Phase noise and temporal pulse characterisation of a Quantum dash laser

In this paper we present the characterisation of the phase noise and temporal shape of a quantum dash laser. The laser generates an optical comb with a line spacing of 24.5GHz, over a 10nm wide spectrum. The device can operate passively mode locked or actively locked to a synthesiser. The phase noise of the device has been measured and compared in both regimes. By actively mode locking the device the electrical line width is reduced from 100kHz to 10Hz. The measured timing jitter of the locked device is 1ps over an integration range of 100Hz to 1MHz. The pulse shape of the device has been measured using a sampling oscilloscope, showing a pulse shape unlike that expected from a mode locked laser. This has been investigated and improved upon using optical filters and single mode fiber.