Ultrafast distributed feedback dye lasers

A distributed feedback dye laser (DFDL) was experimentally studied to determine the utmost lower limit on ultrafast pulse generation. The ultimate aim was to determine its suitability as a cheaper high peak power laser source. The dye cell was excited by the second harmonic of a laboratory built cavity dumped passively q switched and modelocked Nd:YAG Laser to induce temperature phase grating in dye solution. Different features studied include threshold conditions, pulse shortening, by reducing cavity length, polymerization limitations, simultaneous induction of multiple superimposed gratings, line narrowing, polarization, temporal and spectral characteristics. The pump polarization affect on dynamic gratings and threshold conditions indicated the number of lasing lines (maximum nine) or intensity of a single line depends upon the state of pump polarization (SOP). Various types of tuning methods such as Bragg index, refractive index, half angle and state of pump polarization were tested for improved divergence, bandwidth, line-width and wider spectral ranges. The combined effect of coherence length and SOP of excitation laser on emission of multiple lines was studied without using external gratings. The results of this critical and contemporary work on DFDL is in agreement with most of the published results and opens a new era for their potential suitability in optical communication, sensing and photonic devices.