Slotted Photonic Crystal Waveguide Research Articles

ANN-based estimation of dispersion characteristics of slotted photonic crystal waveguides

ANN-based estimation of dispersion characteristics of slotted photonic crystal waveguides

Raman based on-chip photonic quantizers for ADCs

In this work, a model for an on-chip all-photonic analog to digital converter is proposed. Here, the underlying quantization technique is based on slicing the supercontinuum generated inside the highly nonlinear nanocrystal embedded slotted photonic crystal waveguide at specifically chosen wavelengths. It is shown that although both the broadening and splitting of the spectrum can be used for four level quantization, only broadening can be used for designing eight (or more) level quantization. The highly nonlinear device system makes the eight level quantization scheme incremental within a footprint of 50×20µm2, which can convert 0–11 mW analog optical power to respective quantization levels. Although both Kerr and stimulated Raman scattering (SRS) contribute to the generation of the supercontinuum, the giant SRS gain of the silicon nanocrystal essentially outweighs that of the Kerr, with, consequently, unprecedented miniaturization in both operating power and footprint.

Overview of Optical Biosensors for Early Cancer Detection: Fundamentals, Applications and Future Perspectives

Conventional cancer detection and treatment methodologies are based on surgical, chemical and radiational processes, which are expensive, time consuming and painful. Therefore, great interest has been directed toward developing sensitive, inexpensive and rapid techniques for early cancer detection. Optical biosensors have advantages in terms of high sensitivity and being label free with a compact size. In this review paper, the state of the art of optical biosensors for early cancer detection is presented in detail. The basic idea, sensitivity analysis, advantages and limitations of the optical biosensors are discussed. This includes optical biosensors based on plasmonic waveguides, photonic crystal fibers, slot waveguides and metamaterials. Further, the traditional optical methods, such as the colorimetric technique, optical coherence tomography, surface-enhanced Raman spectroscopy and reflectometric interference spectroscopy, are addressed.

Low-power, high-performance, and small-footprint, single-pump optical parametric amplifier for photonic integrated circuits

A single-pump optical parametric amplifier (OPA) is modeled using a p-toluene sulfonate (PTS) filled silicon-based slotted photonic crystal waveguide (SPCW). The PTS-SPCW has CMOS-process compatibility and offers slow-light enhanced nonlinearity of PTS due to extreme optical confinement in SPCW. The adverse effects of two-photon absorption and free carrier absorption are absent in PTS in the standard optical communication window. The coupled nonlinear Schrödinger’s equations have been modified to analyze the OPA under slow-light propagation. Performances of the OPA are evaluated in both the high- and low- dispersive zones of the structure. The high dispersive zone exhibits high group indices to the operating waves, leading to a high parametric gain (≈31 dB) and high conversion efficiency (≈27 dB) utilizing a 350 μm long PTS-SPCW and a pump power of 65 mW. However, this zone degrades the shape of a ≤10 ps pulse due to self-phase and cross-phase modulation. On the other hand, in the low dispersive zone, a similar parametric gain and conversion efficiency (both ≈29 dB) are attained utilizing a 1250 μm long PTS-SPCW and a pump power of 150 mW. Nevertheless, this zone degrades a 5 ps pulse only after a distance of 1500 μm. The analyses show a 30 nm bandwidth considering a gain above 30 dB. Investigation of the effect of fabrication imperfections shows excellent performance sustainability of the OPA up to a random error of 40 nm. These remarkable performances make this low-powered, small-footprint OPA suitable for achieving tunable optical amplification in photonic integrated circuits.

Raman mediated solitonic pulse compression

A comprehensive analysis of Raman mediated solitonic compression of pulses inside a silicon nanocrystal embedded slotted photonic crystal waveguide (SPCW) is presented. The ultrahigh Raman gain coefficient of the silicon nanocrystal material, being fortified further by the intense optical confinement inside the SPCW, essentially outweighs the contribution of the Kerr in the self-phase modulation phenomenon that is responsible for the solitonic propagation of a pulse. This work particularly emphasizes the contribution of Raman nonlinearity in the soliton dynamics, which however has been neglected conventionally, leading to an unprecedented miniaturization in both the operating power and footprint. Spatiotemporal evolution of pulses inside the SPCW has been calculated using the nonlinear Schrödinger equation considering the slow-light regime. A compression factor as high as 44.3 is obtained using a 30 µm long SPCW with a peak input power of 8 mW at 1550 nm.

Analysis on slotted photonic crystal cavity and waveguide combination in silicon-on-insulator platform

In this work, we report the numerical and simulation studies on the coupling behaviors of silicon-on-insulator (SOI) slotted photonic crystal cavity (SPhCC) and slotted photonic crystal waveguide (SPhCW). Coupled mode theory (CMT) based numerical calculations for a coupled structure consisting of SOI SPhCC and SPhCW have shown that the structure reaches a strong coupling when the Qc≥2Qi in which Qi and Qc are the quality factors of the cavity alone and of the cavity when coupled with waveguide, respectively, then the transmission of the output signal is less than 0.25, and the build-up factor is of nanosecond. In the simulation scheme with Plane wave expansion (PWE) and Finite-difference time-domain (FDTD) methods, the slot confined PhC cavity mode, which lies deep below in the band-gap, has been excited properly from the side coupling SPhCW with the obtained transmission of around 0.22. Our study sheds light on the SOI SPhCC-SPhCW coupled structure, knowledge of which may enable its applications in integrated circuits, hybrid silicon platform and sensing.

Slow Light Tuning in Annular Slotted Photonic Crystal Waveguide with Incoming Polymer

An advanced post-processing scheme of reconfigurable dielectric infiltration into an annular slotted photonic crystal waveguide (ASPhCW) is proposed in this paper. Ionic liquids have had prominent effects in enhancing the optical properties of photonic crystals, especially in the aspect of tuning the transmission rate and velocity through optical materials. Using the two-dimensional plane wave expansion method, the flat band dispersion of the slow light is obtained and the tuning of the operating wavelength of the crystal could be realized by incoming polymer technology. The operating wavelength tuning range could be as large as 459.27nm and the group index could be tuned as high as 44.8 with a near zero group velocity dispersion. Using this method, a high group index equaling 45 with the bandwidth equaling 11.3nm and the normalized delay bandwidth product (NDBP) equaling 0.25 is realized. This incoming polymer technology provides an effective method of getting flat band of slow light flexibly and makes it possible to offer longer delay and low group velocity after fabrication.

2D Materials Enabled Next-Generation Integrated Optoelectronics: from Fabrication to Applications.

2D materials, such as graphene, black phosphorous and transition metal dichalcogenides, have gained persistent attention in the past few years thanks to their unique properties for optoelectronics. More importantly, introducing 2D materials into silicon photonic devices will greatly promote the performance of optoelectronic devices, including improvement of response speed, reduction of energy consumption, and simplification of fabrication process. Moreover, 2D materials meet the requirements of complementary metal‐oxide‐semiconductor compatible silicon photonic manufacturing. A comprehensive overview and evaluation of state‐of‐the‐art 2D photonic integrated devices for telecommunication applications is provided, including light sources, optical modulators, and photodetectors. Optimized by unique structures such as photonic crystal waveguide, slot waveguide, and microring resonator, these 2D material‐based photonic devices can be further improved in light‐matter interactions, providing a powerful design for silicon photonic integrated circuits.

All‐optical logic inverter for large‐scale integration in silicon photonic circuits

A new device architecture of an all-optical logic inverter (AOLI) has been proposed in this study. The AOLI functions based on stimulated Raman scattering (SRS) in silicon nanocrystal embedded slotted photonic crystal waveguide (SPCW). The operating power and footprint size of the proposed device have significantly been scaled down to ∼1.5 mW and ∼ 8.5 × 42 μ m 2 , respectively, by combining the benefits of giant SRS gain of silicon nanocrystal and ultra-high spatio-temporal confinement of the SPCW. Cascadability of the proposed AOLI has been investigated using the maximum product criterion of the noise margin. The successful operation of the AOLI has been demonstrated for the repetition rate of the pulses as high as 100 Gbps. Finally, tolerance of performance of the design under different types of fabrication imperfections has also been calculated to establish its sustainability in a practical scenario.

Design and Analysis of a Slot Photonic Crystal Waveguide for Highly Sensitive Evanescent Field Absorption Sensing in Fluids.

The design and modeling of a highly sensitive sensor based on a slot photonic crystal waveguide (slot-PCWG) is presented. The structure consists of cylindrical air rods drilled in a dielectric slab on a triangular lattice, which are filled with SiO2. The waveguide is formed by removing elements from the regular photonic crystal grid in a row, and embedding a slot in the center position. This concept allows for a vast enhancement of the evanescent field ratio, leading to a strong overlap between the field of the waveguide mode and the analyte. In the present work, we show that the sensitivity at the constant slab thickness of the slot-PCWG modes is greatly enhanced, up to a factor of 7.6 compared with the corresponding PCWG modes or Si-slab WGs. The finite-difference time-domain (FDTD) technique and plane wave expansion (PWE) methods were used to study the dispersion and profile of the PCWG mode. The simulation results show the potential of this design, which will be fabricated and tested in the following steps of the project.

High-sensitivity complex refractive index sensor by designing a slot-waveguide side-coupled Fano resonant cavity

In this paper, we proposed an integrated slotted photonic crystal (PhC) waveguide (SPCW) Fano resonant cavity (SPCW-FRC) for complex refractive index (RI) sensing, in which the device consists of three slot-waveguides and a H1 cavity. The light is coupled input and output the PhC structure by the slot waveguide. By adjusting the parameters of the PhC structure, a sharp asymmetric Fano resonance line shape can be obtained around 1550 nm. An optimal structure is achieved and the optimal parameters are 80 nm of the red air hole diameter, 680 nm of W1 (one line missing) waveguide, 120 nm of the gap (G) of the slots, and 100 nm of the slot width (ws), respectively. Through the three dimensional finite-difference time-domain (3D-FDTD) simulation, the sensitivities of the real part and imaginary part for the complex RI sensing are 494 nm/RIU and ∼8850/RIU, respectively. The simulation results show that the proposed structure is a promising candidate for the ternary mixture concentration detection in medical diagnosis and environmental monitoring.

Raman mediated ultrafast all-optical NOR gate.

A new device architecture has been proposed in this paper implementing the all-optical cascadable logic NOR functionality. The device functions based on stimulated Raman scattering (SRS) in silicon nanocrystal embedded slotted photonic crystal waveguide (SPCW). Substantial miniaturizations both in operating power and overall footprint of the device have been achieved owing to the ultrahigh SRS gain of silicon nanocrystal and strong spatio-temporal confinement of the SPCW. Successful operation of the device has been demonstrated at a pulse rate that is as high as 125 Gbps.

Sensitivity analysis of ring-shaped slotted photonic crystal waveguides for mid-infrared refractive index sensing

In this paper, the sensitivity of slotted photonic crystal waveguides (SPCW) with triangular lattice pattern of ring-shaped holes is analyzed in order to realize highly refractive index (RI) sensor devices at mid-infrared wavelengths. The sensing principle is based on the shift of the transmission spectrum edge of these specific ring hole SPCW waveguides giving rise to reinforced light–matter interaction. The 3D simulation results applied to silicon waveguides on membrane show that this guide geometry leads to a very high sensitivity to variations in the ambient environment index, with very dependent trends on the opto-geometric factors of the waveguides. As a matter of example, a $$720 \,\mathrm{nm}$$ wavelength position band edge shift is predicted, corresponding to a sensitivity of more than $$1450 \,\mathrm{nm}$$ per refractive index unit with a device insertion loss level of $$-\,3 \,\mathrm{dB}$$ .

Grating-Coupled Silicon-on-Sapphire Polarization Rotator Operating at Mid-Infrared Wavelengths

We provide an experimental demonstration of mid-infrared polarization rotators built on a silicon-on-sapphire platform at the mid-infrared wavelength of $4.55~\mu \text{m}$ to enable integration of quantum cascade lasers (QCLs) and detectors with slotted photonic crystal waveguide (PCW) gas sensors for on-chip optical spectroscopy applications. The polarization rotators are essential to convert the preferentially transverse magnetic (TM) polarized light from a QCL to transverse electric (TE) polarization to interface with the preferential TE-guiding slotted PCW sensors. The polarization rotator consists of an adiabatic-tapered mode converter followed by a phase shifter and a multimode interferometer that effectively transfers energy from an input fundamental TM00 polarization to a first-order TE10 polarization that is then converted to the fundamental TE00 mode. Polarization-selective sub-wavelength grating couplers are designed and fabricated to effectively couple TE or TM polarizations at the designed wavelengths into and out of the polarization rotator device for efficient device characterization. TM00–TE10 conversion efficiency of 100% is simulated. Fabrication tolerances in the phase shifter result in an experimental 80:20 splitting ratio of the measured output TE00-polarized light between two output arms.

A quantitative analysis of the whispering-gallery-mode lasers in Er[formula omitted]-doped silica glass microspheres towards integration in SOI slotted photonic crystal waveguides

Er3+-doped silica glass microspheres (μS) with diameters of ∼25–40μm were fabricated by using an electrical discharge method. The single-mode optical tapered fibers were used to guide the pumped laser into the μS surface and collect the resulting lasing emission. The observation of whispering-gallery-mode (WGM) at telecom regime is quantified. With the presented scheme, the selective single- or multi-emitted modes of the μS laser can be obtained by adjusting the coupling gap between the collection tapered fiber and the μS surface. To overcome the collection tapered fiber’s vibration at close range of the coupling gap, the guiding and coupling losses, while being compact enough to fit with complementary metal oxide semiconductor (CMOS) device, the integration of a μS with silicon-on-insulator (SOI) slotted photonic crystal waveguides is proposed and modeled with the help of finite-difference time-domain (FDTD) simulations. The designed structures may find application for the promising photonic devices such as the ultrahigh sensitivity sensors, the lasing sources, and towards advanced quantum communications.

InP-based polarization rotator-splitter for mid-infrared photonic integration circuits

We design and experimentally demonstrate the propagation loss of waveguides and the operation of a single-step etched polarization rotator-splitter (PRS) in low index contrast InGaAs-InP material system at 6.15 μm. Propagation losses 4.19 dB/cm for TM mode and 3.25 dB/cm for TE mode are measured. The designed PRS can achieve near 100% conversion efficiency. This study enables the possibility of monolithic integration of quantum cascade devices with TM-polarized characteristics and TE-guiding two-dimensional slotted photonic crystal waveguide gas sensors for on-chip monolithic absorption spectroscopy.

Integrable all‐optical pass switch

A completely new design for an all-silicon all-optical pass switch has been proposed based on the stimulated Raman scattering (SRS) in silicon nanocrystal embedded slotted photonic crystal waveguide (SPCW). Substantial miniaturisation in the device footprint and operating power has been attained by merging the benefits of the giant SRS gain and the ultra-high optical confinement of the SPCW. The proposed switch offers a tremendously high contrast ratio of ∼ 27 dB between the logic levels and an extraordinary bit rate of 125 Gbps.

Silicon slot waveguide Fano resonator.

The growing interest for Fano resonators during the past decade is due to the narrow line shape observable in their optical spectra. The drastic phase shift occurring at the resonance yields a steep drop from a high to low amplitude. Fano resonances can be obtained by a combination of nanostructures. Such a system is extremely sensitive in terms of both geometrical parameters and environmental conditions. Here we study a complex arrangement of photonic crystal cavities and slot waveguides on a silicon chip. Our structure, composed of several cavities in parallel, has a particular response superimposing a shallow photonic bandgap and a resonance with a Fano line shape. It provides a low noise and a clear asymmetric resonance. We demonstrate it experimentally and show the potential of such a device for sensing. A sensitivity of 92 nm/RIU is measured.

Design and optimization of a TE-pass polarization filter based on a slotted photonic crystal waveguide

A transverse-electric (TE)-pass polarization filter based on a slotted photonic crystal waveguide structure is proposed for application in photonic integrated circuits. The silicon-slab-based structure is fabrication-compatible with the standard silicon-on-insulator process technologies. Different structural parameters, such as the r/a ratio of the photonic crystal sections, slab height, slot width, and slot length, are optimized for improved performance. Moreover, the conversion efficiency of a mode of a W1 waveguide to that of a slot waveguide is analyzed for different starting positions of the slot in order to achieve a high extinction ratio of the TE wave over the transverse-magnetic wave. A 3D finite difference time domain simulation methodology, which has been verified against an earlier experimental study made by researchers on another structure, is adopted to evaluate the transmittance of the structure. It shows that the polarization filter, with a footprint of merely 6.28 μm×4.35 μm, offers an extinction ratio in the order of 22 dB; this corresponds to an effective extinction ratio of 3.5 dB μm−1 considering the total length (or 6.5 dB μm−1 considering only the slot length). TE transmittance of the device is calculated as ≈−3 dB at a wavelength of 1550 nm.

Silicon-Based Hybrid Integrated Photonic Chip for K ${}_{u}$ band Electromagnetic Wave Sensing

In this paper, we experimentally demonstrate a highly sensitive on-chip photonic electromagnetic wave sensor operating at 14.1 GHz with a 3 dB bandwidth of 4.84 GHz. The demonstrated electromagnetic sensor has several important advantages over conventional electrical electromagnetic sensors, including high sensitivity, compact in size, and strong immunity to electromagnetic interference. The sensor is comprised of a bowtie antenna and an asymmetric Mach-Zehnder interferometer (MZI). One arm of the MZI is an electro-optic polymer infiltrated one-dimensional slot photonic crystal waveguide (SPCW) and the other is a strip waveguide with teeth of subwavelength pitch. Bowtie antennas are designed and optimized to effectively collect 14.1 GHz microwave signal and applies it across the SPCW. The phase of the light guided in the SPCW therefore changes, and so does the amplitude of the output end of the MZI. The sensor is only 4.6 mm × 4.8 mm in size and has a low insertion loss of ~10 dB. Experimental results show the limit of detection at 14.1 GHz is 4.31 mW/m 2 , which is corresponding to a minimum detectable electric field of 1.8 V/m.