Typically, the C12666MA micro-spectrometer is not suitable for most Raman applications for two primary reasons: resolution and sensitivity.
The C12666MA is a very small, versatile, and relatively low-cost spectrometer. However, achieving these design objectives required trade-offs in spectrometer performance such as spectral resolution. Per the C12666MA data sheet , the maximum resolution of the spectrometer is around 15 nm. This does vary over wavelength (see Fig. 1) with the best resolution occurring around 450 nm.
Figure 1: C12666MA’s spectral resolution
In much of Raman spectroscopy, it is important to have better than 1 nm resolution typically—and sometimes much less than 1 nm—to resolve molecular peaks that may be close in spectral proximity. It is also often important that the spectrometer’s FWHM resolution provide enough granularity and detail in the spectral peaks to be able to properly determine molecular identity and concentration. Generally, the C12666MA’s resolution is not sufficient to resolve closely spaced molecular peaks when analyzing Raman spectral information.
Typical Raman analysis also needs relatively high sensitivity. Because Raman scattering is a low level, inelastic scattering effect and since measurements usually use just the Stokes scattered light, only a portion of all the scattered light is captured during measurements. Most Raman analysis applications deal with very low light levels, so the spectrometer used should have relatively high sensitivity to detect the very low light levels.
The C12666MA is based upon CMOS image sensor technology. It offers good sensitivity for its physical size, cost, spectral range, and resolution but usually does not offer sufficient sensitivity to accomplish most very low light Raman analysis. Fig. 2 shows the C12666MA’s relative sensitivity, which varies across its spectral response range with peak sensitivity occurring around 500 nm. This indicates that Raman signals near the peak sensitivity may be measurable, but perhaps signal peaks at other wavelengths may not be observable.
Figure 2: C12666MA’s relative sensitivity
Spectrometers suitable for Raman
Although the C12666MA is not typically suitable for Raman analysis, a few customers have achieved low-resolution Raman analysis for certain applications using the C12880MA micro-spectrometer data sheet.
The C12880MA has a slightly wider spectral response range (340 to 850 nm, with resolution peaking at around 425 nm) and a higher sensitivity based upon its APS-CMOS (Active Pixel Structure CMOS) image sensor. The APS-CMOS image sensor yields a significant improvement in spectral sensitivity (peaking at around 500 nm) over the sensitivity of the C12666MA, which uses a different CMOS image sensor. The spectral response plots for the C12880MA are shown in Fig. 3 and 4.
Figure 3: C12880MA’s spectral resolution
Figure 4: C12880MA’s relative sensitivity
Resolution should always be considered when selecting a spectrometer, as many applications require a certain resolution to be successful. If you imagine a random spectrum in your head, I bet there are a bunch of peaks large and small. Resolution is essentially the ability to discriminate peaks of the same intensity within a certain wavelength window. A good example would be to think of your typical camera and its ability to focus on certain aspects of an image.
One popular method to define spectral resolution uses the Rayleigh criterion in DIN (Deutsches Institut für Norming) standards, for which the valley between the two peaks must be lower than 81% of the peak value.
On the other hand, a practical alternative for defining spectral resolution is the spectral half-width or FWHM (full width at half maximum). This is the spectral width at 50% of the peak value and directly defines the extent of spectral broadening. The more broadening you have, the more information you may be losing within the peak. The spectral resolution defined as FWHM is approximately 80% of the resolution defined by the Rayleigh criterion. The spectral resolution of Hamamatsu mini-spectrometers is defined by FWHM.
Figure 5a: Resolution defined by Rayleigh criterion
Figure 5b: Definition of FWHM
Another thing to note is that your spectrometer’s resolution may have wavelength dependence. More resolution is especially important in cases of chemical fingerprinting, where minute changes in purity and identification of functional groups depend on the ability to find small differences in interaction.
As an Applications Engineer in the New Jersey office of Hamamatsu, Dana Hinckley’s primary technical focus is on the mini- and micro-spectrometers and MEMS-FPI spectral sensors. He especially enjoys the wide range of applications and the daily dose of education in science, engineering, and spectroscopy, along with the myriad implementations in which our customers employ the spectral analysis tools. In his off-hours, Dana enjoys a wide palette of interests: spending time with family and friends, guitar playing, and music are some of his more predominant pastimes.
Gary Spingarn is a Product Manager in the New Jersey office of Hamamatsu, where he focuses on business development for certain products and exploring new applications. Leveraging his chemistry expertise, Gary supports the mid-infrared (MIR) product lines with a particular knack for process monitoring, gas analysis, and environmental applications. In his spare time, Gary hones his chess skills as well as partakes in strength sports and world travel.
It looks like you're in the . If this is not your location, please select the correct region or country below.
You're headed to Hamamatsu Photonics website for US (English). If you want to view an other country's site, the optimized information will be provided by selecting options below.
For modern websites to work according to visitor’s expectations, they need to collect certain basic information about visitors. To do this, a site will create small text files which are placed on visitor’s devices (computer or mobile) - these files are known as cookies when you access a website. Cookies are used in order to make websites function and work efficiently. Cookies are uniquely assigned to each visitor and can only be read by a web server in the domain that issued the cookie to the visitor. Cookies cannot be used to run programs or deliver viruses to a visitor’s device.
Cookies do various jobs which make the visitor’s experience of the internet much smoother and more interactive. For instance, cookies are used to remember the visitor’s preferences on sites they visit often, to remember language preference and to help navigate between pages more efficiently. Much, though not all, of the data collected is anonymous, though some of it is designed to detect browsing patterns and approximate geographical location to improve the visitor experience.
Certain type of cookies may require the data subject’s consent before storing them on the computer.
This website uses two types of cookies:
There are two ways to manage cookie preferences.
If you wish to restrict or block web browser cookies which are set on your device then you can do this through your browser settings; the Help function within your browser should tell you how. Alternatively, you may wish to visit www.aboutcookies.org, which contains comprehensive information on how to do this on a wide variety of desktop browsers.
Occasionally, we may use internet tags (also known as action tags, single-pixel GIFs, clear GIFs, invisible GIFs and 1-by-1 GIFs) at this site and may deploy these tags/cookies through a third-party advertising partner or a web analytical service partner which may be located and store the respective information (including your IP-address) in a foreign country. These tags/cookies are placed on both online advertisements that bring users to this site and on different pages of this site. We use this technology to measure the visitors' responses to our sites and the effectiveness of our advertising campaigns (including how many times a page is opened and which information is consulted) as well as to evaluate your use of this website. The third-party partner or the web analytical service partner may be able to collect data about visitors to our and other sites because of these internet tags/cookies, may compose reports regarding the website’s activity for us and may provide further services which are related to the use of the website and the internet. They may provide such information to other parties if there is a legal requirement that they do so, or if they hire the other parties to process information on their behalf.
If you would like more information about web tags and cookies associated with on-line advertising or to opt-out of third-party collection of this information, please visit the Network Advertising Initiative website http://www.networkadvertising.org.
We use third-party cookies (such as Google Analytics) to track visitors on our website, to get reports about how visitors use the website and to inform, optimize and serve ads based on someone's past visits to our website.
You may opt-out of Google Analytics cookies by the websites provided by Google:
We inform you that in such case you will not be able to wholly use all functions of our website.