Cheng-Chih Hsu

Heterodyne common-path grating interferometer with Littrow configuration.

This paper presents a heterodyne common-path grating interferometer with Littrow configuration (HCGIL). The HCGIL can effectively overcome environmental disturbance effect and the DC offset and the amplitude variation of the measurement signals. Experimental results match well with the HP5529A results for long-range measurements. Results also show that the estimated measurement resolution is 0.15 ± 0.027 nm. The stability of the HCGIL is -0.41 ± 0.23 nm. Therefore, the HCGIL has potential for subnanometer resolution and long-range applications.

Reusable glucose fiber sensor for measuring glucose concentration in serum

We demonstrate a glucose fiber sensor for measuring glucose concentration in serum. High resolution and rapid measurement are achieved through the integration of highly selective enzymes and heterodyne interferometry. The best resolution and response time obtained are 0.14 mg/dL and 1.3 s, respectively. The stability of the sensor is also verified by investigating the initial phase variation. Experimental results show that the fiber sensor can be reused more than 10 times.

Dual displacement resolution encoder by integrating single holographic grating sensor and heterodyne interferometry

A novel encoder with dual displacement resolution is developed by integrating a multiple-grating-scale holographic displacement sensor and a heterodyne interferometer. With suitable arrangement of the measurement system, two effective grating pitches (0.41 μm and 10.62 μm) can be obtained and the theoretical sensitivities of them are 0.9 °/nm and 0.036 °/nm. Meanwhile, the best resolution of the proposed method can be estimated of 0.3 pm and 7.4 pm, respectively. Furthermore, displacement errors of the proposed method can be better than 0.2% for 1 mm displacement measurement. The experimental results showed that the proposed encoder provided high sensitivity, high resolution, and well against environmental disturbance.

Transparency and water-resistance enhancement of AR coating for the cover glass in the solar cell module

This paper demonstrates the antireflection coating of SiO2 nanospheres applied to cover glass by using the optimal spin-coating method. Because of the hydrolysis and condensation reactions between the SiO2 nanosphere antireflection (AR) coating and n-octadecyltriethoxysilane solution (C18-TEOS), the contact angle of the AR coating with hydrophobic treatment can be enhanced to 110° and the water-resistant remains unchanged which preserved similar transmittance for six weeks. Furthermore, the AR coating with hydrophobic treatment exhibits approximately 3% and 7% improvement in the transmittance of unpolarized light at normal and oblique incidence, respectively. And the transmittances of p- and s- polarization states are shown opposite tendency as incident angle increase. The hydrophobic and omnidirectional AR coating with nanoscale SiO2 particles can be fabricated using the proposed simple and economical method.

Alternative displacement sensor with reflection type holographic grating

In this study, we proposed an alternative displacement sensor which constructed with reflection type holographic diffraction grating. To integrate with the truly phase detection heterodyne interferometer, and then the in-plane displacement can be measured with sub-nanometer displacement resolution. The smallest variation can be observed of proposed method is approximately 20 pm and there are no significant differences between proposed method and comparison methods. Furthermore, we evaluated the thermal property of the hologram and showed that the grating pitch variation is smaller than 0.1 nm for temperature variations within 1 °C. According to these findings, we can conclude that the holographic grating can be an alternative displacement sensor with high sensitivity and high stability.

Common-path laser encoder system for nanopositioning

In this paper a novel common-path laser encoder system for nanopositioning is proposed, that can effectively reduce the environmental disturbance at its lowest level. It has promising potential for nanometer resolution and large range applications. The experimental results of the proposed laser encoder match well with ones of HP5529A for large ranges. The tested results also show that it has the capability of nanometer scale measurement resolution.

Compensated Laser Encoder with Symmetric and Quasi-common-path Heterodyne Interferometry

A novel laser encoder is presented for sub-nanometer displacement measurement. It is based on optical heterodyne interferometry and two arms of compensation optics with a symmetric and quasi-common-path optical configuration in polarization space. High stability and resolution can be achieved for displacement measurements. The theoretical analysis shows that our method can effectively compensate misalignments resulting from the dynamic runout in laser encoders. Experimental results reveal that the laser encoder can measure a displacement in subnanometer scale and in millimeter travel range.