| 1. |
- Kjellberg, T., et al.
(författare)
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Investigation on the spectral characteristics of DFB lasers with different grating configurations made by electron-beam lithography
- 1993
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 11, s. 1405-1415
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Tidskriftsartikel (refereegranskat)abstract
- The single-mode stability for distributed-feedback (DFB) lasers with various electron-beam-written grating configurations has been investigated theoretically and experimentally, for both as-cleaved and AR-coated lasers. Other laser properties interesting for coherent and multichannel communications systems, such as linewidth and tunability, have also briefly been investigated. Lasers with more sophisticated grating structures, such as an optimized multiple phase-shifted or a corrugation-pitch-modulated grating, did not exhibit performance significantly superior to that of lambda;/4-shifted DFB lasers with an appropriate coupling coefficient. Antireflection (AR)-coating of the end facets proved indispensable for obtaining a high yield for lasers with single-mode operation at high output power and for reducing the large chip-to-chip variation seen for the as-cleaved lasers. A theoretical investigation of the effect of end reflections on the stopband and of the problem of determining the coupling coefficient was also made
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| 2. |
- Nilsson, S., et al.
(författare)
-
DFB laser with nonuniform coupling coefficient realized by double-layer buried grating
- 1993
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Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 5, s. 1128-1131
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Tidskriftsartikel (refereegranskat)abstract
- A technique for the realization of a nonuniform grating coupling coefficient kappa , and its implementation in distributed-feedback (DFB) lasers is presented. This technique, which is an extension of the buried-grating concept, offers precise control of the coupling coefficient and enables a kappa -ratio greater than 10. DFB lasers with an asymmetric kappa -variation have been fabricated using this method. A front-to-rear facet output power ratio close to five was obtained, qualitatively in agreement with simulations.<>
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| 3. |
- Kjellberg, T., et al.
(författare)
-
The effect of stitching errors on the spectral characteristics of DFB lasers fabricated using electron beam lithography
- 1992
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 10, s. 1256-1266
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Tidskriftsartikel (refereegranskat)abstract
- Field stitching errors and their effect on the single-mode characteristics of distributed feedback (DFB) lasers fabricated using electron beam lithography were investigated. The stitching errors are associated with small-area, high-resolution electron beam exposure, which has the potential advantage of high-speed writing of laser gratings. Measurements show that the errors are composed of a systematic and a stochastic part. Their effect on the gain margin was simulated both for lambda;/4 phase-shifted and optimized multiple-phase-shifted DFB lasers. Simulations show that the lasers are insensitive to the systematic part of the stitching errors if the number of errors is large enough. The stochastic part was found to give rise to a variation in gain margin of the DFB lasers. It is concluded that the field stitching accuracy in the high-resolution mode of a commercial system for electron beam lithography is sufficient to provide a high yield of single-mode lasers. However, it is essential that certain precautions be taken considering exposure conditions and that a fault tolerant laser design be used
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