Design of rare-earth-doped microbottle lasers

Abstract

Coupling strength in taper-coupled microbottle resonators can be tuned by offsetting the taper along the resonator profile, similar to controlling the air-gap in microsphere excitation, and hence, achieve desired coupling characteristics for a specific mode. Such flexibility makes microbottles attractive and adaptable laser cavities. In this paper, lasing characteristics of Yb 3+-doped microbottle laser (MBL) coupled to tapered fiber are theoretically investigated. It is demonstrated that desired lasing characteristics for a particular mode are achievable by controlling the taper-resonator coupling, intrinsic quality factor (Q) and dopant concentration. Although, high Q whispering gallery cavities provide high internal powers, which is favorable especially for low gain materials, they lack high output powers. Hence, care should be taken in designing MBLs to attain the highest possible output power. Here, we address such issues, and optimized the required resonator parameters (for both pump and signal) for a low threshold pump power, high efficiency and desired lasing wavelength.

Optical bottle microresonators

“…Lasing microresonators can be fabricated of an active material or fabricated of a passive material and post-processed by coating with an active material. The BMR lasers [61][62][63][64][65][66][67][68] have certain advantages compared to other microlasers. In fact, their elongated geometry and fabrication simplicity allows one to fabricate active BMR with predetermined spectrum and facilitate mode selection by patterned pumping much easier than for active microresonators having other geometries.…”

“…Finally, in Section 4, applications of BMRs which either have been demonstrated or seem feasible in the nearest future are considered. These applications include miniature BMR delay lines and dispersion compensators [24,[58][59][60], BMR lasers [61][62][63][64][65][66][67][68], nonlinear BMRs [69][70][71][72][73][74][75], optomechanical BMRs [76][77][78][79][80][81][82][83], BMR for quantum processing [84][85][86][87][88], and BMR sensors [89][90][91][92][93][94][95][96][97].…”

A general model for taper coupling of multiple modes of whispering gallery resonators and application to analysis of coupling-induced Fano interference in a single cavity

“…However, in practice, such tapered fibers are multimoded, and WGMs can couple-out to different fiber modes depending on the resonance type and taper size (as we demonstrated in [32]). Furthermore, our study can be very useful in studying multimode cavities in nonlinear optics and lasers [33] where accurate determination of the internal intensity is important.…”

Efficient excitation and phase matching of fiber-coupled degenerate whispering gallery modes

“…The findings shown in Figs. 7 and 8 can be used to a large extend to define criterions for designing the coupling conditions in spherical lasers and nonlinear devices, since they can be used to decide suitable pumping and modal characteristics for optimum performance [36][37][38]. Note that, such formulation and analysis method can be applied to optimize coupling to any type of degenerate WGMs including the transverse magnetic ones.…”