Study Of Broadband 1.5μm Integrated Quantum Well Superluminescent Diodes And Semiconductor Optical Amplifiers

A semiconductor superluminescent diode is an optical source whoseproperties are intermediate between those of semiconductor laser diode andthose of semiconductor light emitting diode. It's an important optical source,which is emerged and developed by the need of fiber optical gyroscopes. SLDsare widely used in many areas such as fiber optical gyroscope (FOG), opticaltime-domain reflectometer (OTDR), local area net (LAN), optical coherencetomography, optical wavelength-division multiplexing (WDM), optical processtechnology and so on for its high power, wide spectral width and narrow beamwidth. High output power and large spectral bandwidth are key features forthese devices. But output power and bandwidth are two opposite parameters. Itis the key problem to improve these two parameters simultaneously in this study.We improved output optical power of device by monolithically integrated SLDand SOA. And we also used other methods to improve the spectral width. In this paper, we first introduced the history of SLD development. Then theproposing and development of the integrated SLD were introduced. After someassumes and optimizations for this device structure, we simulated the integrateddevice by traveling-wave rate equations. The results showed that this kind ofdevice structure we used could increase the output efficiency of the devicenotably. The simulated radiation was dominated by the forward direction by thiskind of structure. Then the photons to the backward direction were suppressed.And the most of photons in the device cavity propagated to the forwarddirection. Then the output optical power was increased efficiently. The output power and spectral width of SLD were two opposite parameters.The spectral width decreases when the output power increases by increasing theinjected current or increasing the cavity length. It is necessary to increase thespectral width by optimization the device material. Then we designed and grewtwo kinds of nonuniform InGaAsP quantum wells structure wafers withdifferent quantum well numbers to increase the spectral width. The widestspectral width was increased to 98nm by this nonuniform quantum wellsstructure. But we found that the output power of nonuniform quantum wellsdevice much lower than that of the uniform quantum wells device although thespectral width was much wider. It's due to the numbers of each kind of quantumwell in this kind of device decreased compared with the device with normalquantum wells. Each kind of quantum well amplifies a different wave band.Then the device with nonuniform quantum wells will decrease the gain ofrelative wavelength, and the output power of the device would also decrease. The output power of the integrated SLD device will increase rapidly withthe increasing the injected current of SOA. But the spectral width of the devicewill decrease with the increasing of output power. It's due to the SLD region andSOA region were integrated in the same material, which have the same centerwavelength of the output spectrum. Then the gain of the SOA to the inputphotons from SLD region at center wavelength has much higher than that at thewavelength far from center wavelength. And the output power is exponentialgrowth with the gain of SOA. Then the spectral width decreases when theinjected current increases to increase the output power of the device. So we putforward a new integrated device structure of two regions with two differentcenter wavelength. Then the output spectrum of the SLD region and the gainspectrum of the SOA region have two different center wavelengths. In the rangewithin the two center wavelength, the output spectrum of SLD and the gainspectrum of SOA compensate each other. The gain of SOA increases with thewavelength when the output power of SLD decreases with the wavelength. Thenthe spectral width can increase when increase the output power. Commonly, we can use selective area etching and selective area regrowth or quantumwe...