Tunable Quantum Dot External Cavity Laser

Owing to the advantageous features such as large wavelength tuning range, high optical output power, fast tuning speed and easy miniaturization, external cavity lasers(ECLs) have been widely used in many applications, e.g., spectroscopy, interferometry, and coherent communication. Most of the currently available ECLs adopt either Littrow or Littman configuration, where a grating or a mirror must be rotated in order to realize wavelength tuning. This requirement drastically limits the speed of wavelength tuning because of the mechanical characteristics. Wang et. al. proposed a new configuration for dual-wavelength laser output, and later the concept was developed by Struckmeier et. al. and Breede et. al., demonstrating its desirable features of fast tuning speed and multi-wavelength operation. One of the most important parameters in the new external cavity configuration is the width of the aperture for reflection, which majorly determines the laser performance. However, the dependence of the laser characteristics on the width of the aperture has not been systematically studied so far.Quantum dots(QD) laser are attractive devices for their expected superior properties owing to charge carrier three-dimensional confinement. Low threshold current densities, temperature-insensitive threshold current, wide gain spectrum and near-zero linewidth enhancement factor(LEF) α have been reported. we adopt a modified Hakki-Paoli(H-P) method by means of calculating gain of fitting and blue shift of weighted wavelength to evaluate the LEF. The main results are summarized as below:1. First, we elaborated the basic principle of external cavity lasers(ECL) and made the simple introduction to the application of external cavity laser as well as the development present situation. Moreover, different structure of external cavity was made a comparison.2. Gain and differential gain properties of quantum dot lasers were investigated using the modified Hakki-Paoli method. As the current increased, speed of wavelength movement was obtained using the method of weighted wavelength. Moreover, linewidth enhancement factor of In Ga As quantum dot lasers was measured below the threshold, and its value was from 0.12 to 2.75.3. A fourier-transform external cavity based on the DMD was demonstrated, and the ability of wavelength tuning was particularly analyzed. Single mode tuning range and multi-mode tuning of the ECL was tested.4. We systematically study a new ECL configuration which utilizes a stripe mirror and a grating to produce the optical feedback. A series of stripe mirrors with different widths were used to construct the ECLs. The stripe width dependence of ECL performances such as the threshold current, the output power slope efficiency and the SMSR has investigated. Moreover, as very important physics parameters in the ECL, the focused spot size and the distance between the adjacent spot have been revealed theoretically and experimentally.