band (1530–1565 nm), and < 0.7 dB/cm across the L-band (1565–1625 nm) for both transverse electric (TE) and transverse magnetic (TM) polarizations. The reported components were compiled into a process design kit to accompany the platform, which is commercially available through the NanoSOI Design Center operated by Applied Nanotools Inc. with five multi-project wafer runs per year that have fast turnaround times on the scale of weeks rather than months. This provides a route toward the rapid fabrication of silicon nitride chip-based passive and thermo-optic active photonic devices with critical resolution down to 120 nm, making it an attractive solution for entry-level designers, device innovators, and small companies looking to incorporate integrated silicon nitride circuits into early-stage applications of silicon photonics.

In this article, we report a Si/Ge waveguide phototransistor with high responsivity and low dark current under low bias voltages, due to an engineered electric field distribution. The photodetector consists of n -i -p -i-n doping regions and shows a responsivity of 606 A/W at 1 V bias, and 1032 A/W at 2.8V bias with an input optical power of -50 dBm, and dark current of 4 mu A and 42 mu A respectively. This is achieved by placing two p(+) -doped regions in the silicon slab region beneath the Ge epitaxial layer. A measured small signal -3 dB bandwidth of 1.5 GHz with a -80 dBc/Hz phase noise response at 1 KHz frequency offset were demonstrated experimentally.

The integration of a silicon-based light emitter into existing CMOS technology has long been intriguing due to its optoelectronic compatibility with microelectronics [1]. However, the indirect band gap nature of bulk silicon has hindered its effectiveness as a light emitter. In addressing this limitation, rare earth ions have emerged as significantly interesting candidates owing to their unique optical and electronic properties. Rare earth-doped silicon structures have earned special attention as they exhibit sharp light emission in different spectral regions [2] . This notable feature is attributed to the effective excitation of rare earth ions within the host matrix. Efficiently excited rare earth ions can produce visible emissions ranging from infrared to ultraviolet, presenting possibilities in diverse applications such as solid-state lighting, displays, lasers, photovoltaics, and optical communication. The incorporation of rare earth-doped silicon structures presents a promising solution to overcome the challenges posed by silicon's intrinsic properties, thereby paving the way for improved performance across a diverse range of optoelectronic applications. Europium is a attractive rare earth material with two optically active states, Eu 2+ and Eu 3+ , enabling it to generate a diverse range of color emissions extending from blue to red depending on the surrounding matrix [3]. In this study, we investigated the optical properties and compositions of europium (Eu)-doped thin films including silicon oxide, silicon oxynitride, and silicon carbonitride. For this purpose, thin films were fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) with in-situ magnetron sputtering on p-type 3" Si (100) substrates. In-situ Eu doping was performed by a radio frequency (RF) magnetron sputtering gun, using a 0.25 in. thick, 2 in. (diameter) 99.9% pure Eu sputtering target. Precursor gases, including silane (diluted in 90% argon), oxygen (diluted in 90% argon), nitrogen (diluted in 90% argon), and ethane were utilized. Annealing was performed on the as-deposited films over a broad temperature range, from 600° to 1100°C, in a nitrogen (N 2 ) environment. Rutherford backscattering spectrometry (RBS) was performed to determine the atomic concentration of the film constituents. Variable angle spectroscopic ellipsometry (VASE) analysis was conducted to investigate the optical properties of the films. Room temperature photoluminescence (PL) experiments were performed using a laser diode excitation source operating at a wavelength of 375nm. Notably, bright visible emission was observed in some of the thin films. Finally, we discuss the influence of the atomic concentration of Eu and the annealing temperature on the emission properties observed in the photoluminescence experiments. [1] F. Azmi, Y. Gao, Z. Khatami, and P. Mascher, “ Tunable emission from Eu:SiO x N y thin films prepared by integrated magnetron sputtering and plasma enhanced chemical vapor deposition ,” J. Vac. Sci. Technol. A , vol. 40, no. 4, p. 043402, 2022, doi: 10.1116/6.0001761. [2] A. Brik et al. , “Annealing Effects on Structural Characteristics of Europium Doped Silicon-Rich Silicon Nitride,” Silicon , vol. 14, no. 14, pp. 8417–8425, 2022, doi: 10.1007/s12633-021-01636-w. [3] D. Li, X. Zhang, L. Jin, and D. Yang, “Structure and luminescence evolution of annealed Europium-doped silicon oxides films,” Opt. Express , vol. 18, no. 26, p. 27191, 2010, doi: 10.1364/oe.18.027191.

Amorphous aluminum oxide (Al2O3) is a key material in optical coatings due to its notable properties, including a broad transparency window (ultraviolet to mid-infrared) and excellent durability. Moreover, its higher refractive index contrast relative to silica cladding layers and high solubility of rare-earth ions make it well suited for optical waveguides and the development of various functionalities in integrated photonics. In many coatings and integrated photonics applications, the substrates are temperature and stress sensitive, while relatively thick (similar to 1 mu m) alumina layers are required; thus, it is crucial to fabricate low optical loss alumina thin films at low deposition temperatures, while maintaining high deposition rates. In this study, plasma-assisted reactive magnetron sputtering, operated in an alternating current mode, is investigated as a reliable, straightforward, and wafer-scale compatible technique for the deposition of high optical quality and uniform Al2O3 thin films at low temperature. One-micrometer-thick amorphous Al2O3 planar waveguides, deposited at 150 degrees C and a rate of 23.3 nm/min, exhibit optical losses below 1 dB/cm at 638 nm and as low as 0.1 dB/cm in the conventional optical communication band.

Supercontinuum generation (SCG) is an important nonlinear optical process enabling broadband light sources for many applications, for which silicon nitride(Si3N4) has emerged as a leading on-chip platform.To achieve suitable group velocity dispersion and high confinement for broadband SCG the Si3N4 waveguide layer used is typically thick (> 700 nm), which can lead to high stress and cracks unless specialized processing steps are used. Here, we report on efficient octave spanning SCG in a thinner moderate-confinement 400-nm Si3N4 platform using a highly nonlinear tellurium oxide (TeO2) coating. An octave-spanning supercontinuum is achieved at a low peak power of 258 W using a 100-fs laser centered at 1565 nm. Our numerical simulations agree well with the experimental results showing an increase of waveguide's nonlinear parameter by a factor of 2.5 when coating the Si3N4 waveguide with TeO2 film. This work demonstrates highly efficient SCG via effective dispersion engineering and an enhanced nonlinearity in a CMOS-compatible hybrid TeO2-Si3N4 waveguides and a promising route to monolithically integrated nonlinear, linear, and active functionalities on a single silicon photonic chip.