Dr. Julia Majors - Master Oscillator Packaging for the Laser Interferometer Space Antenna (LISA)7/8/2021
Thursday, July 15, 10:00 - 11:00 am (PDT) 5 years after the earth-based gravitational wave observatory, LIGO, made its first detection of gravitational waves, work is already well underway in preparing for the next generation of gravitational wave observatories – in orbit around the sun. Working with NASA Goddard Space Flight Center, we are building what will be the “quietest” oscillator in (and above) the world to serve as the core light source for the interferometric system. The system is based on a non-planar ring oscillator (NPRO) model, which I will discuss along with some of the challenges that arise when developing laser systems for space applications. Student Lecture by KaiKai Liu on Milliwatt Threshold 0.5-Hz Linewidth Si3N4 Brillouin Laser5/25/2021
 Friday May 28 at 1:00 pm
 1:00 PM Friday, April 2nd
Thursday, February 25th, 10 am (PST) via Zoom Meeting ID: 854 2977 2482 Passcode: 230903 Both human vision and imaging systems have limited capability to separate spatial features, and this information can only be extracted from a limited range in depth. These limitations arise from diffraction, i.e., the finite dimensions of the imaging optics and the geometry of the sensor. In this talk, I will present novel photonic approaches to exceed the resolution limitations of geometric optics. I will show how those concepts can be adapted to micro endoscopy as well as to microscopy-related configurations, including ophthalmic devices for correcting visual deficiencies.
Friday, January 29th, 10 am (PST) Infrared detectors and imaging systems are becoming increasingly important in a diverse range of astronomic, military, and civilian applications. This field has gained significant attention while incorporating various materials and architectures into detector designs with a strong focus on applicability into clinical domains. Dr. Perera will discuss recent detector structures, and his latest work on disease detection. Biomedical applications of infrared include an exploration of an Affordable, Sensitive, Specific, User-friendly, Rapid, Equipment-free, and Deliverable (ASSURED) diagnostic regimen and testing its clinical feasibility for inflammatory bowel diseases (IBDs) and cancer screening. A study using Fourier transform infrared (FTIR) spectroscopy in attenuated total reflectance (ATR) sampling mode analyzed body fluids in order to identify reproducible, stable, and statistically significant differences in spectral signatures of the IR absorbance spectra between the control and disease samples. These results show that serum samples can be used to detect the biochemical changes induced by these diseases.
 1:00 PM Friday, January 22nd |
 Yahya Mohtashami Schuller group ECE Dept, UCSB |
In this talk, we show that we can increase the light extraction efficiency of, impart directionality upon, collimate, and focus the spontaneous emission from InGaN/GaN quantum wells, using phased-array metasurfaces. |
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Strong THz laser fields can explore non-linear, non-equilibrium phenomena in matter. The talk will focus on photons emitted by electron/hole re-collisions, and how the polarization of these photons carries information about the semiconductor. |
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Thursday, November 5th, 10 am (PST) via Zoom
Lithium niobate (LN), the workhorse of optoelectronics, is an excellent photonic material with large electro-optic coefficient, Kerr nonlinearity and piezoelectric response, and a wide optical transparency window. Recent advances in nanofabrication technology have allowed for the realization of ultra-low loss LN waveguides and are opening exciting opportunities for next-generation nonlinear photonic technologies with higher integration density and advanced functionalities. In this talk, I will review our recent developments of thin-film LN devices, including optical frequency combs, supercontinuum generation, optical frequency shifting, acousto-optic control. In addition, I will discuss the potential of LN platform for applications in nonlinear frequency conversion, frequency metrology, and microwave photonics.
Following the technical talk, I will give a short professional development talk, including networking and volunteering in the photonics community, and I will cover some career advice for graduate students.
Following the technical talk, I will give a short professional development talk, including networking and volunteering in the photonics community, and I will cover some career advice for graduate students.
Images from https://arxiv.org/pdf/2005.09621.pd
Monday, October 26th, 11 am (PDT) via Zoom
Fiber communications support a wide range of residential, mobile and enterprise services, within core, metro, and access optical networks. The 5G and beyond wireless is expected to have a dramatic impact on the fiber infrastructure, bringing new severe requirements such as higher data rates, ultra-high bandwidth, lower latency, accurate synchronization, network slicing, ultra-high reliability and massive connectivity for many devices. Adaptive, flexible and efficient optical resource management, as well as agile bit-rates are the key technologies to exploit the whole bandwidth of single-wavelength, single-core and single-mode fibers. All-optical orthogonal frequency division multiplexing (OFDM) and Nyquist-optical time division multiplexing (N-OTDM) are the two most suitable approaches to efficiently generate Tb/s superchannels, by optically multiplexing subcarriers or by time interleaving short sinc-shaped pulses. The superchannels are generated in the optical domain, in a power-efficient way, also overcoming the restrictions related to the bandwidth of modulators and digital signal processing devices. A planar arrayed waveguide grating (AWG) can be designed to implement the conventional or fractional Fourier transform and efficiently generate OFDM and Fr-OFDM superchannels, that are less sensitive to nonlinear distortion and chromatic dispersion effects. The ultimate efficiency in physical resource exploitation can be achieved only in a truly flexible system, where it is possible to switch from OFDM to N-OTDM and vice versa, through intermediate fractional grids. Starting from experimental results of a novel approach for hybrid time-frequency multiplexing, this talk will focus on additional multiplexing domains, such as polarization, space, wavelength and code. Suitable AWG configurations can be designed for simultaneous frequency and polarization or mode and frequency multiplexing, as well as for generating optical codes in asynchronous code division multiple access (CDMA) and optical packet switching systems.
Image from https://doi-org/0.1364/OE.25.00349
Gabriella Cincotti is a Full Professor at the Engineering Department, University Roma Tre, Rome Italy; she leads the Photonics Research Group and is in charge of the courses of Photonics and Biophotonics. She is a Fellow of the Optical Society of America (OSA), she was an elected member of the Board of Governors of the IEEE Photonics Society (2017-2019) and currently she is serving in the IEEE Photonics Publications Council. She was a technical program committee (TPC) member of the European Conference on Optical Communications (ECOC) (2010-2012), also serving as Chair of the Access Subcommittee. She was also TPC member of the Optical Fiber Communication Conference (OFC) (2016-2018). She served as an Associate Editor of Optics Letters (2008-2014) and she serves as Deputy Editor of Optica since 2017. She has authored or co-authored over 300 research papers in leading journals and conferences. Her main research interests are in the field of planar lightwave circuits, photonic devices and subsystems for high-speed optical signal processing. Recently, she moved part of her research interests toward super resolution imaging and point of care testing for biomedical and microbiological applications.
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Friday, October 23rd, 11 am (PDT) via Zoom
Dr. Christian Reimer is a physicist and entrepreneur working in the fields of nonlinear optics, integrated photonics and quantum optics. He received graduate degrees from the Karlsruhe Institute of Technology in Germany, Heriot-Watt University in Scotland, and the National Institute of Scientific Research in Canada. He then worked as a postdoctoral fellow at Harvard University, before becoming Co-Founder and Head of Product of HyperLight Corporation. HyperLight, a Venture-Capital funded start-up out of Harvard University, is specialized on integrated lithium niobate technologies for ultra-high performance photonic solutions.
In the scientific part of his talk, Christian will introduce the field of integrated photonics based on thin-film lithium niobate, with a focus on electro-optic applications, as well as recent progress on transforming the field from chip-based proof-of-concept realizations for wafer-scale production. In the professional development section, he will then share his experience transitioning from academia to a start-up company. He will talk about differences and similarities in the work environment, what to expect in terms of tasks and responsibilities, and explain how salaries at start-ups can include combinations of equity and incentives.
In the scientific part of his talk, Christian will introduce the field of integrated photonics based on thin-film lithium niobate, with a focus on electro-optic applications, as well as recent progress on transforming the field from chip-based proof-of-concept realizations for wafer-scale production. In the professional development section, he will then share his experience transitioning from academia to a start-up company. He will talk about differences and similarities in the work environment, what to expect in terms of tasks and responsibilities, and explain how salaries at start-ups can include combinations of equity and incentives.
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Images from hyperlightcorp.com
 | On Henley Hall Prof. John Bowers |  |
Friday, Oct. 16th, 4 pm (PDT) via Zoom
Henley Hall will hold state-of-the-art research facilities for developing energy-efficient technologies. Prof. Bowers will present the research capabilities and expected research ramp-up timeline for the new building.
Thursday, Oct. 8, 1-2 pm (PDT) via Zoom
Meeting ID: 819 4601 6935, Password: 597044
Meeting ID: 819 4601 6935, Password: 597044
Entanglement and encoding in discrete frequency bins – a quantum analogue of wavelength-division multiplexing – represents a relatively new degree of freedom for quantum information with photons. Potential advantages include generation of high-dimensional units of quantum information called qudits, which can carry multiple qubits per photon; robust transmission over fiber; frequency parallelism and routing; and compatibility with on-chip implementations, as well as hyperentanglement with other photonic degrees of freedom. In this talk I first give an overview of manipulating and measuring quantum states encoded and entangled in the photonic frequency degree of freedom. I will then discuss our recent experiments that focus on high-dimensional entanglement and mixing of multiple frequency bins in a single operation, going well beyond nearest neighbor “interactions.
Tuesday, September 8th, 10 am (PDT) via Zoom
Meeting ID: 978 3569 2970 Passcode: 468555
Meeting ID: 978 3569 2970 Passcode: 468555
Infectious diseases and water are some of the greatest, most urgent challenges of the 21st century. III-nitride ultraviolet (UV) light sources, including light emitting diodes (LEDs) and lasers, are the only alternative technology to replace conventional power-hungry, hazardous mercury lamps for disinfection and water purification. Recent studies showed that AlGaN-based UV-C LEDs can readily shred genetic material of viruses and bacterial and achieve 99.9% sterilization of SARS-COV-2. In this talk, I will present the recent advances of AlGaN and BN nanostructures and heterostructures and their applications in UV optoelectronics, including the first demonstration of mid and deep UV laser diodes and tunnel junction UV-C LEDs with significantly improved performance. The recent development of far-UV-C LEDs, in the wavelength range of 207-222 nm, will also be presented, which has shown to be faster and far more effective than traditional UV-C light (~265 nm) in preventing the transmission of microbial diseases, while causing virtually no harm to mammalian skin or eye.
  Schematic for the cross-section of a TACIT mixer (right); Optical image of a TACIT mixer with an SEM image of the active region (top) | Terahertz Heterodyne Detector Based on the Intersubband Transition of a GaAs/AlGaAs Quantum WellWe are developing a new type of THz heterodyne detector based on a high-mobility 2-dimensional electron gas (2DEG) in a GaAs/AlGaAs quantum well for spectroscopic applications in deep-space and planetary missions. Named as Tunable Antenna-Coupled Intersubband Terahertz (TACIT) mixer, the detector is a four-terminal hot-electron bolometer (HEB) mixer that uses intersubband transition for efficient absorption of THz radiation in a 2DEG. The dual gate structure of TACIT mixers, necessary for the precise control of the intersubband absorption characteristics, enables a high coupling efficiency at THz frequencies and tunability in the detection frequency, but also poses challenges in the fabrication, modelling, and operation of the device. In this talk, I will discuss our recent experimental results with a prototype TACIT mixer that we have fabricated with a flip-chip process that enables dual-side processing of a sub-micron thick quantum well membrane.  |
Wednesday, May 20, 2020, 1 p.m.
Sustainability applied to networking is about treating professional support and assistance like a resource, and creating more of it than you take. Dr. Willis will discuss principles and applications of sustainable professional networking, and how to use it to generate success through mutually beneficial professional relationships. She will also discuss her own career path, citing examples that illustrate the value of sustainable networking.
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Engineering robust solid-state quantum systems is amongst the most pressing challenges to realize scalable quantum photonic circuitry. While several 3D systems (such as diamond or silicon carbide) have been thoroughly studied, solid state emitters in two dimensional (2D) materials are still in their infancy. In this presentation I will discuss single defects in an emerging 2D material – hexagonal boron nitride (hBN), that is promising as qubits for quantum photonic applications. In particular, I will focus on ways to engineer these defects deterministically using either chemical vapour deposition growth or ion implantation, and show results on strain tuning of these ultra-bright quantum emitters. I will then highlight promising avenues to integrate the single defects with photonic cavities, as a first step towards integrated quantum photonics with 2D materials. I will summarize by outlining challenges and promising directions in the field of quantum emitters and nanophotonics with 2D materials.
Watch the recorded lecture from April 23, 2020:
12:00 - 1:00 PM Friday, February 21st in Engineering II 3519
 Haojun Zhang DenBaars group ECE Dept, UCSB | Distributed feedback (DFB) laser diodes on GaNI will first talk about the recent work on blue III-Nitride LDs grown on semipolar GaN substrates. Then I will analyze the main hurdles that impeded its performance, focusing on improving the operating voltage, lifetime and mode quality, and discuss the efforts and approaches to further improve the efficiency and high-speed performance. |
 | Terahertz Heterodyne Detector Based on the Intersubband Transition of a GaAs/AlGaAs Quantum Well We are developing a new type of THz heterodyne detector based on a high-mobility 2DEG in a GaAs/AlGaAs quantum well for spectroscopic applications in deep-space and planetary missions. Named as Tunable Antenna-Coupled Intersubband Terahertz (TACIT) mixer, the detector uses intersubband transition for efficient absorption of THz radiation in a 2DEG. The dual gate structure of TACIT mixers, necessary for the precise control of the intersubband absorption characteristics, enables a high coupling efficiency at THz frequencies and tunability in the detection frequency, but also poses challenges in the fabrication, modelling, and operation of the device. In this talk, I will discuss our recent experimental results with a prototype TACIT mixer that we have fabricated with a flip-chip process that enables dual-side processing of a sub-micron thick quantum well membrane. |
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