Novel tunable DFB lasers with FIB-deposited heaters

Abstract

Among various types of tunable lasers, distributed Bragg reflection lasers employing chirped gratings have shown a wide tuning range, but they are difficult to fabricate and require sophisticated control electronics. On the other hand, distributed feedback lasers, although their tuning range is narrower than DBR lasers, do not suffer from the aforementioned problems. Thermally tunable 1.5um DFB and DBR lasers with thin film heaters have been reported, but their heater currents were too high to find practical use. We report on novel tunable DFB lasers at 1.3um with thin film heaters deposited by focused ion beam that require much smaller heater currents than previously reported. The lasers were InGaAsP/InP multiple quantum well DFB lasers grown by metal-organic chemical vapor deposition. Pt heater strips were deposited by FIB processing on the top surface of the completed lasers. Our FIB process can control Pt film resistivities between 24 and 105 ohms-μm. The CW laser threshold was 12mA at room temperature without the heater current, the lasing wavelength was 1309.5nm at 27mW, and the sidemode suppression ratio was over 40dB. As the heater current increased to 13mA, the lasing wavelength shifted to 1314.4nm. The tuning efficiency of 5.9nm/W was almost twice that reported previously. FIB was also employed to deposit Au pads for the lasers. To the best of the authors' knowledge, this is the first application of FIB deposition processes to semiconductor lasers.