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Data are presented to quantify the effect of the conduction band energy barrier (ΔEC,B) in the base region of the transistor laser on the minority carrier transport dynamics, recombination lifetime in the base region, and frequency response of the device. A greater ΔEC,B results in lower transistor current gain (β) and higher optical output power, indicating increased carrier confinement and recombination in the base. For a device with ΔEC,B = 41 meV, the measured bias-dependent optical frequency response and subsequent data fitting yield a short recombination lifetime of 30 ps in the base and a small resonance peak of 1.5 dB. A device with ΔEC,B = 82 meV exhibits a longer recombination lifetime of 70 ps and a larger resonance peak of 4dB. [ABSTRACT FROM AUTHOR]

Several electromagnetic signal types were observed prior to and immediately after 30 October 2007 (Local Time) M5.4 earthquake at Alum Rock, Ca with an epicenter ∼15 km NE of San Jose Ca. The area where this event occurred had been monitored since November 2005 by a QuakeFinder magnetometer site, unit 609, 2 km from the epicenter. This instrument is one of 53 stations of the QuakeFinder (QF) California Magnetometer Network- CalMagNet. This station included an ultra low frequency (ULF) 3-axis induction magnetometer, a simple air conductivity sensor to measure relative airborne ion concentrations, and a geophone to identify the arrival of the P-wave from an earthquake. Similar in frequency content to the increased ULF activity reported two weeks prior to the Loma Prieta M7.0 quake in 1989 (Fraser-Smith, 1990, 1991), the QF station detected activity in the 0.01-12 Hz bands, but it consisted of an increasing number of short duration (1 to 30 s duration) pulsations. The pulsations peaked around 13 days prior to the event. The amplitudes of the pulses were strong, (3-20 nT), compared to the average ambient noise at the site, (10-250 pT), which included a component arising from the Bay Area Rapid Transit (BART) operations. The QF station also detected different pulse shapes, e.g. negative or positive only polarity, with some pulses including a combination of positive and negative. Typical pulse counts over the previous year ranged from 0-15 per day, while the count rose to 176 (east-west channel) on 17 October, 13 days prior to the quake. The air conductivity sensor saturated for over 14 h during the night and morning prior to the quake, which occurred at 20:29 LT. Anomalous IR signatures were also observed in the general area, within 50 km of the epicenter, during the 2 weeks prior to the quake. These three simultaneous EM phenomena were compared with data collected over a 1-2-year period at the site. The data was also compared against accounts of air ionization reported to be associated with radon emission from the ground (Ouzounov, 2007), and a series of laboratory rock stressing experiments (Freund, 2006, 2007a, b, c) to determine if field data was consistent either of these accounts. We could not find a data set with preearthquake radon measurements taken near the Alum Rock epicenter to compare against our field data. However, based on the Alum Rock data set example and another data set at Parkfield, the field tests are at least consistent with the lab experiments showing currents, magnetic field disturbances, air conductivity changes, and IR signatures. This is encouraging, but more instrumented earthquake examples are needed to prove a repeating pattern for these types of pre-earthquake EM signatures. [ABSTRACT FROM AUTHOR]

A single quantum well transistor laser (cavity length L = 300 μm) has been designed and fabricated that operates with threshold ITH = 18 mA at 15 °C and 14 mA at 0 °C. Due to the 'fast' base recombination lifetime (τB < 29 ps), the transistor laser demonstrates reduced photon-carrier resonance amplitude (<4 dB) over its entire bias range and a modulation bandwidth f-3dB = 9.8 GHz at 15 °C for IB/ITH = 3.3 and 17 GHz at 0 °C for IB/ITH = 6.4. Under the same bias conditions, simultaneous electrical and optical 'open-eye' signal operations are demonstrated at 20 and 40 Gb/s data rate modulation. [ABSTRACT FROM AUTHOR]

Data and a phenomenological model for quantum-well (QW) transistor laser operation are presented showing, via the three-port input-output (electrical and optical) characteristics, the strong QW to collector coupling and the influence of bandfilling (QW states, Δhν recombination radiation, sensitivity of Eλ0→Eλ1,λ0→λ1,λ0>λ1) on base-to-collector photon-assisted tunneling and laser operation. Transistor (electrical) and laser (optical) operation are locked and 'slide' up and down as a function of base current (IB), collector-base voltage (VBC or VCE), and the influence of QW bandfilling (with increased sensitivity at Eλ0→Eλ1) on photon-assisted base-collector tunneling. [ABSTRACT FROM AUTHOR]

A quantum well transistor laser with a base cavity length L = 300 μm has been designed, fabricated, and operated at threshold ITH = 25 mA (0 °C). As a consequence of the inherent advantage of the picosecond base recombination lifetime, the transistor laser is able to achieve nearly a quantum shot-noise limited laser relative intensity noise (RIN) with a peak amplitude of -151 dB/Hz at frequency 8.6 GHz. Compared with a diode laser (a charge storage device) at the same output power, the transistor laser (a charge flow device) has a better than 28 dB (number dependent on the laser device design) peak RIN advantage. [ABSTRACT FROM AUTHOR]