Sandeep Ummethala

Diamond-integrated optomechanical circuits

Diamond integrated photonic devices are promising candidates for applications in nanophotonics and optomechanics. Here I present active modulation of diamond-based devices by exploiting mechanical degrees of freedom in free-standing electro-optomechanical resonators.

Silicon-Organic Hybrid (SOH) and Plasmonic-Organic Hybrid (POH) Integration

Silicon photonics offers tremendous potential for inexpensive high-yield photonic-electronic integration. Besides conventional dielectric waveguides, plasmonic structures can also be efficiently realized on the silicon photonic platform, reducing device footprint by more than an order of magnitude. However, neither silicon nor metals exhibit appreciable second-order optical nonlinearities, thereby making efficient electro-optic modulators challenging to realize. These deficiencies can be overcome by the concepts of silicon-organic hybrid (SOH) and plasmonic-organic hybrid integration, which combine SOI waveguides and plasmonic nanostructures with organic electro-optic cladding materials.

Diamond electro-optomechanical resonators integrated in nanophotonic circuits

Diamond integrated photonic devices are promising candidates for emerging applications in nanophotonics and quantum optics. Here, we demonstrate active modulation of diamond nanophotonic circuits by exploiting mechanical degrees of freedom in free-standing diamond electro-optomechanical resonators. We obtain high quality factors up to 9600, allowing us to read out the driven nanomechanical response with integrated optical interferometers with high sensitivity. We are able to excite higher order mechanical modes up to 115 MHz and observe the nanomechanical response also under ambient conditions.

Diamond as a material for monolithically integrated optical and optomechanical devices

Diamond provides superior optical and mechanical material properties, making it a prime candidate for the realization of integrated optomechanical circuits. Because diamond substrates have matured in size, efficient nanostructuring methods can be used to realize full-scale integrated devices. Here we review optical and mechanical resonators fabricated from polycrystalline as well as single crystalline diamond. We present relevant material properties with respect to implementing optomechanical devices and compare them with other material systems. We give an overview of diamond integrated optomechanical circuits and present the optical readout mechanism and the actuation via optical or electrostatic forces that have been implemented to date. By combining diamond nanophotonic circuits with superconducting nanowires single photons can be efficiently detected on such chips and we outline how future single photon optomechanical circuits can be realized on this platform.

Silicon-plasmonic photomixer for generation and homodyne reception of continuous-wave THz radiation

We demonstrate the first silicon-plasmonic photomixer. THz radiation is generated and received by employing two lasers near 1.5 μm. The receiver sensitivity of 28 mA/(W V) compares well with the sensitivity of a commercial system.

Silicon–plasmonic integrated circuits for terahertz signal generation and coherent detection

Optoelectronic signal processing offers great potential for generation and detection of ultra-broadband waveforms in the terahertz range (so-called T-waves). However, fabrication of the underlying devices still relies on complex processes using dedicated III–V semiconductor substrates. This severely restricts the application potential of current T-wave transmitters and receivers and impedes co-integration of these devices with advanced photonic signal processing circuits. Here, we demonstrate that these limitations can be overcome by plasmonic internal-photoemission detectors (PIPEDs). PIPEDs can be realized on the silicon photonic platform, which allows exploiting the enormous opportunities of the associated device portfolio. In our experiments, we demonstrate both T-wave signal generation and coherent detection at frequencies up to 1 THz. To prove the viability of our concept, we monolithically integrate PIPED transmitters and receivers on a common silicon chip and use them to measure the complex transfer impedance of an integrated T-wave device.Transmitters and receivers based on plasmonic internal-photoemission detectors are developed for optoelectronic terahertz signal processing and monolithically integrated on a silicon chip. Proof-of-concept experiments are demonstrated.