DFB LASER-DIODE OPERATION AT 77 K

The low-temperature operation of distributed feedback semiconductor la sers in the vicinity of 1.3 mu m is investigated. The room temperature properties of a sample DFB laser are given and its power and frequenc y characteristics at 77 K are compared. In this way, the linearity of the temperature against frequency relation down to liquid nitrogen tem perature is confirmed and a reduction in the threshold current to near zero is also shown. For spectroscopic purposes, it was found that sta bilization of the laser temperature at 77 K is possible to within 50 m K over a range of about 77-87 K. This corresponds to a frequency chang e of about 120 GHz. The Schawlow-Townes relation predicts a reduction in linewidth with temperature; some evidence for this is given.