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InP-Based Multi-Section Coupled-Cavity Laser Using Deeply Etched Trenches

Author: WangYin
Tutor: HeJianJun
School: Zhejiang University
Course: Optical Engineering
Keywords: deep trench coupled-cavity semiconductor laser single-mode laser tunable laser laser array narrow linewidth dry etching carrier injection second-re-gorwth-free
CLC: TN248
Type: PhD thesis
Year: 2013
Downloads: 106
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Abstract

Wavelength-division multiplexing (WDM) is an important technique in morden optical communication. It multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths enablng bidirectional communications over one strand of fiber, as well as multiplication of capacity. Light source, including single-mode laser and tunable laser, is an essential component in the WDM system. The most widely used lasers are the DFB lasers and DBR lasers. These devices require second re-growth which increase the fabrication cost. Besides, most of the tunable lasers have a very complicated tuning mechanism whcih involve at least2electrodes at the same time.In this thesis, we are trying to propose a novel design called coupled-cavity laser with deep trenches. By coupling several fP cavitieswith deep trenches we are able to realize both single-mode lasers and tunable lasers. Such lasers do not need gratings or second re-growth. Its low manufacture requirement would help to reduce the fabiration cost.We first studied and optimized each fabrication step for the coupled-cavity laser. The process of dry etching has been thoroughly discussed including different effects during the etching, the choice of gas recipe and the etching results of using various mask materials. We discussed a lot on the etching process of deep trenches and developed an specially optimized recipe for the deep etching.The working theory and design principle of the coupled-cavity laser are dicussed for both single-mode lasers and tunable lasers. The effect of the deep trench, as a key component in our laser, has been studied and compared with those reported shallow trenches. It is proved by both theory and experiments that deep trenches can provide more feed back with less loss than the shallow ones. The tested results of the the single-mode laser shows a good spectrum purity, and the linewidth can be as small as78kHz which is the smallest ever reported for semiconductor lasers of similar designs. An8X100GHz Laser arry has been fabricated and demonstrated.We have also successfully fabricated the tunable version of coupled-cavity laser with deep trenches. The device showed agood tunability and was able to achieve all the9100GHz channels by single electrode control. The SMSR of all the channels are larger than30dB and the power variation is less than1.6dBAt the end of this work, we discussed about the futurewrok on our laser design.We believe this coupled-cavity laser with deep trenches can fufill the requirements of future optical communication, especially in WDM and coherent communication. Its tight structure and ease of fabrication will make this novel design a possible candidate of light source in future.

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