In this paper, we demonstrated an improved laser self-mixing grating interferometer (SMGI) with autocollimation design which can avoid the disturbance from the light feedback of the zero-order diffraction beam. In order to obtain higher optical subdivision, SMGI with multiple-diffraction is implemented. Both theoretical analysis and experimental work show that the proposed system for displacement measurement can achieve high sensitivity and low measurement uncertainty. Using the proposed system, different forms of micro-displacement signals applied on the target (grating) have been reconstructed with accuracy of a few nanometers. The work presented in this paper provides a good way to achieve robust and high precision measurement with compact system configuration. Disciplines Engineering | Science and Technology Studies Abstract:In this paper, we demonstrated an improved laser self-mixing grating interferometer (SMGI) with auto-collimation design which can avoid the disturbance from the light feedback of the zero-order diffraction beam. In order to obtain higher optical subdivision, SMGI with multiple-diffraction is implemented. Both theoretical analysis and experimental work show that the proposed system for displacement measurement can achieve high sensitivity and low measurement uncertainty. Using the proposed system, different forms of micro-displacement signals applied on the target (grating) have been reconstructed with accuracy of a few nanometers. The work presented in this paper provides a good way to achieve robust and high precision measurement with compact system configuration. 4550-4556 (2011). 19. T. Bosch and S. Donati, "Optical feedback interferometry for sensing application," Opt. Eng. 40(1), 20-27 (2001). 20. W. Xia, M. Wang, Z. Yang, W. Guo, H. Hao, and D. Guo, "High-accuracy sinusoidal phase-modulating selfmixing interferometer using an electro-optic modulator: development and evaluation," Appl. Opt. 52(4), B52-B59 (2013).

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Spectroscopic ellipsometry is a powerful tool for characterizing thin film, polarization optics, semiconductors, and others. Conventional approaches are subject to restrictions of mechanical instability and measurement speed. The complex locking scheme of previous dual-comb spectroscopic ellipsometry belies its practicability. We present and demonstrate here dynamic spectroscopic ellipsometry based on a simplified phase-stable dual-comb system, which could realize the online dynamic measurement of optical properties of materials. A precision of 1.31 nm and a combined uncertainty of 13.80 nm (k = 2) in the thickness measurement of thin-film samples has been achieved. Moreover, the dynamic performance of the system is investigated under a high data acquisition rate (1 kHz) with a dynamic resolution of ellipsometric parameter better than 0.1 rad.

In this paper, we present an orthogonally polarized self-mixing grating interferometer (SMGI) for simultaneous measurement of in-plane and out-of-plane displacements. The measurement ranges in both directions are limited only by the length of grating. The orthogonally polarized lights emitted from a birefringent He–Ne laser are separated and enter the grating at ±1st-order Littrow angles. The diffraction beams re-enter the laser cavity and cause self-mixing interference. To differentiate the orthogonally polarized lights and obtain high resolution, phase modulation technique is introduced to extract phases from the orthogonally polarized SMGI signals. The measurement results show that the proposed system can reach a submicron accuracy in the experiment. This work provides a good way to achieve high precision two-dimensional displacement measurement with a robust system configuration.

The dual-comb technique is a powerful tool in industrial inspection and scientific research and is capable of realizing ultrahigh-resolution and fast broadband spectral measurements. We propose an absolute angular-position measurement method based on dual-comb spectroscopy. With a simple layout, the absolute angular position can be naturally determined through the traceable and wide-amplitude spectra of the autocollimation diffracted beams of the target grating. We experimentally demonstrate that a precision of 0.12 arcsec in the dynamic range of approximately 6660 arcsec, along with a 1 kHz repetition rate difference, is achieved. Compared with a commercial autocollimator, over 1000 arcsec, the comparison residuals are kept within ±0.3 arcsec.