Single-channel laser Doppler vibrometers integrated on silicon-on-insulator (SOI)

Multi-location velocity measurements of a vibrating surface are of interest recently. By scanning the laser beam of a single-point laser Doppler vibrometer (LDV) across the surface of interest, one can realize the multi-location vibration measurement. However, the recovered velocity values of different locations are not obtained at the same time. In many applications, such as measuring the aortic pulse wave velocity, simultaneous velocity measurements for different locations are required. Multi-channel LDVs can be used in this case, in which multiple laser beams are generated and sent to the surface of interest simultaneously. However, the complexity of realizing the multiple interferometers in a bulk LDV system will increase as the number of channels increases, and thus it is very hard to realize a bulk LDV with many channels We propose to use the silicon-on-insulator (SOI) chip as a platform of the multi-channel interferometers. With the help of silicon photonics and CMOS technology, multiple interferometers can be miniaturized and fabricated on SOI chips. Laser beams are sent into or out of the chip through optimized on-chip grating couplers, with the coupling insertion loss of less than 2 dB per coupler. The total footprint of the integrated multiple interferometers can be very small (several square of millimetres) compared to a bulk LDV system. The cost of the chips will be dramatically decreased for mass production. Additionally, the stability of the integrated interferometers is much better than that of the interferometer built with discrete optical components

Realization of fiber-based laser Doppler vibrometer with serrodyne frequency shifting

We demonstrate a laser Doppler vibrometer (LDV) based on the serrodyne frequency shifting technique. A proof-of-principle system is implemented on the basis of fiber-optic components but opens the way toward an ultracompact integrated LDV system on a silicon chip. With a low laser power of 50 μW, the serrodyne LDV was able to measure submicrometer vibrations with frequencies in the audi

On-chip laser Doppler vibrometer for arterial pulse wave velocity measurement

Pulse wave velocity (PWV) is an important marker for cardiovascular risk. The Laser Doppler vibrometry has been suggested as a potential technique to measure the local carotid PWV by measuring the transit time of the pulse wave between two locations along the common carotid artery (CCA) from skin surface vibrations. However, the present LDV setups are still bulky and difficult to handle. We present in this paper a more compact LDV system integrated on a CMOS-compatible silicon-on-insulator substrate. In this system, a chip with two homodyne LDVs is utilized to simultaneously measure the pulse wave at two different locations along the CCA. Measurement results show that the dual-LDV chip can successfully conduct the PWV measurement

Nonlinear signal errors in homodyne laser Doppler vibrometry induced by strong second-order ghost reflections and their mitigation

A variety of mechanisms can induce distortions in the output signals of a homodyne laser Doppler vibrometer (LDV). In this paper, the nonlinear LDV distortions caused by a strong second-order ghost reflection originating from lens flares are theoretically explained and analyzed. We propose a simple compensation method to mitigate this distortion. The performance and limitations of this method are also explained both in simulation and in experiment. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Mitigation of speckle noise in laser Doppler vibrometry by using a scanning average method

We present a scanning average method used in laser Doppler vibrometry systems for mitigating the noise induced by dynamic speckles. In this method, the measurement beam is scanned over the target surface within the area of interest at a relatively high frequency. Then an averaging operation (e.g., low-pass filtering) is applied to the acquired photocurrent signals to remove the impacts of the scan. Movement signals recovered from the averaged photocurrents turn out to have lower speckle-induced noise. We report the experimental demonstration of this technique through the use of a silicon-based photonic integrated circuit. (C) 2019 Optical Society of Americ