Nonlinear properties of the depressed cladding single mode TeO₂-WO₃-Bi₂O₃ channel waveguide fabricated by direct laser writing

Theoretical Study of Multicascade Raman Microlasers Based on TeO2–WO3–Bi2O3 Glass

“…We assumed that a tellurite fiber taper (transparent in the near-IR and mid-IR) can be used to couple the pump light into a microsphere and extract the generated Raman waves from it. We considered a realistic design and performed a detailed theoretical study using the experimental parameters of the glass reported in [22] and the experimental parameters of the microspheres produced previously from a similar tellurite TeO2-WO3-La2O3 glass [23]. Thanks to the large Raman gain (120 times exceeding the maximum Raman gain of silica glass) and a huge Raman frequency shift of 27.5 THz for this glass (against 13.2 THz for silica glass), the Raman waves at 1.83 µm, 2.21 µm, 2.77 µm, and 3.7 µm in the first, second, third, and fourth cascades, respectively, with a pump For a better understanding of the obtained results, we fixed the detuning value (∆ω 0 /(2π) = 25 MHz) and considered how the powers of the Raman waves depended on the pump power.…”

“…We took into account that the maximum Raman gain is inversely proportional to the pump wavelength [2]. The model Raman gain function of TWB glass in comparison with the Raman gain function of silica glass is plotted in the inset in Figure 1b based on the data presented in [22]. The expected frequencies in the Raman cascades were 191 THz − 27.5 THz = 163.5 THz (in the first cascade), 191 THz − 2 × 27.5 THz = 136 THz (in the second cascade), 191 THz − 3 × 27.5 THz = 108.5 THz (in the third cascade), and 191 THz − 4 × 27.5 THz = 81 THz (in the fourth cascade).…”

“…However, their Raman shifts are relatively low: ~10 THz [19] and ~7 THz [20], respectively. Against this background, special tellurite glasses with a transparency band of ~0.5-5 µm and Raman gains of two orders of magnitude higher than the value for silica glass and the frequency shift corresponding to a maximum of 20-28 THz [21,22] seem to be very promising materials for the implementation of multicascade mid-IR WGM microlasers, even with a pump wavelength belonging to the well-mastered telecommunication range. We recently demonstrated Raman lasing in a tellurite TeO 2 -WO 3 -La 2 O 3 (TWL) microsphere (for the first time for tellurite microresonators) [23].…”

“…Here, we propose and theoretically study multicascade Raman microlasers based on TeO 2 -WO 3 -Bi 2 O 3 (TWB) glass with a maximum Raman gain 120 times exceeding the maximum Raman gain of silica glass [22]. This glass also has a huge Raman frequency shift of ∆f R ~27.5 THz [22], which allows broadband frequency conversion using a reasonable number of cascades.…”

“…Here, we propose and theoretically study multicascade Raman microlasers based on TeO 2 -WO 3 -Bi 2 O 3 (TWB) glass with a maximum Raman gain 120 times exceeding the maximum Raman gain of silica glass [22]. This glass also has a huge Raman frequency shift of ∆f R ~27.5 THz [22], which allows broadband frequency conversion using a reasonable number of cascades. It is important to note that since tellurite glasses have a relatively low glass transition temperature (T g ~370 • C for TWB glass [25]), it is necessary to take into consideration the heating of the microresonator during partial pump thermalization and to control that the maximum temperature should remain below T g , which is also taken into account in the simulation.…”