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The inverse taper (a) linear inverse taper (b) exponential inverse taper (c) quadratic inverse taper (not to scale).
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We have simulated the coupling loss of three types of Inverse Taper and taper-lensed fiber using three dimensional (3D) semi-vectorial beam propagation methods (BPM) respectively. Our results showed that the performances of exponential inverse taper and quadratic inverse taper were better than the commonly used linear inverse taper. Especially, for...
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Citations
... Integrated photonics implement complex photonic systems in small chiplets, including optical trapping [1][2][3], biosensing [4,5], quantum optics [6,7], and optical phase arrays for freespace beam steering [8]. As the on/off-chip interface is critical, many efforts have been dedicated to improving the performance of couplers such as tapers [9][10][11][12][13][14], lensed fiber [15][16][17], and directly coupled on-chip facets [18]. Near-unity coupling efficiency has been demonstrated for grating couplers with fabrication steps far beyond traditional foundry compliance [19][20][21][22][23][24]. ...
Due to their sub-millimeter spatial resolution, ink-based additive manufacturing tools are typically considered less attractive than nanophotonics. Among these tools, precision micro-dispensers with sub-nanoliter volumetric control offer the finest spatial resolution: down to 50 µm. Within a sub-second, a flawless, surface-tension-driven spherical shape of the dielectric dot is formed as a self-assembled µlens. When combined with dispersive nanophotonic structures defined on a silicon-on-insulator substrate, we show that the dispensed dielectric µlenses [numerical aperture (NA) = 0.36] engineer the angular field distribution of vertically coupled nanostructures. The µlenses improve the angular tolerance for the input and reduces the angular spread of the output beam in the far field. The micro-dispenser is fast, scalable, and back-end-of-line compatible, allowing geometric-offset-caused efficiency reductions and center wavelength drift to be easily fixed. The design concept is experimentally verified by comparing several exemplary grating couplers with and without a µlens on top. A difference of less than 1 dB between incident angles of 7°and 14°is observed in the index-matched µlens, while the reference grating coupler shows around 5 dB contrast.
... There are several forms of SSCs that have been explored, including layered polymer waveguide structures [19,20], multi-tip structures [21][22][23], nonlinear anticone structures [24], and subwavelength grating structures [25]. Among these options, a single nonlinear anticone structure may not be suitable for coupling with elliptic light spots from semiconductor optical amplifiers (SOA). ...
We designed a narrow-linewidth external-cavity hybrid laser leveraging a silicon-on-insulator triple Euler gradient resonant ring. The laser’s outer cavity incorporates a compact, high-Q resonant ring with low loss. The straight waveguide part of the resonant ring adopts a width of 1.6 μm to ensure low loss transmission. The curved section is designed as an Euler gradient curved waveguide, which is beneficial for low loss and stable single-mode transmission. The design features an effective bending radius of only 26.35 μm, which significantly improves the compactness of the resonant ring and, in turn, reduces the overall footprint of the outer cavity chip. To bolster the laser power and cater to the varying shapes of semiconductor optical amplifier (SOA) spots, we designed a multi-tip edge coupler. Theoretical analysis indicates that this edge coupler can achieve an optical coupling efficiency of 85%. It also reveals that the edge coupler provides 3 dB vertical and horizontal alignment tolerances of 0.76 μm and 2.4 μm, respectively, for a spot with a beam waist radius of 1.98 μm × 0.99 μm. The outer cavity, designed with an Euler gradient micro-ring, can achieve a side-mode suppression ratio (SMSR) of 30 dB within a tuning range of 100 nm, with a round-trip loss of the entire cavity at 1.12 dB, and an expected theoretical laser linewidth of 300 Hz.
... However, it presents challenges in terms of fabrication processes. Over the past decade, researchers have extensively studied edge couplers and proposed various structural transformations, including edge couplers based on inverse taper with different nonlinear profiles [82] or consisting of double-tip inverse taper [83]. Grating coupling utilizes a grating structure to couple the light signal into the chip at a vertical angle. ...
Integrated photonic chips leverage the recent developments in integrated circuit technology, along with the control and manipulation of light signals, to realize the integration of multiple optical components onto a single chip. By exploiting the power of light, integrated photonic chips offer numerous advantages over traditional optical and electronic systems, including miniaturization, high-speed data processing and improved energy efficiency. In this review, we survey the current status of quantum computation, optical neural networks and the realization of some algorithms on integrated optical chips.
... where n and k are the real and imaginary parts of it, respectively. The width of Si waveguide was chosen as 107 nm to ensure single mode operation [55,56]. For the purpose of absorbing any incident propagating wave or evanescent field, two perfectly matched layers (PML) were defined at the outer regions of the model. ...
Sensors fabricated by using a silicon-on-insulator (SOI) platform provide promising solutions to issues such as size, power consumption, wavelength-specific nature of end reflectors and difficulty to detect ternary mixture. To address these limitations, we proposed and investigated a broadband-thermally tunable vanadium dioxide (VO2)-based linear optical cavity sensor model using a finite element method. The proposed structure consists of a silicon wire waveguide on a silicon-on-insulator (SOI) platform terminated with phase-change vanadium oxide (VO2) on each side to provide light confinement. A smooth transmission modulation range of 0.8 (VO2 in the insulator state) and 0.03 (VO2 in the conductive phase state) in the 125 to 230 THz spectral region was obtained due to the of Fabry–Pérot (FP) effect. For the 3.84 μm cavity length, the presented sensor resulted in a sensitivity of 20.2 THz/RIU or 179.56 nm/RIU, which is approximately two orders of magnitude higher than its counterparts in the literature. The sensitivity of the 2D model showed direct relation with the length of the optical cavity. Moreover, the change in the resonating mode line width Δν of approximately 6.94 THz/RIU or 59.96 nm/RIU was also observed when the sensor was subjected to the change of the imaginary part k of complex refractive index (RI). This property of the sensor equips it for the sensing of aternary mixture without using any chemical surface modification. The proposed sensor haspotential applications in the areas of chemical industries, environmental monitoring and biomedical sensing.
... Such a mismatch is not suitable for PIC systems [9]. To overcome this limitation, two coupling techniques have been proposed in the literature, including the butt-coupling, also called edge coupling or in-plane coupling [10][11][12][13][14][15][16][17], and the grating coupler, also called vertical coupling or off-plane coupling [18][19][20][21][22][23]. Both aim at improving the performance in terms of coupling efficiency, bandwidth, polarization sensitivity and CMOS compatibility. ...
... At the input stage, the fiber mode surrounds the SSC tip up to a certain length where the mode is compressed into a guided one. Several configurations of inverse tapers have been proposed in the literature, e.g., by exploring non-linear profiles [11], double tips [12], and tridents [13]. However, remarkable results in terms of coupling losses (< 1 dB) and size (< hundreds of µm) have been achieved by using complex edge couplers, as with multiple SiN rods, knife edge shapes, or combining different materials [14][15][16]. ...
... Since the dispersion of Si3N4 varies by just 0.06% within the 1530 -1570 nm range, a broadband operation over the C-band has been measured, as shown in Fig. 5(b). The mean value of αcoupling ranges from 0.17 dB to 0.23 dB, demonstrating the feasibility of the proposed SSC in telecom PICs, with outstanding results improvement, in terms of coupling loss, with respect to the state-of-the-art [10][11][12][13][14][15][24][25]. ...
Photonic Integrated Circuits (PIC) provide a solution to overcome the main limitations of electronics, such as the operating frequency and heat generation, pushing the so-called “More than Moore” concept to increase the capacity and the speed of data transmission. In large data centers and optical transmission systems, PICs are interconnected by using fiber-to-chip couplers, which are crucial to improve system performance. An ultra-low loss interconnection (< 1 dB) over a wide bandwidth (≈ 50 nm) is the gold standard. In this context, the silicon nitride (Si
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) platform is a promising candidate, with propagation losses of the order of dB/m at 1550 nm. Here, we propose the design and the experimental results for a silicon nitride-based fiber-to-chip interconnect, acting as a high aspect ratio waveguide Spot-Size Converter (SSC). A coupling loss less than 0.20 dB over the entire C-band and within a footprint of 1,800 μm
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has been experimentally demonstrated, suggesting the proposed interconnect as a promising solution for next-generation high-density PICs.
... This Y junction will be designed such that the centers of its two waveguides A & B in Fig. 4. (separated by the distance Δ) are aligned with the centers of the 2 peaks of the LP 11 mode in the few mode fiber. Actually, these two guides A and B are acting as two inverted tapers to couple the two peaks of the LP 11 mode (Mu et al. 2020;Ren et al. 2011). Each of them will thus have the dimensions of 1.5 µm × 1.8 µm. ...
In this work, we present a new design for an integrated optical field rotator for the mode LP11a to the mode LP11b and vice versa using planar Silica over silicon technology. The structure is designed using a Multilayer Asymmetric Coupler. The coupling efficiency of the coupler could be as high as 99% when its length is about 1 mm. For a shorter coupler of length 550 microns and a coupling efficiency of 91%, a complete structure is designed to couple 2 few mode fibers of diameters 15.4 microns through an inverted taper from one side and a Y junction with two inverted tapers from the other side. The fiber to fiber insertion loss of the proposed structure is less than 3 dB over about 190 nm spectral range around 1550 nm. The 3 dB bandwidth of the structure is greater than 360 nm as demonstrated by the Beam Propagation Method BPM simulation.
... It is composed of a suspended SSC SiO2 and a silicon waveguide. In order to compress the mode size in the vertical direction (Y-axis), a clad material with SiO2 (different refractive index with a core material) is used to coverlid an optical fiber and an SSC design termination, forming a terminated taper [12], [13]. The suspended SSC is also laterally tapered (X-axis) such that the dimensions are larger at the input facet and smaller at the inversed taper. ...
The light propagation in optical waveguide must be able to maintain low propagation loss, low coupling loss and scattering loss condition, especially in the junction. In this research, a spot size converter is proposed to preserve the lowest coupling loss. This optical converter is composed of a single mode optical fiber (SiO2) including inversed taper. The optical input signal from the optical fiber is launched into photonic integrated circuits and then coupled into the Si-Slab waveguide. Furthermore, linear form with the length dependence has been studied to obtain the optimal position of optical fiber and the chip and analyzed the coupling efficiency of it. The purpose of this research is to procure the optimal form of spot size converter. The simulation result shows the coupling loss of linear form is 0.62 dB and 0.24 dB on TE and TM mode condition respectively. Along with the increase in the taper length, the coupling loss obtained tends to decrease as well. So that, it can be assumed the design of a linear form with 100 μm taper length provides the highest coupling efficie ncy.
... In such coupling structure, coupling loss caused by the refractive index contrast and the mode mismatch between the laser diode and the silicon waveguide can be effectively suppressed by the SU-8 3D taper, which leads to improvement of coupling efficiency and misalignment tolerance. The SU-8 3D taper can be fabricated by nanoimprint, pattern transfer or standard photolithography process and is more practical than the 10 nm sized inverse taper for edge coupling [33][34][35][36][37], which usually needs electron beam lithography. ...
We here design and simulate a three-dimensional (3D) SU-8 tapered edge coupler for effectively guiding light from an edge-emitting semiconductor laser diode directly to a silicon waveguide to realize a hybrid on-chip silicon light source. A series of coupling efficiencies for the commonly used top silicon thicknesses of the silicon-on-insulator (SOI) wafers from 220 to 3000 nm are obtained, showing that this polymer taper can largely improve the coupling efficiency when the silicon waveguide thickness is moderate, for instance, from 41% (with no taper) to 67% for the 700- nm- thick silicon waveguide under 1 m gap offset and relax the lateral misalignment tolerance to above one micron by suppressing the butt refractive index contrast and the mode mismatch between the laser diode and the silicon waveguide. Wave transformation inside the tapered coupler and the input silicon waveguide has also been revealed by 3D finite-difference time-domain (FDTD) simulations. This 3D tapered coupler is cost effective and easily fabricated which can have wide practical applications in massive production of various silicon photonic chips based on the present CMOS foundry.
... Many edge coupling structures have been proposed. The main structures of edge couplers include linear tapers [11], nonlinear tapers [12,13], multitapers [14], subwavelength grating structures [15,16], etc. The structure of a linear taper is simple and easy to process but requires extremely large dimensions and limited coupling efficiency. ...
Edge couplers are widely utilized in photonic integrated circuits and are vital for ensuring efficient chip-to-fiber coupling. In this paper, we present a high-efficiency and compact polarization-insensitive multi-segment linear silicon nitride edge coupler for coupling to high numerical aperture fibers. By optimizing the thickness of the up cladding and introducing air slots in the transverse direction, we have further modified the limiting effect of the mode field. This innovative edge coupler scheme boasts a compact structure and is compatible with existing mature standard processes, with a total length of only 38 μm. We numerically demonstrate that the proposed edge coupler exhibits a low coupling loss of 0.22 dB/0.31 dB for TE/TM modes at λ = 1550 nm. Furthermore, the proposed coupler displays high wavelength insensitivity within the range of 1400–1850 nm and maintains a coupling loss of less than 0.2 dB with a manufacturing deviation of ±20 nm.
... Integrated photonics implement complex photonic systems in small chiplets, including optical trapping [1][2][3], biosensing [4,5], quantum optics [6,7], and optical phase arrays for freespace beam steering [8]. As the on/off-chip interface is critical, many efforts have been dedicated to improving the performance of couplers such as tapers [9][10][11][12][13][14], lensed fiber [15][16][17], and directly coupled on-chip facets [18]. Near-unity coupling efficiency has been demonstrated for grating couplers with fabrication steps far beyond traditional foundry compliance [19][20][21][22][23][24]. ...
Due to their sub-millimeter spatial resolution, ink-based additive manufacturing tools are typically considered less attractive than nanophotonics. Among these tools, precision micro-dispensers with sub-nanoliter volumetric control offer the finest spatial resolution: down to 50 µm. Within a sub-second, a flawless, surface-tension-driven spherical shape of the dielectric dot is formed as a self-assembled µlens. When combined with dispersive nanophotonic structures defined on a silicon-on-insulator substrate, we show that the dispensed dielectric µlenses [numerical aperture (NA) = 0.36] engineer the angular field distribution of vertically coupled nanostructures. The µlenses improve the angular tolerance for the input and reduces the angular spread of the output beam in the far field. The micro-dispenser is fast, scalable, and back-end-of-line compatible, allowing geometric-offset-caused efficiency reductions and center wavelength drift to be easily fixed. The design concept is experimentally verified by comparing several exemplary grating couplers with and without a µlens on top. A difference of less than 1 dB between incident angles of 7° and 14° is observed in the index-matched µlens, while the reference grating coupler shows around 5 dB contrast.
