Richard A. Crocombe

There is a growing desire among spectroscopists for having instruments small enough to be taken to the sample, as opposed to bringing the sample to the instrument. The result is that Raman spectrometers are becoming more miniaturized. Because these instruments come at a lower cost and offer distinct advantages over traditional spectrometers, the expectation is that a rapid expansion of when these instruments are applied will come forthwith. We offer a preview of how future miniaturized Raman spectrometers might look.

Portable spectroscopic instruments have not had significant visibility within the scientific community compared with, for instance, the current generation of high-performance laboratory mass spectrometers.

Part II of this series described many of the miniature optical technologies that were developed as a result of the telecommunications boom, and Part III covered conventional small near-infrared (NIR) spectrometers. Here, in Part IV, we bring those themes together and see how the massive investment in telecommunications, microelectro- mechanical systems (MEMS), and micro-opto-electro-mechanical (MOEMS) is starting to impact NIR spectroscopy.

In Part I of this series, we examined recently developed miniature mid-infrared spectrometers (1). In Part II, we surveyed micro electro mechanical systems (MEMS), micro-opto-electro-mechanical systems (MOEMS), and some of the photonics technologies developed for optical communications (2). Here, in Part III, we summarize some of the conventional approaches to miniaturizing near-infrared (NIR) spectrometers, and in Part IV, we will bring these themes together and see how MOEMS and telecommunications photonics are poised to revolutionize NIR spectroscopy with a new generation of miniature instruments.

The author examines NIR spectrometers and the technologies developed during the telecommunications boom of the late 1990s, focusing on miniaturized optical techniques generally called MOEMS.

There are straightforward motivations for miniaturizing an optical spectrometer. If an instrument can be made smaller, it often will also consume less power, enabling it to be portable and eventually handheld, which allows the spectrometer to be taken to the sample. This article describes various miniaturization techniques and focuses on the mid-infrared; subsequent articles will examine near-infrared, UV?vis, and Raman spectrometers.