Showing papers by "Enakshi Bhattacharya published in 2022"
TL;DR: In this paper , a Knudsen force based micro electro mechanical system low pressure sensor consisting of two stacked beams of polysilicon is presented, one acting as a heater and the other as a sensor.
Abstract: Knudsen forces are gas molecular forces, generated due to the presence of a thermal gradient between two surfaces in rarefied gas and can be effectively used for the measurement of low pressures. This work reports on a Knudsen force based micro electro mechanical systems low pressure sensor consisting of two stacked beams of polysilicon—one acting as a heater while the other as a sensor. The structure is fabricated using a double sacrificial layer surface micromachining process. The thermal gradient across the two stacked beams is induced by resistive heating of the heater beam. The effect of using two separate beams for heating and sensing has been investigated at different heater current and the results are compared with the existing works. The provision of two beams has resulted in the sensor functioning at very low pressure of less than 0.1 Pa with an improved sensitivity of 15.5 fF mPa−1.
11 Dec 2022
TL;DR: In this paper , the authors report the in-house development of SiN waveguide devices starting from a 4-inch silicon wafer and show that both the thermally grown buried oxide (BOX) and the LPCVD deposited SiN device layer show excellent uniformities in terms of their thickness and refractive indices.
Abstract: Over the last decade, silicon nitride (SiN) based integrated photonics has become popular due to its CMOS com-patibility, low loss, wide spectral operation band and tolerance to high optical power. It has great potential in different application areas like quantum information processing, microwave photonics, spectroscopy, etc. However, the growth of an optical grade oxide layer (for bottom cladding) and subsequent deposition of SiN device layer on the surface of a handle silicon wafer are the most important aspects for the realization of large- scale photonic integrated circuits with an acceptable waveguide losses and fabrication yields. In this paper, we report the in- house technology development of SiN waveguide devices starting from a 4- inch silicon wafer. Both the thermally grown buried oxide (BOX) and the LPCVD deposited SiN device layer show excellent uniformities in terms of their thickness $(1900\pm 20nm, 400\pm 4nm$, respectively) as well as refractive indices $(n_{SiO_{2}}= 1.45\pm 0.001, n_{SiN}=2.024\pm 0.003$ at $\lambda\sim 1.55\mu m)$ across the full wafer. We have discussed the design and characterization of the grating coupler, single mode waveguides operating at $\lambda\sim 1.55\mu m$ and their fabrication flow as well. The fabricated single mode waveguides (TE polarized) with input/output grating couplers exhibit a 3-dB bandwidth of $\sim 50nm$ with a peak transmission efficiency at $\lambda\sim 1570nm$. The SiN waveguides fabricated out of in-house processed SiN wafer exhibit reasonable third order non-linearity; confirmed by stimulated four wave mixing experiment.