Tunable External Cavity Laser Based On Cage Coaxial System

By introducting an external cavity to exchange the optical feedback, external cavity lasers(ECLs) can select stable wavelength and have been widely used in many applications. Most of the currently ECLs adopt either Littrow or Littman configuration, where a grating or a mirror must be rotated in order to realize wavelength tuning. Wang et. al. proposed a new configuration for dual-wavelength laser output. We used one dimensional translation system equipped with an double silt-gilded mirror instead of a flat mirror to move the slit mirror accurately with the piezoceramics.In this paper, dual-mode semiconductor laser, based on Fourier transform external cavity structure(FTECS) is demonstrated and we have a further research the progress and performance of tuning. By a new design of the external cavity, we can not only make a wide range of movement possible, but also control its movement accurately and = demarcate its adjustment distance with the piezoceramics movement. Stable and counting tuning single and dual mode output achieved by this configuration. The major detail of this paper is as follows:1. The research background and the progress of tunable semiconductor lasers in recent years has been introduced and then the main research content of this paper has been demonstrated.2. They are elaborated in this paper about the basic structure and theories of tunable external cavity laser and the principle of mode select and modulate by the cavity. Then the component preparation in our program has been designed. It is about the grating device, which need a precise calculation based on the optical path and machining based on the draws, and movement device which equipped with double slit device. The movement of this device is designed upon its small movable distance that we need to select the specific parameters of piezoelectric ceramic before installing. The width and angle between two slit mirror and processing technology are needed before optical process is fixed.3. The properties of this semiconductor laser based on the caged coaxial external cavity need to test about the single mode output and dual-mode output. Under the conditions of a wide range of injected current from 8mA to 40 mA, where the threshold current is 8mA and the maximum current allowed is 40 mA, it is possible to achieve the single mode and dual mode output, where the dual mode space changes from 7 to 13 inner modes.4. The stable continuous tuning dual-mode semiconductor laser is fabricated systematically, of which the dual modes have equal peak intensity. In a wide range of injected current from 1.45 Ith to 3.85 Ith, which the threshold current is 8 mA, the laser generates dual-mode output of 1THz gap under the condition of closely moving mirror using piezoceramics. In this way, the side-mode suppression ratio(SMSR) of two peaks can reach more than 30 dB and the difference of intensity is no more than 0.07 dB. We also have a further research on the relationship of the peak intensity of dual mode with the position of striped mirror and injected current. This study has a great significance on the design of miniaturization structure in the future. This results are not reported at home and abroad by companies and units so far.