Dennis S. Greywall

Crystalline silicon tilting mirrors for optical cross-connect switches

This paper discusses a two-piece approach for fabricating two-dimensional (2-D) arrays of tilting MEMS mirrors with application in very-large optical cross-connect switches. In the new process, a two-sided etching of silicon-on-insulator (SOI) wafers is used to create crystalline mirrors on a first wafer that is later aligned and bonded to a separate wafer containing the activation electrodes, traces, and bond pads. The approach allows a very close spacing of mirror elements and a very simple design for the mechanical structures, and also greatly simplifies wire routing.

Specific heat of bcc He 3

The specific heat of bcc

3He-melting-curve thermometry

^{3}mathrm{He}

Monolithic fringe-field-activated crystalline silicon tilting-mirror devices

has been measured at five molar volumes between 21.5 and 24.5

High precision 3He‐vapor‐pressure gauge for use to 0.3 K

{mathrm{cm}}^{3}

Fast cerium magnesium nitrate (CMN) thermometer for the low millikelvin temperature range

and for temperatures between 50 mK and the melting curve. The data below 0.5 K show no evidence of the large anomalous contribution to the specific heat which has been observed in all previous measurements, indicating that this anomaly is not due to an intrinsic property of this quantum solid. Values of the nuclear exchange energy derived from the low-temperature data are in good agreement with values determined by others from various types of measurements. The specific-heat data above approximately 0.5 K are in agreement with previous results and show the large contribution which is generally attributed to thermally activated vacancies. Because of the absence in the present work of the low-temperature anomaly, however, the temperature dependence of the vacancy contribution could be determined more accurately than was previously possible. The measured vacancy contribution shows significant deviations from the expected behavior.

Anomalies in the heat capacity of 2D fluid and solid 3He at low mK temperatures (fifteenth Fritz London memorial award lecture)

Precise measurements of theP-T relation along the melting curve of3He have been made for 8≲T≲330 mK. The results are in excellent agreement with other precise data for temperatures near the extremes of this range. A best-fit relation is provided which describes the melting curve to within ±1 mbar between the superfluid A transition and the pressure minimum. Detailed descriptions of the melting curve and magnetic thermometers used for the calibration are also given.

A fast CMN thermometer with a wide temperature range

A new approach is presented for fabricating monolithic crystalline silicon tilting-mirror microoptoelectromechanical systems (MOEMS) devices. The activation electrodes, etched from a thick silicon layer deposited over insulating oxide onto the top surface of a silicon-on-insulator (SOI) wafer, are displaced from the mirrors and interact with these tilting elements via electrostatic fringing fields. In contrast to the more usual parallel-plate activation, the rotation angle saturates at high voltages. This paper discusses concept, design, and processing, and also compares modeling and measured performance of a specific 9/spl deg/ tilt range device array.

Second-Sound Velocity, Gravitational Effects, Relaxation Times, and Superfluid Density Near the Tricritical Point in 3He-4He Mixtures

The design and performance of a compact, high precision, capacitive, vapor‐pressure gauge is described. The gauge was constructed using a thin electrodeposited copper diaphragm.

Nuclear spin heat capacity of 3He adsorbed on graphite

The construction details and the performance of a CMN susceptibility thermometer of novel design are discussed. The device features a response time of 30 s at 3 mK and less than 2 s at 10 mK. When operated as part of a simple self‐inductance bridge circuit at a drive level sufficient to obtain a resolution of one part in 104, the power dissipation is only 10 pW and the self‐heating is negligibly small. This new thermometer makes possible a new class of experiments in the low mK regime.