Choosing A Light Source For Your Spectrometer

Depending on your spectrometer application, you will probably need at least one illumination or excitation source. For electroluminescence measurements will require of some sort of testing board connected to an external voltage source. However, most characterisation of optical materials require some sort of incident light.

The light source you will need depends on the measurements you are doing. For photoluminescence measurements, you will need a monochromatic light source with a higher energy than the transition you wish to measure. Often a UV light source is chosen due to its high energy. Additionally, you may also need a monochromatic light source if you are using absorbance spectroscopy to measure optical density. However, to find an absorbance spectrum for your material over a significant wavelength range, you will need a broadband illumination source.

There are many things to consider when you are choosing light sources for your optical spectroscopy lab. The best light source for you will depend on:

• The type of measurements you are doing
• The specifications of your USB spectrometer
• Your budget
• The safety restrictions of your lab.
• The time needed to set-up and maintain your light source

One important thing to note is that you will need different light sources for different optical measurements. Therefore, it is quite likely that you will need more than one light source in order to fully characterise your organic electronic materials.

Comparing Different Spectroscopy Light Sources

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In the table below, we have done a brief comparison of different light sources. Here, we have outlined their ideal applications, costs and other important information.

 

	White Light LED	Tungsten Halogen + Deuterium Light Sources	Monochromatic LED Light Source	Lasers
Type	Broadband		Monochromatic
What measurement is this for?	Absorbance measurements Transmission measurements Reflectivity measurements		Photoluminescence Optical Density Measuring concentration of certain molecule	Photoluminescence ASE Time-resolved spectroscopy (for pulsed laser systems)
Advantages	Long bulb lifetimes	Wide spectral range	Long bulb lifetimes	High power (for weak fluorescence) Can emit short pulses for TRPL
Cost	Low price and low running costs	High ($4000-$5000)	Low	High ($1000 – $6500)
Emission Spectra	Broad spectrum (360 nm – 900 nm for Ossila Broadband White Light)	Very broad spectrum (190 nm – 2200 nm)	Well-defined narrowband emission (e.g. 370 nm for Ossila UV light source- 700 nm for the Ossila Infrared Light Source)	Well-defined emissions (can be tunable depending on the laser)
Warm-Up Time	Minimal	30 minutes – 1 hour	Minimal	5–60 minutes (will vary depending on laser material and mode)
Temperature Control Needed?	No	Yes – to stop overheating	No	Most likely – but depends on the laser
Set Up and Calibration Time	Low	Low	Low	High
Safety Considerations	Low	Low	Low–Medium	High

In order to take the broadest range of general spectroscopy measurements, you will need multiple light sources, such as can be found in our LED Light Source Set.

Ossila Light Sources

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Ossila sell many low-cost light sources which are compatible with the Ossila USB Spectrometer, but also with other spectroscopy equipment via the use of standard optical fibers. This will enable you to take a range of spectroscopy measurements quickly and easily.

In combination, these two light sources will provide you with everything you need to take basic spectroscopy measurements. These are compatible with standard spectroscopy fittings (SMA 905 fiber connections, M6 optical breadboard holes) so that they can be easily integrated with any spectroscopy system.

LED Light Sources Set

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