Laser Diode Self-mixing Interferometry Research Articles

A Novel Method for Quadrature Signal Construction in a Semiconductor Self-Mixing Interferometry System Using a Liquid Crystal Phase Shifter

We have established a novel method for quadrature signal construction in a semiconductor laser diode self-mixing interferometry system using two photodiodes and a beam splitter with a liquid crystal phase shifter (LCPS). This method entails placing an LCPS between the photodiode and the beam splitter so that another phase shift self-mixing signal can be obtained. Then, an arctangent phase algorithm can be used to demodulate the pair of quadrature signals to reconstruct the vibration information of the target object. This method simplifies the self-mixing signal demodulation process and the reconstruction of vibration information. Our experimental results demonstrate the feasibility of using self-mixing phase shifter detection for self-mixing optical measurements. The work illustrates a sort of efficient and referable novel design guidance model which supports the quadrature signals construction in a self-mixing interferometer based on a semiconductor laser diode.

Fourier spectrometer built by a permanent magnet cylinder falling uniformly in a conductive tube.

The possibility of constructing a Fourier transform spectrometer by uniform motion of a permanent magnet cylinder falling in an upright conductive tube was researched. Two identical permanent magnet cylinders were reversely connected to two ends of a non-magnetic rod, making a compound permanent magnet cylinder, to reduce the lateral swing of a single permanent magnet cylinder as it falls. Falling velocity fluctuation of the compound permanent magnet cylinder was measured by laser diode self-mixing interferometry. Spectral lines with a frequency interval of about 9GHz could be clearly distinguished on a cosine transform spectrum of the self-mixing interference signal under a weak feedback situation.

Single-Arm Self-Mixing Superluminescent Diode Interferometer for Flow Measurements

Laser-diode self-mixing interferometry is a noncontact technique widely used both in industries and laboratories. In this paper, we propose to extend the self-mixing approach to low-coherence sources such as superluminescent diodes. In particular, we present a fiber-based common-path interferometer exploiting a single-mode-pigtailed superluminescent diode. The developed measuring system has been demonstrated to be able to directly measure the flow in pipes. To the best of our knowledge, it is the first time that flow measurements have been performed by a single-arm self-mixing pigtailed superluminescent-diode. The measuring system exploits the Doppler interference pattern produced by the light back-reflected from the inner facet of the pipe wall and the light back-diffused by the moving particles. Then, the use of a low-coherence source allows to measure the velocity of the scattering particles in a fixed and well-defined region located close to the pipe wall, thus providing good robustness to variations of scatterers concentration and allowing to easily estimate the flow under the laminar flow assumption. Experimental results demonstrated a high linearity (Pearson coefficient of about 99 $\%$ ) and sensitivity of about 16.62 $\pm$ 1.1 cm $^{-3}$ , with flows ranging from 1 to 15 cm $^3$ /s and scatterers volume concentration ranging from 0.015 to 0.36 $\%$ .

Online measurement of nanoparticle size distribution in flowing Brownian motion system using laser diode self-mixing interferometry

Laser diode self-mixing interferometry, which is characterized by self-alignment, compactness, low cost and few additional optical elements required, is promising to be applied to the online measurement of the particle size distribution in a flowing Brownian motion system. In this paper, the online measurement is realized by the laser diode self-mixing interferometry with a quick signal processing technique and a quick inversion algorithm. The total power spectrum of the self-mixing signal is achieved, and the impact of particle motions on the total power spectrum is researched. A method is proposed for retrieving the particle size distribution, which is validated by experimental tests.

Laser diode self-mixing interferometry for velocity measurements

A diode laser velocimeter based on laser self-mixing has been developed and characterized as a reliable, precise, comparably cheap, and compact monitor. The resolution of this sensor at different incident angles and for a variety of solid and liquid targets moving at velocities between 0.1 and 50 m/s is presented. This includes a theoretical analysis of the underlying measurement principle, highlighting possibilities to extend the measurement capabilities to even higher velocities by altering the sensor design. Finally, an outlook on future applications of the sensor for detailed studies of supersonic gas jets used in beam diagnostics and atomic physics applications is given.

Fast and economic signal processing technique of laser diode self-mixing interferometry for nanoparticle size measurement

The size of nanoparticles is measured by laser diode self-mixing interferometry, which employs a sensitive, compact, and simple optical setup. However, the signal processing of the interferometry is slow or expensive. In this article, a fast and economic signal processing technique is introduced, in which the self-mixing AC signal is transformed into DC signals with an analog circuit consisting of 16 channels. These DC signals are obtained as a spectrum from which the size of nanoparticles can be retrieved. The technique is examined by measuring the standard nanoparticles. Further experiments are performed to compare the skimmed milk and whole milk, and also the fresh skimmed milk and rotten skimmed milk.

Infrasound detection by laser diode self-mixing interferometry

An alternative technique for infrasound detection based on the self-mixing (SM) interference of a laser diode is described. The principle involved is the dependence of the power emitted by the laser diode on infrasound-induced membrane vibration. The Fourier transform and fringe-counting methods are used to analyze the self-mixing signal. Infrasound signals are experimentally measured from 2 to 20 Hz with a resolution of 0.25, and the results well agree with the theoretical ones.

基于带通滤波片的激光二极管自混频纳米颗粒干涉测量技术

基于带通滤波片的激光二极管自混频纳米颗粒干涉测量技术

Real time ablation rate measurement during high aspect-ratio hole drilling with a 120-ps fiber laser

We report on the instantaneous detection of the ablation rate as a function of depth during ultrafast microdrilling of metal targets. The displacement of the ablation front has been measured with a sub-wavelength resolution using an all-optical sensor based on the laser diode self-mixing interferometry. The time dependence of the laser ablation process within the depth of aluminum and stainless steel targets has been investigated to study the evolution of the material removal rate in high aspect-ratio micromachined holes.

Quadrature demodulation technique for self-mixing interferometry displacement sensor

A new, to the best of our knowledge, signal processing method based on quadrature demodulation technique is presented for laser diode self-mixing interferometry(LDSMI) displacement sensor. Phase modulation of the laser beam is obtained by an electro-optic modulator (EOM) in the external cavity. Detection of the target's displacement can be easily achieved by sampling the interference signal at those times which satisfied certain conditions. The major advantage of the technique is that it does not involve any complicated calculation and insensitive to the sampling error. Experimental results show that the proposed method can effectively improve the displacement measurement resolution of the laser diode self-mixing displacement sensor to a few nanometers.

Simultaneous measurement of multiple target displacements by self-mixing interferometry in a single laser diode

We demonstrate that a single all-optical sensor based on laser diode self-mixing interferometry can monitor the independent displacement of individual portions of a surface. The experimental evidence was achieved using a metallic sample in a translatory motion while partly ablated by a ps-pulsed fiber laser. A model based on the Lang-Kobayashi approach gives an excellent explanation of the experimental results.

Absolute Distance Measurement With Improved Accuracy Using Laser Diode Self-Mixing Interferometry in a Closed Loop

We present a new method for the measurement of the absolute distance of a remote target based on the laser diode self-mixing interferometry technique, which is assisted by an electronic feedback loop that is capable of improving the measurement accuracy. The feedback loop supplies a periodic change of the emitted wavelength that exactly corresponds to a single interferometric fringe. This allows the measurement of the target distance with higher accuracy, which, in principle, is limited only by the detection shot noise and not by the fringe quantization error that is typical for the conventional fringe-counting approaches. We developed a prototype that is capable of measuring the target distance with 0.3-mm accuracy in the 0.2- to 3-m range.

Self-mixing interferometry based on a double-modulation technique for absolute distance measurement

A new, to the best of our knowledge, method for the measurement of the absolute distance of a remote target based on the laser diode self-mixing interferometry is presented. A double-modulation technique is introduced to improve the measurement resolution. Wavelength modulation of the laser beam is obtained by modulating the injection current of the laser diode. Phase modulation of the laser beam is obtained by an electro-optic crystal in the external cavity. Absolute distance of the external target is determined by the Fourier analysis method. Theoretical analysis and numerical simulations are given. Experimental results show that a resolution of +/-0.3 mm can be achieved for absolute distance ranging from 277 to 477 mm.