Abstract
AbstractTitanium doped sapphire (Ti:sapphire) is a laser gain material with broad gain bandwidth benefiting from the material stability of sapphire. These favorable characteristics of Ti:sapphire have given rise to femtosecond lasers and optical frequency combs. Shaping a single Ti:sapphire crystal into a millimeter sized high quality (Q) whispering gallery mode resonator (Q ≈ 108) reduces the lasing threshold to 14.2 mW and increases the laser slope efficiency to 34%. The observed lasing can be both multi‐mode and single‐mode. This is the first demonstration of a Ti:sapphire whispering‐gallery laser. Furthermore, a novel method of evaluating the gain in Ti:sapphire in the near infrared region is demonstrated by introducing a probe laser with a central wavelength of 795 nm. This method results in decreasing linewidth of the modes excited with the probe laser, consequently increasing their Q. These findings open avenues for the usage of whispering gallery mode resonators as cavities for the implementation of compact Ti:sapphire lasers. Moreover, Ti:sapphire whispering‐gallery laser can also be utilized as an amplifier inside its gain bandwidth by implementing a pump–probe configuration.
Highlights
Titanium doped sapphire (Ti:sapphire) has been the workhorse behind solid state lasers since its invention in 1986 [1]
We present a new take on the material that will allow us to surpass the current records in lasing threshold and slope efficiency by fabricating an ultra-high quality whispering gallery mode resonator out of Ti:Sapphire
We have for the first time demonstrated a Ti:sapphire whispering gallery laser (WGL)
Summary
Titanium doped sapphire (Ti:sapphire) has been the workhorse behind solid state lasers since its invention in 1986 [1]. Dielectric whispering gallery mode resonators (WGMRs) confine the light via total internal reflection at their rotationally symmetric boundary [25] They are well suited for lasing feedback as the gain material itself acts as the cavity. As a laser pumped at 516.6 nm it has an input-power threshold of 14.2 mW and a slope efficiency of 34 % in multimode operation, based on the pump power coupled into the resonator at the onset of lasing. This is the lowest observed Ti:sapphire lasing threshold to the best of our knowledge
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