Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session L32: Physics That Changed the WorldInvited Undergraduate
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Sponsoring Units: FIAP Chair: Eli Yablonovitch, Univ of California - Berkeley Room: LACC 408A |
Wednesday, March 7, 2018 11:15AM - 11:51AM |
L32.00001: Oxide-Confined VCSELs Invited Speaker: Milton Feng The first electrically pumped VCSEL was demonstrated with metal cavities by Iga (1979); however, the threshold current was too high for laser applications. Distributed Bragg reflector (DBR) cavities proposed by Scifres and Burnham (1975) were then adopted for VCSEL to improve the optical cavity loss. Yet, it was not use until the important discovery of the native oxide of AlGaAs by Holonyak and Dallesasse (1990) to provide simultaneous current and optical confinement in semiconductor laser. Subsequently, the first oxide-confined VCSEL with “low threshold” was demonstrated by Deppe (1994). The reliable oxide-confined VCSELs have made into a practical use (2000) for short-range Gigabit energy-efficient optical links and high- performance computer due to the growing demand of faster access to large amounts of information and have revolutionized our daily life from data centers to 3D sensing applications. Today, the oxide-confined VCSELs have advanced error-free data transmission (BER $\leq$ 10 -12 ) up to 57 Gb/s at 25 $\circ$C and 50 Gb/s at 85 $\circ$C, and demonstrated the pre-leveled 16-QAM OFDM data at 104 Gbit/s under back-to- back transmission with the received EVM, SNR, and BER of 17.3\%, 15.2 dB, and 3.8x10$^{-3}$ , respectively. |
Wednesday, March 7, 2018 11:51AM - 12:27PM |
L32.00002: The Ubiquitous SQUID: History and Applications Invited Speaker: John Clarke One-half century after the discovery of superconductivity, superconducting electronics was born in a remarkably short time: 1961 -- 1964. The essential steps were the observation of the quantization of magnetic flux in a superconducting loop in units of the flux quantum, the prediction and subsequent observation of Josephson tunneling, and the invention of the SQUID---Superconducting QUantum Interference Device. The SQUID is an ultrasensitive detector of changes in magnetic flux that one can configure to measure many other physical properties, for example current, voltage, magnetic field gradient and high frequency electromagnetic fields. SQUIDs have a wide range of applications. A widely used commercial system enables the automated measurement of a great variety of magnetic and other physical properties, ranging from high temperature superconductors to blood samples. A SQUID-based geophysical survey technique has discovered the world's largest deposit of silver. In magnetoencephalography (MEG), helmets containing typically 300 SQUIDs detect signals emanating from the human brain. This technique is used in presurgical mapping of brain tumors and locating and presurgical mapping of epileptic centers, as well as in many research topics. Ultralow field magnetic resonance imaging (ULFMRI) at fields comparable with the Earth's field offers high tissue contrast, for example, in imaging tumors. The combination of MEG and ULFMRI using the same SQUID array offers intriguing new clinical possibilities. Astronomical telescopes containing many thousands of SQUIDs reading out superconducting transition edge sensors---with single photon sensitivity---have made major advances in studies of the cosmic microwave background. The Axion Dark Matter eXperiment (ADMX), enabled by a high frequency SQUID amplifier, is the world's most sensitive detector in the search for the axion, a candidate particle for the cold dark matter that is the dominant form of mass in the Universe. |
Wednesday, March 7, 2018 12:27PM - 1:03PM |
L32.00003: How Organic Light Emitting Diodes Revolutionized Displays (and maybe lighting) Invited Speaker: Stephen Forrest Organic light emitting devices, or OLEDs, are very thin (nanometer) devices made primarily with carbon-containing dye compounds. They are extremely attractive due to their simplicity, flexibility, light weight, and ultrahigh efficiency. Following their invention 30 years ago, OLEDs are now exploding into the marketplace, with prospects of ultimately replacing liquid crystal displays for mobile applications, virtual and augmented reality systems, as well as monitors and in televisions. Equally exciting is their imminent entry into the world of lighting. Yet before this revolutionary technology can completely dominate these applications, there are still challenges that must be overcome. These include improving their useful lifetime, improving light outcoupling by cost effective and simple methods, and finding very low cost and rapid methods to pattern very high resolution and low cost pixelated displays. This talk will focus on the evolution of this technology from a simple idea, to the challenges that are still to be faced in perfecting OLED technology. I will provide a perspective about the future of display and lighting technology based on advances yet to come. |
Wednesday, March 7, 2018 1:03PM - 1:39PM |
L32.00004: The Magnetic Hard Disk Drive - How Information is Stored in the Cloud Invited Speaker: Barry Stipe More than 70 percent of the world's information is stored in Hard Disk Drives (HDDs) and this is expected to continue to be true over the next decade despite competition from NAND flash memory. HDDs have the attributes of extremely high capacity at low cost (10x lower than NAND), high data rate (GHz), non-volatility, and reasonable access time (ms). The bit areal density growth of HDDs has often exceeded Moore's Law over the last 60 years resulting in more than a 200 million fold increase. A survey of the various technologies used in HDDs reveals a nanotechnology "playground" for physicists that exists today. For example: 6 nm diameter magnetic grains covered by 2 nm of diamond-like carbon and 1 nm of specially crafted lubricant, bit pitch of 10 nm, sub-25 nm wide magneto-resistive sensors with 1nm tunneling gap (the basic physics of which resulted in the 2007 Nobel Prize), airfoils than maintain a sub-2 nm gap between the head and disk while flying at up to 100 mph under a variety of environmental conditions, and mechanical actuators than can move the head to a desired position on the disk with sub-nanometer precision in only a few milliseconds. In this talk I will describe the physical limits of HDD technology and some ways the industry is pushing these limits further, such as hermetically-sealed helium HDDs and by using near-field energy sources such as plasmonic antennas and spin-torque oscillators. |
Wednesday, March 7, 2018 1:39PM - 2:15PM |
L32.00005: The Double-Heterostructure Concept in Lasers, LED's, and Solar Cells Invited Speaker: Eli Yablonovitch The double hetero-structure concept of Kroemer, Alferov & Kazarinov (1963), solved the basic problem in solid-state electronics, namely, how to keep carriers away from surfaces, which invariably have defects and dangling bonds. The facility of alloying different III-V semiconductors with different bandgaps, made it possible to safely confine both electrons and holes within their own potential wells. As a side-benefit, the small refractive index contrast provides optical wave-guiding for semiconductor lasers, which emerged as the dominant form of laser in the late 20 th century. Since electrons and holes are NOT lost at the surfaces, they become available for light emission in Light Emitting Diodes, or for direct extraction from Solar Cells. The double heterostructure is essential for all these devices. Indeed, it took many decades to recognize that the double heterostructure makes the best Solar Cells. |
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