Basic Concept

Optical spectrum analyzers are an indispensable tool for research, development and maintenance. The number of semiconductor light sources like diode lasers or light emitting diodes (LED), is steadily growing and their spectral characteristics are of great importance for scientists and engineers. Due to this rapid development, miniaturized fibre coupled devices are also common in the size of a match box. This kind of spectrometer is easy to use and handle, since no settings and reading of the grating are needed. Instead of an exit slit, high resolving linear CCD arrays are used. Microprocessors control the device and deliver the full spectrum covered by the grating. Each pixel of the linear sensor, or a couple of them, represents a ��slit�� or channel. Based on the position of the pixel and the illumination intensity, the processor constructs the spectrum. Such devices are also termed optical multi-channel analyzers or in short OMA.

Experimental Set-up

The optical multi-channel analyser and the spectrometer are integrated into one slot-in module. A fibre telescope is used to enhance the incoming light level. As light sources to be investigated, a narrow band diode laser emitting at 830 nm, two LED light sources emitting in the blue green (520 nm) and red (670 nm). Furthermore, a spectral lamp is provided optionally emitting a variety of fixed emission lines for calibrating purposes. In order to connect the individual light sources directly to the spectrum analyser ST and F-SMA adapter for the plastic optical fibre connection of the LED slot-in modules are provided. Two filters complete the equipment. One filter is an RG1000 type, which blocks visible radiation below 1000 nm and the other BG39 blocks radiation above 750 nm. Furthermore, it is possible to analyse environmental light by simply directing the fibre telescope into the position of the emitting source.
Due to the USB connection, all functions can also be remote controlled by a computer using the SMC-10 software.