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Single-Nanowire Single-Mode Laser

Posted on:2012-09-04Degree:MasterType:Thesis
Country:ChinaCandidate:Y XiaoFull Text:PDF
GTID:2178330332484237Subject:Measuring and Testing Technology and Instruments
Abstract/Summary:PDF Full Text Request
Owning to their excellent properties as gain media, resonance cavities and passive waveguides, one dimensional semiconductor nanowires (NWs) have been attracting growing interests in constructing nanoscale photonic and optoelectronic devices and circuits. Among the nanowire-based functional elements such as photodetectors, lasers and light emitting devices, nanowire lasers have gained considerable attentions due to their promises as integrable nanoscale coherent light sources for wide applications including optical communications, sensing and signal processing.Generally, in a semiconductor NW, when a round-trip gain can compensate round-trip losses, the lasing occurs. Typically, the lasing cavity of this kind nanolaser is formed by endface reflection or ring resonance, and lasing emission of the NW is usually multi-mode due to the lacking of mode selecting capability. One possible route to obtain single-mode NW lasers is to expanding the free space range (FSR) of the multi modes by significantly shortening the optical path of the lasing cavity. However, shortening the cavity path will inevitably reduce the round-trip gain, resulting in high threshold for lasing action. The simultaneous realization of single-mode lasing and low lasing threshold is a critical issue in practical application of NW laser. With this consideration, we propose a new type of laser by folding the NW to form one or two Loop Mirrors (LMS) in the NW and selecting the mode via Vernier effect in coupled multiple cavities. Furthermore, we not only realize the single-NW single-mode wavelength laser but also provide a new design for realizing low-threshold single-mode laser using other types of nanostructures.In this work, CdSe NWs with smooth surface, uniform diameter and hexagonal section were prepared via a chemical vapor deposition process. As-prepared CdSe NWs can serve as waveguides and gain medium. The coupled cavities are constructed from the single NW by micromanipulation under a microscope. Single-mode laser emission around 738 nm is obtained with low lasing threshold, and 2.4 nm lasing peak tuning is realized by changing the geometry of the loop mirror.The effect of forming the LM on lasing threshold is also investigated. By forming the single NW from F-P cavity solely relying on endface reflection to double LMs cavity, the lasing threshold decrease from 97μJ/cm2 to 34μJ/cm2. Accompanying the reduction of the lasing threshold, the quality of the lasing peak is significantly improved. Side mode suppression ratio (SMSR) increases from 8.6 (single LM) to 13.5 (double LM).
Keywords/Search Tags:nanowire, single longitudinal mode, Vernier effect, loop mirror, nanolaser
PDF Full Text Request
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