We demonstrate the generation of picosecond acoustic pulses using a piezoelectric-semiconductor-based p-n junction structure. This p-n junction picosecond ultrasonic experiment confirms that the piezoelectric effect dominates the thermal expansion and deformation-potential coupling in the generation of picosecond acoustic pulses. The characteristics of the p-n initiated acoustic pulses are determined by the width and the field strength inside the depletion region. Our study indicates the future possibility to electrically control the acoustic pulse characteristics if we could apply an external bias to modulate the depletion region width.
We report a 2 GHz repetition-rate, all-solid-state femtosecond blue source. Pumped by a 740 mW femtosecond Ti:sapphire laser with the same repetition rate, 150 mW femtosecond pulses at 409 nm can be efficiently generated from the external resonant cavity with a lithium triborate crystal.
Abstract-Piezoelectric semiconductor strained layers can be treated as piezoelectric transducers to generate nanometer-wavelength and THz-frequency acoustic waves. The mechanism of nano-acoustic wave (NAW) generation in strained piezoelectric layers, induced by femtosecond optical pulses, can be modeled by a macroscopic elastic continuum theory. The optical absorption change of the strained layers modulated by NAW through quantum-confined Franz-Keldysh (QCFK) effects allows optical detection of the propagating NAW. Based on these piezoelectric-based optical principles, we have designed an optical piezoelectric transducer (OPT) to generate NAW. The optically generated NAW is then applied to one-dimensional (1-D) ultrasonic scan for thickness measurement, which is the first step toward multidimensional nano-ultrasonic imaging. By launching a NAW pulse and resolving the returned acoustic echo signal with femtosecond optical pulses, the thickness of the studied layer can be measured with <1 nm resolution. This nano-structured OPT technique will provide the key toward the realization of nano-ultrasonics, which is analogous to the typical ultrasonic techniques but in a nanometer scale.
In this paper, we present a low-voltage highspeed antimonide-based compound semiconductor (ABCS) high electron-mobility transistor (HEMT) monolithic microwave integrated circuit (MMIC) process and its single-pole doublethrow (SPDT) broadband switch application. The measured 3-dB bandwidth of the proposed SPDT switch is from dc to 30 GHz. The switch features an insertion loss of less than 4 dB, and an isolation of greater than 18 dB between 10 MHz and 30 GHz. The measured input 1 dB compression point (P 1dB ) and thirdorder intercept point (IP3) at 100 MHz are 12.5 and 27 dBm, respectively. The chip size of the proposed switch is 0.75 × 0.58 mm 2 . These results demonstrate the outstanding potential of ABCS HEMT technology for low voltage switch applications.Index Terms -antimonide-based compound semiconductor (ABCS), high electron-mobility transistor (HEMT), monolithic microwave integrated circuit (MMIC), switch.
Piezoelectric quantum wells can be treated as opto-acoustic transducers to generate and detect acoustic waves with nanometer wavelengths. This opto-acoustic transducer was utilized for ID ultrasonic scan with 1 nanometer demonstrated resolution.
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