
Professor Krishna Coimbatore Balram
PhD.(Stanford), MSc(Stanford)
Expertise
My primary research interest is the development of novel nanofabricated device platforms for manipulating light and sound waves at the nanoscale and engineering controlled interactions between them, and other solid state systems
Current positions
Professor of Nanoscale Device Engineering
School of Electrical, Electronic and Mechanical Engineering
Contact
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Research interests
My primary research interest is the development of novel nanofabricated device platforms for manipulating light and sound waves at the nanoscale and engineering controlled interactions between them, and other solid state systems. My current research thrusts are along three main directions, all underpinned by advances made in my group on pushing the operation frequency and efficiency of light-sound interactions in guided wave devices: building resonant acousto-optic quantum transducers to translate quantum states between the microwave and optical frequency domains for connecting distributed superconducting, spin and trapped ion qubit platforms [Balram et al., Nat. Phot. 2016; Valle et al., Opt. Lett. 2019; Wu et al. Phys. Rev. Appl. 2020]; shrinking mobile RF front-ends by ~100x by applying ideas from integrated photonics to guided wave acoustics [Valle et al., Appl. Phys. Lett. 2019]; and applying modern developments in RF engineering to an old problem (spin detection) and providing a route towards improved sensitivity by ~8 orders of magnitude.
My work pushes the state of the art in nanofabrication methods and, the performance of devices and systems enabled by this establishing Bristol as a centre for excellence in nanofabrication. To enable this, my group also develops novel metrology tools that allows us to probe and quantify wave phenomena at the nanoscale. My interest in metrology is a natural outgrowth of spending three very enjoyable years as a postdoctoral fellow, working with Kartik Srinivasan at NIST Gaithersburg. Before that, I was a PhD student with David Miller at Stanford.
You can find more about my work at my personal webpage, or check out my papers.
PhD projects:
If you are interested in building nanoscale devices to engineer efficient light matter interactions, please drop me an email. A list of PhD projects I am actively looking to recruit on:
- Photonic-phononic integrated circuits for (quantum) microwave to optical signal transduction:
- Cavity QMD: Piezoelectric micro-resonators as efficient near field transducers for readout and manipulation of nanoscale spin systems:
Projects and supervisions
Research projects
New directions in piezoelectric phononic integrated circuits
Principal Investigator
Managing organisational unit
School of Electrical, Electronic and Mechanical EngineeringDates
01/09/2024 to 31/08/2029
Next generation Acoustic Wave Filter Platform
Principal Investigator
Managing organisational unit
Department of Electrical & Electronic EngineeringDates
01/09/2023 to 31/08/2026
Next generation Acoustic Wave Filter Platform
Principal Investigator
Managing organisational unit
Department of Electrical & Electronic EngineeringDates
01/09/2023 to 31/08/2026
Next generation Acoustic Wave Filter Platform
Principal Investigator
Managing organisational unit
School of Electrical, Electronic and Mechanical EngineeringDates
01/09/2023 to 31/08/2026
Micromechanical Elements for Photonic Reconfigurable Zero-Static-Power Modules
Principal Investigator
Managing organisational unit
School of Electrical, Electronic and Mechanical EngineeringDates
01/01/2023 to 31/12/2025
Thesis supervisions
Mid-infrared quantum optics in silicon
Supervisors
Classical Control Systems for Photonic Quantum Computing
Supervisors
Gallium Nitride on Silicon Carbide Platform for Integrated Acoustic Devices
Supervisors
Human activity recognition using millimetre-wave radars with machine learning
Supervisors
Scaling down acoustic manipulation technology and its applications in the biomedical sector
Supervisors
Efficient spin-photon interfaces for distributing entanglement
Supervisors
Nanoelectromechanical technology for radiation and temperature harsh environments
Supervisors
Spatial and spectral control of diamond NV centres for scalable spin-photon interfaces.
Supervisors
Piezo-optomechanical signal transduction using hybridized mechanical supermodes
Supervisors
Quantum sensing with bright Gaussian states of light
Supervisors
Publications
Recent publications
01/01/2024Low-loss GHz frequency phononic integrated circuits in Gallium Nitride for compact radio-frequency acoustic wave devices.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Piezoelectric microresonators for sensitive spin detection
Physical Review Applied
Piezoelectric phononic integrated circuits
Applied Physics Letters
Heterogeneous Integration of Solid-State Quantum Systems with a Foundry Photonics Platform
ACS Photonics
Quantifying and mitigating optical surface loss in suspended GaAs photonic integrated circuits
Optics Letters
Teaching
I currently teach Advanced Optoelectronic Devices (EENGM6000) and Digital Circuits and Systems (EENG 14000). In the past, I have taught Optoelectronic Devices and Systems (EENG 30004), Projects (EENG 18020) and the lab modules for Lines and Waves (EENG 25000) and Communications (EENG 22000).
For teaching advanced optics and electromagnetism in general, I believe modern numerical solvers play an important role in introducing students to modelling 'real-world' problems. The coursework in AOD, for instance, introduces students to nonlinear wave mixing in integrated photonics using COMSOL Multiphysics.