Hyperspectral imaging spectrometer is an important measurement and analysis instrument, which combines imaging with spectrum technology. Nowadays, it has been widely used in research fields of atmosphere, ocean, geology, ecology, astronomy and so on. Convex blazed grating is a key component in the hyperspectral imaging spectrometer. At present, holographic-ion beam etching is an important method to fabricate convex blazed gratings. The common way of holographic-ion beam etching is that to etch the photoresist grating mask directly. However it is difficult to control the groove of photoresist mask accurately. This paper proposes a method of fabricating convex blazed grating by native substrate grating mask, ion beam etching and reactive ion beam etching are used to fabricate a native substrate grating mask based on photoresist grating. The diffraction efficiency of the convex blazed grating is investigated by FDTD (Finite Difference Time Domain) theory. The first-order diffraction efficiency can be over 45% within visible to near-infrared waveband through controlling the blaze angle from 6.4° to 7.2°. Furthermore, a convex blazed grating has been fabricated with the period of 2.45um, the blaze angle of 6.8° and the anti-blaze angle of 60°, theoretical analysis shows that the first-order diffraction efficiency is more than 50% within visible to near-infrared waveband.
Tunable Fabry-Perot filter is an important device in optics. It is widely used in high resolution spectroscopy, laser linewidth measurement, laser frequency stabilization and so on. The filtering characteristics of the Fabry-Perot filter are directly related to the cavity length, and the performance is greatly influenced by the parallelism of the cavity mirrors. For a tunable Fabry-Perot filter with parallel cavity, it is difficult to directly measure the cavity length and determine the parallelism of the cavity in the tuning process. In this paper, a tunable Fabry-Perot filter with an automatic cavity-length stabilization and monitoring system is designed. Four metallic electrodes are deposited on each cavity mirror of the FP filter, thus to form 4 parallel-plate type capacitive sensors. With the help of a capacitance measurement circuit and a micro-controller circuit, the capacitances of the sensors can be acquired. After calibration, the mean value of the capacitances is used to determine the cavity length of the FP filter, while the differential capacitance values in two orthogonal directions are used to monitor the tilt of the cavity mirrors. A feedback control system composed by PZTs, a MCU and the capacitive sensors is therefore constructed to automatically stabilize the F-P cavity length and to adjust the parallelism between the cavity mirrors. The automatic cavity-length stabilizing and monitoring system has the advantages of high accuracy, strong disturbance resistance and high measuring speed. Experimental results prove that it can effectively measure the cavity length of the tunable Fabry-Perot filter, and can stabilize the FP filter as well.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.