Inversed Vernier effect based single-mode laser emission in coupled microdisks.

Meng Li,Nan Zhang,Jiankai Li,Shumin Xiao,Qinghai Song,Kaiyang Wang

doi:10.1038/srep13682

Abstract

Recently, on-chip single-mode laser emissions in coupled microdisks have attracted considerable research attention due to their wide applications. While most of single-mode lasers in coupled microdisks or microrings have been qualitatively explained by either Vernier effect or inversed Vernier effect, none of them have been experimentally confirmed. Here, we studied the mechanism of single-mode laser operation in coupled microdisks. We found that the mode numbers had been significantly reduced to nearly single-mode within a large pumping power range from threshold to gain saturation. The detail laser spectra showed that the largest gain and the first lasing peak were mainly generated by one disk and the laser intensity was proportional to the wavelength detuning of two set of modes. The corresponding theoretical analysis showed that the experimental observations were dominated by internal coupling within one cavity, which was similar to the recently explored inversed Vernier effect in two coupled microrings. We believe our finding will be important for understanding the previous experimental findings and the development of on-chip single-mode laser.

Highlights

To well understand the suppression of lasing modes, we have theoretically studied the possible mode interaction by a toy model. Both the Vernier effect and inversed Vernier effect are based on the interaction between two resonances can be quantum mechanically described by a 2 × 2 matrix[20,21,22,23,24]
E1,2 are the energy of states away from mode coupling and J2 is the coupling constant
By comparing the results under three types of pumping conditions, we found the single-mode operation in coupled cavities were mainly induced by the mode coupling within one cavity

Summary

Results and Discussions

When the resonances are far away from crossing point at RR = 5.095 μ m, mode-1 was mainly confined within the gain cavity (Fig. 2(c)) and mode-2 was localized within two cavities (Fig. 2(d)). As the other cavity was defined as absorption in the numerical model, mode-2 had much larger loss than mode-1. When two resonances approached the crossing point, the corresponding field patterns showed that they were strongly mixed (see Fig. 2(e,f)). The modes around ARC had much larger thresholds and were not to be excited All these numerical results are consistent with the theoretical analysis well

Experimental results

Conclusion

Method