RECENT DRDO DEVELOPMENTS

Diode Array Pumped Nd : YAG Laser

Diode Array Pumped Nd:YAG  LaserThe Laser Science & Technology Centre (LASTEC) , Delhi, has successfully developed the state-of-the-art Diode Pumped Solid-State Laser (DPSSL) Technology as a part of DRDO Photonics Programme. The solid-state lasers are conventionally pumped by noble gas (Xenon or Krypto) filled flash lamps or arc lamps. These lamps produce broad raDIATion from ultraviolet to infrared, but only a very small portion of this wide band raDIATion is used by the absorbing active element. Consequently, the electrical efficiency of the system is extremely poor, typically of the order of 1 per cent. The diode laser pump source for solid-state lasers brings the advantages of high efficiency, long operation life and high spectral brightness by selectively pumping the absorption bands of the ion-doped crystal and glasses. It also reduces the size, weight, power consumption and waste heat dissipation, hence resulting in compact and efficient systems suitable for military applications.

LASTEC has demonstrated various bench models of diode array pumped Nd: YAG laser. The figure shows Nd:YAG
laser rod with 5 mm diameter and 50 mm length being pumped by four quasi-CW laser diode (GaAlAs, peak wavelength 808 nm) arrays connected in series. The system generates 12 mJ energy per pulse at 10 pps@1064 nm in 200 ms duration with 18 per cent optical efficiency. By employing six such diode arrays to pump the same rod in circular symmetry, laser energy of 23 mJ has been achieved with 21 per cent optical efficiency. The system is under packaging. Such lasers have potential applications in the field of laser range finders etc. Some critical technologies involved in the development of DPSSL have been indigenised. These are :

  • QCW Laser Diode Array Driver capable of driving six linear arrays-
  • Side Pumping Configurations with linear and circular symmetry-
  • Close Optical Coupling Schemes including semi-cylindrical/segmented reflectors.
  • Free Running Planoconcave Laser Resonators with high mechanical stability.