Heterodyne laser Doppler vibrometers integrated on silicon-on-insulator based on serrodyne thermo-optic frequency shifters

Abstract

Miniaturized laser Doppler vibrometers (LDVs) have many advantages over conventional bulk LDVs. In this paper, the realization of a miniaturized heterodyne LDV integrated on silicon-on-insulator substrate is reported. The optical frequency shifters in these on-chip LDVs employ a serrodyne technique, and they generate a frequency shift at 2 kHz. Vibrations of a mirror for the frequency range between 1.1 and 123 Hz and the velocity range between 0.8 and 400 μm∕s are measured by both an on-chip LDV and a commercial LDV. The measurement results agree well. A compensation method for the influence of on-chip spurious reflections is also demonstrated.

Integrated nanophotonic frequency shifter on the silicon-organic hybrid (SOH) platform for laser vibrometry

“…Serrodyne frequency shifters can be realized by driving a single phase modulator with a sawtooth signal, but this concept poses stringent requirements on the electrical drive signal to obtain large SMSR and good CE [14]. A serrodyne frequency shifter has recently been demonstrated on the silicon photonic platform [5,15], resulting in a remarkable SMSR of 39 dB, while the frequency shift was limited to 10 kHz due to the speed of the employed thermo-optic phase shifters. Another approach is based on combining the output of two Mach Zehnder modulators (MZM) with a π/2 phase shift, hence realizing a device that acts independently on the in-phase (I) and quadrature (Q) component of the optical signal.…”

“…Employing integrated optics [1] to reduce costs or increase functionality of optical sensors has been discussed since many years and several publications have been written in the field of integrated optics for laser-Doppler sensing techniques such as laser-Doppler velocimetry [2] or laser-Doppler vibrometry [3,4,5]. However, heterodyne interferometry [6] has been proven to be a necessary technology for accurate and reliable laser-Doppler sensing.…”

Integrated design for integrated photonics: from the physical to the circuit level and back

“…25 While this device has a quite good efficiency in transmission (about -0.3dB insertion loss), it does have a non-negligible reflection. When used in a circuit which requires bidirectional propagation, such as a laser-doppler vibrometer, 30 these reflections cause spurious interferences in the return signal. We investigated the source of the backreflection by running an FDTD simulation on the standard MMI component.…”

Silicon photonic integrated circuit for fast and precise dual-comb distance metrology

“…However, while early demonstrations of PIC for interferometric distance measurements made use of GaAs/AlGaAs and LithiumNiobate (LiNbO 3 ) as integration platform [5][6][7], there are only very few examples where large-scale silicon photonic integration has been exploited for applications in optical metrology. Using the silicon-on-insulator (SOI) platform, Laser Doppler vibrometers and optical frequency shifters have been demonstrated [8][9][10] and an optical coherence tomography system has been realized [11]. An integrated heterodyne interferometer for measurements of relative displacements with a standard deviation of 2 nm was demonstrated in [12].…”