Photonic integrated circuits provide a scalable platform for photonics-based quantum technologies. However, integrating quantum emitters and electro-optic cavities within this platform remains an open challenge proving to be a major hurdle from implementing key functionalities for quantum photonics, such as single photon sources and nonlinearities. Here, we address this shortcoming with the hybrid integration of InAs/InP quantum dot emitters on foundry silicon photonics and the implementation of photonic crystal cavities in thin-film lithium niobate. Co-integrated on-chip electronics allow us to tune the emission properties of the quantum dots while enabling GHz-rate coherent modulation over photons trapped in the cavities, thus providing a new level of programmability over interactions between optical fields and atom-like systems in integrated circuits. Our results open the door to a new generation of quantum information processors that can be manufactured in leading semiconductor foundries.
Large-scale quantum photonics requires the integration of several elements on the same chip, including quantum emitters and memories, active photonics, and single-photon detectors. In this talk, I will report on i) our recent work integrating superconducting nanowire single-photon detectors (SNSPD) with mechanically reconfigurable integrated photonics, and ii) our recently developed method for integration of SNSPDs onto arbitrary photonic substrates.
Thin Film Lithium Niobate (TFLN) photonic integrated circuits offer several improvements over other platforms in terms of material loss, energy efficiency, and operational bandwidth. We review our recent demonstration of quadrature phase shift keying in an ultrasmall TFLN photonic crystal-based IQ modulator. Our modulator features a footprint of 40 × 200 μm2 along with quality factors approaching 105 providing it with a Vπ = 1.16 V [H. Larocque et al. CLEO 2023, paper STh1R.3; H. Larocque et al. arXiv:2312.16746]. We discuss an extension to and optimization of quadrature amplitude modulation encoding schemes tailored to the device’s voltage response, including the use of a deep neural network for streamlining bit error rate minimization.
Photonics integration continues to be a main driver for innovation in multiple aspects, including wafer-scale integration, new materials, sub-micron alignment of components and protection from harsh environment. We show cost-effective fabrication technologies of micro-optical components by UV wafer-scale replication into chemically stable polymers. Furthermore, for simplified fiber coupling and packaging, a novel 90° optical interconnect is presented, integrated with self-alignment structures. Replicated, space compliant microlenses on packaged CMOS imagers show improved light sensitivity by a factor 1.8. A laser based, low stress bonding process is explored to generate wafer-scale hermetic enclosures for harsh environment applications ranging from space to implants.
Nanomechanical resonators are exquisite force sensors and have recently been used to “feel” the vacuum fluctuations of a laser field. I’ll describe a system consisting of a glass nanostring coupled to an optical microcavity and how it has been used to not only sense radiation pressure shot noise, but also squeeze it, to cool a vibration of the string to near its ground state, and to witness its zero-point energy as motional sideband asymmetry—all long-standing goals in the field of optomechanics. Underlying these advances are new insights into dissipation of nanomechanical resonators. Combining strain and mode-shape engineering, we've recently fabricated strings with effective masses of picograms, frequencies of megahertz, and quality factors approaching 1 billion at room temperature. These numbers spark the imagination, inviting speculation about applications ranging from ultrasensitive accelerometry to tests of quantum collapse models.
The pursuit of resonators with ultra-high coherence has led to intense study of “dissipation dilution”, where the stiffness of a material is effectively increased without added loss. Interestingly, the paradigm has to date relied on weak strain produced during material synthesis—the use of geometric strain engineering techniques, capable of producing local stresses near the material yield strength, remains largely unexplored. We show that geometric strain combined with soft-clamping can produce exceptionally high Q mechanical oscillators.
Loss due to curvature at the clamping points has been a major limiting factor in engineering of high Q mechanical oscillators. Soft-clamped resonators recently developed by Tsaturyan et al. bypass this limitation by localizing the mode away from the clamping points. We adapt their technique to 1D nanobeams. By corrugating the width of the nanobeam, we create a bandgap in the mechanical mode spectrum. A defect in the center of the beam allows a localized mode to exist in the bandgap. Then, by tapering the overall width of the nanobeam, we increase the stress in the center of the beam to near the yield strength. This combined strategy produces picogram-mass flexural modes with room-temperature Q factors as high as 800 million and Qf products of 10^15 Hz—both unprecedented for a mechanical oscillator of any size. Additionally, strain-engineering allows us to tune the frequency of the ultra-high Q mode from 1-6 MHz while retaining Qf products above 10^14 Hz. The extremely low dissipation and low effective mass of these devices make them promising for performing cavity quantum optomechanics.
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