Germanium Immersion Grating Research Articles

Real-time high-spectral-resolution mid-infrared spectroscopy with a signal-to-noise ratio of ten thousand.

We developed a mid-infrared spectroscopy system with high spectral resolution and a high signal-to-noise ratio using an extremely high-order germanium immersion grating. The spectroscopic system covers wavelengths from 3 to 5 µm and has a spectral resolution of 1 GHz with a single-shot bandwidth of 2 THz. We proposed a method of improving the signal-to-noise ratio and achieved a ratio of over 3000 with a data acquisition rate of 125 Hz in the presence of fluctuations in the light source and environment. A signal-to-noise ratio of 10,000 was achieved with 0.1-s integration for 100-µW mid-infrared light.

大型超精密鏡面加工システム“N-aou-VEL”による大型赤外用回折格子“ゲルマニウムイマージョングレーティング”加工

大型超精密鏡面加工システム“N-aou-VEL”による大型赤外用回折格子“ゲルマニウムイマージョングレーティング”加工

Micro V-Groove Grinding Technique of Large Germanium Immersion Grating Element for Mid-Infrared Spectrograph

The 8.2m SUBARU large space telescope in Hawaii requires a mid-infrared high dispersion spectrograph with a resolution of 200000 at 10µm which employs a Germanium Immersion Grating (GIG) element. For this, the GIG element with a large number of sharp and smooth micro V-grooves must be fabricated. Previous studies were focused on the fabrication of a prototype GIG element. The grinding system developed however was not applicable for the fabrication of practical larger GIG element due to insufficient machining space and fast wear of the small grinding wheel used. The ultimate goal of this project was therefore to develop a new grinding system capable of fabricating larger GIG elements for practical use. This paper discusses the results achieved in the first phase of the research, which focused on the principle of the grinding process and grinding system, as well as describes results of micro-truing and micro-grinding experiments using a #4000 metal bonded diamond grinding wheel. Wear variation of the grinding wheel and its effects on the corner radius of micro V-grooves are also discussed. The minimum wheel tip radius of 8.2µm was achieved using this #4000 grinding wheel by micro-truing, and V-groove corner radiuses ranging from 15µm to 25.8µm were also achieved using the same grinding wheel.

204 Micro V-grooves Grinding Technique of Large Germanium Immersion Grating Element for Mid-infrared Spectrograph

204 Micro V-grooves Grinding Technique of Large Germanium Immersion Grating Element for Mid-infrared Spectrograph

Ultraprecision Micro-Grinding of Germanium Immersion Grating Element for Mid-Infrared Super Dispersion Spectrograph

The design of a mid-infrared high dispersion spectrograph with a resolution of 200,000 at 10μm employing germanium immersion grating elements is required for the ‘SUBARU’ large space telescope. The authors applied an ultraprecision micro-grinding technique using fine-diamond grinding tools whose edges have been sharpened by electrical and mechanical processes to fabricate the element, and successfully obtained the required element with a sharp and smooth V-faced grating structure using germanium. The successful fabrication of this element is expected to contribute to the production of a compact and efficient high dispersion spectrograph in the development of the most advanced image analyzer.