Lance A. Glasser

Picosecond pulse generation with a cw GaAlAs laser diode

We report the generation of 20‐ps optical pulses at microwave repetition rate from a GaAlAs double‐heterostructure diode operating cw at room temperature. The diode is operated in an external optical resonator and is actively modulated at 3 GHz. The pulses are measured by autocorrelation using SHG in LiIO3. They are the shortest pulses ever reported for a cw laser diode.

Delay and Power Optimization in VLSI Circuits

The problem of optimally sizing the transistors in a digital MOS VLSI circuit is examined. Macro-models are developed and new theorems on the optimal sizing of the transistors in a critical path are presented. The results of a design automation procedure to perform the optimization is discussed.

The Analog Behavior of Digital Integrated Circuits

The analog behavior of digital VLSI circuits is investigated. A theory based on nonlinear Thevenin equivalent circuits and RC ladder networks is developed. We obtain closed from expressions for the upper and lower bounds on propagation delay through a string of inverters. We generalize this to multiple-input, multiple-output gates and show that the problem of estimating signal propagation delays in VLSI circuits may be reduced to the problem of summing the step responses of a set of linear RC networks. As well as having implications for a computationally efficient timing simulator, the theory begins the formalization of the fundamental properties of digital integrated circuits.

Frequency limitations in circuits composed of linear devices

The author investigates limitations on the frequency response of networks constructed out of components specified by their small signal models. Tellegens theorem is used to find tight bounds on the maximum frequency of oscillation. The problem is reduced to deciding whether zero is in the numerical range of a complex non-Hermitian matrix. A decision method is presented, and transistor and negative resistance amplifier examples are developed. >

Continuous models for communication density constraints on multiprocessor performance

Fundamental limits on the communication capabilities of massively parallel multiprocessors are investigated. It is shown that in the limit of machines of infinite extent in which the number of processors per unit volume is constant and in which the communication bandwidth from each processor to its neighbors depends only on their separation distance, interprocessor communication must fall off faster than the fourth power of distance. For machines of finite size, communication energy density is used as a metric to compare various machine sizes and packaging densities. For instance, for machines with spherical symmetry and uniform communication requirements, the peak density depends on the number of processors to the 4/3 power and the number of processors per unit volume to the 2/3 power. >