Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session K5: Microelectronics for Mid-Infrared through Terahertz |
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Sponsoring Units: FIAP Chair: Mark Lee, Sandia National Laboratories Room: Baltimore Convention Center 309 |
Tuesday, March 14, 2006 2:30PM - 3:06PM |
K5.00001: Multi-Wavelength and Nonlinear Quantum Cascade Lasers Invited Speaker: Quantum Cascade (QC) lasers are a rapidly evolving mid-infrared technology well suited for chemical sensing applications. For sensing of trace gas mixtures, large molecules, or liquids, probing at a single wavelength is often not sufficient, but the analyte must be sampled at various wavelengths. Here, we will discuss various means of providing multi-wavelength emission from QC lasers. Four different routes are currently being investigated. First, the active waveguide core of a QC laser can be subdivided into substacks of different active regions, hence allowing for multi-wavelength emission. We will discuss the design optimization procedures employed to develop a multi-wavelength laser module with several wavelengths covering the 7 -- 13 $\mu $m wavelength range. Second, QC lasers can be designed to emit different wavelength light when operated at different (positive or negative) bias settings. We have recently developed such a QC laser capable of emitting at $\sim $ 8 and $\sim $ 11 $\mu $m. Third, nonlinear QC lasers that in addition to QC laser active regions also include nonlinear mixing regions emit light not only at the fundamental frequency, but also at nonlinear frequencies. Second harmonic generation with up to 2 mW of nonlinear light has recently been demonstrated. Finally, QC lasers with very broad gain spectra can in principle be used to tune over significant wavelength ranges using an external cavity. A key component for such tunability is a low reflectance laser facet to suppress laser action based on feedback from the laser facets. We will show approaches to facet reflection reduction through sub-wavelength facet patterning. This work is supported through collaboration with Pacific Northwest National Labs / Battelle by DARPA L-PAS, the DOE, and the NSF ECS-0400615. This work is being conducted in collaboration with A. Dirisu, S.S. Howard, Z. Liu, O. Malis, G. Shu, D.L. Sivco, and F. Toor. [Preview Abstract] |
Tuesday, March 14, 2006 3:06PM - 3:42PM |
K5.00002: Ultrasensitive Quantum-Limited Far-Infrared Detectors Invited Speaker: Superconducting tunnel junction (STJ) direct detectors have been developed for submillimeter astronomy. Photons with energy greater than the superconducting gap of the aluminum absorber break Cooper pairs and generate excess quasiparticles, inducing an extra tunneling current through the STJ. To monitor the response of the STJ with large readout bandwidth and maximal sensitivity, we use a novel readout which uses radio frequency (RF) reflectometry, like the readout invented for the RF-SET.(1) For calibration of the detector, we have developed a in-situ, on-chip, hot-cold submillimeter photon source, a gold microbridge. When it is voltage biased, emitted noise from the microbridge couples via a microstripline to the detector. This provides a calibrated photon source with near unity coupling, very fast ($<$ ns) chopping, and calculable power output. Cooling is by outdiffusion of hot electrons (2). We present recent detection results in the range 100 – 140 GHz. These demonstrate the expected good responsivity, high sensitivity, and fast response times. The readout approach is easily used with a frequency multiplexed readout, allowing economy of cold electronics. Ultimate sensitivity may require the use of an RF-SET as the readout, for NEP below NEP below 10$^{-20}$ W/(Hz)$^{1/2}$. -Research with J.D. Teufel, M. Shen, L. Frunzio, C. M. Wilson, T.J. Stevenson and R.J. Schoelkopf. \newline \newline -(1). R.J. Schoelkopf et al., Science v. 280 p.1238 (1998). \newline -(2). D.E. Prober, Appl. Phys. Lett. v. 62 p.2119 (1993). \newline -(3). D.E. Prober, LTD11 Conf. (2005), invited, to appear. [Preview Abstract] |
Tuesday, March 14, 2006 3:42PM - 4:18PM |
K5.00003: Electronically Tunable Terahertz Detection Using Plasmons Invited Speaker: Spectroscopy in the millimeter-wave to THz frequencies has received a great deal of recent interest for security applications and chemical identification. This talk will address detectors that utilize plasmons in high-mobility GaAs/AlGaAs quantum well structures to provide a frequency tunable detector response. While there are various competing detection schemes based on plasmons, here we will cover the grating-gate detector along with a variant having enhanced performance called the split-grating gate detector. The basic device consists of source and drain electrical contacts along with a single grating-gate that spatially modulates both the incident radiation and the carrier density in a quantum well channel. The plasmon frequency underneath the gate lines is tuned by changing the carrier density with an applied gate bias. When this plasmon frequency is in resonance with the incident radiation field, a resonant peak is found in the photoresponse. The split-gate devices work in a similar fashion, except with additional gates in the device used to build larger non-linearities into the system. By doing so, we have observed a several order of magnitude increase in responsivity. Currently, the grating-gate style of detector covers a frequency range from 150GHz to 800GHz at temperatures ranging from 4K to 80K, however, the ultimate frequency and temperature limits of these detectors are not currently known. The ability to tune the detector response by simply changing a gate voltage leads to an attractive ‘spectrometer-on-a-chip’ where no moving parts would be needed for THz spectral analysis. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Tuesday, March 14, 2006 4:18PM - 4:54PM |
K5.00004: Designing the emission of THz Quantum Cascade Lasers with surface plasmon photonic structures. Invited Speaker: The development of quantum cascade lasers operating at terahertz frequencies is proceeding at a very rapid pace. For their successful practical implementation, specific requirements have now to be addressed, particularly concerning the properties of the emitted radiation. Single-mode THz lasers with distributed feedback resonators have been achieved and a new technique involving surface plasmon gratings has been demonstrated to improve performances. The latter also offers the possibility of constructing distributed Bragg gratings as a replacement for high-reflection coatings or to implement vertical emitting devices. Solutions allowing broad tuneability are examined, either relying on external cavity set-ups or more unconventional external electrical control. [Preview Abstract] |
Tuesday, March 14, 2006 4:54PM - 5:30PM |
K5.00005: Mid-Infrared Through Terahertz Cameras Based on Superconducting Technology Invited Speaker: A new generation of cameras is set to make a tremendous impact on the field of mid-infrared to Terahertz astronomy. Take for example, the SCUBA-II instrument to be deployed on the James Clerk Maxwell Telescope at Mauna Kea , Hawaii. The existing SCUBA instrument has two arrays of 37 and 91 pixels, observing at 850 $\mu$m and 450 $\mu$m. The SCUBA-II arrays have 5120 pixels each and the noise contribution from the detectors is less than the sky load noise. As a result, large regions of the sky can be mapped about 1000 times faster. Superconducting thin film devices play multiple critical roles in these large format arrays. We will discuss the superconducting detector, multiplexing, and amplifier technology developed at NIST Boulder by the Quantum Sensors Project and the integration all of these technologies into a science grade imaging array. We will also survey the role that superconducting detectors, multiplexers, and thin film refrigerators will play in future instruments at both longer and shorter wavelengths. [Preview Abstract] |
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