In this work, we propose and implement a bi-junction depletion-type silicon electro-optic phase shifter. The phase shifter has a lateral profile of implants, that closely resembles that of a common bipolar junction transistor, and thus, has two polarities. These are acceptor-donor-acceptor (PNP) as well as donor-acceptor-donor (NPN). We realize both variants in IMEC ISIPP50G open-access silicon photonic technology and compare them to lateral and interleaved phase shifters. Both PNP and NPN phase shifters exhibit a VπLπ figure that is at least 14.47% and up to 45.1% lower than that of the lateral and interleaved phase shifters realized in the same technology. Bi-junction phase shifters can be implemented in any planar silicon photonic technology that offers bipolar implantations within silicon photonic waveguides.
Doubly-clamped pre-stressed silicon nitride string resonators excel as high Q nanomechanical systems enabling room temperature quality factors of several 100,000 in the 10 MHz eigenfrequency range. Dielectric transduction ideally complements the silicon nitride strings, providing an all-electrical control scheme while retaining the large mechanical quality factor [1,2]. It is mediated by an inhomogeneous electric field created between adjacent electrodes. The resulting gradient field provides an integrated platform for actuation, displacement detection, frequency tuning as well as strong mode.
Dielectrically controlled silicon nitride strings are an ideal testbed to explore a variety of dynamical phenomena ranging from multimode coupling to coherent control. Here I will focus on the nonlinear dynamics of a strongly driven string [3,4]. While the response of the string is described by the cubic nonlinearity of the well-established Duffing model, the power spectrum reveals a series of interesting satellite peaks. I will show how they reflect the dynamics of the driven string in the presence of thermal noise, enabling insights into the squeezing of thermal fluctuations as well as nonlinear switching phenomena.
[1] Q. P. Unterreithmeier et al., Nature 458, 1001 (2009).
[2] J. Rieger et al., Appl. Phys. Lett. 101, 103110 (2012).
[3] M. Seitner et al., Phys. Rev. Lett. 118, 254301 (2017).
[4] J. Huber et al., in preparation
The coupling of mechanical oscillators with light has seen a recent surge of interest, as recent reviews report. 1,2 This
coupling is enhanced when confining light in an optical cavity where the mechanical oscillator is integrated as backmirror
or movable wall. At the nano-scale, the optomechanical coupling increases further thanks to a smaller
optomechanical interaction volume and reduced mass of the mechanical oscillator. In view of realizing such cavity nanooptomechanics
experiments, a scheme was proposed where a sub-wavelength sized nanomechanical oscillator is coupled
to a high finesse optical microcavity. 3 Here we present such an experiment involving a single nanomechanical rod
precisely positioned into the confined mode of a miniature Fabry-Pérot cavity. 4 We describe the employed stabilized
cavity set-up and related finesse measurements. We proceed characterizing the nanorod vibration properties using
ultrasonic piezo-actuation methods. Using the optical cavity as a transducer of nanomechanical motion, we monitor
optically the piezo-driven nanorod vibration. On top of extending cavity quantum electrodynamics concepts to
nanomechanical systems, cavity nano-optomechanics should advance into precision displacement measurements near the
standard quantum limit 5 , investigation of mechanical systems in their quantum regime, non-linear dynamics 6 and sensing
applications.
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