The top cladding is an important factor when designing photonic devices. It has implications on waveguide properties such as mode guidance and optical loss. Silicon dioxide (SiO2) is a commonly used cladding material for photonic devices as it has low optical loss and also enables a large refractive index contrast between the waveguide core and cladding. We performed an investigation into the material properties of SiO2 thin films deposited by different methods, namely, plasma-enhanced chemical vapor deposition (PECVD) undoped silicate glass (USG), high density plasma (HDP), PECVD tetraethyl orthosilicate (TEOS), and low pressure chemical vapor deposition (LPCVD) TEOS. Material properties including refractive index, surface roughness, absorption, and film stress were characterized for the different SiO2 cladding samples. Our results show that the surface roughness of HDP films was around 55 times better than that of USG films. In terms of film stress however, USG films had the lowest, whereas PECVD TEOS films were found to have the highest film stress, more than twice of that of the USG films. These findings indicate that when deciding on a particular deposition method for the SiO2 cladding, besides considerations of thermal budget and device application, an equally important compromise needs to be made to give a balance among the various material properties.
Aluminum nitride (AlN) is a promising photonics material contributed by its wide transparency window and remarkable nonlinear optical property. Moreover, its nonlinear effect can be further enhanced by doping Scandium (Sc). Such nonlinear optical property brings potential for high efficiency in nonlinear optical generation processes, such as 2nd harmonic generation and frequency comb generation. Although the nonlinear optical property of Sc-doped AlN looks promising, its waveguide is facing challenge on loss reduction. In this work, we report Sc-doped AlN photonic integrated circuit with reduced waveguide loss of 6 dB/cm around 1550 nm. The waveguide has Sc doping concentration of 10%. Its etching process is tailored through a design of experiment (DoE) approach to achieve smooth surface. An annealing process is also applied to patterned waveguide for optical loss reduction. A loaded Q of 1.41×104 has also been reported from microring resonator on the same wafer. The reported result paves the way towards low-loss Sc-doped AlN for photonic integrated circuits.
We develop H2 gas sensors based on CMOS compatible 20% ScAlN-based pyroelectric detectors fabricated in-house. Leveraging on the high thermal conductivity of H2, ScAlN-based pyroelectric detector is used in the H2 sensor for H2 to conduct away thermal energy received by the detector, resulting in a drop in signal received by the detector, thereby leading to different voltage signals measured for different H2 gas concentrations. The higher the H2 gas concentration, the lower the voltage measured as more thermal energy is conducted away from the detector. We successfully demonstrate H2 gas sensing with the signal received by the pyroelectric detector at concentration ranging from 400 ppm to 1% H2 concentration. The gases are cycled at 2-minute intervals between different concentrations of H2, using N2 as the reference gas. Our measurements show H2 sensing down to 400 ppm gas concentration with response time ranging from ~3-7 s. In addition, a linear relationship is also observed between the measured output signal from the H2 gas sensor and the H2 gas concentration flowing across the pyroelectric detector. The results show promise in using CMOS compatible 20% ScAlN-based pyroelectric detectors for development of thermal conductivity H2 gas sensor in H2 leakage sensing to increase confidence towards adoption of H2 as a clean energy as we move towards a sustainable society.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.