Young’s modulus (denoted by E) is an intrinsic and valuable quantity for appropriate estimation of material performance. E can be obtained from the resonant frequency from the vibration of the tested material sample excited by the external forces. In this paper, we present a system design for determining the parameter by using an optical feedback self-mixing interferometry (OFSMI) system. An OFSMI system consists of a laser diode (LD), a micro-lens and an external target. The material sample to be tested is used as the external target. The vibration of the sample causes the variation of the length of the external cavity, and then causes a modulated laser power of the LD. The modulation contains the vibration information of the tested samples. The OFSMI system can achieve high measurement accuracy with an extremely simple and inexpensive set-up, thus can be thought as a good candidate for the evaluation of material properties. The system design in this work includes the mechanical part for holding and exciting the tested samples and the optical part for picking up the vibration information from the samples. In order to accurately determinate E, the exclusive supporting system is used for holding the material sample of specific dimension. The complex waveform of the LD output power is studied and simulated by using our proposed system model. The proposed method is verified by simulation and experiments, and satisfied accuracy of the experiments is achieved.
This paper presents a novel approach for determining the Young’s modulus by using a self-mixing laser diode (SMLD).
An SMLD system consists of a laser diode (LD), a microlens and an external target. With a small portion of light
backscatterd or reflected by the target re-entering the LD inside cavity, both the amplitude and frequency of the LD
power are modulated. This modulated LD power is referred as a self-mixing signal (SMS) which is detected by the
photodiode (PD) packaged in the rear of the LD. The external target is the tested sample which is in damping vibration
excited by a singular elastic strike with an impulse tool. The vibration information from the tested sample is carried in
the SMS. Advanced data processing in frequency-domain is applied on the SMS, from which the resonant frequency of
the vibration can be retrieved, and hence Young’s modulus is calculated. The proposed method has been verified by
The Alpha factor, also known as the linewidth enhancement factor, is one of the fundamental parameters for semiconductor lasers (SLs) as it characterizes many properties of the SLs, such as the responses to the electrical injection and the optical injection. Due to the great importance of alpha factor in research analysis and application design, the high accuracy of the experimental alpha measurement is required. The optical feedback self-mixing interferometry (OFSMI) based method for the alpha measurement is one of the popular approaches in the past twenty years due to its easy implementation and inexpensive, self-aligned experiment set-up. This paper proposes an effective data processing method applied in the frequency-domain based self-mixing approach for alpha factor measurement. The alpha value is estimated from the complex frequency spectrum of the feedback phase signal in an OFSMI system. However, some of the estimated results with large deviations are found in the experimental estimation due to the noises in practice. The work presented in the paper is twofold. Firstly, the errors of alpha estimation are analyzed. Secondly, the algorithm using distance-based outlier removal is proposed for optimizing the estimation results of alpha. The results show that the estimation accuracy of alpha can be achieved to 6.725% and 1.923% for the optical feedback level in the OFSMI system.