Amersfoort, The Netherlands: German laser manufacturer nanoplus is using Yokogawa’s AQ6375 optical spectrum analyser to characterise its distributed feedback (DFB) lasers (see the figure). These lasers are used to detect trace gases in gas mixtures with concentrations of less than one part per billion, for example, to detect gas leaks or to optimise industrial processes. They are even used in space to study other planets.
The laser manufacturer is using a spectral characterisation technique based on molecular excitation to test the lasers. The Yokogawa spectrum analyser is particularly suited to the task because its spectral range extends beyond typical wavelengths for telecommunications (around 1700 nm). It can be used to characterise DFB laser products used to detect water vapour (around 1877 nm), carbon dioxide (2004 nm), and carbon monoxide (2332 nm), like those supplied by nanoplus for NASA’s Curiosity Rover, which is on its way to Mars.
The AQ6375 can clearly resolve the individual Fabry-Pérot laser modes. In addition, the high dynamic range enables the demonstration of single-mode laser operation with a side-mode suppression ratio of more than 50 dB.
To achieve a high throughput, nanoplus uses a fully automated test setup using the AQ6375’s general-purpose interface bus (GPIB). Despite the relatively complex measurement process, the test setup allows for a quick determination of the lasers’ tuning properties at different chip temperatures and operating currents. The lasers are tested from 1200 to 2400 nm before they are supplied to the customers, according to their applications.