<p>A method of tapering waveguides using fixed-electronic-beam-moving-stage (FBMS) paths is presented. The tapering is achieved by joining two FBMS paths to a common point. Compared to conventional area and FBMS tapering methods, the proposed method offers smooth and alignment-error-free tapering between waveguides of different widths. We experimentally demonstrate a fully functional FBMS patterned photonic circuit with a power splitter, wire-to-slot coupler, slot waveguide, and a slotted ring resonator. The device response with an insertion loss of −1.35 dB is measured around 1550-nm wavelength.</p>
In this paper, we demonstrate a compact Silicon photonics-based on-chip integrated interference vibrometer. Unlike conventional readout methods, the demonstrated system is alignment-free and offers multiplex sensing. The intensity that is modulated by the cantilever motion by a photodetector. We present the static and dynamic response of the cantilever by electrostatic excitation validated using ac commercial Laser-Doppler-Vibrometer. We also present a detailed simulation, optimisation and sensitivity analysis of the proposed on-chip vibrometer. Furthermore, the tunability of the sensor to achieve maximum sensitivity is demonstrated.
In this paper, we present a hybrid process to make a flexible photonic circuit. The photonic circuit is fabricated on a Silicon substrate with PECVD Silicon Nitride (SiN) as a waveguide layer on an oxide layer. The SiN waveguide circuit is fabricated using conventional lithography and dry etching followed by Si substrate thinned down to 10micrometer. The thin-film photonic circuit integrity after wafer-thinning and layer transfer is characterized by the waveguide performance, grating coupler efficiency and ring resonator performance. We observe no degradation in device and circuit performance. We present detailed process flow, SiN-to-PDMS embedding process and detailed device characterization.
We present a method to write a tapered waveguide using fixed-beam-moving-stage (FBMS) in an electron-beam lithography system. FBMS allows writing of large patterns without stitch-error, however, restricts only a few primitive shapes. For patterning tapers, a combination of FMBS with area-mode is used that typically results in alignment errors. The proposed method offers smooth and alignment-error-free tapering of sub-micron featured Silicon waveguide. We experimentally demonstrate a fully FBMS patterned photonic circuit with power splitter, wire-to-slot coupler, slot waveguide and a slotted ring resonator. The device response with insertion loss -1.35dB is measured using a tunable laser source around 1550 nm wavelength.
Wavelength-selective integrated photonic devices in silicon-photonic platform require tuning to match the operating wavelength of multiple devices. The operating wavelengths are generally in the near-IR band. The conventional method of choice is to thermally tune the refractive index of silicon using metal micro-heaters. However, metals absorb near-IR wavelengths and must be placed away from the waveguides to avoid optical losses. This significantly reduces the power-efficiency of the heaters. Graphene-based local heaters on top of waveguides have been recently explored. Although the absorption in graphene is less than that of metals, it is still large enough to necessitate the placement of a thin spacer between the waveguide and the heater. We observe that metallic carbon-nanotubes (CNTs) are comparatively more transparent in the C-band. We implement heaters made of solution-processed metallic CNTs directly on top of a silicon-on-insulator micro-ring resonator. We demonstrate thermo-optic tuning of 60 pm/mW on a micro-ring resonator having a free-spectral range (FSR) of 1.75 nm. The estimated power efficiency is 29 mW/FSR, which is at par with previously implemented graphene-based heaters, that has higher absorption and better than conventional metal heaters. The proposed configuration offers compact and efficient thermal-tuner integration.
In this paper, we demonstrate a compact silicon photonics based vibrometer using an on-chip photonic grating (OPG) based sensor. OPG works on the principle of interference where the motion of the cantilever is captured at the output as an intensity variation. The advantage of OPG based sensor over conventional Laser Doppler vibrometer is increased tolerance to alignment errors as both the grating and the cantilever can be integrated on a single chip. The grating parameters were optimized using 2D-FDTD to achieved maximum sensitivity to the displacement of a cantilever. OPG with on-chip germanium photodetector is studied, which indicates a sensitivity of 54 μW/nm. We experimentally demonstrate the feasibility of the proposed sensor that can achieve a displacement sensitivity of 5.3 μW/nm.