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Si3N4 has emerged as a prominent material for expanding the capability of silicon photonics to wavelengths below < 1 μm. However, realizing an efficient optical modulator, a key building block for any integrated optics platform, remains a major challenge in Si3N4
mainly because this material has a vanishing Pockels coefficient. Here, we propose a...
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Citations
... The graphene layer is considered to be undoped, so the C Q has an unremarkable impact on the total capacitor [31]. Due to the C Q being much larger than the C d , and because they form a series relationship, we ignore C Q in the establishment of the equivalent circuit [32][33][34][35]. Here, the C d exists between the outer and inner graphene layer and the C air is considered to exist between two electrodes and the air [36]. ...
The phase change material vanadium dioxide ( ${{\rm VO}_2}$ V O 2 ) is suitable for building high-efficiency light modulators due to the different absorption efficiency of light in metallic and insulating states. The structure of an electro-absorption modulator based on ${{\rm VO}_2}$ V O 2 and graphene proposed in this paper is formed by two layers of single-layer graphene wrapped around ${{\rm VO}_2}$ V O 2 , with a silicon waveguide in the middle and silica on both sides as the main path for light transmission. The input light of TE mode is limited to the ${{\rm SiO}_2}$ S i O 2 layer on both sides to increase the contact area with ${{\rm VO}_2}$ V O 2 layers, which make it almost impossible to pass through when the metal electrode is connected to an external bias voltage and ${{\rm VO}_2}$ V O 2 is in the metallic state. On the contrary, the input light passes through the main path of the modulation region with low loss without bias voltage. Finally, the modulator proposed in this paper has achieved a high extinction ratio of 27.3 dB and a low insertion loss of 0.66 dB (when ${{\rm VO}_2}$ V O 2 is in insulating state) at a single wavelength of 1550 nm when the device length is 2 µm. In addition, the bias voltage of the modulator is 1.1 V with the modulation speed at 200 MHz, and the energy consumption is only 8.3083 fJ/bit at work, which is an ideal choice for photonic integrated systems today.
... These unique characteristics make graphene a prospective option for an active material to create innovative optical modulators [12], [13], [14]. They have also been found beneficial for numerous broadband and ultra-compact applications such as polarizers [13], [14] photodetectors [15], [16], modulators [1], [17], [18], [19], and sensors [20], [21], [22]. Typically, the material and thickness of a dielectric layer, the structure of a waveguide, and the size of the graphene directly affect the operating characteristics, resulting in a tradeoff between absorption depth and bandwidth. ...
This work presents a novel contribution to graphene/TiO2 electro-optical modulators based on silicon-on-silica waveguide with a hybrid plasmonic waveguide to achieve ultrafast switching and low-voltage states. Waveguide structure consists of a rectangular silicon core covered by a high relative permittivity TiO2 dielectric layer with two layers of graphene, air-clad, and silica lower cladding. Effective refractive indices can be tailored to support the propagation of the transverse magnetic mode with a suitable design related to an electro-absorption modulator for simulation results. Modulation depth and bandwidth were enhanced by the waveguide width and dielectric thickness, respectively. Maximum and minimum absorption depths at the driving voltage states can determine modulators. The simulation produced the highest efficient modulator with high speed at 3dB bandwidth of 93.7 GHz using a low energy consumption of 210.6 fJ/bit, a small footprint (24 μm
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), and a broad operating spectrum range from 1310 to 1550 nm. This is because the physical process acts according to the modulator at the Fermi energy of graphene and the structure of the waveguide. These modulators can have practical applications due to their distinctive advantages, including a small device footprint, low voltage operation, ultrafast modulation switching across a broad wavelength range, and low-energy operation.
... based on the SOCF platform with VO 2 as an active material. In addition, the proposed modulator achieves a better ER than those reported in (Abdelatty et al. 2018;Alrayk et al. 2021;Das and Arya 2021a, b;Janjan et al. 2020;Jin et al. 2018;Phatak et al. 2016;Sadeghi et al. 2020;Shah et al. 2018) with comparable IL as summarized in Table 3. ...
Efficient mid-infrared (MIR) optical modulator is reported and numerically analyzed for both the transverse electric (TE) and transverse magnetic (TM) polarized modes. The proposed design is based on the silicon-on-calcium-fluoride platform with vanadium dioxide (VO2) as a phase changing material. Due to the attractive property of its phase transition between dielectric (ON) and metallic (OFF) states under the effect of an applied electric field, VO2 is utilized to enable the modulation process. At an operating wavelength of 3.5 μm, the reported modulator realizes an extinction ratio (ER) of 10.9 dB/μm with an insertion loss (IL) of 0.24 dB/μm for the TE polarized mode. However, for the TM polarized mode, an ER, and IL of 9.5 dB/μm, and 0.19 dB/μm, respectively are achieved. Additionally, the suggested design has a good fabrication tolerance of ± 10% where the ER is better than 10.4 dB/μm and 8.6 dB/μm for the TE and TM polarized modes with IL less than 0.26 dB/ μm. Therefore, the suggested modulator can play a pivotal role in different MIR applications including imaging, sensing, security, and communications.
... At mid-infrared frequencies, the applicability of noble metals-based plasmonic structures degrades due to high propagation loss and poor field confinement [11]. Moreover, graphene due to its exceptional thermal properties such as high thermal conductivity up to 5300 Wm -1 K -1 enables high-speed optical devices [12]- [14]. ...
... Hybrid SOI platforms based on a range of materials such as graphene [6], indium tin oxide (ITO) [2], zinc oxide [7], and zinc sulfide (ZnS) [7] have overcome the abovementioned issue. Optical phase change materials (O-PCMs) such as VO 2 [8,9], Ge-Sb-Te (GST) alloys [1,3], and Ge 2 Sb 2 Se 4 Te 1 (GSST) [4,[10][11][12], Sb 2 Se 3 [13,14], and Sb 2 S 3 [14,15] have become quickly attractive as an alternative option for hybrid SOI structures due to their desired characteristics [4]. Many O-PCM applications employ a reversible phase transition between opaque and transparent states via a source of actuation that can be induced, thermally [5,8,16], electrically [8,9], or optically [17]. ...
... Optical phase change materials (O-PCMs) such as VO 2 [8,9], Ge-Sb-Te (GST) alloys [1,3], and Ge 2 Sb 2 Se 4 Te 1 (GSST) [4,[10][11][12], Sb 2 Se 3 [13,14], and Sb 2 S 3 [14,15] have become quickly attractive as an alternative option for hybrid SOI structures due to their desired characteristics [4]. Many O-PCM applications employ a reversible phase transition between opaque and transparent states via a source of actuation that can be induced, thermally [5,8,16], electrically [8,9], or optically [17]. As a result, a range of optical devices based on O-PCM materials including modulators [9,[18][19][20], switches [4], memories [21], metasurfaces [22], Bragg gratings [23], phase shifters [13], and light manipulation devices [1] have been introduced recently. ...
... Optical phase change materials (O-PCMs) such as VO 2 [8,9], Ge-Sb-Te (GST) alloys [1,3], and Ge 2 Sb 2 Se 4 Te 1 (GSST) [4,[10][11][12], Sb 2 Se 3 [13,14], and Sb 2 S 3 [14,15] have become quickly attractive as an alternative option for hybrid SOI structures due to their desired characteristics [4]. Many O-PCM applications employ a reversible phase transition between opaque and transparent states via a source of actuation that can be induced, thermally [5,8,16], electrically [8,9], or optically [17]. As a result, a range of optical devices based on O-PCM materials including modulators [9,[18][19][20], switches [4], memories [21], metasurfaces [22], Bragg gratings [23], phase shifters [13], and light manipulation devices [1] have been introduced recently. ...
Optical phase change materials (O-PCMs) are emerging as promising active materials for exploitation in silicon photonics platforms, due to their compatibility with CMOS fabrication technology and the tunability of their optical characteristics via external excitation. Despite their advantages, O-PCMs suffer from relatively high insertion loss hindering efficient modulation. Also, the change of the imaginary part of the refractive index in O-PCMs is large and the realization of a Mach-Zehnder modulator (MZM) based on O-PCM materials becomes challenging. To overcome these issues, we consider the variation of both real and imaginary parts of the refractive index, facilitated by a GSST-based MZM design. To achieve this, we design an active waveguide that is constructed via depositing an ITO layer (as the microheater) surrounding the pre-fabricated GSST layer on a silicon rib-waveguide. The active length of the proposed MZM is designed ∼4.3 µm at the wavelength of 1.55 µm. The simulations indicate that a compact MZM can be achieved by eliminating the S-bends in the MZM structure without affecting the modulation. The proposed bend-less MZM demonstrates an insertion loss less than 1.7 dB and an extinction ratio greater than 35 dB over the entire optical C-band.
... Hybrid SOI platforms based on a range of materials such as graphene [6], indium tin oxide (ITO) [2], zinc oxide [7], and zinc sulfide (ZnS) [7] have overcome the abovementioned issue. Optical phase change materials (O-PCMs) such as VO 2 [8,9], Ge-Sb-Te (GST) alloys [1,3], and Ge 2 Sb 2 Se 4 Te 1 (GSST) [4,[10][11][12], Sb 2 Se 3 [13,14], and Sb 2 S 3 [14,15] have become quickly attractive as an alternative option for hybrid SOI structures due to their desired characteristics [4]. Many O-PCM applications employ a reversible phase transition between opaque and transparent states via a source of actuation that can be induced, thermally [5,8,16], electrically [8,9], or optically [17]. ...
... Optical phase change materials (O-PCMs) such as VO 2 [8,9], Ge-Sb-Te (GST) alloys [1,3], and Ge 2 Sb 2 Se 4 Te 1 (GSST) [4,[10][11][12], Sb 2 Se 3 [13,14], and Sb 2 S 3 [14,15] have become quickly attractive as an alternative option for hybrid SOI structures due to their desired characteristics [4]. Many O-PCM applications employ a reversible phase transition between opaque and transparent states via a source of actuation that can be induced, thermally [5,8,16], electrically [8,9], or optically [17]. As a result, a range of optical devices based on O-PCM materials including modulators [9,[18][19][20], switches [4], memories [21], metasurfaces [22], Bragg gratings [23], phase shifters [13], and light manipulation devices [1] have been introduced recently. ...
... Optical phase change materials (O-PCMs) such as VO 2 [8,9], Ge-Sb-Te (GST) alloys [1,3], and Ge 2 Sb 2 Se 4 Te 1 (GSST) [4,[10][11][12], Sb 2 Se 3 [13,14], and Sb 2 S 3 [14,15] have become quickly attractive as an alternative option for hybrid SOI structures due to their desired characteristics [4]. Many O-PCM applications employ a reversible phase transition between opaque and transparent states via a source of actuation that can be induced, thermally [5,8,16], electrically [8,9], or optically [17]. As a result, a range of optical devices based on O-PCM materials including modulators [9,[18][19][20], switches [4], memories [21], metasurfaces [22], Bragg gratings [23], phase shifters [13], and light manipulation devices [1] have been introduced recently. ...
Optical phase change materials (O-PCMs) are emerging as promising active materials for exploitation in silicon photonics platforms, due to their compatibility with CMOS fabrication technology and the tunability of their optical characteristics via external excitation. Despite their advantages, O-PCMs suffer from relatively high insertion loss hindering efficient modulation. Also, the change of the imaginary part of the refractive index in O-PCMs is large and the realization of a Mach-Zehnder modulator (MZM) based on O-PCM materials becomes challenging. To overcome these issues, we consider the variation of both real and imaginary parts of the refractive index, facilitated by a GSST-based MZM design. To achieve this, we design an active waveguide that is constructed via depositing an ITO layer (as the microheater) surrounding the pre-fabricated GSST layer on a silicon rib-waveguide. The active length of the proposed MZM is designed ∼4.3 µm at the wavelength of 1.55 µm. The simulations indicate that a compact MZM can be achieved by eliminating the S-bends in the MZM structure without affecting the modulation. The proposed bend-less MZM demonstrates an insertion loss less than 1.7 dB and an extinction ratio greater than 35 dB over the entire optical C-band.
... Presently, the most vital problem of float glass is that small Na + ions can easily diffuse into the VO 2 film, which results in poor thermochromic properties [24]. VO 2 thin films have been prepared on Si 3 N 4 [25], TiO 2 [26], ZnO [27], SnO 2 [28], and other buffer layers, but the preparation methods and properties were quite different. For application in smart windows, the VO 2 film's visible transmittance should be above 60%, and the key performance of the transition temperature must be reduced to a practical range of 25-30 • C. Tungsten doping and oxygen vacancy production have been considered to be effective methods [29][30][31], but the mechanisms of tungsten doping for reducing the phase transition temperature and the equivalent effect of oxygen vacancy are still not clear. ...
In this paper, VO2 thin films with good optical properties are fabricated on practical float glass by magnetron sputtering and a professional annealing method. The near-infrared switching efficiency (NIRSE) of the prepared film reaches 39% (@2000 nm), and its near-infrared energy modulation ability (ΔTir) reaches 10.9% (780–2500 nm). Further, the highest integral visible transmittance Tlum is 63%. The proposed method exhibits good reproducibility and does not cause any heat damage to the magnetron sputtering machine. The crystalline structure of the VO2 film is characterized by X-ray diffraction (XRD). The lattice planes (011) and (−211) grow preferentially (JCPDS 65-2358), and a large number of NaV2O5 crystals are detected simultaneously. The microstructures are characterized by scanning electron microscopy (SEM), and a large number of long sheet crystals are identified. The phase transition temperature is significantly reduced by an appropriate W doping concentration (Tc = 29 °C), whereas excessive W doping causes distortion of the thermal hysteresis loop and a reduction in the NIRSE. Oxygen vacancies are created by low pressure annealing, due to which the phase transition temperature of VO2 film decreases by 8 °C. The addition of an intermediate SiO2 layer can prevent the diffusion of Na+ ions and affect the preparation process of the VO2 thin film.
... Assuming a linear loss of 1.5 dB/cm, an efficiency of 1.2 × 10 −5 % is calculated for a pump power of 10 μW which increases to 0.013% for a pump power of 10 mW. The achieved SHG efficiency is orders of magnitude larger than those obtained by the strained [32] or electric field-induced Si 3 N 4 waveguide [19]. Although this value is low compared to the structure realized by traditional χ (2) materials such as LiNbO 3 [22], these materials suffer from poor compatibility with CMOS technology and are expensive. ...
ABC-metamaterial, structured by repeating atomic layer deposition of three dielectric material-stack layers, opens the new possibility for creating second-order nonlinearity in CMOS-compatible photonics platforms. Here, the design and simulation of Si
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N
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub>
waveguide with embedded ABC-metamaterial for generating second-harmonic (SH) of 1.55
${\mu }\text{m}$
wave is presented. High-overlap-integral modal phase matching between the fundamental mode of the fundamental frequency and second-order mode of the SH is attained by properly engineering the waveguide geometry. Numerical analyzes show an absolute efficiency of 0.013% for 10 mW pump power in the straight waveguide which can be enhanced to at least 13.4% by employing a microring resonator.
... The multiphysics electro-thermal simulations using the 3D finite element method (3D-FEM) are performed based on the material parameters including material density, thermal conductivity, and heat capacity. These thermal parameters of ITO, VO 2 , SiO 2 and Si are reported [29], [31], [32]. Note that, ITO is considered as the conductive material of choice for the heater and electrodes. ...
Vanadium dioxide (VO
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>
) has emerged as a prominent optical phase change material (O-PCM) for creating high performance devices based on hybrid silicon platforms. However, realizing an efficient and compact optical modulator required for Mach-Zehnder interferometer (MZI) structures, still remains a major challenge in active Si-platforms enabled by VO
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>
. This is mainly due to the simultaneous variation of both real and imaginary parts of the refractive index during the phase transition process, which is a significant issue. A modified MZI structure is proposed in this paper while the refractive index variation issue is overcome by operating in the wavelength range between 1.5 to
$1.6~\mu \text{m}$
including the optical C-band. An indium tin oxide (ITO) layer is considered as the microheater for the thermal excitation. An optimized triggering signal with an amplitude of 12.5 V along with an arm length of
$2.35~\mu \text{m}$
of the MZI device (
$V_{\pi }L_{\pi }= 30 \,\,\text {V}\cdot \mu \text{m}$
) established a
$\pi $
-shift at the output of the device. The proposed device has ER >35 dB at the entire optical C-band and consumes
$\sim 26$
pJ for modulating a single bit with a delay of 3.5 ns.
... Graphene is a 2D material consisting of carbon atoms which possesses unique electrical, optical, mechanical and thermal properties. Various types of graphene-based optical devices including logic gates [37], polarizers [38][39][40], optical switches and modulators [41][42][43][44] have already been investigated. The large surface area, high carrier mobility [45,46] and the capability to effectively adsorb and immobilize various biomolecules especially those with carbon ring based structures (e.g. ...
In recent years, optical biosensors widely applicable for medical applications, have received much attention. In this paper, we propose a high-performance polarization-insensitive optical biosensor based on a graphene-dielectric metasurface. The metasurface consists of an asymmetric dielectric disk array that supports a high Q-factor Fano resonance. The provided sharp Fano resonance results in an enhanced light-matter interaction leading to a highly sensitive biosensor. The proposed structure is analyzed using the finite element method and the corresponding transmission and reflection spectra are calculated. According to the presented results, a sensitivity of as high as 550 nm/RIU, linearity R2 value of 0.999 with a figure of merit (FOM) more than 378 RIU-1 around the operating wavelength of 1550 nm are obtained. This is the largest FOM ever reported for a polarization-insensitive biosensor. Such a large FOM accompanied by high sensitivity and linearity make our proposed graphene-based biosensor promising for the effective detection of biomolecules like hemoglobin.
