Silicon Photonic Devices Research Articles

Silicon Photonic 16 × 16 Cyclic AWGR for DWDM O-Band Interconnects

In this article, we present for the first time to our knowledge, a DWDM 16 × 16 silicon photonic cyclic-frequency AWGR device. The AWGR features a channel spacing of 1.06 nm (189 GHz), a free spectral range of 17.80 nm (3.16 THz) and a 3-dB channel bandwidth of 0.65 nm (116 GHz). Its proper cyclic-frequency operation was experimentally verified for all 16 × 16 channels with channel peak insertion loss values in the range of 3.90 dB to 8.37 dB, yielding a channel loss non-uniformity of 4.47 dB. Its compact footprint of 0.27 mm × 0.71 mm and its low crosstalk value of 21.65 dB highlight its potential for employment in future AWGR-based interconnect schemes in O-band.

Eight‐channel hybrid‐integrated laser array with 100 GHz channel spacing

An eight-channel hybrid-integrated light source with 100 GHz channel spacing fabricated by a passive alignment technology is demonstrated. Side mode suppression ratios of better than 40 dB were obtained via grating couplers under eight-channel simultaneous operation at a continuous wave current of 600 mA and 25°C. The surface slotted laser array fabricated by standard lithography butt-joint with silicon photonic devices was demonstrated for the first time, to the best of the authors’ knowledge.

Thermo-Optic Multistability and Relaxation in Silicon Microring Resonators with Lateral Diodes

We demonstrate voltage-tunable thermo-optic bi- and tri-stability in silicon photonic microring resonators with lateral p-i-n junctions and present a technique for characterizing the thermo-optic transient response of integrated optical resonators. Our method for thermo-optic transient response measurement is applicable to any integrated photonics platform and uses standard equipment. Thermo-optic relaxation in encapsulated waveguides is found to be approximately logarithmic in time, consistent with the analytic solution for 2D heat diffusion. We develop a model for thermo-optic microring multi-stability and dynamics which agrees with experiment data over a wide range of operating conditions. Our work highlights the fundamental connection in semiconductor waveguides between active free-carrier removal and thermo-optic heating, a result of particular relevance to Kerr soliton state stability and on-chip frequency comb generation. The devices studied here were fabricated in a CMOS foundry process and as a result our model is useful for design of silicon photonic waveguide devices.

Experimental demonstration of silicon photonic devices optimized by a flexible and deterministic pixel-by-pixel technique

We present the experimental realization of photonic devices optimized by a pixel-by-pixel binary optimization method, which can straightforwardly take into account the technological constraints such as minimum feature sizes in the fabrication process. In this approach, for each iteration, one considers all the candidate structures that differ by a single pixel from the starting structure and update by adopting the structure that has the best figure of merit among all candidate structures. This approach can be implemented with high computational efficiency using a Green's function method. The devices optimized by this approach have been realized on 200 mm and 300 mm Silicon-On-Insulator platforms, using either e-beam lithography or deep-UV immersion lithography. Characterizations experimentally demonstrate the reliability of the method, given the technological constraints of Silicon Photonics.

High-Frequency Mechanical Excitation of a Silicon Nanostring with Piezoelectric Aluminum Nitride Layers

A strong trend for quantum based technologies and applications follows the avenue of combining different platforms to exploit their complementary technological and functional advantages. Micro and nano-mechanical devices are particularly suitable for hybrid integration due to the easiness of fabrication at multi-scales and their pervasive coupling with electrons and photons. Here, we report on a nanomechanical technological platform where a silicon chip is combined with an aluminum nitride layer. Exploiting the AlN piezoelectricity, Surface Acoustic Waves are injected in the Si layer where the material has been localy patterned and etched to form a suspended nanostring. Characterizing the nanostring vertical displacement induced by the SAW, we found an external excitation peak efficiency in excess of 500 pm/V at 1 GHz mechanical frequency. Exploiting the long term expertise in silicon photonic and electronic devices as well as the SAW robustness and versatility, our technological platform represents a strong candidate for hybrid quantum systems.

Key Multimode Silicon Photonic Devices Inspired by Geometrical Optics

On-chip optical interconnect has been widely accepted as a promising technology to realize future large-scale multiprocessors. Mode-division multiplexing (MDM) provides a new degree of freedom for ...

High spectro-temporal purity single-photons from silicon micro-racetrack resonators using a dual-pulse configuration.

Single-photons with high spectro-temporal purity are an essential resource for quantum photonic technologies. The highest reported purity up until now from a conventional silicon photonic device is 92% without any spectral filtering. We have experimentally generated and observed single-photons with 98.0±0.3% spectro-temporal purity, an upper bound of the stimulated emission tomography, using a conventional micro-racetrack resonator and an engineered dual pump pulse.

SOI Suspended membrane waveguide at 3.39 µm for gas sensing application

In this letter, we present a numerical study on the designing of silicon-on-insulator (SOI) suspended membrane waveguide (SMW). The waveguide geometry is optimized at 3.39 µm TE-polarized light which is the absorption line of methane gas by utilizing a 3D finite element method (FEM). The transmission loss (TL) and evanescent field ratio (EFR) of the waveguide are calculated for different geometric parameters such as the width of core, the height of core and period of the cladding. We found out that TL is directly related to EFR. Therefore, a waveguide geometry can be designed which can offer high EFR at the cost of high TL or low EFR with low TL, as desired. Based on the geometric parameters used in this paper, we have obtained a TL and EFR which lies in the range of 1.54 dB-3.37 dB and 0.26-0.505, respectively. Full Text: PDF ReferencesL. Vivien et al., "High speed silicon-based optoelectronic devices on 300mm platform", 2014 16th International conference on transparent optical networks (ICTON), Graz, 2014, pp. 1-4, CrossRef Y. Zou, S. Chakravarty, "Mid-infrared silicon photonic waveguides and devices [Invited]", Photonic Research, 6(4), 254-276 (2018). CrossRef J.S. Penades et al., "Suspended SOI waveguide with sub-wavelength grating cladding for mid-infrared", Optics letters, 39(19), 5661-5664 (2014). CrossRef T. Baehr-Jones, A. Spott, R. Ilic, A. Spott, B. Penkov, W. Asher, and M. Hochberg, "Silicon-on-sapphire integrated waveguides for the mid-infrared", Opt. Express, 18(12),12127-12135 (2010). CrossRef J. Mu, R. Soref, L. C. Kimerling, and J. Michel, "Silicon-on-nitride structures for mid-infrared gap-plasmon waveguiding", Appl. Phys. Lett., 104(3), 031115 (2014). CrossRef J.S. Penades et al., "Suspended silicon waveguides for long-wave infrared wavelengths", Optics letters, 43 (4), 795-798 (2018). CrossRef J.S. Penades et al., "Suspended silicon mid-infrared waveguide devices with subwavelength grating metamaterial cladding", Optics Express, 24, (20), 22908-22916 (2016). CrossRef M.A. Butt, S.N. Khonina, N.L. Kazanskiy, "Modelling of Rib channel waveguides based on silicon-on-sapphire at 4.67 μm wavelength for evanescent field gas absorption sensor", Optik, 168, 692-697 (2018). CrossRef S.N. Khonina, N.L. Kazanskiy, M.A. Butt, "Evanescent field ratio enhancement of a modified ridge waveguide structure for methane gas sensing application", IEEE Sensors Journal CrossRef M.A. Butt, S.A. Degtyarev, S.N. Khonina, N.L. Kazanskiy, "An evanescent field absorption gas sensor at mid-IR 3.39 μm wavelength", Journal of Modern Optics, 64(18), 1892-1897 (2017). CrossRef S. Zampolli et al., "Selectivity enhancement of metal oxide gas sensors using a micromachined gas chromatographic column", Sensors and Actuators B Chemical, 105 (2), 400-406 (2005). CrossRef N. Dossi, R. Toniolo, A. Pizzariello, E. Carrilho, E. Piccin, S. Battiston, G. Bontempelli, "An electrochemical gas sensor based on paper supported room temperature ionic liquids", Lab Chip, 12 (1), 153-158 (2011). CrossRef V. Avetisov, O. Bjoroey, J. Wang, P. Geiser, K. G. Paulsen, "Hydrogen Sensor Based on Tunable Diode Laser Absorption Spectroscopy", Sensors, 19 (23), 5313 (2019). CrossRef M.A. Butt, S.N. Khonina, N.L. Kazanskiy, "Silicon on silicon dioxide slot waveguide evanescent field gas absorption sensor", Journal of Modern Optics, 65(2), 174-178 (2018). CrossRef Nikolay Lvovich Kazanskiy, Svetlana Nikolaevna Khonina, Muhammad Ali Butt, "Subwavelength Grating Double Slot Waveguide Racetrack Ring Resonator for Refractive Index Sensing Application", Sensors, 20, 3416 (2020). CrossRef H. Tai, H. Tanaka, T. Yoshino, "Fiber-optic evanescent-wave methane-gas sensor using optical absorption for the 3.392-μm line of a He–Ne laser", Opt. Lett., 12, 437-439 (1987). CrossRef M.A. Butt, S.N. Khonina, N.L. Kazanskiy, "Hybrid plasmonic waveguide-assisted Metal–Insulator–Metal ring resonator for refractive index sensing", Journal of Modern Optics, 65(9), 1135-1140 (2018). CrossRef S.A. Degtyarev, M.A. Butt, S.N. Khonina, R.V. Skidanov, "Modelling of TiO2 based slot waveguides with high optical confinement in sharp bends", 2016 International Conference on Computing, Electronic and Electrical Engineering, ICE Cube, Quetta, 2016, 10-13 CrossRef

Enhanced Kerr Nonlinearity and Nonlinear Figure of Merit in Silicon Nanowires Integrated with 2D Graphene Oxide Films.

Layered two-dimensional (2D) graphene oxide (GO) films are integrated with silicon-on-insulator (SOI) nanowire waveguides to experimentally demonstrate an enhanced Kerr nonlinearity, observed through self-phase modulation (SPM). The GO films are integrated with SOI nanowires using a large-area, transfer-free, layer-by-layer coating method that yields precise control of the film thickness. The film placement and coating length are controlled by opening windows in the silica cladding of the SOI nanowires. Owing to the strong mode overlap between the SOI nanowires and the highly nonlinear GO films, the Kerr nonlinearity of the hybrid waveguides is significantly enhanced. Detailed SPM measurements using picosecond optical pulses show significant spectral broadening enhancement for SOI nanowires coated with 2.2 mm long films of 1-3 layers of GO and 0.4 mm long films with 5-20 layers of GO. By fitting the experimental results with theory, the dependence of GO's Kerr nonlinearity on layer number and pulse energy is obtained, showing interesting physical insights and trends of the layered GO films from 2D monolayers to quasi bulk-like behavior. Finally, we show that by coating SOI nanowires with GO films, the effective nonlinear parameter of SOI nanowires is increased 16-fold, with the effective nonlinear figure of merit (FOM) increasing by about 20 times to FOM > 5. These results reveal the strong potential of using layered GO films to improve the Kerr nonlinear optical performance of silicon photonic devices.

Thermally-Reconfigurable Silicon Photonic Devices and Circuits

Reconfigurable photonic integrated devices and circuits are very important for many applications. Among various mechanisms for realizing reconfigurability, thermo-optic effect is popular because of the availability for many materials, the design simplicity and the fabrication ease. In particular, silicon has a large thermo-optic coefficient as well as a high heat conductivity, and thus it is promising to realize efficient thermally-reconfigurable silicon photonic integrated devices and circuits. Recent progress is reviewed in this paper. First, thermally-tunable silicon photonic filters based on different structures are summarized, including microring resonators (MRRs) and MRRs-assisted Mach-Zehnder interferometers (MZIs). Second, silicon photonic switches based on MZIs and MRRs are reviewed. Finally, a review is given for thermally-reconfigurable silicon photonic integrated circuits developed for the applications in quantum photonics, microwave photonics, and optical interconnects.

Hybrid silicon photonic devices with two-dimensional materials

Abstract Silicon photonics is becoming more and more attractive in the applications of optical interconnections, optical computing, and optical sensing. Although various silicon photonic devices have been developed rapidly, it is still not easy to realize active photonic devices and circuits with silicon alone due to the intrinsic limitations of silicon. In recent years, two-dimensional (2D) materials have attracted extensive attentions due to their unique properties in electronics and photonics. 2D materials can be easily transferred onto silicon and thus provide a promising approach for realizing active photonic devices on silicon. In this paper, we give a review on recent progresses towards hybrid silicon photonics devices with 2D materials, including two parts. One is silicon-based photodetectors with 2D materials for the wavelength-bands from ultraviolet (UV) to mid-infrared (MIR). The other is silicon photonic switches/modulators with 2D materials, including high-speed electro-optical modulators, high-efficiency thermal-optical switches and low-threshold all-optical modulators, etc. These hybrid silicon photonic devices with 2D materials devices provide an alternative way for the realization of multifunctional silicon photonic integrated circuits in the future.

Giant Faraday rotation of cobalt ferrite thin films deposited on silicon substrates for silicon photonic nonreciprocal device applications

In this study, crystalline cobalt ferrite thin films with large Faraday rotation (FR) coefficient were deposited on silicon by radiofrequency magnetron sputtering. An (100)-oriented MgO buffer layer was employed to solve the film/substrate discrepancy. A giant FR coefficient of 25 600 deg cm−1 was achieved for a cobalt ferrite film deposited at a substrate temperature (ST) of 600 °C. Moreover, the magnetic easy axis of the films switched from in-plane (IP) to out-of-plane orientation with increasing ST. This switching in the easy axis could be attributed to induced IP stress in the films with high deposition temperatures.

Subwavelength structured silicon waveguides and photonic devices

Abstract Subwavelength structures such as subwavelength gratings (SWGs) and subwavelength metamaterials are capable of tailoring the optical properties of materials and controlling the flow of light at the nanoscale. The effective indices of the subwavelength structured strip and slab waveguides can be changed in a wide range by choosing an appropriate duty cycle or a filling factor of silicon, which provides an effective method to manipulate the optical field and achieve effective index matching for functional devices. Recent advances in nanofabrication techniques have made it possible to implement subwavelength structures in silicon strip and slab waveguides. Here we review various approaches used to design subwavelength structures and achieve exotic optical responses and discuss how these structures can be used to realize high-performance silicon photonic devices. Both one-dimensional SWG devices and two-dimensional subwavelength metamaterial devices are covered in this review, including subwavelength structure–based polarization handling devices, mode manipulation devices, and building blocks for integrated optical interconnects. Perspectives on subwavelength structured silicon photonic devices are also discussed.

Nonlinear Photon Pair Generation in a Highly Dispersive Medium

Photon pair generation in silicon photonic integrated circuits relies on four wave mixing via the third order nonlinearity. Due to phase matching requirements and group velocity dispersion, this method has typically required TE polarized light. Here, we demonstrate TM polarized photon pair production in linearly uncoupled silicon resonators with more than an order of magnitude more dispersion than previous work. We achieve measured rates above 2.8 kHz and a heralded second order correlation of $g^{(2)}(0) = 0.0442 \pm 0.0042$. This method enables phase matching in dispersive media and paves the way for novel entanglement generation in silicon photonic devices.

Laser trimming of the operating wavelength of silicon nitride racetrack resonators

We demonstrate the possibility of post-fabrication trimming of the response of nitrogen-rich silicon nitride racetrack resonators by using an ultraviolet laser. The results revealed the possibility to efficiently tune the operating wavelength of fabricated racetrack resonators to any point within the full free spectral range. This process is much faster than similar, previously presented methods (in the order of seconds, compared to hours). This technique can also be applied to accurately trim the optical performance of any other silicon photonic device based on nitrogen-rich silicon nitride.

Advances in Interfacing Optical Fibers to Nanophotonic Waveguides Via Mechanically Compliant Polymer Waveguides

Interfacing standard optical fibers with high index-contrast photonic waveguides remains a substantial challenge restricting the cost-efficiency and scalability of silicon photonic devices. To address this, we have proposed a mechanically compliant polymer interface, formed of a standard fiber connection and a flexible ribbon with lithographically defined polymer waveguides. Self-aligned mechanical assembly and optical mode evolution designs are employed for low cost and large spectral bandwidth. In this paper, we review our progress leading to the full demonstration of this concept with −1.8 dB peak transmission from a plugged-in standard fiber connector to Si wire waveguides. This with 0.7 dB roll-off on a 100 nm bandwidth and all polarization. We present a comprehensive analysis of loss sources and discuss intermediate results, self-alignment accuracy, and reliability.

Scalable 3D Silicon Photonic Electronic Integrated Circuits and Their Applications

This paper investigates the opportunity and challenges of 3D silicon photonic electronic integrated circuits (3D EPICs) scaling to wafer-scale and beyond. The continuing demand for more data and information is driving new computing, communications, imaging, and information processing at higher throughput and energy-efficiency at lower manufacturing cost. The newly developed 3D silicon photonic devices including vertical U-turns and vertical lightpipes enable through-silicon-optical-vias (TSOVs) that can interconnect multiple layers of 2D silicon photonic electronic integrated circuits consistently with the industry's through-silicon-via (TSV) based 3D electronic integrated circuit manufacturing. Heterogeneous integration technology based on transfer printing allows wafer-scale (or beyond wafer-scale) heterogeneous integration of dissimilar materials (e.g., III-V semiconductor layers) on silicon at room temperature and 3D ultrafast laser inscription technologies allow arbitrary optical interfaces for high-density input/output between the 3D EPICs and many strands of multi-core-fibers (MCFs). We will discuss applications in neuromorphic computing, 3D LiDAR, photonic-integrated-interferometric-telescopes, 3D-fine-grain-memory, and 3D processor-memory realized by large-scale 3D EPICs.

Review of Recent Progress on Silicon Nitride-Based Photonic Integrated Circuits

Silicon photonic devices used in the photonics industry over the past three decades have helped in realizing large-scale photonic integrated circuits. Silicon nitride (Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) is another CMOS-compatible platform that provides several advantages such as low loss, high optical power tolerance, and broad spectral operation band from visible to infrared wavelengths. Recently, the combination of Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> waveguide technology with silicon photonics and III-V materials has opened up new areas in on-chip applications. Researchers in the field are primarily focusing on its applications such as on-chip gas sensing, nonlinear optical signal processing, and label-free biosensors based on photonic integrated circuits. In this review paper, we discuss Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> material-based platforms for a variety of applications with devices ranging from passive to active and hybrid photonic devices.

Compact Low-Loss Electroabsorption Modulator Using a Graphene-Inserted Metal-Slot-Added Waveguide

Metal slots have been used to obtain strong light-graphene interaction, which usually requires them to be a few tens of nanometers wide. However, narrow metal slot waveguides have a large intrinsic loss; they are not efficiently connected to conventional silicon photonic waveguides; they are not easy to fabricate. To address the issues, a graphene-inserted metal-slot-added (GIMSA) waveguide and an electroabsorption modulator (EAM) based on it are theoretically investigated. The GIMSA waveguide consists of a silicon strip embedded in silicon dioxide and a metal slot aligned above the silicon strip with double graphene layers between them. The EAM is composed of the GIMSA waveguide and input and output couplers connecting it to silicon photonic waveguides. In order to achieve the good performance of the EAM in terms of length and insertion loss, the GIMSA waveguide and the couplers are designed. When the silicon strip and the metal slot are respectively 320 nm and 316 nm wide, the total length of the EAM with an extinction ratio of 3 dB is 6.23 μm, and its on-state insertion loss is 1.01 dB. Compared to previous graphene-based EAMs embedded in silicon photonic integrated circuits, this EAM is shorter and has a quite small insertion loss. The EAM's large feature size may enable fabrication using 248 nm optical lithography, and the EAM is expected to function as a compact modulator, well-integrated with silicon photonic devices.

Silicon-Based Mode Converter and Demultiplexer for Wavelength Division Multiplexing Transmission by Using Multimode Interference Couplers

We present a mode converter and demultiplexer structure for wavelength division multiplexing (WDM) transmission by employing multimode interference (MMI) on Silicon-on-Insulator (SOI) platform. The mode converter and demultiplexer have a compact size of less than 2.7 μm × 43.7 μm. Moreover, the crosstalk between neighboring wavelength channel within C band (1530 nm to 1570 nm) can be reduced by utilizing the tapered phase shifter cascaded with MMI. The simulated results indicate that this structure has a low insertion loss of less than 1 dB, a low crosstalk of better than ?15 dB and a relatively high fabrication tolerance of ~10 nm. Such structure may find many potential applications in silicon photonic integrated devices.