Simple laser velocimeter that uses photoconductive semiconductors to measure optical frequency differences

Abstract

The dc photocurrents generated by steady-state moving space-charge fields inside photoconductive semiconductors containing deep level donors and traps can be used to determine the relative frequency differences between the two interfering optical fields that establish the space-charge fields. A simple laser velocimeter that uses a semi-insulating GaAs:Cr sample to detect the Doppler frequency shift between two laser beams is demonstrated.

Enhanced detection bandwidth for optical doppler frequency measurements using moving space charge field effects in GaAs multiple quantum wells

“…As a result, blue shifts or reds shifts in frequency experienced by the signal optical field can be determined simply by measuring the flow direction of the resultant photocurrent. 3 Three MQW samples were investigated. One was a standard-temperature grown sample ͑STG͒ consisting of 85 periods of 75 Å GaAs wells and 100 Å Al 0.1 Ga 0.9 As barriers.…”

Crystal growth technology of binary and ternary II–VI semiconductors for photonic applications

“…Using these procedures we have successfully grown undoped and transition metal-doped binary and ternary II-VI crystals including semi-magnetic crystals of both IIa-VI and IIb-VI compounds. We have used these crystals to demonstrate novel applications [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][32][33][34] of which we have discussed two applications in which we used these II-VI crystals for mid-IR solid-state lasing and remote laser vibrometry.…”

“…These photocurrents can be used to deduce information about the optical frequency spectrum of the optical fields that form the interference pattern. These photo-EMF sensors, as they are called, can be used in various applications such as highly precise velocimeters and vibrometers [20][21][22][23]. In this paper, we discuss the application of using a photo-EMF pulsed laser vibrometer (PPLV) to measure human life signs.…”

“…At Brimrose Corporation, we have produced bulk crystals of a variety of IIa-VI and IIb-VI binary and ternary bulk crystals and demonstrated their applications along with various collaborators [16][17][18][19][20][21][22][23][24][25][26][27][28][29]. In this paper, we discuss two of the recent and novel applications of CdTe and CdMnTe crystals for: (i) room temperature operating tunable mid-IR lasers and (ii) remote laser vibrometers for monitoring vital signs.…”

Non-steady-state photoelectromotive force effect under linear and periodical phase modulation: application to detection of Doppler frequency shift

“…It was demonstrated earlier [6,7] that dc photo-emf can be used for this purpose. In this configuration the amplitude of the output signal is proportional to the fringe velocity, so the Doppler frequency shift can be evaluated by measuring the absolute value of the dc current flowing through the sample.…”