Ultra-high spectral resolution system for laser diode characterization

The heart of the measurement system is 1 meter FHR1000 Horiba Jobin Yvon high-resolution Czerny-Turner design monochromator with a 3600 and 2400 groove per mm diffraction grating and a Synapse 2048 x 512 CCD camera, cooled down to -75°C by a thermoelectric cooler. Such a setup provides a very high resolution, better than 6.9 pm (for 3600 g/mm grating, at 400 nm, with slit width matching the size of the single pixel width), which allows not only to clearly see the spectral Fabry-Pérot modulations resulting from the light oscillations between the chip facets but, what is more important, to precisely determine the amplitude (intensity of the modulation) and spectral position of the maximum of each mode – which is used for precise gain measurements and estimation of the thermal resistance.

The setup provides high resolution measurements in the range of 300-500 nm with 3600 g/mm grating and 300-650 nm with 2400 g/mm grating. The system can be used with huge variation of the LD package – from custom made, to TO 5.6, TO 9, CS-mount etc. The devices can be investigated in CW mode up to 5 A/20 V with Thorlabs ITC4005QCL and 20 A/11 V with Thorlabs ITC4020. For pulse operation the setup can supply up to 5 A/20 V with pulse width from 25 ns to 1 µm and duty cycle from 0.01% to 5%. The temperature is controlled by TEC element and water cooling.