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Category: computing – Page 468

High current gain transistor laser

Circa 2016 face_with_colon_three

A transistor laser (TL)1,2,3, having the structure of a transistor with multi-quantum wells (MQWs) near its base region, bridges the functionality gap between lasers and transistors. From a TL, an electrical signal can be outputted simultaneously with a light signal by inputting one electrical signal, making it suitable for future high performance optoelectronic integrated device applications4. As a new kind of semiconductor laser or transistor, TLs have aroused many interests since its invention. For example, in 2006, the paper2 reporting the first room temperature operation of TLs was voted as one of the five most important papers published by Applied Physics Letters in over 40 years5. Because of the transistor structure, many interesting characters have been demonstrated, including resonance free frequency response, large direct modulation band width6, voltage controlled mode of operation7, low relative intensity noise (RIN) close to the shot-noise limit8 and low 3rd order intermodulation distortion (IMD)9.

However, light emission for all the TLs reported up to now is produced at the expense of current gain. Taking npn TLs as an example, in the devices, electrons injected from the emitter into the base layer first recombine with holes radiatively before the left being collected by the collector4. The majority of the electrons are consumed by stimulated light emissions, leading to a current gain which is a lot lower than the gain of a traditional transistor. The common emitter (CE) mode current gain (collector current/base current) is lower than 5 for most, if not all, of the TLs studied, either experimentally1,2,3,6,7,8,9,10 or numerically11,12,13. The low current gain may limit the performance of systems that use TLs. For example, it is much easier to integrate monolithically a heterojunction bipolar transistor (HBT) and a TL than to integrate an HBT with a laser diode (LD) because of the dual functionality of TLs. For such applications, a large current gain of TL (used as HBT) is desired for the amplification of electrical signal to drive the laser.

In this work, we propose a novel TL structure which has an n-doped InP layer inserted in the emitter ridge, forming a flow aperture in the center of the emitter ridge for only holes. Here after, the TLs having the hole current aperture is designated as a-TLs. The properties of the a-TLs are systematically studied numerically. It is shown that while the light emission power of a-TLs is comparable with that of TLs without the aperture at the same base current, the CE current gain of a-TLs can be over 15 times larger.

Femtosecond Laser-Assisted Device Engineering: Toward Organic Field-Effect Transistor-Based High-Performance Gas Sensors

Organic electronic-based gas sensors hold great potential for portable healthcare-and environment-monitoring applications. It has recently been shown that introducing a porous structure into an organic semiconductor (OSC) film is an efficient way to improve the gas-sensing performance because it facilitates the interaction between the gaseous analyte and the active layer. Although several methods have been used to generate porous structures, the development of a robust approach that can facilely engineer the porous OSC film with a uniform pore pattern remains a challenge. Here, we demonstrate a robust approach to fabricate porous OSC films by using a femtosecond laser-processed porous dielectric layer template. With this laser-assisted strategy, various polymeric OSC layers with controllable pore size and well-defined pore patterns were achieved.

Clever Machines Learn How to Be Curious

“You can think of curiosity as a kind of reward which the agent generates internally on its own, so that it can go explore more about its world,” Agrawal said. This internally generated reward signal is known in cognitive psychology as “intrinsic motivation.” The feeling you may have vicariously experienced while reading the game-play description above — an urge to reveal more of whatever’s waiting just out of sight, or just beyond your reach, just to see what happens — that’s intrinsic motivation.

Humans also respond to extrinsic motivations, which originate in the environment. Examples of these include everything from the salary you receive at work to a demand delivered at gunpoint. Computer scientists apply a similar approach called reinforcement learning to train their algorithms: The software gets “points” when it performs a desired task, while penalties follow unwanted behavior.

Zuckerberg Wants Facebook to Build a Mind-Reading Machine

Zuckerberg likes to quote Steve Jobs’ description of computers as “bicycles for the mind.” I can imagine him thinking, “What’s wrong with helping us pedal a little faster?”

And while I reflexively gag at Zuckerberg’s thinking, that isn’t meant to discount its potential to do great things or to think that holding it off will be easy or necessarily desirable. But at a minimum, we should demand a pause to ask hard questions about such barrier-breaking technologies—each quietly in our own heads, I should hasten to add, and then later as a society.

We need to pump the brakes on Silicon Valley, at least temporarily. For, if the Zuckerberg reflection tour has revealed anything, it is that even as he wrestles with the harms Facebook has wrought, he is busy dreaming up new ones.

Interview with author/futurist Arthur C. Clarke, from an AT&T-MIT Conference, 1976

Arthur C. Clarke, science fiction author and futurist, crossed paths with the scientists of the Bell System on numerous occasions. In 1945, he concurrently, but independently, conceived of the first concept for a communications satellite at the same time as Bell Labs scientist, John Robinson Pierce too, was a science fiction writer. To avoid any conflict with his day job at Bell Labs, Pierce published his stories under the pseudonym J.J. Coupling.

In the early 1960s, Clarke visited Pierce at Bell Labs. During his visit, Clarke saw and heard the voice synthesis experiments going on at the labs by John L. Kelly and Max Mathews, including Mathews’ computer vocal version of “Bicycle Built for Two”. Clarke later incorporated this singing computer into the climactic scene in the screenplay for the movie 2001: A Space Odyssey, where the computer HAL9000 sings the same song. According to Bob Lucky, another Bell Labs scientist, on the same visit, Clarke also saw an early Picturephone, and incorporated that into 2001 as well.

In 1976, AT&T and MIT held a conference on futurism and technology, attended by scientists, theorists, academics and futurists. This interview with Clarke during this conference is remarkably prescient—especially about the evolution of communications systems for the next 30+ years.

The interview was conducted for an episode of a Bell System newsmagazine, but this is the raw interview footage.

Footage courtesy of AT&T archives and history center, warren, NJ.

IBM announces the world’s fastest quantum computer with 433 qubits

Beating the previous record of 127 qubits.

IBM unveiled its most powerful quantum computer to date at the IBM Summit 2022 on Wednesday. Named “Osprey,” the 433 qubit processor has the largest qubit count of any IBM processor and is triple the size of the company’s previously record-breaking 127-qubit Eagle processor.

“The new 433 qubit ‘Osprey’ processor brings us a step closer to the point where quantum computers will be used to tackle previously unsolvable problems,” said Dr. Darío Gil, senior vice president of IBM and Director of Research.

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