TiO₂-Doped Single-Mode Fiber as Active Material for Raman Lasers

Abstract

The properties of TiO2-doped fiber are considered as optoelectronic material in our work. The advantages of such fiber have been studied with the aim of its application to active medium in Raman fiber lasers. The comparison of spontaneous Raman spectra and corresponding gain profiles in TiO2-doped and GeO2-doped fiber is presented. Raman gain profiles were obtained over a broad spectral range of Stokes shifted frequencies up to 1400 cm-1(42 THz). The spectral decomposition using multimode Gaussian components has been performed for both Raman gain profiles. High accuracy analytic form of Raman gain profile of TiO2-doped fiber is obtained using 12 components. The pump power of Raman gain threshold is introduced as the function of wavelength within the telecommunication windows for both fiber types. Our spectroscopic analysis allows presenting the numerical results on lasing bandwidth and Raman gain threshold inTiO2-doped single-mode fiber. It has been shown that the lasing bandwidth in TiO2-doped fiber may be almost twice wider than the lasing bandwidth in standard GeO2-doped fiber.

Spectroscopic Features of Raman Gain Profiles in Single-Mode Fibers Based on Silica Glass

“…The internal resonator on the fiber Braggs grating in the Raman (GeO 2 -doped) fiber performs a 4-fold Stokes conversion on ∼420 cm −1 of the pumping wavelength from 1100 nm to 1347 nm. A certain alternative to GeO 2 -doped fibers, in our opinion, can present a fiber with a TiO 2 dopant [33]. Figure 10 shows the modeling results for the full transparency function (26) in a TiO 2 -doped fiber at = 1.35 m, which demonstrates the possibility of forming several lasing areas.…”

“…Note that the amorphous nature of silica glass significantly complicates the solution of such rather standard spectroscopic problems in almost every case of optical fiber, and their general solutions have not been obtained yet. However, we succeeded to find a special solution to this problem in a number of individual cases, in particular, in the case of TiO 2 -doped fiber [21], [22]. In this paper, we also give an analytic expression for the Raman gain profile in a phosphoric silicate fiber, which has explicit prospects for the use as an active medium in modern devices of fiber nonlinear optics.…”

“…and belongs the Gaussian type. Both profiles (20) and (21) are presented in Fig. 2 for two values of relative phonon's damping, namely for Γ/Ω = 0.05 and 0.1.…”

“…The broadening is mostly heterogeneous in such amorphous materials as glass. Below, we continue to use the Gaussian components (21) in order to decompose the complex Raman spectra in optical fibers.…”

“…It is appropriate to be taken separately from the spectroscopic simulation of Raman gain profiles. In fact, the main frequency dependence in a Raman gain profile is given by the imaginary part of the nonlinear polarizability (3) (18) due to the resonant denominator (14), which arises in a phonon harmonic oscillator and leads to the oscillating mode lineform with the form-factor (20) or as the Gaussian function (21).…”