D. Murrell

Bio: D. Murrell is an academic researcher from Air Force Research Laboratory. The author has contributed to research in topics: Quantum dot laser & Quantum well. The author has an hindex of 8, co-authored 40 publications receiving 149 citations. Previous affiliations of D. Murrell include University of New Mexico & Virginia Tech.

Analytical Modeling of the Temperature Performance of Monolithic Passively Mode-Locked Quantum Dot Lasers

Abstract: This paper examines and models the effect of temperature on the mode-locking capability of monolithic two-section InAs/GaAs quantum dot passively mode-locked lasers. A set of equations based on an analytic net-gain modulation phasor approach is used to model the observed mode-locking stability of these devices over temperature. The equations used rely solely on static material parameters, measured on the actual device itself, namely, the modal gain and loss characteristics, and govern the limit describing the onset of mode-locking. Employment of the measured gain and loss characteristics of the gain material over temperature, wavelength and current injection in the model provides a physical insight as to why the mode-locking shuts down at elevated temperatures. Moreover, the model enables a temperature-dependent prediction of the range of cavity geometries (absorber to gain length ratios) where mode-locking can be maintained. Excellent agreement between the measured and the modeled mode-locking stability over a wide temperature range is achieved for an 8-stack InAs/GaAs quantum dot mode-locked laser. This is an attractive tool to guide the design of monolithic passively mode-locked lasers for applications requiring broad temperature operation.

A passively mode-locked quantum-dot laser operating over a broad temperature range

Abstract: Broad temperature operation is demonstrated from 20 to 110 °C in a 5-GHz monolithic two-section InAs/GaAs quantum dot passively mode-locked laser with an optimized absorber to gain section length ratio of 0.11. Stable pulses of less than 19 ps full-width-half-maximum are measured over this entire temperature range. For a grounded absorber, mode-locking from the ground-state occurred over the range 20–92 °C, dual-mode lasing involving both ground and excited states from 93 to 98 °C and exclusively from the excited-state from 99 to 110 °C. The observed broad temperature operation agrees with theoretical analysis based on measured gain and absorption data that predicted improved temperature performance for a short absorber. The results are promising for the development of temperature-insensitive pulsed sources for uncooled applications such as data multiplexing and optical clocking.

Terrestrial link rain attenuation measurements at 84 GHz

Abstract: We present 560 m terrestrial link rain attenuation measurements at 84 GHz in Albuquerque, New Mexico. Both empirical and theoretical rain attenuation models such as ITU-R, Mie and Rayleigh will be examined with the measurements. This study will contribute to the understanding of signal propagation phenomena and the utilization of the W/V-bands for satellite communication.

Estimating Rain Attenuation at 72 and 84 GHz From Raindrop Size Distribution Measurements in Albuquerque, NM, USA

Abstract: The raindrop size distribution (DSD) is essential information for understanding rain attenuation effects at millimeter wavelengths. The DSD was measured in Albuquerque, NM, USA, as a part of the W/V-band Terrestrial Link Experiment. An optical disdrometer from Thies Clima was used to measure both size and velocity of rain droplets. The measured DSD consistently showed a unique property of two log-linear distributions regionally separable by drop size under variable rain rates. The functional fit that best represents our measured data with rain rates under 40 mm/h is presented. Based on the DSD, rain specific attenuation is estimated at 72 and 84 GHz with Mie scattering theory. These estimated rain attenuations can be used and validated for rain attenuation analysis of the millimeter wave propagation experiments under similar climate conditions. This letter will guide millimeter wave communication system designers to estimate the rain attenuation based on their own DSD measurements.

W/V-band terrestrial link experiment, an overview

Abstract: The Air Force Research Laboratory in partnership with NASA Glenn Research Center and the University of New Mexico have initiated the W/V-band Terrestrial Link Experiment (WTLE) to conduct propagation analysis at W/V-band frequencies. An overview is provided of the system and ancillary equipment to facilitate the propagation experiment.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Subpicosecond laser timing stabilization

Abstract: Mode-locked laser systems generate extremely short optical pulses and are widely used for measurements of ultrafast phenomena. In these experiments, the effect of laser pulse timing fluctuations (jitter) is suppressed by exciting the system under test by the pulsed laser and probing with a delayed portion of the same optical pulse. If the experiment cannot be laser-excited or must be excited and probed by different lasers, timing jitter degrades the time resolution and introduces noise.

High speed 850 nm VCSEL with 30 GHz modulation bandwidth

Abstract: GaAs-based 850 nm VCSELs are the standard light source in short-reach high-speed optical interconnects in datacenters and supercomputers. The last few years have seen an impressive increase in VCSEL speed, reaching modulation bandwidths of 28 GHz and single-channel data rates of 57 Gbit/s (non-equalized) and 71 Gbit/s (equalized) under direct NRZ modulation [1-3]. Future optical interconnects will require even faster VCSELs capable of higher-speed transmission at lower energy dissipation. Here we present the results from our new generation of high-speed 850 nm VCSELs, a further development of our previous VCSEL design [1-3].

Real Measurement Study for Rain Rate and Rain Attenuation Conducted Over 26 GHz Microwave 5G Link System in Malaysia

Abstract: In this paper, real measurements were conducted to investigate the impact of rain on the propagation of millimeter waves at 26 GHz. The measurements were accomplished using a microwave fifth generation radio link system with 1.3 km path length implemented at Universiti Teknologi Malaysia Johor Bahru, Malaysia. The implemented system consisted of Ericsson CN500 mini E-link, radio unit, rain gauge, and data logger. The measurements were attained and logged daily for a continuous year, with 1-min time intervals. Next, the MATLAB software was used to process and analyze the annual rain rate and rain attenuation, including for the worst month. From the analyzed results, it was found that at 0.01% percentage of time, the rain rate was 120 mm/hr; while the specific rain attenuation was 26.2 dB/km and the total rain attenuation over 1.3 km was 34 dB. In addition, the statistics acquired from the measurements for the worst month were lower than what was predicted by the international telecommunication union (ITU) model; around 51% and 34% for the rain rate and rain attenuation, respectively. The average percentage of error calculated between the measurements and predicted results for the rain rate and rain attenuation were 143% and 159%, respectively. Thus, it can be concluded that the statistics for the worst month in Malaysia is lower than what was predicted by the ITU model.

A rapid-scanning autocorrelation scheme for continuous monitoring of picosecond laser pulses

Abstract: We describe a scheme for rapidly introducing a periodic linear time delay to a train of picosecond laser pulses. By incorporating this scheme in one arm of the Michelson interferometer of a conventional autocorrelator, the second order intensity autocorrelation function of a cw train of picosecond pulses is continuously displayed on an oscilloscope.