Optics and Electronics Seminar

Optics & Electronics seminar: Energy Efficient, Multi-Terabit Photonic Connectivity for Disaggregated Computing

Topic: 
[AP483] Energy Efficient, Multi-Terabit Photonic Connectivity for Disaggregated Computing
Abstract / Description: 

TBA


 

Spring 2021 speakers organized by Prof. David A.B. Miller

Date and Time: 
Monday, May 3, 2021 - 4:15pm

Optics & Electronics seminar: Playing Hide-and-Seek at the Nanoscale – Tailored Field Landscapes for Precise Particle Tracking and More

Topic: 
[AP483] Playing Hide-and-Seek at the Nanoscale – Tailored Field Landscapes for Precise Particle Tracking and More
Abstract / Description: 

Intensity, phase, and polarization of electromagnetic fields can be tailored to form bespoke distributions. This spatial structure of light is an intriguing playground. It finds a wide range of applications in optical communications, sensing, imaging, and beyond. However, the real beauty of structured fields comes to light when considering strongly confined electromagnetic fields, which naturally feature complex three-dimensional distributions. These engineered light fields can be utilized, for example, to selectively excite individual nanosystems, extending the range of possible applications even further by enabling advanced single-particle spectroscopy, nanoscale traffic control, nano-metrology, and more.

In this talk, we introduce a novel scheme for ultra-precise particle localization and tracking, which is based on the interaction of structured light and individual nanoparticles. We show that by utilizing the strongly position-dependent scattering pattern as a ruler, we can retrieve the exact particle position from the far-field scattering signal. Besides the fundamental ingredients and recipe of this technique, we also highlight selected next steps and future plans. For instance, we also discuss the fundamental idea behind next generation camera technology to boost the capabilities of our nanometrology schemes. These novel pixels and cameras based on light-processing circuitry are jointly developed, together with other European and international experts, as part of the 'SuperPixels' project (https://www.superpixels.org/). They will allow for a simultaneous measurement of polarization and phase distributions in addition to light's intensity.

[This project has received partial funding from the European Commission Horizon 2020 research and innovation program under the Future and Emerging Technologies Open Grant Agreement Super-Pixels No. 829116]


 

Spring 2021 speakers organized by Prof. David A.B. Miller

Date and Time: 
Monday, April 19, 2021 - 12:00pm

Optics & Electronics seminar: Semiconductor Nanocrystal Optoelectronics: A Journey from Colloidal Quantum Dots to Wells

Topic: 
[AP483] Semiconductor Nanocrystal Optoelectronics: A Journey from Colloidal Quantum Dots to Wells
Abstract / Description: 

Semiconductor nanocrystals have attracted great interest for color conversion and enrichment in quality lighting and displays. Optical properties of these solution‑processed nanostructures are conveniently controlled by tailoring their size, shape, and composition in an effort to realize high‑performance light generation and lasing. These colloids span different types and heterostructures of semiconductors in the forms of quantum dots and rods to the latest sub‑family of nanocrystals, the colloidal quantum wells (CQWs). In this talk, we will introduce the emerging field of semiconductor nanocrystal optoelectronics, with most recent examples of their photonic structures and optoelectronic devices employing such atomically‑flat, tightly‑confined, quasi‑two‑dimensional CQWs, also popularly nick-named 'nanoplatelets'. Among their various extraordinary features, we will show that these CQWs enable record high optical gain coefficients [1] and can achieve gain thresholds at the level of sub‑single exciton population per CQW on average [2], empowered by carefully engineering their heterostructure [3]. Next, we will present a new, powerful, large-area self‑assembly tool for orientation controlling of these nanoplatelets [4], which provides us with the ability to tune and master their excitonic properties in their ensemble, as well as the level of achievable energy transfer among them and with other nearby species. Using three‑dimensional constructs of face‑down self‑assembled slabs of CQWs with monolayer precision, we will demonstrate ultrathin optical gain media and lasers of these oriented CQW assemblies [5]. Finally, we will show record high‑efficiency colloidal LEDs using CQWs employed as the electrically‑driven active emitter layer [6] and record low-threshold solution lasers using the same CQWs employed as the optically‑pumped fluidic gain medium [7]. Given their current accelerating progress, these solution‑processed quantum well materials hold great promise to challenge their epitaxial thin‑film counterparts in semiconductor optoelectronics in the near future.

[1] B. Guzelturk et al., HVD, Nano Letters 19, 277 (2019)
[2] N. Taghipour et al., HVD, Nature Comm 11, 3305 (2020)
[3] Y. Altıntas et al., HVD, ACS Nano 13, 10662 (2019)
[4] O. Erdem et al., HVD, Nano Letters 19, 4297 (2019)
[5] O. Erdem et al., HVD, Nano Letters 20, 6459 (2020)
[6] B. Liu et al., HVD, Advanced Materials 32, 1905824 (2020)
[7] J. Maskoun et al., HVD, Advanced Materials (2021), in print, DOI:(10.1002/adma.202007131)


Spring 2021 speakers organized by Prof. David A.B. Miller

Date and Time: 
Monday, April 12, 2021 - 12:00pm

Optics & Electronics seminar: Creation of Time Reversed Optical Waves

Topic: 
[AP483] Creation of Time Reversed Optical Waves
Abstract / Description: 

In this talk, a new type of beam shaper will be discussed, capable of generating arbitrary vector spatiotemporal beams, where the user can define the amplitude, phase, and polarization independently for each point in space and time. This beam shaper was recently used to demonstrate time reversed optical waves. Such waves propagate through complex media, as if watching a traditional scattering process in reverse - starting as a complicated ‘pre-scattered’ wave, which then becomes a desired target field at the distal end of the complex media.


Spring 2021 speakers organized by Prof. David A.B. Miller

 

Date and Time: 
Monday, April 5, 2021 - 4:15pm

EST Seminar presents "Oxide Semiconductor Electronics: from BEOL thin film circuits to high-voltage UWBG"

Topic: 
Oxide Semiconductor Electronics: from BEOL thin film circuits to high-voltage UWBG
Abstract / Description: 

Oxide semiconductors' unique properties – a wide bandgap, reasonably high electron mobility, and ease of bulk and thin film preparation – make them prime material candidates for a variety of electronic devices. In this talk, I will describe my group's recent work on amorphous and crystalline oxide semiconductors for back end of line (BEOL) thin film circuitry and for high-voltage ultra-wide bandgap (UWBG) power devices, respectively. First, we exploit the thermodynamics of interfacialin situredox reactions with amorphous zinc tin oxide (a-ZTO) semiconductor to make MISFETs, MESFETs, Schottky diodes, and resistive memory devices that can be monolithically integrated with silicon CMOS. We demonstrate rectifiers that can harvest RFID wireless power and inverters that are compatible with low voltage silicon ICs. Furthermore, we develop novel, scalable atomic layer deposition processes to realize high-qualitya-ZTO semiconductor films, high-kAl2O3gate insulators and passivation layers, and Al:ZnO source/drain electrodes. Combining an innovative electro-hydro-dynamic jetting process with additive and subtractive selective area ALD, we realize thin film transistors with channel lengths below the ink-jet printing limit. I'll also describe our recent work on p-type oxide TFTs using Cu2O, and explain the key challenges in device architecture and materials physics that limit p-TFT performance. Finally, I'll explain how we've taken the learning from thin film oxides and used it to realize ultra-stable ohmic contacts and MOS capacitors to crystalline beta-phase gallium oxide, an ultra-wide bandgap semiconductor of interest for multi-kV power devices.

Date and Time: 
Tuesday, March 30, 2021 - 1:00pm

Mapping urban emissions with neighborhood resolution

Topic: 
Mapping urban emissions with neighborhood resolution
Abstract / Description: 

Most people on earth live in cities and they are responsible for the majority of greenhouse gas emissions. Cities are also where exposure to poor air quality is most frequent and most variable. Understanding and managing the path to net-zero greenhouse gas emissions, improved public health and lower public health inequities requires a view into the emissions and atmospheric chemistry of cities with the fine-grained detail that allows evaluation of specific processes and variations from one neighborhood to another. In this talk, I will describe the development of the Berkeley Environment, Air Quality and CO2 Network (BEACO2N http://beacon.berkeley.edu/about/), a dense network for mapping urban CO2, NOx, CO, O3 and aerosol. Each node of the network contains multiple optical and ChemFET sensors which accurately quantify the trace gases and are calibrated in the field using a variety of cross-referencing methods and comparisons with traceable standards. Integration of the BEACO2N maps with simple Gaussian plume models and sophisticated inversions employing high resolution weather models provide unique observational constraints on spatial and temporal patterns of CO2 and other emissions. Examples from the COVID shelter-in-place and testing models of fuel efficiency vs. vehicle speed in the SF Bay Area will be described along with prospects for further extension to other cities and other chemicals.



Organized by Stanford OSA/SPIE Student Chapter with SPRC and Ginzton Lab

Date and Time: 
Tuesday, March 9, 2021 - 1:30pm

Phonon Light Switches: Leveraging Vibrations to Create Actively Tunable IR Devices

Topic: 
Phonon Light Switches: Leveraging Vibrations to Create Actively Tunable IR Devices
Abstract / Description: 

Light possesses a wave nature. Phonons do too. Within the infrared portion of the spectrum, these waves have comparable energies leading to their interaction. Here, the interaction is leveraged to create tunable infrared filters that control transmission and reflection with no moving parts at the "push of a button" for applications in next generation imaging and on-chip spectroscopy. Practically, waferscale tunable infrared filters are first demonstrated by altering graphene's plasmonic dispersion using the dielectrics surrounding it resulting in gate-tunable variations (V < 10V) of reflectance by over 1 μm. These same filters are then integrated directly atop a broadband infrared detector in a proof-of-principle demonstration of a dynamically tunable pixel. Second, field induced changes in the phonons energies of lead zirconate titante (PZT) ferroelectric bilayers result in a tunable IR filter possessing high speed, latchable operation, and scalable fabrication. Taken together, the case studies highlight the utility of harnessing phonons to sculpt the spectral response of IR elements.

Date and Time: 
Thursday, February 25, 2021 - 1:30pm

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