Chromium-doped zinc selenide gain media: From synthesis to pulsed mid-infrared laser operation

This paper provides an overview of the experimental work performed in our research group on the synthesis, spectroscopic investigation, and laser characterization of chromium-doped zinc selenide (Cr[superscript 2+]:ZnSe). By using diffusion doping, 40 polycrystalline Cr[superscript 2+]:ZnSe samples with ion concentration in the range of 0.8 × 10[superscript 18] to 66 × 10[superscript 18]ions/cm[superscript 3] were prepared. From the absorption data, temperature-dependent diffusion coefficient of chromium and losses at the lasing wavelength were measured. In luminescence measurements, the concentration dependence of the fluorescence lifetime and fluorescence quantum efficiency was determined. During continuous-wave operation, the optimum concentration for lasing was determined to be 8.5 × 10[superscript 18] ions/cm[superscript 3] at an incident pump power of 2.1 W for 1800-nm pumping. During gain switched operation, intra-cavity pumping with a 1570-nm optical parametric oscillator resulted in continuous tuning between 1880 and 3100 nm. By employing dispersion compensation with a MgF[superscript 2] prism pair, Kerr-lens mode-locked operation was also demonstrated at 2420 nm, resulting in the generation of 95-fs pulses with an average output power of 40 mW and spectral bandwidth of 69 nm. The time-bandwidth product of the pulses was further measured to be 0.335 close to the expected value of 0.315 for sech[superscript 2] pulses.Network of Excellence on Micro-Optics (Organization)Sixth Framework Programme (European Commission) (2004-2008)Türkiye Bilimsel ve Teknolojik Araştırma Kurumu (TBAG-2030)Türkiye Bilimsel ve Teknolojik Araştırma Kurumu (108T028

Graphene mode-locked femtosecond Cr:ZnSe laser at 2500 nm

We report, for the first time to our knowledge, femtosecond pulse generation from a graphene mode-locked Cr:ZnSe laser at 2500 nm. To minimize the insertion losses at the lasing wavelength, high-quality monolayer graphene transferred on a CaF2 substrate was used in the experiments. Once mode-locking was initiated, the laser generated a stable train of 226 fs pulses with a time-bandwidth product of 0.39. The mode-locked laser operated at a pulse repetition rate of 77 MHz and produced 80 mW output power with an incident pump power of 1.6 W. To our knowledge, this is the longest laser wavelength at which graphene-based passive mode-locking has been demonstrated to date. (C) 2013 Optical Society of Americ