In-phase evanescent coupled implant defined vertical cavity laser arrays

Ann C. Lehman, Kent D. Choquette

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Arrays of vertical cavity surface emitting lasers (VCSELs) have been studied extensively for coherent coupling between lasers [1-8]. Coherent coupling allows for increased power in the far field at a single frequency, which may be used in applications such as optical logic, imaging, and beam steering. Because of the loss between evanescently coupled VCSELs, a phase-shift of 180 degrees is typically observed between neighboring lasers [1]. This creates an out-of-phase mode with an on-axis null which is undesirable for most applications. Phase-adjusted arrays [2] and anti-guided VCSELs [5, 6] can overcome this setback at the cost of a complicated fabrication process. It is also possible to achieve in-phase coupling with photonic crystal VCSELs [7]; however, the hole(s) between lasers frequently promote the out-of-phase mode. In this work, we show that proton implantation may be used to define individual elements in the coupled array. This approach adds no fabrication complexity to that of a conventional implant VCSEL. A cross-sectional sketch of this device is shown in Fig. 1, and the implant geometry is shown in Fig. 2. Because the implant provides electrical confinement without adding optical loss, the lasers tend to lock in-phase. A near-field image and a far-field pattern for a 2×1 array are shown in Fig. 3, at an injection current of 4.3 mA (1.4 times threshold). In the near-field image of Fig. 3, the minor lobe located between the two major lobes of the array elements is out of phase with the major lobes. As with the case of anti-guided arrays [5, 6], the distance separating the lasing elements affects the number of minor lobes which occur. This type of modal structure allows for an on-axis maximum in the far-field. In order to further test the coupling mechanism, a 2×1 array was operated under pulsed conditions with 100 ns pulses and 1 μs period. Although the coherence between lasers (as measured in the far-field) [8] decreased as compared with continuous wave (CW) operation, an interference pattern was still visible as seen in Fig. 4. This indicates that electronic coupling between array elements persists in these devices despite lacking the thermal lens from heating effects. In-phase coupling is also achieved for two-dimensional arrays. Fig. 5 shows the near-field image and the far-field pattern, respectively, for a 3-element two-dimensional array. In this case, the minor lobes are out-of-phase with the defect elements except for the center lobe, which is in-phase with the defect elements. Fig. 6 depicts the calculated far field pattern for 3 in-phase Gaussian emitters with no lobes between implanted regions. The differences between our calculated and measured results are likely due to a difference in intensities between lasing regions, the lobes between emitting regions, and the non-circular emission centers as seen in the near field. This 3-element geometry provides the minimum number of emitters that would be necessary for two dimensional beam-steering. As injection current is increased to these implant-defined arrays, higher-order transverse modes turn on, which limits the single-mode output power. Ongoing efforts are to suppress these higher order modes and thus allow these evanescently coupled arrays to operate in-phase with higher injection current.

Original languageEnglish (US)
Title of host publication19th Annual Meeting of the IEEE Lasers and Electro-Optics Society, LEOS
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages2
ISBN (Print)0780395557, 9780780395558
StatePublished - Jan 1 2006
Event19th Annual Meeting of the IEEE Lasers and Electro-Optics Society, LEOS - Montreal, QC, Canada
Duration: Oct 29 2006Nov 2 2006

Publication series

NameConference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS
ISSN (Print)1092-8081


Other19th Annual Meeting of the IEEE Lasers and Electro-Optics Society, LEOS
CityMontreal, QC

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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    Lehman, A. C., & Choquette, K. D. (2006). In-phase evanescent coupled implant defined vertical cavity laser arrays. In 19th Annual Meeting of the IEEE Lasers and Electro-Optics Society, LEOS (pp. 446-447). [4054249] (Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS). Institute of Electrical and Electronics Engineers Inc..