High thermo-optic tunability in PECVD silicon-rich amorphous silicon carbide

Abstract

In this work, the thermo-optic coefficient (TOC) of the silicon-rich amorphous silicon carbide (a-SiC) thin film deposited by plasma-enhanced chemical vapor deposition (PECVD) was characterized. We found that the TOC of the film increases as its silicon content increases. A more than threefold improvement in the TOC was measured, reaching a TOC as high as 1.88×10−4∘C−1, which is comparable to that of crystalline silicon. An efficient thermo-optic phase shifter has also been demonstrated by integrating the silicon-rich a-SiC micro-ring structure with a NiCr heater. Tunability of 0.117 nm/mW was demonstrated, and a corresponding tuning efficiency P π as low as 4.2 mW has been measured at an optical wavelength of 1550 nm. These findings make silicon-rich a-SiC a good candidate material for thermo-optic applications in photonic integrated circuits.

High-Quality Amorphous Silicon Carbide for Hybrid Photonic Integration Deposited at a Low Temperature

“…For the devices made on a-SiC deposited at 150 °C, a thermo-optic coefficient of 7.3 × 10 –5 /°C is obtained, which is 3 times higher than PECVD SiN . As a reference, thermo-optic measurements of a-SiC deposited via PECVD at 400° C are also shown, with a thermo-optic coefficient of 5.1 × 10 –5 /°C, overall in agreement with previous works …”

“…37 As a reference, thermo-optic measurements of a-SiC deposited via PECVD at 400°C are also shown, with a thermo-optic coefficient of 5.1 × 10 −5 /°C, overall in agreement with previous works. 41…”

Thermo‐Optical Switches Based on Spin‐Crossover Molecules with Wideband Transparency

“…In all cases, it has to be minimized to enable efficient and high‐speed optical modulation. Expressing P π and τ in terms of material‐based parameters, while including the thermal expansion effect, leads to the following expression: [ 53 ] $$$$\begin{equation}{{P}_\pi }\tau \ = \frac{{\lambda A \cdot {{C}_p}\rho }}{{2\left| {\frac{{\partial {{n}_{{\mathrm{eff}}}}}}{{\partial T}} + {{n}_{{\mathrm{eff}}}}{{\alpha }_{\mathrm{L}}}} \right|\ }}\ \end{equation}$$$$where n eff is the effective refractive index of propagation in the material, ∂n eff / ∂T is the thermo‐optic coefficient, α L is the thermal expansion coefficient, C p is the specific heat capacity, ρ is the mass density, λ is the wavelength of operation, and A is the effective heated area. To draw out a fair comparison between the reported devices and the above‐described structure, we have chosen to calculate the wavelength‐ and configuration‐independent figure‐of‐merit, FOM = P π τ / (λA) .…”

“…This mean value is typically one to two orders of magnitude greater than that observed in other materials commonly used for thermo-optical switches (see Table 1). Beyond the TOC, a routinely used criterion for the optimization of thermo-optical switches [51][52][53] is the product of the power needed to thermally induce a shift of the optical phase by 𝜋, P 𝜋 , by the thermal time constant, 𝜏. This metric turns out to be rather generic as P 𝜋 not only corresponds to the power needed to induce the full contrast change of Mach-Zehnder modulators but also to the power needed to shift the resonance of a device over its full free spectral range.…”

“…In all cases, it has to be minimized to enable efficient and high-speed optical modulation. Expressing P 𝜋 and 𝜏 in terms of material-based parameters, while including the thermal expansion effect, leads to the following expression: [53] P…”