Cascade Brillouin Lasing in a Tellurite-Glass Microsphere Resonator with Whispering Gallery Modes

Abstract

Brillouin microlasers based on microresonators with whispering gallery modes (WGMs) are in high demand for different applications including sensing and biosensing. We fabricated a microsphere resonator with WGMs from a synthesized high-quality tellurite glass with record high Q-factors for tellurite microresonators (Q ≥ 2.5 × 107), a high Brillouin gain coefficient (compared to standard materials, e.g., silica glasses), and a Brillouin frequency shift of 9 ± 0.5 GHz. The high density of excited resonance modes and high loaded Q-factors allowed us to achieve experimentally cascade Stokes-Brillouin lasing up to the 4th order inclusive. The experimental results are supported by the results of the theoretical analysis. We also theoretically obtained the dependences of the output Brillouin powers on the pump power and found the pump-power thresholds for the first five Brillouin orders at different values of pump frequency detuning and Q-factors, and showed a significant effect of these parameters on the processes under consideration.

Comprehensive Numerical Analysis of Temperature Sensitivity of Spherical Microresonators Based on Silica and Soft Glasses

“…Glass-based microresonators are routinely manufactured by melting the tip of an optical fiber: under the action of surface tension forces a solid sphere is formed [ 7 ]. This can be done, for example, using a CO 2 laser for any type of glass [ 7 , 23 , 32 ]. A regular telecommunication fiber splicer may also be used to make fused silica microspheres [ 33 ], and a microheater to make soft glass microspheres [ 22 , 34 ].…”

“…The light propagates along a thin fiber taper placed in the “equatorial” plane of the spherical microresonator (also denoted as z = 0). Regardless of the sphere material, a standard telecommunication silica fiber can be used to manufacture the microtaper [ 22 , 32 , 36 , 37 ], for example, employing a gas torch to soften and stretch the glass [ 33 ]. The suggested pumping setup facilitated the excitation of near-surface microsphere eigenmodes localized in the “equatorial” plane.…”

Switchable Cascade Raman Lasing in a Tellurite Glass Microresonator

“…The technology for the microsphere fabrication was developed previously and allowed us to demonstrate a high-quality 75 μm microsphere from TeO 2 –WO 3 –La 2 O 3 –Bi 2 O 3 glass with a maximum Q -factor of 2.5 × 10 7 , which was a record high for tellurite microspheres . The technology details can be found in ref . Here, we fabricated microspheres with diameters ranging from 30 to 100 μm and with similar Q -factors almost independent of the size.…”

“…The smaller the size, the stronger the light localization and the smaller the effective mode volume V eff . For the presented microsphere with the diameter d = 30 μm, the calculated mode volume for the fundamental WGM near 1.55 μm was as low as 350 μm 3 (and larger for higher modes). The calculated dispersion was normal for the fundamental and higher WGMs (>200 ps 2 /km); the free spectral range was FSR = 1.6 THz.…”

“…As far as we know, Raman generation has not yet been demonstrated in microresonators made of tellurite glasses. This fact seems very surprising, taking into account the great attention paid by different research groups to tellurite microresonators over the past 20 years, − as well as the huge successes achieved in the field of nonlinear optics exploiting Raman effects in tellurite glass fibers, including supercontinuum generation, , soliton self-frequency shift, and a widely tunable continuous wave (CW) Raman laser . We also note that technologies for integrating tellurite microresonators on chips are currently being actively developed, , which clearly indicates the great interest that they represent for real applications.…”