Temperature effects on tunable cw Alexandrite lasers under diode end-pumping

Temperature dependence of Alexandrite effective emission cross section and small signal gain over the 25-450 °C range

“…Moreover, the results are combined with the excited state absorption data from the literature [38] to estimate the effective gain line shapes at different temperatures, and detailed comparison with earlier experimental data have been performed for confirmation of the models accuracy. Variation of the net small signal gain as a function of temperature is also investigated for several different wavelengths, which confirmed the measured improvement in laser performance with temperature [3,13,14,39]. To our knowledge, this is the first detailed study presenting the temperature dependence of the effective emission cross section and small signal gain spectra in Alexandrite.…”

“…As an example, for an inversion level of 20%, the short wavelength cut-off is around 702± 2 nm. A short wavelength tuning limit of 724 nm is reported in [11] at room temperature, and a short wavelength tuning limit of 714 nm is reported in [14] at a crystal holder base temperature of 10 . Tuning down to 701 nm was obtained in [1] while pumping with high energy Xe-flashlamps.…”

“…In the early years of its development, these favorable properties made Alexandrite the laser of choice in the development of flashlamp pumped high energy and high power Q-switched laser systems especially for biomedical applications. Over the last decade, the advancement of higher brightness laser and light-emitting diodes in the red spectral region, generated a renewed interest towards Alexandrite [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and continuous-wave laser output powers above 25 W have already been achieved from compact diode-pumped systems [12]. Mode-locking of Alexandrite using Saturable Bragg Reflectors (SBRs) [26], Kerr-lensing [27,28], and graphene saturable absorbers [29] has also been demonstrated recently.…”

“…On top of these, excited state absorption also exists in the pumping wavelength region of Alexandrite [31]. The effect of pump excited state absorption on pumping efficiency has been discussed in [14,32,33]; and its temperature dependence is investigated in [33].…”

“…However, the progress has been relatively slow especially for the development of ultrashort pulse laser/amplifier sources, and there is currently a need for better understanding of Alexandrite laser gain media, for accurate modeling of its laser potential. Recent detailed work by Kerridge-Johns et al on the effect of pump and laser excited state absorption on laser performance has been an important step towards this aim [14,32,33]; however, efforts in this direction face a challenge due to the limited availability of spectroscopic data. For a laser design engineer, a thorough modeling of laser dynamics and its potential as an efficient laser requires detailed knowledge of wavelength and temperature dependence of all the relevant cross sections (σ em , σ esa , and σ a ) as well as the temperature dependence of fluorescence lifetime (τ F ).…”