D. L. White

Bio: D. L. White is an academic researcher from Bell Labs. The author has contributed to research in topics: Drift velocity & Amplifier. The author has an hindex of 2, co-authored 2 publications receiving 586 citations.

Amplification of Ultrasonic Waves in Piezoelectric Semiconductors

Abstract: An ultrasonic wave traveling in certain directions in a piezoelectric semiconductor such as cadmium sulfide can be amplified or attenuated by application of a dc electric field. The direct current flowing through the medium in the presence of an ultrasonic wave creates a traveling ac field which interacts with the ultrasonic wave. Amplification occurs when the drift velocity of the electrons exceeds the velocity of sound. For strongly piezoelectric semiconductors, amplification of as much as several percent per wavelength of path is obtainable. Calculations show that for properly prepared material, significant amplification is expected up to the microwave frequencies. At high frequencies, gain is reduced because electron diffusion smooths out the electron bunching necessary for amplification. The dc power required increases rapidly with frequency, and at frequencies above one or two thousand megacycles only pulsed operation seems feasible. Applications as a tool in ultrasonic studies, and for devices such as delay lines and amplifiers, are also discussed.

Amplification of Ultrasonic Waves in Piezoelectric Semiconductors

Abstract: Ultrasonic waves traveling in certain directions in piezoelectric semiconductors can be amplified by application of an electric field. The conditions for amplification are that the average drift velocity of the charge carriers exceed the velocity of sound and that the carriers travel in the same direction as the sound. Ultrasonic amplification has been observed in single crystal CdS, CdSe and ZnO from frequencies of 10mc/sec to over 1000 mc/sec. The gain is large enough (up to 0.3db per wavelength) to stimulate effort on devices like electrical amplifiers, long loss-less ultrasonic delay lines, etc., especially in the VHF, UHF region. Characteristics of ultrasonic amplifier devices, such as frequency limitations, power requirements, stability, and noise, will be discussed.

Surface elastic waves

Abstract: Many of the recently discovered characteristics and applications to electronics of surface elastic waves are discussed. First the propagation of various elastic waves at the surfaces of solids is considered, followed by descriptions of the many ways which have been demonstrated for transduction between surface elastic waves and electromagnetic waves. Surface-wave amplification, primarily in semiconductors, and wave guiding, focusing, and reflection are examined. The properties of these waves suit them for use in a number of applications, which are discussed, ranging from realization of electronic amplifiers, frequency and analog time-domain filters, and coding devices, to the modulation of light beams and the measurement of surface properties of solids. Many references to the recent surface-wave literature are included.

Materials chemistry and engineering in metal halide perovskite lasers

Abstract: The invention and development of the laser have revolutionized science, technology, and industry. Metal halide perovskites are an emerging class of semiconductors holding promising potential in further advancing the laser technology. In this Review, we provide a comprehensive overview of metal halide perovskite lasers from the viewpoint of materials chemistry and engineering. After an introduction to the materials chemistry and physics of metal halide perovskites, we present diverse optical cavities for perovskite lasers. We then comprehensively discuss various perovskite lasers with particular functionalities, including tunable lasers, multicolor lasers, continuous-wave lasers, single-mode lasers, subwavelength lasers, random lasers, polariton lasers, and laser arrays. Following this a description of the strategies for improving the stability and reducing the toxicity of metal halide perovskite lasers is provided. Finally, future research directions and challenges toward practical technology applications of perovskite lasers are provided to give an outlook on this emerging field.