Fast measurement of the thickness and group refractive index distribution of solid plates by line-field dispersive interferometry.

Real-time measurement of the thickness and group refractive index is crucial for semiconductor devices. In this paper, we proposed a fast synchronous method for measuring the thickness and group refractive index distribution of solid plates based on line-field dispersive interferometry. The proposed method measured the line-field distribution in an illuminated region through a single step. A low-cost spectrometer calibration method using an eight-channel dense wavelength division multiplexer was developed for verification. The line-field distribution of a three-step silicon wafer was successfully measured within 3.3 ms. The combined uncertainties for the geometrical thickness and group refractive index were <50 nm and 4 × 10-4, respectively.

Compression-coding-based surface measurement using a digital micromirror device and heterodyne interferometry of an optical frequency comb.

We propose a compression-coding-based surface measurement method that combines single-pixel imaging and heterodyne interference using an optical frequency comb. The real and imaginary parts of the heterodyne interference signals are used to obtain the depth information rapidly. By optimizing the ordering of the Hadamard measurement basis, we reconstruct a three-step sample with heights of approximately 10, 20, and 30 µm without an iterative operation in 6 ms, with a precision of 5 nm. Compared with the uncompressed measurement, the sampling times reduced to 20%, and the measurement time reduced by five times without measurement accuracy loss. The proposed method is effective for rapid measurements, particularly for objects with a simple surface topography.

Multi-color method for the self-correction of the air refractive index.

We propose a multi-color method for the self-correction of the air refractive index based on the dispersive interferometry of an optical frequency comb. This method can be applied to correct the air refractive index for long-distance measurements in moist air. Optical lengths of multiple wavelengths were obtained simultaneously by the dispersive interferometry of an optical frequency comb. Interferometric measurement results and calculations from the empirical equation of air refractive indices were similar, with a standard deviation of 2.0×10-9 throughout the 2 h continuous measurement period. By applying the multi-color method, correction of the air refractive index with an uncertainty of 3.5×10-7 was achieved.

Overexpression of chromodomain helicase DNA binding protein 5 (CHD5) inhibits cell proliferation and induces cell cycle arrest and apoptosis in chronic myeloid leukemia.

BACKGROUND: Chromodomain helicase DNA binding protein 5 (CHD5) was reported to be a tumor suppressor and our previous work showed CHD5 was epigenetically inactivated in human chronic myeloid leukemia (CML). This study aimed to investigate the effect of its overexpression on CML tumorigenesis. METHODS: Quantitative reverse-transcriptase PCR and Western blotting analysis were used to detect the expression of CHD5 in human CML cell lines. The endogenous CHD5 expression was activated in two CML cell lines by CRISPR/dCas9-SAM system. In vitro cell function experiments were performed including proliferation, colony formation, apoptosis, autophagy, senescence and differentiation assays. Furthermore, tumorigenicity was evaluated in vivo in nude mice xenograft model. RESULTS: CHD5 was down-regulated in CML cell lines compare to normal bone marrow mononuclear cells (MCs). Cell proliferation after activating CHD5 was significantly inhibited. Moreover, overexpression of CHD5 induced G2/M phase arrest and apoptosis in CML cells. In a tumor xenograft mouse model, CHD5 restoration was found to sharply repress tumor growth. Compared with the control group, overexpression of CHD5 enhanced the expression of p21 and cdc2 phosphorylation, whereas decreased the protein level of Cyclin B1. Furthermore, experiments revealed that up-regulation of CHD5 activated caspase-3, while anti-apoptosis protein Bcl-2 expression was reduced in CML cells. CONCLUSIONS: CHD5 plays a role of anti-tumorigenic effects involved in CML cell proliferation, cell cycle arrest and apoptosis.

Chromodomain Helicase DNA-Binding Protein 5 Inhibits Renal Cell Carcinoma Tumorigenesis by Activation of the p53 and RB Pathways.

Chromodomain helicase DNA-binding protein 5 (CHD5) plays a crucial tumor suppressor role in multiple types of tumors. For this study, we investigated its clinical significance and the molecular mechanism(s) underlying tumorigenesis in renal cell carcinoma (RCC). Initially, CHD5 expression was assessed in primary tumor tissue and in tissue array. Correlations among CHD5 expression and clinicopathological characteristics were analyzed. Next, lentivirus-mediated CHD5 overexpression in the ACHN and 769-P cells was used to assess effects on proliferation, migration, invasion ability, and the regulation of the p14ARF/p53 and p16INK4a/RB signaling pathways. Finally, a xenograft mouse model was used to verify its impact on tumor growth in vivo. Results demonstrated that CHD5 was downregulated in tumor tissues and that low CHD5 expression was correlated with advanced TNM stage, high Fuhrman grade, lymph node metastasis, and poor survival. Overexpression of CHD5 inhibited proliferation, migration, and invasion in vitro; prompted cell cycle G1 phase arrest; induced apoptosis; and suppressed tumor growth in vivo. Furthermore, we confirmed that CHD5 activates the p53 and RB pathways to inhibit tumorigenesis in RCC. In summary, CHD5 is involved in the initiation and progression of RCC and may serve as a diagnostic biomarker and a potential therapeutic target for RCC.

Large-field step-structure surface measurement using a femtosecond laser.

We present a femtosecond laser-based interferometry for step-structure surface measurement with a large field of view. A height axial scanning range of 348 µm is achieved by using the method of repetition frequency scanning with reference to the Rb atomic clock and the optical path length difference design for 21 times of the pulse interval. A combined method, which includes the envelope peak positioning method for rough measurement, synthetic-wavelength interferometry for connection, and carrier wave interferometry for fine measurement, is proposed to reconstruct the surface. A three-step specimen with heights of approximately 20, 50, and 70 µm was successfully measured with a height precision of 7 nm, and the accuracy was verified by a commercial white light interferometer. The diameter of the field of view that was demonstrated was 17.3 mm, which could be much larger owing to the high spatial coherence of the femtosecond laser. The results show that the femtosecond laser system combines the step-structure measurement performance of white light interferometry and the high-precision large-field performance of phase shifting interferometry, indicating its potential for widespread use in ultra-precision manufacturing of micro/nano-devices, such as semiconductor chips, integrated circuits, and micro-electro-mechanical systems.

Simplified phase-stable dual-comb interferometer for short dynamic range distance measurement.

A simplified phase-stable dual-comb interferometer for absolute distance measurement within a short dynamic range is proposed in this paper. The experimental results demonstrate that stable phase-difference information and lower timing jitter can be obtained within a time delay of 2000 ns between the reference interference signal and measurement interference signal. Using the proposed technique, the time-of-flight (TOF) result can link directly to the carrier-wave interferometric (CWI) result in an average time of 20 ms and can reach 2 nm precision in 0.5 s averaging time. Millimeter-scale measurement dynamic range and nanometer-level precision can thus be achieved without additional noise suppression. This method can also be applied at different stand-off distances.

Femtosecond laser-based phase-shifting interferometry for optical surface measurement.

This paper demonstrates an unequal-path phase-shifting interferometer for precise optical surface measurement using a femtosecond laser. According to the periodic low temporal coherence of the femtosecond laser, the relative time delay between pulses from the reference and target surfaces is scanned by sweeping the repetition frequency for phase shifting when the optical path length difference is set to integer times of the pulse interval, which removes mechanical scanning devices in the interferometer. In particular, we employ an iterative least-squares fitting algorithm to derive the phase. With this method, a glass slide surface is reconstructed that agrees well with the surface measured using a commercial Fizeau interferometer. The comparison results show that the difference in the peak-to-valley value is 0.050 µm.

Synthetic wavelength interferometry of an optical frequency comb for absolute distance measurement.

We present a synthetic-wavelength based heterodyne interferometer of optical frequency combs with wide consecutive measurement range for absolute distance measurement. The synthetic wavelength is derived from two wavelengths obtained by two band-pass filters. The interferometric phase of the synthetic wavelength is used as a marker for the pulse-to-pulse alignment, which greatly improves the accuracy of traditional peak finding method. The consecutive measurement range is enlarged by using long fiber to increase the path length difference of the reference and measurement arms. The length of the long fiber is stabilized according to the interferometric phase of a CW laser. The experimental results show the present system can realize an accuracy of 75 nm in 350 mm consecutive measurement range.

Stabilizing carrier-envelope offset frequency of a femtosecond laser using heterodyne interferometry.

We propose a time-domain fceo stabilization method of a femtosecond laser using heterodyne interferometry. A femtosecond pulse train that is delayed by a spatial delay line interferes with the original pulse train. The phase difference between heterodyne interference signals extracted from different spectral regions is used to stabilize the relative position of the two pulse trains; then the heterodyne interference phase is used to stabilize the carrier-envelope offset frequency fceo. The experimental results show that, after being stabilized, the relative Allan deviations of fceo are 1.0×10-9 at 0.5 s and 4.6×10-10 at 50 s.

Parameter optimization of a dual-comb ranging system by using a numerical simulation method.

Dual-comb system parameters have significant impacts on the ranging accuracy. We present a theoretical model and a numerical simulation method for the parameter optimization of a dual-comb ranging system. With this method we investigate the impacts of repetition rate difference, repetition rate, and carrier-envelope-offset frequency on the ranging accuracy. Firstly, the simulation results suggest a series of discrete zones of repetition rate difference in an optimal range, which are consistent with the experimental results. Secondly, the simulation results of the repetition rate indicate that a higher repetition rate is very favorable to improve the ranging accuracy. Finally, the simulation results suggest a series of discrete optimal ranges of the carrier-envelope-offset frequency for the dual-comb system. The simulated results were verified by our experiments.